No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Temperature-Dependent in Situ Reduction of 4,4 '-Azobispyridine via Solvothermal Reaction
Abstract
Solvothermal reactions of 2,2'-biphenyldicarboxylate (H(2)dpa) and 4,4'-azobispyridine (azpy) in the presence of transition metal ions produce six new complexes, namely, [Co(dpa)(bphy)](n) (1), [Co(dpa)(azpy)(H2O)](n)center dot 0.5nH(2)O (2), [Zn(dpa)(bphy](n) (3), [Zn(dpa)(azpy)(H2O)](n) (4), [Mn(dpa)(azpy)(H2O)]center dot 0.5nH(2)O (5), and [Mn(dpa)(azpy)(n)center dot nH(2)O center dot nMeOH (6) (bphy = 1,2-bis(4-pyridyl)hydrazine). The crystal structure analyses reveal that complexes 1 and 3 are isostructural which features a plywood-like structure, while complex 4 exhibits a parallel chains array. Complexes 2 and 5 afford a two-dimensional chiral (4,4) network, and complex 6 shows a (4,4) network. It was noteworthy that the in situ reduction of azpy to bphy was found in complexes 1 and 3, which were confirmed by single-crystal structures and LC-MS analyses. However, this in situ reduction was not found at a low reaction temperature in the syntheses of complexes 2, 4, and 5. The second-harmonic-generation (SHG) properties of 1 and 3 and the solid circular dichroism (CD) properties of 2 and 5 were investigated. In addition, luminescent properties of complexes 3 and 4 as well as magnetic properties of complexes 1, 2, 5, and 6 were also studied.
... The emission spectra of the free ligands are displayed in Figure 4. H 4 btec exhibits somewhat structured emission at 370 nm in line with previous studies, 34,35 while 4,4 0 -azopyridine on the other hand shows a less structured emission band at 414 nm. 36 The photoluminescence spectrum of CTH-14 shows emission at 351 nm, whereas CTH-15 has a more intense emission at 400 nm, both consistent with similar compounds 37,38 ( Figure S25). ...
Metal-organic frameworks made from multi-metal-ion units in the shape of clusters and rods (termed dot-MOFs and rod-MOFs) are well known. Here, we introduce MOFs with multi-metallic units in the form of sheets—sheet-MOFs. We show exemplars of all three types of units based on structures containing Y³⁺, Ce³⁺, or Gd³⁺ linked by benzene-1,2,4,5-tetracarboxylate to give crystals of a dot-MOF in H2NMe2[Y(btec)(H2O)] CTH-14, a sheet-MOF in [Ce3(btec)(Hbtec)(OAc)(HCO2)] CTH-15, and a rod-MOF in 4,4′-azopyridinium[Gd2(btec)2] CTH-16. Cyclic voltammetry shows that CTH-15 stabilizes Ce(IV). Given the fact that sheet-MOFs represent an intellectual advance in the evolution of MOFs, a unified approach is proposed for the topological classification of dot-, rod-, and sheet-MOFs. It is suggested that the stability of MOFs follow in the trend dot < rod < sheet. For CTH-14-16, the sheet- and the rod-MOF have higher thermal stability. We suggest sheet-MOFs as an additional strategy for making robust MOFs.
... The emission spectra of the free ligands are displayed in Figure 4. H 4 btec exhibits somewhat structured emission at 370 nm in line with previous studies, 34,35 while 4,4 0 -azopyridine on the other hand shows a less structured emission band at 414 nm. 36 The photoluminescence spectrum of CTH-14 shows emission at 351 nm, whereas CTH-15 has a more intense emission at 400 nm, both consistent with similar compounds 37,38 ( Figure S25). ...
... The design and synthesis of metal-organic coordination polymers (MOCPs) is an emerging area in the field of advanced materials research in recent years. [1][2][3][4] The study of MOCPs is exciting due to their diverse structures, properties and compositions. Their easy customizability in addition to fascinating structural topologies has further drawn the attention of many researchers, for their potential application as advanced functional materials in the fields of catalysis, non-linear optics, medicine, etc. [5][6][7][8][9] Consequently, many efforts have been devoted to the study of transition metalorganic coordination polymers. ...
A novel water-soluble carboxylate-bridged copper(II) coordination polymer, Cu-BIG was formed by the reaction of \(\hbox {Cu}(\hbox {ClO}_{4})_{2}\cdot \hbox {6H}_{2}\hbox {O}\) and tridentate benzimidazole-glycine conjugate ligand, 2-((1H-benzimidazol-2-yl)methylamino) acetic acid, BIGH and its structure has been determined by IR, UV, powder XRD, VSM, CV, TGA, DTA, EPR and single crystal X-ray diffraction. Crystallographic studies indicate it to be a coordination polymer with Pī Space group. The asymmetric unit of complex contains two Cu(II) ions with elongated square pyramid geometry. The axial positions of the Cu(II) atoms are occupied by the carbonyl oxygen of the carboxylate group with the bond distances \(\hbox {Cu}(1)\)–\(\hbox {O}(5)_{{axial}},\, 2.28\, {\AA }\), and \(\hbox {Cu}(2)\)–\(\hbox {O}(2)_{{axial}},\, 2.26\, {\AA }\). The two Cu(II) are connected through the carboxylic group present in BIGH, which provides electron mobilisation in the molecule and hence results in the soft ferromagnetic polymer. An in vitro antibacterial activity study of BIGH and Cu-BIG showed moderate activity against Bacillus subtilis. The DNA binding studies showed the interaction of Cu-BIG with CT-DNA.
... Considerable interest continues to be focused on the rational design and syntheses of novel coordination polymers, because of their intriguing architectures and their potential applications as functional materials [1,2].Auseful strategy to synthesize such networked compounds involves the selection of appropriate multidentate bridging ligands and metal ions displaying appropriate electronic and steric properties that will act in concert to promote the formation of desired polymeric architectures [3][4][5]. Thus, the flexible triazole-containing ligand 4,4'-bis-(1,2,4-triazol-1-ylmethyl)biphenyl(btmb) has widely been utilized to construct coordination polymers because of its variable conformations and versatile coordination modes [6][7][8][9]. Herein we present the title polymeric compound [Co(C 18 H 16 N 6 )(C 7 H 5 O 2 ) 2 (H 2 O) 2 ] n (I), assembled from btmb, benzoic acid and Co II .The asymmetric unit of (I)containsone Co II ion, onebenzoate ligand,halfabtmb ligand andone coordinated watermolecule. ...
C32H30CoN6O6, monoclinic, P2(1)/c (no. 14), a = 16.452(3) angstrom, b = 5.495(1) angstrom, c = 17.295(4) angstrom, beta = 113.39(3)degrees, V = 1435.0 angstrom(3), Z = 2, R-gt(F) = 0.0482, wR(ref)(F-2) = 0.1203, T = 293 K.
... To the best of our knowledge, CPs with d 10 metal centers emitting green light at room temperature are exceedingly rare. For compound 3, the small blue shifts with respect to the free 4,4′-tmbpt ligand may be caused by the intraligand charge transition since its similarity to the emission of the free 4,4′-tmbpt ligand [46,47]. ...
Three coordination polymers based on multidentate N-donor ligands and polycarboxylate anions, namely, [Co-3(4,4'-tmbpt)(4)(btc)(2)].9.5H(2)O (1), [Ag-4(4,4'-tmbpt)(btec)(H2O)(2)]center dot H2O (2) and [Zn(4,4'-tmbpt)(btec)(0.5)(H2O)]center dot 0.5H(2)O (3) (4,4'-tmbpt = 1-((1H-1,2,4-triazol-1-yl)methyl)-3,5-bis(4-pyridy1)-1,2,4-triazole, H(3)btc = 1,3,5-benzenetricarboxylic acid,000 and H(4)btec = 1,2,4,5-benzenetetracarboxylic acid) have been prepared under hydrothermal condition. Compound 1 displays a 3D (3,6,8)-connected framework with (4.6(2))(4(4).6(10).8)(4(14).6(12).8(2)) topology. Compound 2 is a 3D (4,5,8)-connected framework with (4(3).6(2).8)(4(3).6(5).8(2))(4(8).6(2))(4(10).6(10).8(8)) topology. Compound 3 exhibits a 2D -> 3D polythreading architecture. The photoluminescent spectra indicate that at room temperature, compounds 2 and 3 emit green and blue luminescence, respectively.
In this work, two copper coordination compounds, ([Cu(phen)(L)(OH)(NO3)]NO3-) (ML1) and ([Cu(L)4(H2O)2)]( NO3-)2) (ML2), have been synthesized and characterized (SC-XRD). ML1 is a long polymeric chain with a stable distorted octahedral geometry that is assembled from ligands such as 1,10-phenanthroline (Phen), 2-amino-5-methyl-1,3,4-thiadiazole (L), hydroxide (OH), and nitrate (NO3-). In contrast, ML2 is made up of water molecules and L ligands, forming the usual octahedral geometry. Furthermore, in the crystal structures of ML1 and ML2, the nitrate anion is essential for the formation of distinct supramolecular clusters. To confirm the structural integrity, we applied Hirshfeld surface analysis and Density Functional Theory (DFT) computations. We also evaluated the antibacterial efficacy of these compounds computationally and experimentally, which confirmed their potential to serve as potent inhibitors of drug-resistant microbial infections.
A new coordination polymer, [Cu(pmaeOH)Cl2]n, based on the copper(II) ion and 2-(2-pyridine-2-ylmethylamino)ethanol (pmaeOH) ligand was obtained from a methanol solution. The coordination polymer was characterized by elemental analysis, infrared spectroscopy, X-ray single-crystal diffraction, magnetic susceptibility measurements, and DNA cleavage effect. The crystal structure of the polymer consisted of a one-dimensional (1-D) chain with each copper(II) atom six-coordinated (by three nitrogen atoms and three chlorine atoms) in a severely distorted octahedral geometry. The polymer exhibited ferromagnetic behavior within the 1-D chain (J = 6.35 cm⁻¹) through the long bond distances of copper(II) and chloride ions. The copper(II) complex cleaves scDNA through oxidative pathways, where the reactive oxygen species (ROS) involved in DNA cleavage are the superoxide radical (⋅O2–), singlet oxygen (¹O2), and hydrogen peroxide (H2O2). This paper reports the new synthesis of a ferromagnetically coupled polymer bridged with a chloride ion and its DNA cleavage effect for molecular memory devices and DNA repair applications.
Three new coordination polymers with the formulas of {[Co(nip)(bibp)]·0.5(H2O)}n (1), [Co(nip)(bimh)]n (2), {[Co(nip)(titb)]·H2O}n (3) (H2nip = 5-nitro-isophthalic acid, bibp = 4,4′-bis(imidazol-1-yl)biphenyl, bimh = 1,6-bis(imidazol-1-yl)-hexane, titb = 1,3,5-Tris(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene) were synthesized and structurally characyerized. Compound 1 has 2D (3⁶)-hxl layer topology structure. Compound 2 shows a two-fold interpenetrating 2D 4⁴ square-grid planar network (4⁴-sql) in which 1D [Co(nip)]n chains are interconnected by bimh ligand. Compound 3 possesses a 3D (3,5)-connected topological structure with a (6³)(6⁹·8) Schläfli symbol. Furthermore, the heterogeneous catalytic oxidation activity of 1 toward methylene blue in the presence and abserence of H2O2 are investigated in aqueous solution. And both compounds 1 and 3 exhibit selective sensing toward Fe³⁺ through the luminescent quenching experiments.
Herein, the reaction of (1‐methyl‐1 H‐benzo[d]imidazol‐2‐yl)methanamine (L1) with Co(H2O)6Cl2, in CH3CN at 120 °C, leading to the 2,3,5,6‐tetrakis(1‐methyl‐1 H‐benzo[d]imidazol‐2‐yl)pyrazine (3), isolated as a dimeric cluster {[CoII2(3)Cl4]⋅2 CH3CN} (2), is reported. When O2 and H2O are present, (1‐methyl‐1 H‐benzo[d]imidazole‐2‐carbonyl)amide (HL1′) is first formed and crystallized as [CoIII(L1)2(L1′)]Cl2⋅2 H2O (4) before fusion of HL1′ with L1, giving 1‐methyl‐N‐(1‐methyl‐1 H‐benzo[d]imidazol‐2‐carbonyl)‐1 H‐benzo[d]imidazol‐2‐carboxamide (HL2′′) forming a one‐dimensional (1D) chain of [CoII3(L2′′)2Cl4]n (5). The combination of crystallography and mass spectrometry (ESI‐MS) of isolated crystals and the solutions taken from the reaction as a function time reveal seven intermediate steps leading to 2, but six steps for 5, for which a different sequence takes place. Control and isotope labeling experiments confirm the two carbonyl oxygen atoms in 5 originate from both air and water. The dependence on the metals, compared with FeCl3⋅6 H2O leading to a stable triheteroarylmethyl radical, is quite astounding, which could be attributed to the different oxidation states of the metals and coordination modes confirmed by DFT calculations. This metal and valence dependent process is a very useful way for selectively obtaining these large molecules, which are unachievable by common organic synthesis.
Four new metal-organic frameworks [Zn3(HL)2(btc)2(H2O)2]·H2O (1), [Mn(H2L)(btc)(H2O)] (2), [Zn2(L)(HL)(SIP)(H2O)]·4H2O (3) and [Cd(H2L)(SIP)(H2O)]·3H2O (4) were obtained by reactions of the different metal(II) salts with mixed ligands including 1,2,3-benzenetricarboxylic acid (H3btc), sodium 5-sulfoisophthalate (NaH2SIP) and 1-(4-(1H-imidazole-5-yl)phenyl)-1H-1,2,4-triazole (HL), respectively. All compounds were characterized by single-crystal X-ray diffraction, FT-IR spectroscopy, and elemental analysis. The study shows that the natures of organic ligands as well as metal ions play key roles in modulating the resulting frameworks of 1–4. The complex 1 is a (3, 4, 4)-connected three-dimensional (3D) net with the point (Schläfli) symbol of (4²·6³·8)4(6⁴·8·10), while 2 is a two-dimensional (2D) layer structure referred as fes net with a Point (Schläfli) symbol of (4·8²). Complex 3 has 2-nodal (3, 3, 4)-connected rare tfc net with a Point (Schlafli) symbol of (8³)2(8⁵·10), while 4 is a supramolecular polymer constructed from infinite one-dimensional (1D) chains by the interaction of rich hydrogen bonds and π - π stacking. The luminescent properties have been investigated for the compounds 1, 3, and 4 containing metal d¹⁰ Zn(II) and Cd(II) atoms.
Two interesting nona-cyanometalate-based coordination polymers (CPs) {[µ4-M(CN)9Mn2(dpo)2(DMF)4]·DMF}n (M = W 1, Mo 2) were obtained from the reaction of 2,5-di(4-pyridyl)-1,3,4-oxadiazole (dpo) and (Bu3NH)3[M(CN)8] (M = W, Mo) with Mn(NO3)2·6H2O in DMF solvent. It is noteworthy that the in-situ generated [M(CN)9]4– (M = W, Mo), the first nona-cyanometalate-based example of precursors, plays the roles as not only the charge-balancing counter anion but also the molecular building blocks in inducing the neutral structures of CPs 1 and 2. Single-crystal diffraction analysis reveals that CPs 1 and 2 crystallize in the tetragonal crystal system with the I4/m space group and possess the same 3D framework structure in a (4,4)-connected mot topology with the point symbol {66}{64·82}2. Variable-temperature magnetic susceptibility measurements in the temperature range of 2 to 300 K reveal that there are antiferromagnetic interactions between the MV (M = W, Mo) of nona-cyanometalate [M(CN)9]4– and MnII spin centers in both CPs 1 and 2.
