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Self-assembly properties of Salamo-type trinuclear Cu(II) and Co(II) complexes based on the regulation of H+/OH-
Abstract
A novel naphthalenediol‐based bis(salamo)‐type tetraoxime compound (H4L) was designed and synthesized. Two new supramolecular complexes, [Cu3(L)(μ‐OAc)2] and [Co3(L)(μ‐OAc)2(MeOH)2]·4CHCl3 were synthesized by the reaction of H4L with Cu(II) acetate dihydrate and Co(II) acetate dihydrate, respectively, and were characterized by elemental analyses and X‐ray crystallography. In the Cu(II) complex, Cu1 and Cu2 atoms located in the N2O2 sites, and are both penta‐coordinated, and Cu3 atom is also penta‐coordinated by five oxygen atoms. All the three Cu(II) atoms have geometries of slightly distorted tetragonal pyramid. In the Co(II) complex, Co1 and Co3 atoms located in the N2O2 sites, and are both penta‐coordinated with geometries of slightly distorted triangular bipyramid and distorted tetragonal pyramid, respectively, while Co2 atom is hexa‐coordinated by six oxygen atoms with a geometry of slightly distorted octahedron. These self‐assembling complexes form different dimensional supramolecular structures through inter‐ and intra‐molecular hydrogen bonds. The coordination bond cleavages of the two complexes have occurred upon the addition of the H+, and have reformed again via the neutralization effect of the OH−. The changes of the two complexes response to the H+/OH− have observed in the UV–Vis and 1H NMR spectra. Two new supramolecular complexes have been synthesized and structurally characterized. The coordination bond cleavages of the two complexes have occurred upon the addition of H+, and reformed again via the neutralization effect of the OH−.
... Absorptions near 371 nm attributed to the n → π* transi- tion associated with azomethine red shift on complexation, indicating coordination of azomethine nitrogen. [36,37] These characteristic were consistent with common spectral features of d-block metal complexes and the spectral studies reveal octahedral geometry around M (II) for two complexes. [38] TABLE 3 Hydrogen bonding distances (Å) and angles (deg) of 1 and 2 ...
Two two‐dimensional and three‐dimensional supramolecular complexes [M (L)2] (NO3)2·2CH3OH (M = Cu(1) and Co(2), L = 2‐(4‐imidazolyl)‐4‐methyl‐1,2‐quinazoline‐N³‐oxide), were synthesized and characterized by FT‐IR and UV–Vis spectroscopy, as well as elemental analysis. The spectroscopic data of both complexes were compared with the ligand L. Both complexes were determined by X‐ray single‐crystal diffraction and display similar coordination geometry and have a 2:1 ligand‐to‐metal ratio. All the central M (II) atoms are hexa‐coordinated with perfect octahedral geometries. In the crystal structures, complexes 1 and 2 form an infinite 1‐D chain‐like and 2‐D, 3‐D supramolecular frameworks. X‐ray photoelectron spectrum (XPS) and thermal stability of 2 was investigated. Moreover, electrochemical properties and antimicrobial activities of both complexes were also studied.
The ligand 2-(3-ethoxy-2-hydroxyphenyl)-4-methyl-1,2-dihydroquinazolin 3-oxide (HL¹, H is the deprotonatable hydrogen) has been synthesized, and two metal complexes, namely [Ni(L²)2]·2CH3OH (1) and [Co(L²)2]·NO3·H2O (2) (where HL² =1-(2-{[(E)-(3-ethoxy-2-hydroxybenzylidene]amino} phenyl)ethanone oxime) were obtained via complexation reaction between HL¹ and nickel(II) acetate tetrahydrate or cobalt(II) nitrate hexahydrate. HL¹ and both complexes were characterized by elemental analysis, as well as compared by spectroscopic methods such as FT-IR, UV–Vis and fluorescence spectroscopy. X-ray crystallography revealed that both complexes have distorted octahedral geometries but with a different configuration of the two tridentate (L²)– ligands around the metal centers. Complex 1 contained two lattice methanol molecules whereas 2 were counterbalanced by a nitrate anion beside an uncoordinated water molecule. The crystal structures show a 2-D and 3-D supramolecular architecture due to intermolecular interaction. Electrochemical properties of both complexes were tested by cyclic voltammetry and Electron paramagnetic resonance (EPR) spectroscopy of 2 was also investigated. Fascinatingly, antibacterial efficiencies of all compounds were compared. Furthermore, molecular electrostatic potential (ESP) was computed for both complexes to predict the reaction sites of electrophilic and nucleophilic attacks. Density Functional Theory (DFT) calculations were done to ascertain the optimum geometric configurations. The non-covalent interaction was determined using the Hirshfeld program.
In this paper, a salamo-based copper(ii) complex probe L-Cu2+ was synthesized, which combined with copper(ii) ions to form L-Cu2+ for the detection of S2- and had a good fluorescence chemical response. Through spectral analysis, we found that S2- could be identified with high sensitivity and selectivity in the presence of various anions and could be used for the detection of S2- by the naked eye. With the addition of S2-, the solution color changed from colorless to bright yellow. UV absorption, fluorescence and other characterization methods were carried out, and the mechanism of action was determined. In addition, we performed a visual inspection of H2S gas, and the probe L-Cu2+ could detect S2- in the gas molecules, revealing its potential application value in biology and medicine.