In this study, a dinuclear nona‐coordinated acetate bridged [Y2(μ3‐CH3COO)2(CH3COO)4(OH)4]. 4H2O (1) complex was synthesized and its luminescence, dye degradation and DNA binding properties were evaluated. The complex 1 belonged to triclinic crystal system with P‐1 space group and the structure consisted of [YIII2(μ3‐OR)2(μ‐OR)4(OH)4] asymmetric “butterfly” units, where R is the rest of a CH3CO2 group linked together in the form of a loop by alternating anti, anti (μ3‐O2CMe)2 and (μ‐O2CMe)2 units attached with the Y wingtip atoms. Interestingly, the co‐ordination number of each Y atom was nine in crystal 1, which was unprecedented and the oxidation states of both the Y atoms were +3 and confirmed by BVS calculation. The inter‐ and intra‐molecular H‐bonding in the molecule gave rise to a layer type of structure. The luminescence property of the Complex 1 reveals that the emission band arises at 279 nm which indicates the Complex 1 had efficient luminescence activity. The Complex 1 exhibited an exciting performance towards degradation of a model pollutant methylene blue and also showed good DNA‐ binding ability.
Pillar-layered Metal-Organic Frameworks (MOFs) are among the most striking research areas in crystalline materials. Due to great number of reports related to pillar-layered MOFs, investigating their structure diversity, properties and applicability as multi donor porous frameworks is of great interest. Modifying pillar moieties as a third building block of pillar-layered MOFs, together with metal nodes and oxygen donor linkers can enhance controlling structure assembly, leading to specific properties into the obtained structures. Although the past decade has witnessed remarkable advances in this research area, pillar-layered MOFs have never been reviewed as an independent subject until now. Therefore, a review summarizing their performance is highly expected. This review covers issues related to pillar-layered MOFs, including structure properties, synthesis, stability, diversity in linkers, and improved applicability. Finally, the pillar linkers are studied separately according to the diverse donor atoms and functional groups.
Employing the mixed ligands to react with Cd(NO3)2·4H2O afforded a new 3D coordination polymer [Cd3(BPTC)(bmp)2(ox)(H2O)4] (1) (H4BPTC = biphenyl-3,3′,4,4′-tetracarboxylic acid, bmp = 3,6-bis(imidazol-1-yl)pyridazine, H2ox = oxalic acid), in which ox²⁻ was from the in situ oxidation of ethanol. Compound 1 bears a novel trinodal (4,6,6)-connected net structure, and it is the first replica of the theoretically predicted sqc111 topology net. Moreover, the thermal and photoluminescent properties for 1 were also investigated.
A series of four new copper(II) based metal-organic frameworks containing 1,4-phenylenedipropionic acid and different N,N′-donor coligands, namely, [Cu(ppa)(bpy)]n (1), {[Cu(ppa)(azp)(H2O)](H2O)}n (2), {[Cu(ppa)(tdp)(H2O)](H2O)2}n (3), and {[Cu(ppa)(tdp)](H2O)}n (4), (H2ppa = 1,4-phenylenedipropionic acid, bpy = 4,4′-bipyridine, azp = 4,4′-azobipyridine, tdp = 4,4′-thiodipyridine) have been successfully synthesized and structurally characterized by elemental analysis, IR, UV–vis, TGA, XRPD and single-crystal X-ray diffraction. Compound 1 containing a short and rigid bpy coligand displays a 2D square lattice (sql) topology while 2 and 3 which contain more flexible and longer azp and tdp coligands possess two-fold interpenetrating diamond-like (dia) 3D framework. Finally, the thermal-induced compound 4 is transformed from compound 3 by heating, through single-crystal-to-single-crystal transformation, adopting a CdSO4-like (cds) 3D framework. Additionally, the solid stated compounds 1–4 exhibit the energy band gaps of 3.50, 3.16, 3.53 and 3.31 eV, respectively. Thus, the photocatalytic properties of 1–4 have been investigated. Approximately 84.9% for 1, 93.3% for 2, 82.0% for 3 and 85.4% for 4 of methylene blue were decomposed within 105 min.
Two series of twelve polycarboxylate lanthanide coordination polymers (CPs), namely, [Ln(cpida)(H2O)]n{Ln=La (1), Ce (2), Pr (3) and Nd (4)} and {[Ln(cpida)(H2O)]⋅2H2O}n {Ln=Sm (5), Eu (6), Gd (7), Tb (8), Dy (9), Ho (10), Er (11) and Yb (12)} {H3cpida=N-(4-carboxyphenyl) iminodiacetic acid}, have been synthesized by self-assembly and characterized by IR, TGA, X-ray crystallography, powder XRD and elemental analysis. CPs 1–4 and 5–12 are isomorphic respectively, featuring 2D double layer structures. In CPs 1-4, each metal atom connects five [cpida]3− anions and each ligand is bound to five metal cations. However, in 5-12 each [cpida]3− anion only connects four metal cations due to the lanthanide contraction. Further, PL spectra of CPs 6, 8 and 12 show the strong characteristic luminescence of Eu(III), Tb(III) and Yb(III) ions, respectively, suggesting that [cpida]3- is able to sensitize the luminescence of lanthanide ions efficiently. The magnetic properties of Gd (7) and Dy (9) complexes have also been investigated.
Two novel metal-organic frameworks (MOFs) based on transition metals, namely [Ni(sbdc)(4,4′-bbibp)(H2O)2]n (1) and [Co(sbdc)(4,4′-bbibp)]n (2) (H2sbdc = 4,4′-stilbenedicarboxylic, 4,4′-bbibp = 4,4′-bis(benzoimidazo-1-ly)biphenyl), have been designed and successfully synthesized under solvothermal conditions. Single-crystal X-ray diffraction analysis reveals that complex 1 features a 5-fold classical Ia interpenetrated dia framework with 4-connected (6⁶) sqc6 topology and complex 2 displays a 7-fold classical Ia interpenetrated dia network. Further, the photocatalytic properties of complexes 1–2 have been investigated. Significantly, the complexes 1–2 are good photo-catalysts for the degradation of organic dyes (MB/MV/RhB).
Four novel coordination polymers with distinct different structures, {[CdL(H2O)]·0.5H2O}n (1), {[ZnL(H2O)]·H2O}n (2), {[CoL(H2O)2]·2H2O}n (3), and {[NiL(H2O)2]·2H2O}n (4) (L = 5-(1-H-imidazole-1-yl) isophthlate) have been synthesized by the reaction of different transition metal cations with a rigid bi-functional ligand L. 1 possesses three-dimensional (3D) network framework, in which Cd(II) center is six coordinated by four L ligands and one aqua molecule. In compound 2, Zn(II) center adopts tetrahedral geometry and coordinated by three L ligands and one aqua molecule. 2 displays a [-AB-(H2O)n-AB-(H2O)n-] fashion 3D supramolecular network, in which A and B are two types of 2D covalent coordination layers. 3 and 4 are isostructural, metal center is six coordinated by three L ligands and two aqua molecules, and the 2D coordination layers construct the 3D supramolecular network with 1D rectangular channels via O-H···O hydrogen bonds. The structural variation depends on the nature of metal cations. Solid-state luminescent for compounds 1-2 and magnetic properties for compounds 3-4 have been investigated.
Four novel Ni(II)-metal-organic frameworks, namely [Ni(azp)(ppa)(H2O)(2)](n) (1), [Ni(tmdp)(ppa)(H2O)(2)](n) (2), {[Ni(bpetha)(ppa)]center dot 1.7H(2)O}(n) (3), and {[Ni(bpy)(H2O)(4)](ppa)}(n) (4) (azp = 4,4'-azodipyridine, H(2)ppa = 1,4-phenylenedipropionic acid, tmdp = 4,4'-trimethylenedipyridine, bpetha = 1,2-bis-(4-pyridyl)ethane, bpy = 4,4'-bipyridine) were synthesized and structurally characterized. With the differences in the length and flexibility of N,N'-donor coligands, Ni(II)-MOFs with the diversities of structural architectures and coordination modes of dicarboxylate ppa ligand were obtained. Compound 1 is 2D (4,4)-grid sheet whereas 2 shows 2-fold interpenetrating 2D (4,4)-layers. Compound 3 exhibits 3-fold interpenetrating coordination 3D framework with the alpha-Po topology while 4 shows 1D chain. Remarkably, compounds 1-4 exhibit energy band gaps of 3.27, 3.66, 3.58 and 3.36 eV, respectively. The photocatalytic activities of these materials for degradation of methylene blue (MB) were investigated with the degradation efficiencies within 90 min of 96.8%, 64.4%, 67.4%, and 75.0% for 1-4, respectively.
Three new Ni(II) coordination polymers exhibiting different 1D and 2D framework structures have been hydrothermally synthesized: [Ni(L 1)(1,3-BDC)(H 2O) 3] ⋅H2O (1), [Ni(L 1)(1,3,5-HBTC)(H 2O) 3] (2), [Ni 3(L 2)3(1,3,5-BTC) 2(H 2O) 8] ⋅12H 2O (3) [L 1= N,N ′-bis(pyridin-3-yl)cyclohexane-1,4-dicarboxamide, L 2= N,N ′-bis(3-pyridyl)octandiamide, 1,3-H 2BDC = 1,3-benzenedicarboxylic acid, 1,3,5-H 3BTC = 1,3,5-benzenetricarboxylic acid]. X-ray single crystal diffraction analyses revealed that polymer 1 is a 2D interlaced layer based on the 1D [Ni(L 1)(1,3-BDC)(H 2O) 3] meso-helical chains. Polymer 2 is a 1D wave-shaped chain derived from the 1D [Ni(L 1)] n chain and monodentate coordinated 1,3,5-HBTC anions. Polymer 3 possesses an interesting 2D layer containing the trinuclear [Ni 3(1,3,5-BTC) 2] substructural unit and 1D zigzag [Ni(L 2)] n chain, representing a 3,4-connected {6 ⋅8 2} 2 {62⋅82⋅10⋅12} topology. Finally, the adjacent 1D chains or the 2D layers are connected through hydrogen bonding interactions to construct 3D supramolecular networks. Further, the thermal stability, solid state fluorescent property and photocatalytic activity of 1–3 have been investigated. Graphical AbstractThree new Ni(II) coordination polymers have been hydrothermally synthesized by self-assembly of two bis-pyridyl-bis-amide ligands (L1, L2) and two aromatic polycarboxylates (1,3-H2BDC, 1,3,5-H3BTC). The thermal stability, fluorescent properties and the photocatalytic activities of polymers 1–3 have been studied.
Hydrothermal reactions of 2′-carboxybiphenyl-4-ylmethylphosphonic acid (H3L) with Cd(CH3COO)2·2H2O and 1,10-phenanthroline (phen) under different reaction temperatures afforded three new compounds, namely [Cd(phen)(HL)]·H2O (1), [Cd3(phen)4(L)2(H2O)]·9H2O (2) and [Cd4(phen)5(HL)(L)2]·2.5H2O (3). Compounds 1–3 have the same component but different structures. Compound 1 synthesized at 100 °C displays a one-dimensional chain structure containing mononuclear Cd. Compounds 2 and 3 formed at 160 °C exhibit one-dimensional chain structure containing trinuclear Cd unit and zero-dimensional structure containing hexanuclear Cd unit, respectively. The compounds have been characterized by elemental analyses, infrared spectra (IR), UV–vis spectra, single-crystal X-ray diffraction analyses and thermogravimetric analyses. The optical band gaps and photoluminescent properties of compounds 2 and 3 have been investigated.
Graphical Abstract
Three compounds have been synthesized with the same reactant ratio and solvent system by varying the reaction temperatures, where the effects of the reaction temperatures on the structures have been discussed. Moreover, the optical band gaps and photoluminescent properties have also been studied. Open image in new window
Two metal–organic frameworks (MOFs), [Ag2(H2L)(4,4′-bipy)(μ3-OH)]n (1) and [Zn3(L)2(bpe)2(H2O)2]n (2) were synthesized under hydrothermal conditions using the tricarboxylate and N-containing ligands (H3L = 3-(3-carboxyphenoxy) phthalic acid, 4,4′-bipy = 4,4′-bipyridine, bpe = 1,2-di(pyridine-4-yl)ethene), and structurally characterized by single-crystal X-ray diffraction analysis, FT-IR spectroscopy, powder X-ray diffraction (PXRD) and thermogravimetric analysis (TGA), furthermore, fluorescent spectra and absorption properties are discussed. Structural analysis reveals that Complex 1 is built from H3L, 4,4′-bipy and trinucleated Ag to form a three-dimensional (3D) network with a (4,4)-connected topology and a symbol of (6³.8³)4(8⁶). As for 2, a trinucleate secondary building units (SBU), linked by the H3L ligand generated a one-dimensional (1D) chain, then the two adjacent 1D chains are joined together by bpe ligand, yielding a 1D trapezoidal chain. Our successive application studies indicate that complex 1 shows rapid uptake for methyl orange (MO) and iodine (I2), compound 2 is an impressive Zn-MOF based sensor for detecting Fe³+ ions in aqueous solution.
To further explore the coordination possibilities of the flexible tripodal ligand, 4,4′,4′′-(benzene-1,3,5-triyl-tris(oxy))tribenzoic acid (H3BTTB), two solvent-controlled three-dimensional (3D) manganese(II) coordination polymers, [Mn3(BTTB)2(H2O)4](H2O)2 (1) and [Mn3(BTTB)2(DMF)2](DMF)2 (2), were synthesized and characterized. Single crystal X-ray diffraction analysis indicates that in the MnII complexes the BTTB ligands exhibit two coordination modes, which have not been reported previously. Complexes 1 and 2 involve different one-dimensional (1D) rod-shaped metal–carboxylate secondary building units (SBUs). The 1D SBUs are further extended to afford two different three-dimensional (3D) frameworks with similar flu topology via linkage of the BTTB ligands. The results demonstrate that the reaction solvent as well as conformation and coordination mode of BTTB ligands play key roles on the formation of the final framework structures. Additionally, their luminescent properties were investigated.
Two distinct copper coordination polymers, namely [Cu-2(II)(2,5-pydc)(2)(bpp)(2)]center dot H2O (1) and (Cu2CuII)-Cu-I(2,5-pydc)(2)(bpp)(2) (2) (2,5-pydc = pyridine-2,5-dicarboxylic acid, bpp = 1,3-bi(4-pyridyl)propane), have been successfully synthesized through hydrothermal conditions under different temperatures. Single-crystal X-ray structural analysis revealed that both complexes 1 and 2 are 3D frameworks. Complex 1 is an 8-connected 2-fold interpenetrating network based on [Cu(2,5-pydc)](4) molecular building block (MBB), and also can be simplified as a 4-connected net if the Cu(II) ion is regarded as an independent node, whereas 2 shows a (4,4)-connected non-interpenetrated framework which contains mixed valence Cu(I/II) centers. The results demonstrate that temperature plays a significant role in the final structures of the complexes.
Solvothermal reactions of 2,3,5,6-tetra(2-pyridyl)pyrazine (tppz) and sodium azide with different cadmium salts including CdCl2·2.5H2O, Cd(NO3)2 and Cd(CH3COO)2·2H2O at 80 °C produce three new coordination polymers, namely, {[Cd2(N3)2(tppz)Cl2]·2H2O}n (1), [Cd2(N3)2(tppz)(NO3)2]n (2) and {[Cd2(N3)2(tppz)(CH3COO)2]·2H2O}n (3), respectively. Single-crystal X-ray diffraction analysis reveals that the anions of the Cd(ii) salts all participate in coordination in compounds 1-3. Compound 1 features an infinite one-dimensional (1D) chain with loops-and-rods topology, compound 2 exhibits a 1D ladder-like chain, while compound 3 possesses a 2D honeycomb-like network structure with (6,3) topology. The low-dimensional structures of compounds 1-3 are further stabilized by diverse supramolecular interactions such as hydrogen bonds and π⋯π stacking. Interestingly, when the temperature is increased to 100 °C, similar reactions of tppz and sodium azide ligands with CdCl2·2.5H2O, Cd(NO3)2 and Cd(CH3COO)2·2H2O lead to three other novel 3D Cd(ii) coordination polymers formulated as [Cd3(N3)6(tppz)]n (4), {[Cd2(N3)2(tppz)(NO3)2]·MeOH}n (5) and [Cd4(N3)6(tppz)(CH3COO)2]n (6), respectively. The anions of the Cd(ii) salts again take part in coordination in compounds 5 and 6 but disappear in the final structure of 4. Compound 4 displays a rare sxd-type 3D framework with the Schläfli symbol of (3³·4⁶·5⁵·6) if each V-shaped trinuclear [Cd3(μ1,1-N3)4] secondary building unit (SBU) is regarded as a 6-connected node. In compound 5, both the Cd1 and Cd2 atoms serve as 3-connected nodes to construct an uncommon binodal (3,3)-connected 3D framework with (6·10²)(6²·10) topology. Compound 6 contains another type of V-shaped trinuclear [Cd3(μ1,1-N3)2(μ3-CH3COO)] SBU, which acts as a 7-connected node to fabricate a unique uninodal 7-connected 3D framework with a completely new topology of (3⁶·4²·5¹⁰·6³). The present results reveal that both anions and temperature play essential roles in the structural and topological diversity of such six new Cd(ii) coordination polymers. Moreover, the IR spectra, thermogravimetric analysis curves, and solid-state luminescence properties of all the compounds have been also investigated. Compared with the free tppz ligand, compounds 1-6 exhibit superior luminescence properties with largely enhanced emission, indicating that they may be good candidates for optical materials.
A 3-D metal − organic framework [Cd(BPHY)(SA)]n 1 (BPHY = 1.2-bis(4-pyridyl)hydrazine, H2SA = succinic acid) has been solvothermally synthesized. Compound 1 features a 2-fold pillar-layered structure and crystallizes in a non-centrosysmmetric space group (I2). It is testified to be second harmonic generation (SHG) active. The blue photoluminescence of 1 is attributed to BPHY-centered charge transition demonstrated by theoretical calculation.
A new linker, [1,1':2',1''-terphenyl]-4',5'-dimethoxy-4,4''-dicarboxylic acid (H2L) has been used along with 4,4'-azobispyridine (azpy) as the co-linker to solvothermally synthesize of six coordination polymers (CPs). These compounds are formulated as {[Zn(L)(azpy)0.5]•(0.5H2O)}n (1), {[Zn2(L)2(azpy)]•(DMF)•(1.5H2O)}n (2), {[Zn(L)(bphy)]•(DMF)}n (3), [Cd(L)(azpy)0.5(DMF)(H2O)]n (4), {[Co(L)(azpy)](2H2O)}n (5) and {[Co3(L)2(bphy)2(HCOO)2(H2O)2](6DMF)(6H2O)}n (6) (bphy = 1,2-bis(4-pyridyl)hydrazine). Interestingly, 1 and 2 synthesized at 90 and 120 oC respectively, are found to be orientation isomers. When the solvothermal reactions are carried out at 140 oC, the azo-bond in the co-linker azpy is reduced to bphy as found in 3 and 6. All the complexes exhibit sql topology. They are characterized by X-ray crystallography, elemental analysis, thermogravimetry, powder X-ray diffraction and infrared spectroscopy. Solid state photoluminescence studies show an intra-ligand π–π* transition in each case.
In order to systematically investigate the influence of factors on the structures of coordination complexes, {[Cu(imta)2]•2.5H2O}n (1), [M(imta)2]n M=(Co, Mn, Cd) (2~4); [Pb(imta)2]n (5); [M(imta)2(H2O)4]•2H2O] M=(Co, Mn, Ni, Zn) (6~9) {H-imta=2-[4-(1H-imidazole-1-ylmethyl)-1H-1,2,3-triazol-1-yl] acetic acid}, have been prepared and characterized by single-crystal X-ray diffraction analyses. 1 is a 2-D MOF with one-dimensional open channels, 2, 3 and 4 are isostructural and display (3,6)-connected 3D frameworks which can be simplified into novel Schläfli symbols of (4•62)2(42•610•83). 5 features a (3,6)-connected topology with the Schläfli symbol (42•6)2(44•62•89). 6~9 are isostructural and mononuclear, which are further stretched to a 3D supramolecular structure through hydrogen bonding. Based on complexes 2 (or 3) and 6 (or 7), a systematic and comprehensive investigation of temperature, solvent, M/L ratios and anion on complex architectures were carried out. The present results may help unravel the mechanism for the roles that synthesis parameters play in the formation of complex structures, and provide insight into the discovery of new interesting compounds. In addition, the photoluminescent properties of 2~9 were also studied.
Utilizing a series of positional isomers of tetrachlorinated benzenedicarboxylic acid ligands, seven La(III)-based coordination polymers were solvothermally synthesized and structurally characterized. Their structural dimensionalities varying from 1D double chains, to 2D 3,4,5-connected network, to 3D 6-connected pcu topological nets are only governed by the positions of carboxyl groups on the tetrachlorinated benzene ring. A comprehensive analysis and comparison reveals that the size of the carbonyl solvent molecules (DMF, DEF, DMA, and NMP) can affect the coordination geometries around the La(III) ions, the coordination modes of carboxylate groups, the packing arrangements, and the void volumes of overall crystal lattices. One as-synthesized framework further shows an unprecedented structural transformation from 3D 6-connected network to 3D 4,5-connected net through the dissolution and reformation pathway in water, suggesting that these easily hydrolyzed lanthanide complexes may server as precursors to produce new high-dimensional frameworks. The bulk solvent-free melt polymerisation of glycolide utilizing these La(III) complexes as initiators has been reported herein for the first time. All complexes were found to promot the polymerization of glycolide over a temperature range of 200 to 220 °C, producing poly(glycolic acid) (PGA) with molecular weight up to 93280. Under the same experimental conditions, the different catalytic activities for these complexes may result from their structural discrepancy.
Five new Cd(II) coordination polymers with N-benzoyl-L-glutamic acid (H2bzgluO) and different N-donor ligands, [Cd(bzgluO)(2,2′-bipy)(H2O)]n (1), [Cd(bzgluO)(2,4′-bipy)2(H2O)·3H2O]n (2), [Cd(bzgluO)(phen)·H2O]n (3), [Cd(bzgluO)(4,4′-bipy)(H2O)]n (4), [Cd(bzgluO)(bpp)(H2O)·2H2O]n (5) were synthesized (2,2′-bipy=2,2′-bipyridine, 2,4′-bipy=2,4′-bipyridine, phen=1,10-phenanthroline, 4,4′-bipy=4,4′-bipyridine, bpp=1,3-di(4-pyridyl)propane). Compounds 1-2 exhibit a 1D single-chain structure. Compound 1 generates a 2D supramolecular structure via π-π stacking and hydrogen bonding, 3D architecture of compound 2 is formed by hydrogen bonding. Compound 3 features a 1D double-chain structure, which are linked by π-π interactions into a 2D supramolecular layer. Compounds 4-5 display a 2D network structure. Neighboring layers of 4 are extended into a 3D supramolecular architecture through hydrogen bonding. The structural diversity of these compounds is attributed to the effect of ancillary N-donor ligands and coordination modes of H2bzgluO. Luminescent properties of 1-5 were studied at room temperature. Circular dichroism of compounds 1, 2 and 5 were investigated.
A novel homochiral manganese (III) Mn(5-Brsalen) coordination polymer with left-handed helical character by spontaneous resolution on crystallization by using Mn(5-Brsalen) and 4,4-bipyridine, [MnIII(5-Brsalen)(4,4-bipy)]·ClO4·CH3OH (1) (4,4-bipy = 4,4-bipyridine) has been synthesized and structurally characterized by X-ray single-crystal diffraction, elemental analysis and infrared spectroscopy. In compound 1, each manganese(III) anion is six-coordinate octahedral being bonded to four atoms of 5-Brsalen ligand in an equatorial plane and two nitrogen atoms from a 4,4-bipyridine ligand in axial positions. The structure of compound 1 can be described a supramolecular 2D-like structure which was formed by the intermolecular π-stacking interactions between the neighboring chains of the aromatic rings of 4,4-bipyridine and 5-Brsalen molecules. UV-vis absorption spectrum, electrochemistry and magnetic properties of the compound 1 have also been studied.
The coordination polymers {[Cd(o-BDC-Cl4)(H2O)2]·EtOH}n (1) and {[Cd(p-BDC-Cl4)(DMF)]·H2O}n (2) (o-BDC-Cl4 = tetrachlorophthalate and p-BDC-Cl4 = tetrachloroterephthalate) were synthesized in different solvents using two isomeric tetrachlorinated benzenedicarboxylic acids. Complex 1 based on o-BDC-Cl4 features an extremely rare 2D trinodal (3,4,6)-connected network constructed by the combination of 1D [Cd-H2O]n chains and 1D [Cd2(o-BDC-Cl4)2]n loop-like motifs. Complex 2 based on p-BDC-Cl4 has a 3D framework and shows a uninodal 4-connected sra topology. Complexes 1 and 2 were characterized by elemental analyses, IR spectroscopy, single-crystal X-ray diffraction and thermogravimetric (TG) analyses. The photoluminescence of 1 and 2 were investigated in the solid state at room temperature.
A 2D wave-like layered framework based on benzotriazole-5-carboxylic acid(H2btca), 2,2’-bipy and zinc ions: [Zn(btca)(2,2’-bipy)]n (1) has been resoundingly designed and synthesized by solvothermal method. By changing DMF solvent to DMA, a 3D porous framework: [Zn2(btca)2(bpy)(H2O)]n•n(DMA) (2) was obtained. Complex 1 and 2 have been determined by single-crystal X-ray diffraction analysis and further characterized by powder X-ray diffraction (PXRD), elemental analysis, IR spectra, and thermogravimetric (TG) analysis. Complex 1 shows AA packing 2D layer structure and complex 2 displays 3D open honeycomb framework with a (3,4)-connected 2-nodal fsc topology. Moreover, gas adsorption of 2a(the actived form of 2) and luminescence properties of 1, 2 and 2a have also been investigated intensively.
Self-assembled bi- and polymetallic complexes of Co(II), Ni(II), Zn(II) and Cd(II) have been obtained in reaction of 4,4'-azopyridine (azpy) with respective metal tri-tert-butoxysilanethiolates (Co 1, Cd 2), acetylacetonates (Ni 3, Zn 4) and acetates (Cd 5). All compounds have been characterized by single-crystal X-ray structure determination, elemental analysis, FT-IR and thermogravimetry. Complexes 1, 2 and 4, 5 exhibit diverse structural conformations: 1 is bimetallic, 2 and 4 1D coordination polymer and 2D coordination framework constructed by bimetallic units of 5. Obtained complexes contain metal atoms bridged by molecule of azpy. Luminescent properties of 1-5 have been investigated in solid state.
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Three manganese(II) coordination polymers, namely [Mn(L)0.5(bipy)0.5(H2O)]n (1), [Mn2(L)(1,4-bimb)(H2O)2]n (2) and [Mn(L)0.5(4,4′-bibp)0.5(H2O)2]n (3), where H4L = 5,5′-([1,1′-biphenyl]-4,4′-diylbis(oxy))diisophthalic acid, bipy = 4,4′-bipyridine, 1,4-bimb = 1,4-bis(imidazol-1-ylmethyl) benzene and 4,4′-bibp = 4,4′-di(1H-imidazol-1-yl)-1,1′-biphenyl, have been successfully constructed using the hydrothermal method. To understand these compounds completely, single crystal X-ray diffraction, IR, powder X-ray diffraction (PXRD) and thermogravimetric studies have been carried out. Complexes 1 and 2 possess three-dimensional (3D) pillared-layer frameworks, and 2-fold and 3-fold interpenetration take place in 1 and 2, respectively. In complex 3, 2D layers are linked by hydrogen bonds, resulting in a 3D supramolecular architecture. Meanwhile, the magnetic behaviors of complexes 1 and 2 have been investigated and weak antiferromagnetic interactions between two Mn(II) centres within the polymers have been revealed.
Six Co(II) and Mn(II) coordination polymers, [Co(BIMB)(AIP)]n (1), [Co(BIMB)0.5(H2O)(AIP)]n (2), [Co(BMIB)0.5(AIP)]n∙(H2O)n (3), [Mn2(BIMB)2(AIP)2]n (4), [Mn(BMIB)(H2O)2(AIP)]n(DMF)n (5) and [Mn(BIMB)0.5(PAIP)]n•(H2O)n (6) (AIP = 5-aminoisophthalate, PAIP = 5-(2-pyridylmethyl)aminoisophthalate, BIMB = 1,4-bis(imidazol-1-yl-methyl)benzene and BMIB = 1,4-bis(2-methylimidazol-1-yl-methyl)benzene), were synthesized and well characterized. AIP in 1-5 originates from in situ deprotection of 5-(4-oxopentan-2-ylideneamino)isophthalic acid in synthetic process. Complex 1 is a 2D3D interdigitating network, hydrogen bonds between uncoordinated amino and carboxylate oxygen atoms of the adjacent layers further stabilize the 3-D framework. Different from AIP in 1, amino of AIP in 2 and 3 participates in coordination, 3-bridged AIP connects Co(II) into 1-D double chain and 2-D layer, respectively, subsequent bridge by BIMB and BMIB results in the formation of 2-D layer and 2-D pillared-bilayer network, respectively. Notably, the coordinated water in complex 2 may be reversibly removed with the concomitant color change and the maintenance of original structural framework. Amino of AIP in 4 and 5 is not involved in coordination, AIP and anti-conformationed BIMB in 4 link Mn(II) into a 2-D layer consisting of dinuclear Mn(II)-carboxylate units, while AIP and gauche-conformationed BMIB in 5 links Mn(II) ions into a 1-D chain. Complex 6 is a 3-D pillared-layer structure. It should be mentioned that the extensive hydrogen bonds are formed in complexes 1-6. Magnetic study of complex 4 shows that there is a dominant antiferromagnetic coupling above 40 K, while a weak ferromagnetic order is caused by spin-canting at lower temperature.
Two polycatenated coordination polymers, {[Zn-3(adc)(3)(bPP)(4)](2)center dot 3H(2)O}(n) (1) and {Zn(adc)(bphy)](n) (2) (adc = azobenzene-4,4'- dicarboxylate, bpp = 1,3-bis(4-pyridyl)propane, bphy = 12-bis(4-pyridyl)hydrazine), have been obtained from Zn(NO3)(2)center dot 6H(2)O, linear H(2)adc ligand and arched bpp/azpy (azpy = 4,4'-azobispyridine) ligands by hydro(solvo)thermal reactions. Compound 1 presents a 2-D structure catenated from 1-D double ladders (1-D -> 2-D polycatenation), while compound 2 displays a 3-D structure catenated from 2-D (4,4) stair-stepping layers (2-D 3-D polycatenation). Luminescence properties of 1 and 2 have been explored, together with study of photoluminescent mechanism by density of states (DOS) calculation.
Two new complexes, [Eu2(NIPH)2(H2O)14](HNIPH)2(H2O)7 (1) [Co2(abtc)(phen)4(H2O)]·12(H2O) (2) (H2NIPH = 5-nitroisophthalic acid, H4abtc = 3,3′,5,5′-azobenzenetetracarboxylic acid, phen = 1,10-phenanthroline, DMF = N,N′-dimethylformamide) have been synthesized and characterized by infrared spectrum, thermal gravimetric analysis, X-ray single crystal diffraction and photoluminescence properties. Complex 1 upon slow evaporation at room temperature gave a 0-D structure, and seven independent water molecules and their equivalent held together by hydrogen bonds with an ordered proton arrangement form a 1-D hydrogen-bonded water tape. An unusual water tape notated T10(0)A0 is observed in 2. A 1-D water tape by connecting five-ten-five membered water rings through hydrogen bonds. Multiple hydrogen bonds and π-π stacking interactions play important roles in the formation of the 3-D networks. Fascinatingly, these lattice water molecules display unprecedented water cluster and play important roles in the stabilizing the whole network.
Presented here are two d10 metal–organic coordination polymers (CPs), [Zn(C4O4)0.5(μ
3-OH)]n
(1) and [Cd(C4O4)0.5(OX)0.5(H2O)]n
(2) (H2OX = oxalic acid) constructed from squaric acid (H2C4O4) tectons. Single-crystal X-ray diffraction studies indicated that both 1 and 2 show 3D structures. The two 3D CPs are assembled from 1D {[Zn(μ
3-OH)]
n
+} chains to 3D structure linked through C4O42− ligands for 1 and 2D {[(Cd1)2(C4O4)]2+} layers pillared by OX2− ligands for 2. The structure of compound 1 can be described as a trinodal (3,6,6)-connected net with the point symbol of {43}2{44·610·8}{45·610}2, whereas 2 possess a trinodal (4,5,6)-connected {42·84} {46·66·83} {48·62}2 topology. Furthermore, the fluorescent and thermal stabilities properties of these two compounds were investigated.
Four metal-organic coordination polymers [Cd(4-bpcb)1.5Cl2(H2O)] (1), [Cd(4-bpcb)0.5(mip)(H2O)2]·3H2O (2), [Co(4-bpcb)(oba)(H2O)2] (3), and [Ni(4-bpcb)(oba)(H2O)2] (4) [4-bpcb = N,N′-bis(4-pyridinecarboxamide)-1, 4-benzene, H2mip = 5-methylisophthalic acid, and H2oba = 4, 4′-oxybis(benzoic acid)] were synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction, elemental analyses, IR spectroscopy, powder X-ray diffraction, and TG analysis. In complex 1, two Cl– anions serve as bridges to connect two Cd-(μ1-4-bpcb) subunits forming a dinuclear unit, which are further linked by μ2-bridging 4-bpcb to generate 1D zigzag chain. Complex 2 shows a 2D 63 network constructed by [Cd-mip]n zigzag chains and μ2-bridging 4-bpcb ligands. Complexes 3 and 4 are isostructural 2D (4, 4) grid networks derived from [M-oba]n (M = Co, Ni) zigzag chains and [M-(4-bpcb)]n linear chains. The 1D chains for 1 and the 2D networks for 2–4 are finally extended into 3D supramolecular architectures by hydrogen bonding interactions. The roles of dicarboxylates and central metal ions on the assembly and structures of the target compounds were discussed. Moreover, the thermal stabilities, photoluminescent properties, and photocatalytic activities of complexes 1–4 and the electrochemical properties of complexes 3 and 4 were investigated.
Hot-solution reactions of Zn(NO3)2·6H2O, pyridine (py) with isophthalic acid (H2ip) in N-methyl-pyrrolidone (NMP) yields one-dimensional (1D) coordination polymer. Single crystal analysis show that compound 1, {[Zn(ip)(py)2]·NMP}n with 1D zigzag chains and every two chains face to face to form the slide fastener. Crystal data of 1 are, orthorhombic, space group P, a = 8.5960(3), b = 10.1091(4), c = 26.2070(10), Z = 4. The results indicate that the geometry of ligands play the important roles in the frameworks of products.
Eight highly connected metal-organic frameworks (MOFs) based on flexible tricarboxylate ligands, namely, Na[Zn5(L)2(μ3-OH)5] (1), (HTEA)[Zn3(L)2(μ3-OH)]·0.25H2O (2), [Zn3(L)2(BIME)(H2O)2] (3), [Cd3(L)2(BIME)(H2O)2] (4), [Pb7(L)4(μ3-OH)2(H2O)2]·8H2O (5), [Zn4(L)2(BET)(μ4-O)] (6), [Zn2(HL)2(PBIB)]·2H2O (7), and [Zn3(L)2(PBIB)2]·4H2O (8) (H3L = (3,5-dicarboxylphenyl)-(4-(2′-carboxylphenyl)benzyl) ether, TEA = triethylamine, BIME = 1,2-bis(imidazol-1-yl)ethane, BET = 1,2-bis(1,2,4-triazole-1-yl)ethane, and PBIB = 1,4-bis(imidazol-1-ylmethyl)benzene) have been synthesized under hydrothermal conditions. Compound 1 exhibits a three-dimensional (3D) (3,12)-connected framework based on decanuclear [Zn10(μ3-OH)10(COO)12] units. Compound 2 displays a 3D (3,6)-connected framework based on trinuclear [Zn3(μ3-OH)(CO2)6] units. Compounds 3 and 4 display unusual 2-fold interpenetrated 3D (3,6)-connected frameworks with the same (42·6)2(44·62·88·10) topology. Compound 5 features a 3D tetranodal (3,3,4,8)-connected framework based on pentanuclear [Pb5(COO)8(μ3-OH)2(H2O)2] units. Compound 6 exhibits an unprecedented 2D (3,8)-connected network with (3·42)(46·57·68·73·8) topology based on tetranuclear [Zn4(μ4-O)(COO)6] units. Compound 7 reveals a wavy 2D sheet with (44·62) topology. Further, each sheet is interdigitated by two others in a parallel fashion to yield an unusual 2D → 3D interdigitated framework. Compound 8 displays a 3D rare trinodal (3,4,6)-connected framework with (3·4·5)2(32·103·11)(32·42·52·103·114·12·13) topology. These compounds have been characterized by IR spectra, UV-vis spectra, TGA, and powder XRD patterns. The optical band gaps and photoluminescent behaviors of 1-8 have been investigated in detail. In addition, surface photovoltage spectroscopies of compounds 1-4 indicate that these compounds possess positive surface photovoltage (SPV) responses in the range of 300-600 nm.
Under ambient conditions, reactions of CdCl2/Cd(CH3COO)2, SCN(-) and various organic amine molecules in strongly acidic solutions afforded the five new thiocyanatocadmates [H2(abpy)][CdCl2(SCN)2] (abpy = azobispyridine) , [H(apy)][Cd(SCN)3] (apy = 4-aminopyridine) , [H(ba)]2[CdCl2(SCN)2] (ba = tert-butylamine) , [H2(tmen)][Cd3Cl6(SCN)2] (tmen = N,N,N',N'-tetramethylethylenediamine) , and [H(dba)]2[Cd2(CH3COO)2(SCN)4] (dba = dibutylamine) . In compound only, the CH3COO(-) ions in Cd(CH3COO)2 were completely displaced by SCN(-), producing a chained thiocyanatocadmate [Cd(SCN)3](-). In the other four compounds, the Cl(-) or CH3COO(-) ions appeared in the final inorganic anion frameworks. In compound , the Cl(-) ions doubly bridge the Cd(2+) centers, forming a one-dimensional (1-D) infinite chain, and the SCN(-) group exists in a terminal form, whereas in compound , the reverse situation is observed. Due to a trans-mode arrangement for two terminal Cl(-) or SCN(-) ions around each Cd(2+) center, the inorganic anion chains in compounds and both show a linear shape. In compound , Cd(2+) and Cl(-) first aggregate to form a 1-D endless chain with a composition of Cd3Cl6, which can be described as a linear arrangement of the open double cubanes. SCN(-) serves as the second connector, propagating the Cd3Cl6 chain into a three-dimensional (3-D) network with the occluded H2(tmen)(2+) cations. In compound , the SCN(-) groups doubly bridge the Cd(2+) centers, forming a 1-D zigzag-shape chain. The formation of the zigzag chain likely derives from chelation of the CH3COO(-) group to the Cd(2+) center. The thermal behavior and the photoluminescence properties of the title compounds were also investigated.
Reactions of metal ions with a rigid linear ligand 4-H(2)IBA incorporating 4-imidazolyl and carboxylate functional groups [4-H(2)IBA = 4-(1H-imidazol-4-yl)benzoic acid] under variable reaction conditions gave 11 new coordination polymers, [Cu(4-HIBA)(2)(H2O)(4)] (1), [(CuCuI)-Cu-II(4-HIBA)-(4-IBA)(H2O)(2)]center dot 2.3H(2)O (2), [Cu(4-HIBA)(Cl)] (3), [Cu-3(4-HIBA)(6)]center dot 7.8H(2)O (4), [Cd(4-HIBA)(2)(H2O)]center dot 2H(2)O (5), [Cd(4-HIBA)(2)] (6), [Cd(4-HIBA)(2)] center dot 2DMF (7), [Cd-2(4-HIBA)(4)]center dot H2O (8), [Zn(4-HIBA)(2)].H2O (9), [Zn(4-HIBA)(2)]center dot C2H5OH center dot DMF (10), and [Co(4-HIBA)(2)]center dot 2DMF (11). The copper complexes 1-4 are discrete molecules to three-dimensional (3D) infinite networks. Complexes 1 and 2 formed in different reaction temperatures exhibit a mononuclear motif and one-dimensional (1D) chain, respectively. Compounds 3 and 4 were obtained through controlling reaction solvent systems, and 3 features a two-dimensional (2D) (4,4) network by taking the binuclear [Cu-2(Cl)(2)] as 4-connecting nodes, whereas 4 is a 3-fold interpenetrating mog net with Point (Schlafli) symbol of (4.6(4).8)(2)(4(2).6(2).8(2)). The 4-HIBA(-) ligands act as rod-type two-connectors to connect metal Cd(II) centers into 4-connected 3D frameworks with different topologies: binodal 4-connected network with a Point (Schlafli) symbol of (8(6)) (5) and uninodal (6(5).8) net (6), uninodal 4-connected [2 + 2] interpenetrating (6(6)) dia net (7), and 5-fold interpenetrating dia net (8), respectively. Complex 9 has a 1D double chain structure, while 10 and 11 are isostructural as 7. Fluorescence and gas adsorption properties of the compounds have also been explored.
Solvothermal reactions of a tricarboxylate ligand 5-(4-carboxybenzoylamino)-isophthalic acid (H3L), dipyridyl linkers (bpe, bpa and bpy) and divalent metal ions (Co2+, Cd2+, Zn2+ and Ni2+) provided a highly efficient approach to the syntheses of multi-dimensional framework materials containing interesting structural motifs: [Co3L2(bpe)4]·2DMF·2H2O (1), [Cd3L2(bpe)4]·3H2O (2), [Zn2L(OH)(bpe)]·5.5H2O (3), [Co7L4(bpa)2(OH)2(H2O)4]·4H2O (4), Ni(HL)(bpa)(H2O) (5) and [Zn2(HL)2(bpy)2(H2O)2]·(bpy)·6H2O (6) (bpe = 1,2-bis(4-pyridyl)ethene, bpa = 1,2-bis(4-pyridyl)diazene, bpy = 4,4′-bipyridine). Solids 1 and 2 are isostructural and each features a three-dimensional (3D) pillar-layer architecture generated from bpe-pillared M-L3− layers. Complex 3 has a 3D structure in which the secondary building unit (SBU) is a rare example of a tetranuclear Zn4(μ3-OH)2(COO)6(bpe)4 unit, whereas 4 exhibits an interesting sandwich-shaped architecture with a trimeric unit [Co3(COO)4(OH)(N2)] serving as the SBU. Complex 5 provides an unusual example of a (4,4) grid layer structure bearing free carboxylic acid (-COOH) units. The layered structure of 6 is generated from hydrogen bonded [Zn(HL)(bpy)(H2O)] chains, with free bpy and guest water molecules accommodated inside. Furthermore, the thermal behavior, powder X-ray diffraction (PXRD) and solid state photoluminescence properties correlated with the corresponding structural features were investigated.
Two distinct La(III)-naphthalenedicarboxylate frameworks, namely La-2(NDC)(3)(e-urea)(3) (1; H2NDC = 2,6-naphthalenedicarboxylic acid; e-urea = ethyleneurea) and La(NDC)(1.5)(e-urea) (2), have been successfully synthesized through urothermal synthesis under different temperatures. Single-crystal X-ray structural analysis revealed that both compounds 1 and 2 feature three-dimensional (3D) structures with open channels occupied by the coordinated e-urea molecules. Interestingly, e-urea molecules and NDC ligands adopt distinct coordination modes in two structures. Furthermore, thermal analyses of 1 and 2 were also investigated. (c) 2013 Elsevier B.V. All rights reserved.
This work presents seven Co-II, Cd-II, Zn-II, Mn-II, and Ni-II supramolecular complexes synthesised by hydrothermal reactions from a bent dipyridyl ligand 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (4-bpo) and 2-phenylmalonic acid (2-phmalH(2)). Interestingly, the in situ generation of 2-phenylacetic acid (Hpa) by decarboxylation of the 2-phenylmalonic acid precursor is observed in all the complexes. Single-crystal X-ray diffraction reveals that these complexes display a variety of 1D (for 2-7) and monomeric (for 1) coordination motifs, which are further extended into polymeric supramolecular architectures by multiple secondary interactions, such as hydrogen bonding and aromatic stacking. The results evidently demonstrate that the structures of 1-7 are significantly affected by the metal centres and the counter anions of inorganic salts. The photoluminescence properties of complexes 1-7 have also been investigated and discussed.
Self-assembly of Cd(II) ions with five positional isomeric flexible bipyridyl benzene and 2,2'-azodibenzoic acid ligands yield five interesting coordination polymers, [Cd2L2(3-pbpmb)3]n (1), [Cd2L2(2-pbpmb)]n (2), {[CdL(4-mbpmb)2]∙MeOH}n (3), {[Cd2L2(3-mbpmb)3]∙2.5H2O}n (4) and [Cd2Cl2L(3-obpmb)2]n (5) where H2L = 2,2'-azodibenzoic acid, 3-pbpmb = 1,4-bis(pyridine-3-ylmethoxy)benzene, 2-pbpmb = 1,4-bis(pyridine-2-ylmethoxy)benzene, 4-mbpmb = 1,3-bis(pyridine-4-ylmethoxy)benzene, 3-mbpmb = 1,3-bis(pyridine-3-ylmethoxy)benzene and 3-obpmb = 1,2-bis(pyridine-3-ylmethoxy)benzene. Their structures have been determined by single-crystal X-ray diffraction analyses, elemental analyses, IR spectra, powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA). Compound 1 is a 3D architecture constructed by 1D ladder-like [Cd4(3-pbpmb)4]n chains as well as L linkers, and displays an interesting 5-connected net with a 4664 topology. Compound 2 comprises a 3D framework built from 2D wrinkled [Cd2L4]n networks and 2-pbpmb bridges with a 6-connected pcu net. Compound 3 bears a 2D network based on [Cd2(4-mbpmb)2] building units and 1D [CdL]n chains. Compound 4 features a 2D network in which the helical [Cd(3-mbpmb)]n chains are alternately arranged in a right- and left-handed sequence. Compound 5 exhibits a 2D network constructed by the 1D [Cd2Cl2(3-obpmb)2]n chains and L linkers. The results reveal that the diverse coordination networks of 1–5 can be adjusted by the positional isomeric effect of flexible bipyridyl benzene building blocks. Moreover, the luminescent properties of compounds 1–5 in the solid state have also been investigated
A series of coordination polymers constructed from tripodal N-donor ligands and polycarboxylate anions, namely, [Ag6(3,4 '-tmbpt)(btc)2]center dot 2H(2)O (1), [Ag-2(3,4 '-tmbpt)(H(2)btec).H2O-120 (2), [Ag-2(4,4 '-tmbpt)(Hbtc).H2O (3), [Cd-3(4,4 '-tmbpt)(btc)(2)(H2O)6]center dot 7H(2)O (4), [Co(4,4'-tmbpt)(btec)0.5(F120)1 (5) and [Ni(4,41-tmbpt)(btec)0.5 (H2O)] (6), where 3,4 '-tmbpt = 1-((1H-1,2,4-triazol-1-yl)methyl)-3-(4-pyridy1)-5-(3-pyridy1)-1,2,4-triazole, 4,4 '-tmbpt = 1 -((1H-1,2,4-triazol-1-y1)methyl)-3,5-bis(4-pyridy1)-1,2,4-triazole, H(3)btc = 1,3,5-benzenetricarboxylic acid, and RIbtec = 1,2,4,5-benzenetetracarboxylic acid, have been hydrothermally prepared. Single crystal X-ray diffraction analyses indicate that compound 1 exhibits a 3D (3,4,6)-connected framework with (4.6(2))(2)(6.8(5))(2)(4.6(2),8(3).12) topology. Compound 2 has a 3D (3,4)-connected framework with (6(3))2(4(2).6(4))(4(2).6(3).8) topology. Compound 3 exhibits a 2D layer structure. Compound 4 shows a 3D 2-fold interpenetrating framework with (6.10(2)) topology. Compounds 5 and 6 exhibit similar 2D -> 3D polythreading architectures. These compounds have been characterized by infrared spectra (IR), elemental analyses and powder X-ray diffraction (PXRD) analyses. The effects of the organic anions on the structures of the compounds have been discussed. Moreover, the photoluminescent properties of the compounds have been investigated.
Hydrothermal reactions of Zn(NO3)2·6H2O with 1,3-benzenedicarboxylic acid (1,3-H2BDC) and 1,4-bis[2-(4-pyridyl)ethenyl]benzene (1,4-bpeb) under pH = 2.5 or 8.0 gave rise to two coordination polymers {[Zn6(μ-OH2)(1,3-BDC)6(1,4-bpeb)4]·MeCN}n (1) and {[Zn8(1,3-BDC)8(1,4-bpeb)4]·2H2O}n (2). Both compounds were characterized by elemental analysis, IR, powder X-ray diffraction, and single-crystal X-ray diffraction. Compound 1 has two types of dinuclear zinc cores as nodes and displays an intriguing three-dimensional (3D) three-fold interpenetrating (4,6)-connected network with an unprecedented (3264)(3244687)2 topology. Compound 2 exhibits an unusual 3D two-fold interpenetrating pcu net with a Schlafli symbol 41263. The formation of 1 and 2 provided an interesting insight into the effect of pH values on the construction of coordination polymers under solvothermal conditions. Thermal stability and photoluminescence properties of 1 and 2 were also investigated.
Three In(III) MOFs based on diphenic acid and nitrogen-donor ancillary ligands were obtained as pure phases. Two of them have 1D chain structures, and the third forms 2D zig-zag layers. The different torsion angles adopted by the diphenic ligand along with the existence of several non-covalent interactions govern the crystal packing and determine the formation of a centrosymmetric one-dimensional compound (1) or a non-centrosymmetric helical chain-based compound (3). Reaction with 2,2 0 -bipyridyl under certain conditions leads also to the formation of two dimeric precursors (compounds 4 and 5). The topological study of all their nets is reported.
The literature on open-framework materials has shown numerous examples of porous solids with additional structural, chemical, or physical properties. These materials show promise for applications ranging from sensing, catalysis and separation to multifunctional materials. This critical review provides an up-to-date survey to this new generation of multifunctional open-framework solids. For this, a detailed revision of the different examples so far reported will be presented, classified into five different sections: magnetic, chiral, conducting, optical, and labile open-frameworks for sensing applications. (413 references.)
Four novel cobalt(II) coordination polymers [Co2(OA)(dib)2(H2O)] (1), [Co2(OA)(bbi)2]·3H2O (2), [Co3(HOA)2(bpe)2(H2O)6]·2H2O (3), and [Co2(OA)(dpe)(H2O)2] (4) were obtained by hydrothermal reactions of Co(NO3)2·6H2O with 3,3′,4,4′-oxidiphthalic acid (H4OA) and corresponding N-donor ligands, namely, 1,4-di(1-imidazolyl)benzene (dib), 1,1′-(1,4-butanediyl)bis(imidazole) (bbi), 1,2-bis(4-pyridyl)ethane (bpe), and 1,2-di(4-pyridyl)ethylene (dpe), respectively. Single crystal X-ray diffraction analysis revealed that 1 is a two-dimensional (2D) network containing infinite -(Co–O–C–O)n- chains, while 2 features a 2D double-layered structure with two types of homochiral helical chains filled in the cavities. Complex 3 is a three-dimensional (3D) framework with (64.82)(66) topology containing infinite 2D networks pillared by bpe bridging ligands. 4 is a (44.66) topological 3D framework with coordinated dpe molecules occupied in the channels. The results revealed that the flexible multi-carboxylate and N-donor auxiliary ligands are effective building blocks in constructing coordination polymers with diverse architectures. In addition, the magnetic properties of 1, 3, and 4 were investigated, and the results showed that weak ferromagnetic interactions occurred between Co(II) ions in 1 and 3, while 4 displays a weak antiferromagnetic behavior.
A series of Mn(II), Cd(II), and Co(II) metal–organic frameworks, namely, {[Mn(L1)(NCS)2(CH3OH)2]·2(CH3OH)}n (1), {[Mn(L2)2(NCS)2(CH3OH)2]}n (2), {[Mn(L3)2(NCS)2]·0.5(CH3OH)·4.5H2O}n (3), {[Cd(L1)(I)2]·3(H2O)}n (4), {[Cd(L2)(I)2]}n (5), {[Cd(L3)(NCS)2]·2.5(H2O)}n (6), {[Co(L1)2(NCS)2]·4(H2O)}n (7), {[Co(L2)2(NCS)2]·(HCCl3) }n (8), and {[Co(L3)2(NCS)2]·3(H2O)}n (9) (where L1 = N,N′-bis(4-pyridylmethyl)-pyromellitic diimide, L2 = N,N′-bis(3-pyridylmethyl)-pyromellitic diimide, L3 = N,N′-bis(4-pyridylmethyl)-naphthalene diimide), were synthesized and structurally characterized by elemental analyses, thermogravimetric (TG) analyses, powder X-ray diffraction, IR spectroscopy, and single-crystal X-ray diffraction. In Mn(II) complexes 1–3, L1 connects the adjacent metal centers to form an infinite one-dimensional (1D) zigzag coordination polymeric chain, L2 acts as a monodentate ligand to give mononuclear coordination motifs, while L3 bridges two metal ions to generate two-dimensional (2D) networks of the (4, 4) net topology containing rhombic grids. In Cd(II) complexes 4–6, L1, L2, and L3 act as bidentate ligands and coordinate with two metal ions to form three different coordination polymers that display diversified structures, that is, infinite 1D zigzag chain in 4, single-stranded double helical chain in 5, and 2D networks of the (4, 4) net in 6. For three Co(II) complexes, 7 is a three-dimensional (3D) framework with 3-fold interpenetrating dia topology, while 8 and 9 have similar two-dimensional (2D) networks of the (4, 4) net topology. The results show that the conformation and coordination mode of organic ligands and the coordination geometry of metal centers play important roles in determining the structure and topology of the complexes. Furthermore, the gas sorption properties were measured, and complex 7 shows a highly selective sorption behavior toward CO2, which can be a promising candidate as adsorbents for CO2/N2 separation. In addition, the luminescence properties of 5–6 were studied in the solid state at room temperature.
Etude de complexes du ruthenium avec des coordinats heterocycliques azotes. Reactivite electrochimique: differents etats d'oxydation du metal et oxydation electrochimique du coordinat. Presentation des resultats d'etude par les techniques electrochimiques et spectrometriques
Three three-dimensional coordination polymers, namely, [NH2(CH3)2][Co2(MDIP)(OH)(H2O)]·C3H7NO·H2O (1), [NH2(CH3)2]2[Mn3(MDIP)2]·2C3H7NO (2), and [NH2(CH3)2][Mg3(MDIP)(HMDIP)(C3H7NO)]·4H2O (3) (DMF = N,N′-dimethylformamide), have been synthesized by the solvothermal reaction of Co(II), Mn(II), or Mg(II) salts with methylenediisophthalic acid (H4MDIP). All compounds have been characterized by thermogravimetric analysis, IR spectroscopy, elemental and single-crystal X-ray diffraction analyses. Complexes 1–3 are anionic frameworks with [NH2(CH3)2]+ ions occupying the voids, built upon tetra-, tri- and asymmetrical trimetallic cores, respectively. In particular, the asymmetrical trinuclear Mg(II) unit in complex 3 was scarcely observed. Topological analyses show that the three compounds possess binodal (4,8)-connected alb topology with a Schläfli symbol of (410.614.84)(45.6)2. Magnetic investigations indicate that antiferromagnetic couplings are dominant in compounds 1 and 2.
Five new metal–organic frameworks, [Zn2.5(SIP)(azopy)1.5(OH)2(H2O)]n (1), {[Zn1.5(SIP)(azopy)1.5(H2O)2]·0.5(azopy)·2H2O}n (2), {[Cd1.5(SIP)(azopy)1.5(H2O)2]·0.5(azopy)·2H2O}n (3), {[Cd2.25(SIP)0.5(μ3-OH)3(H2O)]·0.5H2O}n (4), and [Cu3(SIP)(CH3COO)(μ3-OH)2(μ2-H2O)(H2O)]n (5) were produced by hydrothermal reactions of NaH2SIP (NaH2SIP = 5-sulfoisophthalic acid monosodium salt) with azopy (azopy = 4,4′-azobispyridine). They were structurally characterized by single-crystal X-ray diffraction and elemental analysis. In the formation of these compounds, transition-metal carboxylate clusters as secondary building units (SBUs) play important roles. 1 crystallizes in the triclinic P space group and exhibits a 3D metal–organic framework with typical pcu topology. 2 and 3 are isomorphic and crystallize in the monoclinic space groupP2/c, both feature an interesting 3D coordination framework with an unprecedented {62.84}{63}2{64.82}2 topological structure, which has been deposited in the Reticular Chemistry Structure Resource (RSCR) named as zlm net. 4 crystallizes in the monoclinic C2/m space group and displays a 3D architecture with interesting coordination modes. 5 crystallizes in the triclinic space groupP and possesses a 2D coordination configuration with a hexanuclear Cu6O4(COO)6cluster as the secondary building unit. The luminescence analysis on 1–3 and the magnetic analysis on 5 were performed and discussed.
Five novel metal–organic frameworks (MOFs) have been hydrothermally synthesized, namely, [Co(bimb)(2,4′-bpdc)(H2O)2]·H2O (1), [Co2(bimb)3(2,4′-bpdc)2(H2O)2]·H2O (2), [Co(bix)(2,4′-bpdc)] (3), [Co(bix)0.5(2,4′-bpdc)(H2O)0.25] (4) and [Co(bimh)(2,4′-bpdc)] (5), based on mixed ligands, 2,4′-biphenyldicarboxylic acid (2,4′-H2bpdc) as organic linkers and different bis(imidazole) ligands as co-ligands: (1,4-bis(imidazol-1-yl)-butane (bimb), 1,4-bis(imidazol-1-yl-methylene)-benzene (bix) and 1,6-bis(imidazol-1-yl)-hexane (bimh)). The coordination polymers were characterized by single-crystal X-ray diffraction, thermogravimetric analysis (TGA) and element analysis (EA). Reactions between CoCl2·6H2O, 2,4′-H2bpdc and neutral bimb ligand afforded two crystallographically different coordination polymers (1 and 2) through tuning the ligand/metal ratio meticulously. Compound 1 crystallizes in a noncentrosymmetric Pna21 space group with 65·8 CdSO4-type topology, while compound 2 is isolated with P21/c space group and displays a 4-connected 66 network. By substituting bix for bimb ligand, alteration of the metal/ligand ratio in the initial reaction system induced a transition from 2D layer (compound 3) to 3D architecture (compound 4). Notably, the structure of 4 is constructed from [Co(2,4′-bpdc)] layers, which are further pillared by bix ligands into a 3D 3,4-connected (63)·(63·103) network. In 5, the left- and right-handed helical chains constructed by Co(II) and bimh ligands are bridged by 2,4′-bpdc2− anions to form a layer-like structure.
Two novel cobalt(II) complexes [Co(L)(NO3)] (1) and [Co(L)(H2O)2]ClO4 (2) were synthesized by reactions of 3,5-di(1H-imidazol-1-yl)benzoic acid (HL) with corresponding cobalt(II) salts, and their structures were determined by single crystal X-ray diffraction analysis. In the title complexes, the carboxylategroup of L− ligand adopts a µ2–ŋ1:ŋ1-bridging mode to connect two cobalt(II) atoms, and each L− ligand acts as a 4-connector, and the cobalt(II) has distorted octahedral coordination geometry. In 1, one oxygen atom of the nitrate anion links two cobalt(II) atoms to complete a 3D structure which is a binodal (4,6)-connected net with Schläfli symbol of (3·42·52·6)(32·42·52·64·74·8). While in 2, the 3D structure has topology related to SrAl2, CeCu2 and KHg2 with Schläfli symbol of (42·63·8) and there are 1D channels filled with perchlorate anions. The results revealed that the nature of the counteranions, such as their shape, size and coordination ability, has a remarkable influence on the structure of the complexes. The results of the magnetic measurements showed that there are antiferromagnetic interactions between the neighboring Co(II). Furthermore, complex 2 exhibited a modest second-harmonic-generation (SHG) efficiency and anion-exchange property.
The crystal structure of trans-4-(trifluoromethyl) cinnamic acid (1) has been determined in the triclinic space groupP. Differential scanning calorimetry showed that 1 undergoes a single fully reversible temperature induced phase transition at around 132/131 K (cooling/heating). Single crystal structure determinations, carried out at 200, 145 and 120 K, revealed that the volume of the unit cell quadruples as the crystal is cooled through the phase transition with Z′ increasing from 2 to 8. The structures are stabilised by the presence of O–HO hydrogen bonding and C–HO interactions. The results of DSC, single crystal and powder X-ray diffraction studies on 1 are reported.
The cyclic voltammetric behaviour of 2,2′-, 3,3′-, and 4,4′-azopyridine, and 2-, 3-, and 4-phenylazopyridine in CH3CN is compared with that of azobenzene. From the results obtained when CH3CN and PhCH2CO2Et are added to solutions of azobenzene and 2,2′-azopyridine in super-dry dimethylformamide it is concluded that the azopyridines and phenylazopyridines are reduced by a mechanism analogous to that of azobenzene, and that their dianions deprotonate CH3CN to give –CH2CN.
The reactions of the low-valent titanocene sources [Cp*2Ti(η2-C2(TMS)2)] (2) and [tBuCp2Ti(η2-C2(TMS)2)] (3) with trans-4,4′-azobispyridine (8) leads to novel supramolecular squares [(Cp*2Ti)4(μ2-N,N′;η2-N,N′-C10H8N4)2] (10) and [(tBuCp2Ti)4(μ2-N,N′;η2-N,N′-C10H8N4)2] (11). These complexes consist of four bent-titanocene corner units and two azo ligands 8. Within this self-assembly process the azo ligands experience a conformational rearrangement from trans to cis. The titanocene moieties are embedded with two different N-donor environments, provided by the pyridyl rings and the azo functionality of 8. Single-crystal X-ray analyses of the tetranuclear compounds 10 and 11 revealed the structural features of these molecular polygons. Exclusively cis-configurated azopyridine units are detected in 10 and 11. Comparison of bond lengths and angles in coordinated and free ligands shows a reduced state of the bridging ligands in the low-valent titanium complexes 10 and 11. In such a way, the Nazo−Nazo distances are elongated from 1.251(2) Å in 8 to av 1.405(3) Å (10) and 1.434(3) Å (11), respectively. The syntheses and attributes of these novel compounds are discussed. From the reaction of [Cp2Ti(η2-C2(TMS)2)] (1) with 8, 1,2-bis(4-pyridyl)hydrazine (13) was isolated and fully characterized as a subsequent product.
A simultaneous redox, alkylation, self-assembly reaction under solvothermal conditions afforded a novel copper(I) chain polymer constructed of luminescent Cu3I4- and unprecedented EtS-4-C5H4N+Et components (Et = CH3CH2).
A microporous metal organic framework structure, Zn(2)(bpdc)(2)(bpee).2DMF (DMF: N,N-dimethylformamide), has been synthesized via solvothermal reactions. The compound is a new member of the RPM series (RPM = Rutgers Recyclable Porous Material) that possesses a flexible and recyclable three-dimensional framework containing one-dimensional channels. It exhibits interesting and multifold functionality, including porosity, commensurate adsorption for hydrocarbons, high hydrogen binding energy (determined by isosteric heats of hydrogen adsorption and confirmed by van der Waals density functional calculations) as a result of multifold binding to aromatic ligands (determined by IR spectroscopy), strong photoluminescence emission, and reversible fluorescence quenching properties.
Three cyclodextrin-based complexes, 1-3, bearing external coordination sites for metal cations were prepared in satisfactory yields (over 50%) by reactions of alpha-, beta-, and gamma-cyclodextrins with 4,4'-dipyridine in aqueous solutions. Subsequently, these inclusion complexes were further assembled to form linear polypseudorotaxanes 4-6 through the coordination linkage of Ni(II) or Cu(II) ions, and their assembly behaviors were comprehensively investigated in both solutions and the solid state by means of 1H NMR, FT-IR, UV-vis spectroscopy, conductivity titration, powder X-ray diffraction patterning, thermogravimetric and differential thermal analysis, scanning electron microscopy, scanning tunneling microscopy, and transmission electron microscopy. The results showed that these polypseudorotaxanes existed as individual linear arrays at a low concentration but tended to form polymeric rodlike fibers at a relatively high concentration. Significantly, the volume of the cyclodextrin cavity used not only determined the inclusion complexation stoichiometry between cyclodextrin and 4,4'-dipyridine but also predominated the morphology of resulting polypseudorotaxanes.
Six new coordination polymers, namely, [Cd(HL)(4,4′-bpy)(H2O)]·H2O (1), [Cd3(L)2(4,4′-bpy)3(H2O)]·2.5H2O (2), [Co(HL)(4,4′-bpy)]·H2O (3), [Co2(L)(4,4′-bpy)0.5(μ3-OH)(H2O)2]·H2O (4), [Zn(HL)(BIMB)]·2H2O (5), [Zn3(L)2(BIMB)2]·3H2O (6), where H3L = 5-(4-carboxybenzyloxy)isophthalic acid, 4,4′-bpy = 4,4′-bipyridine, BIMB = 1,4-di(1H-imidazol-1-yl)benzene, have been synthesized under hydrothermal conditions and characterized by single crystal X-ray diffraction. In complexes 1, 3 and 5, H3L ligand is partially deprotonated in the form of HL2−; while in 2, 4 and 6, it is completely deprotonated due to the influence of different pH values. Complexes 1 and 5 are 2D layer structures, the hydrogen bonds between lattice-water molecules and carboxylategroups of HL2− ligands extend the 2D layer into a 3D framework; while complex 3 is a 3D framework with α-Po topology. Complex 2 is a 3D fourfold interpenetrating (3,4,4)-connected net with (63)(62·84)(64·82) topology. Complex 4 is a twofold interpenetrating (3,8)-connected net with (43)2(46·618·84) topology. And complex 6 is a twofold interpenetrating (3,4,6)-connected net with (4·62)(64·72)(42·66·74·8·92) topology. In addition, powder X-ray diffraction and thermogravimetric analyses for 1–6, photoluminescent properties for 1, 2, 5, 6 and magnetic properties for 3, 4 are investigated in detail.
Two mixed azide-hmt bridged compounds were obtained with neutral 3D networks, Co2(N3)4(hmt)(H2O) (1) and Ni2(N3)4(hmt)(H2O) (2), hmt = hexamethylenetetramine. In 1, the azide ions present three kinds of coordination modes in the connection of two unique Co2+ ions. Each Co1 is connected by trans-EE- azide ions and hmt into extended (4,4) layers, and each Co2 is connected by EO-azide ions into dimers which are located between the neighboring (4,4) layers. The cis-EE-azide ions connect the dimers to the neighboring layers to form rare 3D networks. The Co12+ and Co22+ ions have four and three connections through azide bridges to the neighboring Co2+ ions, respectively. Twisted torsion angles of cis/trans-EE azide bridges are observed in 1, with a value of 83.39 and 117.43°, respectively. The Ni analogue 2 is isostructural with 1 revealed by IR, elemental analysis and Powder X-ray diffraction. Magnetic investigation shows that 1 is a weak ferromagnet below Tc = 15.0 K, with a large coercivity of 1 T at 2 K, while 2 is a soft ferromagnet below Tc = 10.0 K.
Four new high-spin cobalt(II) complexes of formulae [Co2(bta)(4,4′-bpy)2(H2O)2]n (1), {Hbpe[Co(Hbta)(bpe)(H2O)2]}n (2), {[Co(H2bta)(azpy)(H2O)2]·azpy}n (3) and {[Co2(bta)(bpa)2(H2O)4]·8H2O}n (4) with H4bta = 1,2,4,5-benzenetetracarboxylic acid, 4,4′-bpy = 4,4′-bipyridine, bpe = trans-1,2-bis(4-pyridyl)ethene, azpy = 4,4′-azobispyridine and bpa = trans-1,2-bis(4-pyridyl)ethane, have been prepared and characterized by single crystal X-ray diffraction. Compounds 1–4 exhibit two-dimensional networks where the fully (1 and 4) or partially (2 and 3) deprotonated tetracarboxylic ligand connects two (2 and 3) or four (1 and 4) cobalt(II) ions through two trans-carboxylate (1–3) or all the carboxylategroups (4) whereas the co-ligands 4,4′-bpy (1), bpe (2), azpy (3) and bpa (4) act as two-fold connectors in trans- (bpe and azpy) and gauche- (bpa) conformations. The cobalt(II) ions in 1 are five-coordinated with two nitrogen atoms from two 4,4′-bpy ligands in the axial positions and a water molecule and two carboxylate-oxygens building the trigonal plane. Six-coordinated cobalt(II) ions occur in 2–4 with two pyridyl-nitrogen atoms, two carboxylate-oxygens and two trans-coordinated water molecules in a somewhat distorted octahedral surrounding. The magnetic properties of 1–4 have been investigated in the temperature range 1.9–300 K. Compound 1 shows a weak antiferromagnetic interaction between the five-coordinated cobalt(II) ions (0.13 ≤ |J| ≤ 0.28 cm−1, Ĥ = −JŜ1·Ŝ2), the exchange pathway involved being the double carboxylate bridges in the syn–syn conformation [cobalt–cobalt separation] of 3.6465(9) Å. As the magnetic interactions between the cobalt(II) ions through the phenyl ring of the bta group in 2–4 and those across the extended bpe (2), azpy (3) and bpa (4) bridges are negligible, the strong decrease of χMT upon cooling observed for 2–4 is mainly due to the depopulation of the higher Kramer doublets of the six-coordinated cobalt(II) ions.
Two new extended chromophoric systems, in which a
4-aminoazobenzene moiety is linked to a cyclo-bridged hexatriene electron
withdrawing group, have been synthesized, and show large optical
nonlinearities and unexpected blue-shifted absorption in comparison with
shorter chain analogues.
An achiral anthracene−pyrimidine derivative (5-(9-anthracenyl)pyrimidine, 1) forms adduct 1·Cd(NO3)2·H2O·EtOH (2) in chiral space group P21. The metal ion is hexacoordinated with two pyrimidine ligands (equatorial cis), water and ethanol (equatorial cis), and two nitrate ions (axial trans). The chirality arises from a pyrimidine−Cd2+ helical array and is preserved not only in each crystal via homochiral interstrand water−nitrate hydrogen bonding but also in all the crystals in the same chirality as a result of single-colony homochiral crystal growth. Compound 1 also forms achiral (Pbca) trihydrate adduct 1·Cd(NO3)2·3H2O (3) having nonhelical pyrimidine−Cd2+ zigzag chains. Achiral zigzag polymer 3 and chiral helical polymer 2 are interconvertible with each other in the solid states upon exchange of volatile ligands (ethanol and water). The helix winding associated with the conversion of adduct 3 to 2 can be made homochiral by seeding.
The cis-trans isomerization of 2-hydroxy-5-methylazobenzene in water and ethanol solutions was studied by flash photolysis. In aqueous acetate buffer the thermal cis → trans conversion of the neutral cis molecule HC follows the rate law -d[HC]/dt = (k s + k H+[H +] + k HOAc[HOAc] + k OAc-[OAc -])[HC], with k s = 4 × 10 2 sec. -1; k H+ = 7.5 × 10 7,k HOAc = 3.8 × 10 4 and k OAc- = 6.0 × 10 3 l. mole -1 sec. -1 at 30.0°. The mechanism for the proton catalysis proceeds with the cis→trans conversion of the cation as the rate-determining step; rate constant = 2.1 × 10 4 sec. -1 at 30.0°. The anion in water also undergoes cis-trans isomerization. Above pH 12, the thermal relaxation of the cis anion C - follows the rate law -d C -]/dt = k H+′[H +] [C -], with k H+′ = 2.0 × 10 13 l. mole -1 sec. -l. The rate-determining step appears to be the solvent-catalyzed cis → trans conversion of the neutral species, with rate constant = k s. pK values of 2.9 and 10.7 were deduced for the cis cation and cis neutral species, respectively, as compared to -1.5 and 9.4 determined for the trans species. The same general results for the cis → trans conversions were obtained in acetate buffered ethanol and sodium ethoxide solutions. An additional, faster transient, probably the hydrazone tautomer, was observed under weakly acidic conditions. Activation energies were estimated for all transformations.
The electrochemical behavior of a series of aromatic azo compounds in dimethylformamide solutions was studied by polarography, cyclic voltammetry, controlled-potential coulometry, electron spin resonance spectroscopy, and ultraviolet spectroscopy. The electrochemical reduction of these compounds is generally similar to that of the aromatic hydrocarbons in aprotic media. The reduction occurs in two one-electron steps. The product of the first electron transfer is a stable anion radical. The second electron transfer to the dianion is followed by a chemical reaction producing a protonated species which is oxidizable to the parent azo compound. The product of the second electron transfer also produces the corresponding arylhydrazine in a following reaction.
Rate data have been obtained for cis-trans isomerizations of phenylazopyridines and symmetrical azopyridines in n- heptane. Activation energies ranged from 21 to 22.6 kcal mol-1, with the 2- and 4-substituted compounds showing lower activation energies. Although the 2-substituted dyes had low Ea terms, the ΔS* terms were considerably more negative than those of other compounds in the series. The slower isomerization rates for these compounds are attributed to coulombic interactions between the pyridyl nonbonded electrons and the azo electrons in the activated complex. The 2- and 4-substituted compounds showed a high sensitivity to acid catalysis. An activation energy of 9 kcal mol-1 was associated with the acid-catalyzed isomerization of cis-4-phenylazopyridine. CNDO/2 calculations were performed on the cis and trans configurations of these dyes and for the transition states. Inversion of one of the azo nitrogens was calculated to be overwhelmingly favored over rotation. Analysis of the results of the MO calculations showed facile inversion to be aided by electron withdrawal by the ring attached to the rehybridizing nitrogen which is manifested by a high C-Nazo π density and by a lowered electron density at the p orbital bearing the nonbonded electrons.
The change in absorbance in the region of the intervalence transition for μ-4,4′-bipyridyl-bis(pentaammineruthenium) when the fully oxidized state is titrated with a reducing agent is used to obtain the comproportionation constant for reaction I This value (24 ± 1 at 19.0°C) was used to calculate the extinction coefficient (8.8 × 102 M-1 cm-1) at the band maximum (1030 nm in D2O) and the oscillator strength corresponding to the transition. The stabilization resulting from electron delocalization in turn is calculated from the oscillator strength as 48 cal and falls far short of the stability of the mixed-valence compared to the isovalent state, which amounts to 5 × 102 cal. It seems likely that the major contribution to the stability of the mixed-valence state is the electrostatic interaction between the positively charged ends, which will favor the mixed-valence state. Calculation of this contribution using the macroscopic dielectric constant for the solvent, however, falls far short of accounting for the experimental value. When, as in this case, the contribution to stability from electron delocalization is small, the measurements would seem to provide a rather direct way of exploring the electrostatic term.
The synthesis and spectroscopic and structural characterization of several substituted diphosphanes and hydrazines have been carried out in order to estimate the relative importance of rehybridization and pi-bonding in N-N and P-P double-bond lengths. The presence of the -BMes2 (Mes = 2,4,6-Me3C6H2) group in the compounds Mes2B(1-Ad)PPPh2 (1) (1-Ad = 1-adamantyl), [Mes2B(1-Ad)P]2 (2), and [Mes2B(Mes)P]2 (3) induces essential planarity at the boryl-substituted phosphorus atoms and dramatic changes in the P-P bond lengths. Normally, single P-P bonds are about 2.22 angstrom long, as is observed in [Mes(I)P]2 (4), whereas in 1 the P-P bond length is near 2.17 angstrom and in 2 and 3 it is near 2.11 angstrom. The latter distance is about halfway between those of normal single and double P-P bonds. The use of the -BMes2 group as a substituent on hydrazines also results in planarity at the boryl-substituted nitrogen and in the shortening of the N-N bonds. In this case, however, the percentage change in the N-N bond length is not as great as that seen in the phosphorus compounds. For example, the N-N bond length in Mes2B(Ph) NN(H)Ph (5) is near 1.44 angstrom and in Mes2B(H)NN(H)BMes2 (6) it is 1.41 angstrom whereas in hydrazine the N-N distance is 1.46 angstrom (cf. N-N double bond almost-equal-to 1.25 angstrom). Oddly, the N-N bond length in 1,2-diphenylhydrazine (7) is 1.39 angstrom. In this case, however, the nitrogen is almost planar and the N-C bond is short. The larger changes observed in the diphosphanes have been interpreted on the basis of the relative weakness of the P-P pi-bond and the fact that the hybridization changes in phosphorus are significantly greater than those observed for nitrogen. Similarly, comparison of the data for 1-7 with the normal bond lengths for P-P and N-N double bonds, which are 2.02 and 1.25 angstrom long, respectively, leads to the conclusion that p-p pi-bonds account for only about half of the shortening in P-P double bonds whereas they account for approximately 70-75% of the contraction in the case of N-N double bonds.
Six supramolecular polypseudorotaxanes (2−7) like the missing link have been constructed by coordination of the β-cyclodextrin/4,4‘-dipyridine inclusion complex (1) with cobalt chloride, cobalt acetate, cobalt nitrate, zinc chloride, zinc acetate, and zinc nitrate, respectively, and investigated using 1H NMR spectroscopy, circular dichroism, FT-IR, gel permeation chromatography, powder X-ray diffraction, thermogravimetric and differential thermal analysis, transmission electron microscopy, and cyclic voltammetry. The obtained results indicate that polypseudorotaxanes 2−7 could self-assemble to form square or rodlike nanostructures. The counteranions play critical roles in the formation of the polypseudorotaxane nanoarchitectures. Especially polypseudorotaxane 2 shows better electrochemical property as compared with that of other polypseudorotaxanes 3−7, which may potentially be used as an electroactive soft material.
The self-assembly processes between binuclear [Zn2] and [Cu2] complex cations and exo-bidentate ligands [trans-4,4′-azo-pyridine (azpy), 4,4′-bipyridine (4,4′-bipy), 1,2-bis(4-pyridyl)ethane (bpeta), 1,3-bis(4-pyridyl)propane (bpp)] generate two types of complexes: tetranuclear species with a rectangular topology and one-dimensional (1-D) coordination polymers: [{L2(μ-OH)Cu2}(μ-azpy)2{Cu2(μ-OH)L2}][{L2(μ-OH)Cu2(H2O)}(μ-azpy)2{(H2O)Cu2(μ-OH)L2}](ClO4)8 (1); [{L1Cu2(H2O)2}(μ-azpy)2{Cu2L1(H2O)2}](ClO4)4·(azpy)·2H2O (2); 1∞[{Cu2(μ-OH)L3}(μ-bpp)](ClO4)2 (3); 1∞[{L3Zn2(μ-OH)}(μ-4,4′-bipy)](ClO4)2·2H2O (4); 1∞[{L3Zn2(μ-OH)}(μ-bpeta)](ClO4)2 (5a); 1∞[{L3Zn2(μ-OH)}(μ-bpeta)](ClO4)2·THF (5b); 1∞[{L2Zn2(μ-OH)}(μ-4,4′-bipy)2](ClO4)2·2H2O (6) (H2Ln are compartmental Schiff-base ligands resulting from condensation reactions between 2,6-diformyl-p-cresol with, respectively, 1,3-diamino-propane, 2-aminoethyl-pyridine, and N,N-dimethyl-ethylenediamine). The zinc complexes exhibit luminescence properties.
Solvothermal reactions of CuI with 4,4′-dipyridyl disulfide (dpds) and oxalic acid in toluene and acetonitrile at three different time periods gave rise to three Cu/I/S-based coordination polymers, [Cu6(μ-4-SpyH)4I6]n (1), {[Cu2(μ-I)(μ-4-SpyH)3]I}n (2), and [Cu5(μ-4-SpyH)7(μ-I)I4]n (3). The preparation of 1−3 was involved in the in situ formation of the zwitterionic pyridium-4-thiolate (4-SpyH) molecule from the S−S cleavage of the dpds ligand. These compounds were characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis (TGA), X-ray powder diffraction (XRPD), and single crystal X-ray diffraction. Compound 1 contains an adamantine-type [Cu6S4] core that links the neighboring ones via double iodide bridges to form a three-dimensional (3D) diamond-like net. Compound 2 has a one-dimensional (1D) cationic {[Cu2(μ-I)(μ-4-SpyH)3]n}n+ polymeric chain with disordered iodides embedded between chains. Compound 3 contains the [Cu5(μ-I)I4(μ-4-SpyH)7] species that is interconnected with its neighboring ones through two μ-4-SpyH ligands to form a 1D neutral chain. The formation of 1−3 provided an interesting example that different coordination polymers could be produced from the same components under solvothermal conditions at different time periods. In addition, optical absorption and electric conductivity experiments revealed that 1−3 exhibited good semiconducting performances.
In our efforts to investigate polydentate ligands bearing bulky backbones, we used a bulky ligand, 2,3,6,7-anthracenetetracarboxylic acid (H4ata), to react with ZnII ions under different conditions, yielding four new coordination polymers, {[Zn(ata)0.5(DMF)(H2O)]·DMF·H2O}n (1), {[Zn(ata)0.5(4,4′-bipy)0.5(DMF)]·DMF}n (2), {[Zn(ata)0.5(azpy)0.5(DMF)]·DMF}n (3), and {[Zn(ata)0.5(4,4′-bipy)(DMAC)]·(DMA)0.5}n (4) (DMF = N,N-dimethylformamide, 4,4′-bipy = 4,4′-bipyridine, azpy = 4,4′-azopyridine, DMAC = N,N-dimethylacetamide, DMA = dimethylamine), which were characterized by IR and single crystal X-ray diffraction. Complex 1 forms a two-dimensional (2D) network with (4,4) topology assembled by ata4− ligands and ZnII ions. Complexes 2 and 3 are three-dimensional (3D) frameworks with {83}2{85;10} topology containing infinite 2D networks pillared by 4,4′-bipy and azpy, respectively. Complex 4 takes a 2D structure with (4,4) net containing infinite one-dimensional chains constructed by ZnII ions with 4,4′-bipy and ata4− ligands. These results show that the reaction of 2,3,6,7-anthracenetetracarboxylic acid with ZnII in DMF tends to yield a layer structure which could be pillared by bipyridine-like ligands into 3D frameworks, and the final structure of the coordination polymer is greatly influenced by the solvent. Furthermore, the luminescence properties of 1−4 were studied in the solid state at room temperature.
Treatment of [Cu(dipic)(OH2)3] [dipic2 = pyridine-2,6-dicarboxylate (dipicolinate)] 1 with diverse bipyridyl bridging ligands of varying length [pyrazine (pyz), 4,4′-bipyridine (bipy), trans-4,4′-azobis(pyridine) (azpy), 1,2-bis(pyridin-4-yl)ethene (bpe), 3,6-bis(pyridin-4-yl)-1,2,4,5-tetrazene (pytz) and 1,4-bis{2-(pyridin-4-yl)ethenyl}benzene (bpeb)] under a variety of conditions yielded [Cu2(dipic)2(bipy)]·4H2O, 2, [Cu2(dipic)2(bpe)]·2H2O, 3, [{Cu(dipic)(OH2)}(μ-pyz)0.5]·H2O, 4, [{Cu(dipic)(OH2)}(μ-pyz)0.5], 5, [{Cu(dipic)(OH2)}(μ-bipy)0.5][{Cu(dipic)(OH2)0.75(OHMe)0.25}(μ-bipy){Cu(dipic)(OH2)}]·2.25H2O·0.5CH3OH, 6, {[{Cu(dipic)}2(μ-bipy)]·2H2O·CH2Cl2}∞, 7, [{Cu(dipic)(OH2)}(μ-bpe){Cu(dipic)}]·3H2O, 8, {[{Cu(dipic)}(μ-azpy)0.5]·CH2Cl2}∞, 9, {[{Cu(dipic)}(μ-azpy)0.5]·CH3OH}∞, 10, [{Cu(dipic)(OH2)}2(μ-pytz)]·2H2O, 11, [Cu2(dipic)2(bpeb)]·4H2O, 12 and [{Cu(dipic)(OHMe)}2(μ-bpeb)], 13. Complexes 4−11 and 13 were characterized by single crystal X-ray diffraction which confirmed the presence of binuclear building blocks in which two square-pyramidal Cu(II) centers are linked by bipyridyl bridges. The differences in the structures lie in the choice of ligand located at the apical site of the Cu(II) center, the basal sites being occupied by one N- and two O-donors of the mer-bound dipicolinate ligand and an N-donor from the bridging heterocyclic ligand. In the presence of excess coordinating solvent such as H2O or MeOH, recrystallization affords products with the apical sites occupied by solvent molecules to give extensive hydrogen-bonding networks within 3-D matrices in 4−6, 8, 11, 13. With reduced levels of coordinating solvent in the crystallizing medium, the apical sites are occupied by carboxylate oxygens of adjacent [Cu(dipic)] moieties giving 2-D coordination polymers of 63 topology as in 7, 9, 10.
A series of molybdenum/tungsten polyoxometalate compounds, namely, [(MII(HL)2)Mo3O10] (M = Mn (1), Co (2), Ni (3)), [CuII2(L)2(HL)2]2(Mo8O26) (4), [Zn(HL)2(MoO4)]2·HL·4H2O (5), [CuII4(L)6WO4)]·3H2O (6) (HL = 3-(2-pyridyl)pyrazole), were designed and synthesized under hydrothermal conditions. X-ray diffraction analyses reveal that compounds 1−3 have an isostructural wavelike chain structure consisting of the asymmetric building blocks of [Mo3O10], in which the ratio of octahedron {MoO6} and square pyramid {MoO5} is 1:2. The hexacoordinated transitional metal cation, just like one “anchor” to fix the above wavelike chain, is linked by two terminal oxygen atoms belonging to two edged asymmetric molybdate [Mo3O10]2− units, and further chelated by two 3-(2-pyridyl)pyrazole ligands. Although a similar synthetic method in preparation of 1−5 was employed, compounds 4 and 5 show a completely different structure compared to compounds 1−3. Compound 4 is composed of two separate parts of the [CuII2(L)2(HL)2]2+ dimer and the ε-[Mo8O26]4− unit. Compound 5 consists of a bimetallic tetranuclear cluster that is constructed from corner-sharing {MoO4} tetrahedra and {ZnN4O2} distorted octahedron forming a cyclic {Zn2Mo2O4} core. For compound 6, a one-dimensional structure is composed of WO42− linked by the centrosymmetric tetranuclear copper grids, in which two approximately planar [CuII(L)]2 units with an inversion center stack parallel and face-to-face linked by two additional deprotonated ligands of L−1 perpendicularly.
We report the hydrothermal syntheses, single-crystal structure determinations, and the thermal and magnetic properties of five binuclear complexes obtained from either a mixture of P and M 2,2′-biphenyldicarboxylate, (2,2′-bpdc)2−, or a mixture of cis- and trans-1,4-cyclohexanedicarboxylate, (1,4-chdc)2−, as bridging ligands, di-2-pyridylamine (dpa) as a capping terminal ligand, and a divalent transition metal (Cu, Co, and Ni). All five compounds, [Co2(2,2′-bpdc)2(dpa)2] (1), [Cu2(2,2′-bpdc)2(dpa)2]·4H2O (2a), [Cu2(2,2′-bpdc)2(dpa)2]·2(2,2′-bpdcH2)·H2O (2b), [Co2(cis-chdc)2(dpa)2] (3), and [Ni2(cis-chdc)2(dpa)2] (4), consist of neutral molecular squares of two metal centers bridged by two elbowed dicarboxylate, and each metal is capped by the chelating di-2-pyridylamine. In 1, the Co(II) adopts a tetrahedral coordination from two oxygen atoms of monodentate 2,2′-bpdc2− and two nitrogen atoms from dpa. In 2a and 2b, the Cu(II) adopts distorted octahedral geometry from two bidentate 2,2′-bpdc2− and one bidentate dpa. 1, 2a, and 2b contain both P and M forms of 2,2′-bpdc2−. 3 and 4 contain octahedral metal coordination with only the chair form of cis-chdc2− as bridging ligands in bidentate mode and bidentate peripheral dpa. In each of these complexes, hydrogen bonds between the amine nitrogen and a carboxylate oxygen atom and π−π overlap between the pyridine rings of the dpa define the supramolecular interactions which contribute to the crystals’ stability. The magnetic properties are those of paramagnets with weak exchange interactions, as a consequence of the distant exchange pathway between nearest neighbor moment carriers.
Twelve structurally diverse complexes, [Pb2(pzp)2(adip)(NO3)2] 1, [Pb(pzp)(glu)] 2, [Pb(pzp)(chdc)]·[Pb(pzp)(chdc)]·pzp·H2O 3, [Pb2(ndc)2(pzp)2(H2O)]·0.5H2O 4, [Pb(pzp)(1,3-bdc)(H2O)0.5]·H2O 5, [Pb(pzp)(1,2-bdc)]·H2O 6, [Pb2(ptc)2(adip)(NO3)2] 7, [Pb(ptc)(glu)] 8, [Pb(ptc)(chdc)] 9, [Pb(ptc)(dpdc)]2 10, [Pb(ptc)(1,3-bdc)]·2.5H2O 11, and [Pb(ptc)(1,4-bdc)]·0.75H2O 12, where H2adip = adipic acid, H2glu = glutaric acid, H2chdc = 1,4-cyclohexanedicarboxylic acid, H2ndc = 1,4-naphthalenedicarboxylic acid, 1,4-H2bdc = benzene-1,4-dicarboxylic acid, H2dpdc = 2,2′-diphenyldicarboxylic acid, 1,3-H2bdc = benzene-1,3-dicarboxylic acid, 1,2-H2bdc = benzene-1,2-dicarboxylic acid, pzp = pyrazino[2,3-f][1,10]phenanthroline, and ptc = 2-phenyl-1H-1,3,7,8,-tetraaza-cyclopenta[l]-phenanthrene, have been hydrothermally synthesized. Compounds 7 and 10 possess dinuclear structures, which are further extended by π−π interactions to form supramolecular layers and chains, respectively. 1−6, 8−9, and 11−12 feature chain structures, which are then stacked by π−π interactions to result in 2D or 3D supramolecular architectures. The structural differences among such complexes show that the organic acids and neutral chelating ligands have important influences on the structures.
The combination of semiflexible terephthaloyl-bis-β-alaninate (TBbA2–) and metal ions at room temperature in aqueous solution results in the formation of five new compounds formulated as [Ca(TBbA)(H2O)3]·H2O (1), [Mn(TBbA)(H2O)2]·H2O (2), [Co(TBbA)(H2O)4]·2H2O (3), [Ni(TBbA)(H2O)4]·2H2O (4), and [Zn(TBbA)(H2O)4]·3H2O (5). Compounds 1 and 2 are two- and three-dimensional coordination polymers, respectively, possessing a 3,4L13 and sra topology. Compounds 3–5 are one-dimensional coordination polymers; 3 and 4 have a “plywood” conformation, and 5 has a zigzag conformation. The difference in the conformation of the three pseudopolymorphs 3–5 can be attributed to the different orientations of the ligand. Notably, in the reaction system of compounds 3 and 4, a second product can be obtained. Powder X-ray diffraction (XRD) studies show that these products have a structure similar to 5, indicating the existence of additional pseudopolymorphs, 3′ and 4′. Thermal and rehydration studies show that polymorphs 3′ and 4′ are transformed to 3 and 4, respectively, upon heating and rehydrating.
Six new coordination polymers, namely, [Cd3(L)2(dpa)2(H2O)] (1), [Co3(L)2(dpa)2(H2O)2]·H2O (2), [Cd(L)(chda)0.5] (3), [Cd(L)(dc)0.5(H2O)] (4), [Cd2(L)2(cca)]·2H2O (5), and [Cd2(L)2(cppa)]·2H2O (6) [HL = 3,5-di(imidazol-1-yl)benzoic acid, H2dpa = diphenic acid, H2chda = 1,4-cyclohexanedicarboxylic acid, H2dc = 1,4-benzenediacrylic acid, H2cca = 4-carboxycinnamic acid, H2cppa = 3-(4-carboxyphenyl)propionic acid] have been obtained under hydrothermal conditions. Complexes 1 and 2 are novel (3,6)-connected three-dimensional (3D) frameworks based on trinuclear subunits. Complex 3 shows a rare 4-fold interpenetrating 3D dmc net, and 4 features a uninodal 6-connected 3D self-penetrating framework. Both 5 and 6 possess unusual 3-fold interpenetrating 3D (3,4)-connected InS nets. In 1−6 each metal atom is coordinated by the combination of L− and auxiliary carboxylate ligands. In 1 and 2 the auxiliary carboxylate ligand plays an important role in the formation of metal cluster based subunits. In 3−6 the auxiliary carboxylate ligands pillar the metal - L− two-dimensional networks to form entangled 3D frameworks. Furthermore, the photoluminescence and thermal stabilities of complexes 1−6 were investigated. The temperature-dependent magnetic susceptibility measurements of compound 2 show the ferromagnetic interactions between the metal centers mediated through the μ-O and/or O−C−O linkages.
Two semirigid ditopic ligands, 1,4-bis(benzimidazol-1-ylmethyl)-2,3,5,6-tetramethylbenzene (L1) and 1,3-bis(benzimidazol-1-ylmethyl)-2,4,6-trimethylbenzene (L2), reacted with Ag+ salts to result in two series of complexes, namely [Ag2(L1)2](CF3SO3)2 (1-R), [Ag2(L1)3](CF3SO3)2 (1-C), {[Ag2(L1)3](CF3SO3)2·CH3CN}n (1-P), and [Ag2(L2)2](ClO4)2·1.5CH3CN (2-R), {[Ag3(L2)2](ClO4)3}n (2-P). All complexes have been structurally characterized by single-crystal X-ray diffraction with the phase purity of bulk samples attested by powder X-ray diffraction (PXRD). Four types of structures are formed: (1) a discrete M2L2 ring with two Ag+ ions and two cis-L ligands comprising a molecular rectangle (1-R and 2-R), (2) a discrete M2L3 cage with two Ag+ ions and three cis-L ligands comprising a trigonal cage (1-C), (3) a one-dimensional [M2L3]n loop-and-chain with 3-connecting Ag+ ions bridged by both cis- and trans-L ligands (1-P), and (4) a two-dimensional [M2L3]n network of (6,3) topology with 3-connecting Ag+ ions bridged by trans-L ligands (2-P). The M2L3 cage 2-C was not obtained as a solid-state complex but observable in solution by ESI mass spectrometry. The complexes 1-C, 1-P and 2-C, 2-P contain comparable 3-connecting M2L3 building blocks, constituting two pairs of ring-opening isomers corresponding to single ring-opening (1-C to 1-P) and double ring-opening (2-C to 2-P) polymerization processes via cis-L to trans-L ligand conformation change, respectively. Investigations on solution behaviors by 1H NMR and ESI-MS and structural conversions monitored by PXRD disclose that the thermodynamically favored M2L2 ring can be converted to a thermodynamically disfavored M2L3 cage in solution through an L addition mechanism, which causes crystallization of isomeric structures of an M2L3 cage or [M2L3]n polymer due to ring-opening isomerization. Formation of an M2L3 cage or [M2L3]n polymer is influenced by kinetic or thermodynamic effects as well as the solubility-product constant (Ksp), implying predictable syntheses by controlling the crystallization conditions.
Use of unsymmetric ligand 1,2,4-benzenetricarboxylic acid (1,2,4-H3BTC) and controlling the reaction pH value enabled isolation of two novel chiral 3d-3d heterometallic complexes [Zn2Co(tib)3(H2O)5][Zn6(tib)2(1,2,4-BTC)6]·12.7H2O (1) and [ZnCo(tib)(1,2,4-BTC)(H2O)2]Cl·3H2O (2) [tib =1,3,5-tris(1-imidazolyl)benzene]. Comparative study revealed that the use of symmetric ligand 1,3,5-benzenetricarboxylic acid (1,3,5-H3BTC) resulted one achiral 3d-3d heterometallic complex [ZnCo(tib)(1,3,5-BTC)Cl] (3) with 3D structure. Complex 1 is a 2D network with cationic and anionic layers arranged alternately, while 2 is a 3D framework with rare 1D helical water chains. Furthermore, complex 1 displays ferroelectric behavior with a remnant electric polarization (Pr) of 0.177 μC/cm2 and an electric coercive field (Ec) of 17.68 kV/cm.
A new microporous metal–organic framework (MOF) material [Ni4(dpa)4(pyz)4(H2O)8]·11H2O (1) with BCT zeolite topology has been hydrothermally synthesized. The framework components undergo dynamic structural transformation in response to removal and rebinding of the suitable guest molecules.
To determine the influence of metal ions on the formation of metal−organic frameworks, five new coordination polymers, [Pb6(dpa)4O2]n (1), [Ag2(dpa)]n (2), [Nd2(dpa)3(H2O)2]n (3), [Zn(dpa)(H2O)]n (4), and [Cd2(dpa)2(phen)2(H2O)2]n (5), have been hydrothermally synthesized from 1,1‘-biphenyl-2,2‘-dicarboxylate acid (dpa). Complex 1 is a one-dimensional chain structure constructed from a new building unit, Pb6O18, which is connected by four different dpa molecules. Complex 3 is also a one-dimensional chain structure but is composed of a different building unit bridged by three dpa molecules. This complex is further extended into a two-dimensional supramolecular framework. Like complex 3, complex 4 is a two-dimensional supramolecular framework, which is connected by one-dimensional chains through π−π interactions and hydrogen bonding interactions. Complex 5 is a three-dimensional metal−organic supramolecular coordination polymer that possesses rectangular cavities. Different from the above four complexes, complex 2 is a two-dimensional covalence structure. To our knowledge, this is the first two-dimensional coordination polymer composed of metal ions and the dpa ligand. Furthermore, at room temperature, complex 4 exhibits strong photoluminescence.
Six tetranuclear cadmium(II) complexes, Na[Cd4(hmt)2(H2O)6(dpa)4(NO3)]·8H2O (1), Na[Cd4(hmt)2(CH3OH)2(H2O)4(dpa)4I]·8H2O (2), Na[Cd4(hmt)2(H2O)6(dpa)4Br]·8H2O (3), Na2[Cd4(hmt)2(H2O)6(dpa)4(SCN)2]·4H2O (4), {Na[Cd4(hmt)2(H2O)6(dpa)4Cl](H2O)4}n (5), and {[Cd4(hmt)3(H2O)5(dpa)4](H2O)10}n (6) (hmt = hexamethylenetetramine, H2dpa = diphenic acid), were synthesized by reactions of H2dpa, hmt, and CdX2 (X = NO3-, I-, Br-, Cl-, SCN-, and OAc-). All the complexes contain a basic unit [Cd4(dpa)4], in which four dpa ligands in a chelating bis-bidentate coordination mode link two six-coordinate and two seven-coordinate cadmium(II) centers. The research result demonstrates that the nature of the counterions has an important effect on the assembly process of neutral and anionic mixed ligands with metal ions. In 1−3, NO3-, I-, or Br- bridges the two seven-coordinate CdII centers of the unit to form a discrete tetranuclear molecule with a cis-conformation and hmt as a terminal ligand coordinated to each of the two six-coordinate cadmium(II) centers. Two SCN- in 4 acting as terminal ligands generate a discrete trans-conformational tetranuclear cluster anion. The hmt in 5 acting as a μ-ligand links cis-conformational tetranuclear units by Cd−N bonds to generate a one-dimensional chain structure, while the hmt in 6 acting as a μ-ligand links the tetranuclear units by Cd−N bonds to generate a two-dimensional layer structure composed of a planar-conformation [Cd4(dpa)4] unit. The fluorescent studies in the solid at room temperature show that the six complexes exhibit strong violet or blue emissions in the range 370−500 nm arising from the charge-transfer transition and that the bridging anions have a significant effect on their fluorescent properties.
Benzylation of 4,4′-azopyridine, followed by counterion exchange, yields the bis(hexafluorophosphate) salt of the dibenzyl-4,4′-azopyridinium dication, which is bound by bis-p-phenylene-34-crown-10 (BPP34C10) and by 1,5-dioxynaphtho-38-crown-10 (1/5DN38C10) with Ka values of 90 and 880 M−1, respectively, in acetonitrile. When a 4,4′-azopyridinium unit is introduced along with a bipyridinium unit into a tetracationic cyclophane — either in its free or catenated forms — spontaneous reduction to the 4,4′-hydrazopyridinium unit occurs. The X-ray structural analysis of a [2]catenane, incorporating this tetracationic cyclophane and BPP34C10, shows that the 4,4′-hydrazopyridinium unit is located alongside the cavity of the macrocyclic polyether while the other dicationic unit of the tetracationic cyclophane — namely the 4,4′-bipyridinium unit — is located inside. Variable temperature 1H NMR spectroscopy demonstrated that the 4,4′-hydrazopyridinium unit rotates in solution around the [N···N] axis defined by its two pyridinium nitrogen atoms. The energy barrier for this dynamic process is ca. 14 kcal mol−1 in both the free tetracationic cyclophane and in the [2]catenane incorporating BPP34C10. However, the energy barrier for this dynamic process is only 11.7 kcal mol−1 in a [2]catenane incorporating the same tetracationic cyclophane and 1/5DN38C10. In this latter [2]catenane, the 4,4′-bipyridinium unit and the inside 1,5-dioxynaphthalene ring system rotate (ΔGc‡ 14.0 kcal mol−1) in solution about their [N···N] and [O···O] axes, respectively. In the former [2]catenane, incorporating BPP34C10, the macrocyclic polyether circumrotates through the cavity of the tetracationic cyclophane against an energy barrier of 11.7 kcal mol−1.
The self-assembly properties of the proximal p-tert-butylcalix[4]dihydroquinone compound have been studied to investigate the role played by crystallization conditions in driving the formation of a previously reported cubic porous framework. In chloroform and anhydrous ethyl acetate, the mutual inclusion of the tert-butyl groups is favored, leading to the cubic porous structure; otherwise, in the presence of a higher water amount, the OH groups provide H-bonds with bridging water molecules and a new triclinic crystal structure is obtained, in which the calixarene molecules include chloroform inside their cavities. By exposing a cubic/triclinic powder mixture to acetonitrile vapors, a new monoclinic chiral crystal structure is obtained by supramolecular assembly of calixarene, acetonitrile, and water molecules with the formation of single handed helices.
This article reviews progress in the research of transition metal–lanthanide (d–f) bimetallic complexes. Through efficient energy transfer, sensitized luminescence of lanthanide ions from the visible range (EuIII) to the near-infrared region (NdIII, YbIII, ErIII and PrIII) is obtained in these bimetallic assembles. The d-block in d–f bimetallic complexes mainly contributes to the improvement of lanthanide emission efficiency and the extension of the excitation window for the lanthanide complexes. Examples are catalogued by various transition metals, such as RuII, OsII (FeII), PtII (AuI), PdII, ReI, CrIII, CoIII, ZnII and IrIII. The relevant synthetic procedures, crystal structures and photophysical properties of these d–f complexes are briefly described. Additionally, the molecular properties responsible for the performance of certain d–f systems, such as energy levels, nuclear distances and coordination environments, will be discussed.
This paper provides a short review of recent progress in the synthesis and characterization of homochiral metal-organic coordination networks (MOCNs) and their applications in the areas of asymmetric catalysis and chiral separations. Although chiral MOCNs can be constructed from achiral components, the resulting bulk solids tend to be racemic and are thus not useful for enantioselective processes. A couple of examples of homochiral solids built from achiral bridging ligands are presented along with more prevalent homochiral MOCNs built from chiral bridging ligands that are categorized based on their network dimensionality. Preliminary applications of these homochiral solids in asymmetric catalysis and chiral separations are also presented.
Salt formation is an approach to improve the physicochemical properties of the solid forms of an active pharmaceutical ingredient. As the anticonvulsant drug Lamotrigine presents low water solubility, a set of its salts with four different counterions has been obtained, and the influence of the counterion on the salt properties has been investigated. Lamotrigine salts have been obtained from succinic acid, fumaric acid, DL-tartaric acid, and saccharin. Powder samples of each salt have been characterized by infrared spectroscopy, powder X-ray diffraction, and thermal methods. Single crystal structures of four of these salts have been solved from single crystal X-ray diffraction data. The salts crystallized in P2(1)/c and P2(1)/n space groups, being isostructural dicarboxylic acid salts of lamotrigine. Crystal structures of these salts are built up by hydrogen bond interactions of type N((+))-H center dot center dot center dot O((-)), N-H center dot center dot center dot O((-)), O-H center dot center dot center dot N, and N-H center dot center dot center dot O. The water solubility of these salts has been determined and appears directly related to the solubility of the precursor acid. The isostructural nature of the studied salts allows connection of their properties with those of the counterion involved. The importance of the counterion solubility on the final solubility of the salts is rationalized considering their crystal structures.
A pillared-paddlewheel type metal-organic framework material featuring bodipy- and porphyrin-based struts, and capable of harvesting light across the entire visible spectrum, has been synthesized. Efficient-essentially quantitative-strut-to-strut energy transfer (antenna behavior) was observed for the well-organized donor-acceptor assembly consituting the ordered MOF structure.
A thermoresponsive, 3D hinged metal-organic framework (HMOF-1) assembled from meso-tetra(4-pyridyl)porphine and CdI(2) exhibits a 3D "lattice fence" topology with extraordinary thermal expansion and shrinkage. A simple structural model is established to elucidate such a drastic thermal response. The hinged structure model presented here can also be applied to other "lattice fence" topologies with little or no modification, depending on the symmetry of the molecular building blocks.
Two NbO-type MOFs based on ditopic pyridyl substituted diketonate ligands were reported. One exhibits a reversible SC-SC water encapsulation, while the other shows an interesting guest-driven luminescent property based on M(III) acetylacetonate (M = Eu and Fe) guest species.