The effective monitoring of water pollution and further purification are pressing yet challenging issues for guaranteeing the health of human and the stabilization of ecological system. For this purpose, the...
A series of hetero-trinuclear Zn(II) complexes, [Zn2Ca(L)(OAc)2]·CHCl3 (1), [Zn2Sr(L)(OAc)2] (2) and [Zn2Ba(L)(OAc)2] (3) with a bis(salamo)-type tetraoxime ligand H4L were synthesized and characterized by elemental analyses, IR, UV-vis spectra etc. Spectral titrations and X-ray crystallography clearly show that the stoichiometry of the heterotrinuclear complexes are all 1 : 2: 1 (ligand/Zn(II)/M(II)). The different natures of the N2O2 and O6 sites of the ligand H4L lead to the site-selective introduction of two different kinds of metal(II) atoms. All the Zn(II) atoms are penta-coordinated with distorted square pyramidal geometries. The coordination numbers of Ca(II), Sr(II) and Ba(II) atoms in the O6 environment are all 8, and they have slightly distorted square antiprism geometries. Furthermore, ion competitive experiments show that the coordinating capability in the central O6 site is in the order of Ca(II) > Sr(II) > Ba(II).
Three heterometallic Ni(II)–M(II) (M = Ca, Sr and Ba) complexes, two discrete heterotrinuclear complexes [Ni2(L)Ca(OAc)2(CH3OH)2]·2C2H5OH·2CHCl3 (1) and [Ni2(L)Sr(OAc)2(CH3OH)2]·2CH3OH·2CH2Cl2 (2) and a discrete heterohexanuclear dimer [Ni2(L)Ba(OAc)2(CH3OH)2(H2O)]2·2CH3OH (3), were synthesized with a naphthalenediol-based acyclic bis(salamo)-type ligand (H4L), and characterized by elemental analyses, IR, UV-vis spectra, fluorescence spectra and X-ray crystallography. The heterometallic complexes were acquired by the reaction of H4L with 2 equiv. of Ni(OAc)2·4H2O and 1 equiv. of M(OAc)2 (M = Ca, Sr and Ba). The crystal structures of complexes 1–3 have been determined by single-crystal X-ray diffractions. Owing to the different nature of the N2O2 and O6 sites of the ligand H4L, the introduction of two different metal(II) atoms to the site-selective moiety, leads to the two Ni(II) atoms occupied both the N2O2 sites, an alkaline earth metal atom occupied the O6 site of the ligand (L)⁴⁻ unit, respectively. Furthermore, the fluorescence properties have been discussed.
This paper reports the syntheses of two new complexes, [Co(L¹)(H2O)2] (1) and [{Zn(L²) (μ-OAc)Zn(n-PrOH)}2] (2), from asymmetric halogen-substituted Salamo-type ligands H2L¹ and H3L², respectively. Investigation of the crystal structure of complex 1 reveals that the complex includes one Co(II) ion, one (L¹)²⁻ unit and two coordinated water molecules. Complex 1 shows slightly distorted octahedral coordination geometry, forming an infinite 2D supramolecular structure by intermolecular hydrogen bond and π–π stacking interactions. Complex 2 contains four Zn(II)ions, two completely deprotonated (L²)³⁻ moieties, two coordinated μ-OAc⁻ ions and n-propanol molecules. The Zn(II) ions in complex 2 display slightly distorted trigonal bipyramidal or square pyramidal geometries.
An erbium (III) complex of a pentadentate Schiff base ligand [(NO3)Er(μ-L)2Er(NO3)].2H2O [H2L=bis(N-salicylidene)-3-oxapentane-1,5-diamine] has been synthesised, characterised and its structure confirmed by
X-ray crystallography. H2 L and the Er(III) complex both bind to DNA via a groove binding mode, and the Er(III) complex binds to DNA more strongly than H2 L. The complex shows strong scavenging effects for hydroxyl radicals (OH·) and superoxide radicals (O2
–·).
The tri-nuclear cobalt(II) complex, [(CoL)2(μ-OAc)2Co]·2CHCl3(H2L = 5,5'-dimethoxy-2,2'-[(ethylene)dioxybis(nitrilome thylidyne)]diphenol), has been synthesised. Its X-ray structure shows it to contain two acetate ions coordinating to the three cobalt(II) atoms through Co–O–C–O–Co bridges, and four μ-phenoxo-oxygen atoms from two [CoL] chelates also coordinating to the central cobalt(II) atom. The complex possesses two penta- and one hexa-coordinated cobalt atoms. The crystal packing of the CoII complex shows that a 2D-layer supramolecular network parallel to the ab-plane is formed through intermolecular C–H···O and C–H···Cl hydrogen bonding interactions.
The emergence of multi-drug resistant bacteria compounded by depleting arsenal of antibiotics has accelerated efforts towards development of antibiotics with novel mechanism of action. In this report we present a series of small molecular antibacterial peptoid mimics which exhibit high in-vitro potency against a variety of Gram-positive and Gram-negative bacteria, including drug-resistant species such as methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecium. Highlight of these compounds is their superior activity against the major nosocomial pathogen Pseudomonas aeruginosa. Non-toxic towards mammalian cells, these rapidly bactericidal compounds primarily act by permeabilization and depolarization of bacterial membrane. Synthetically simple, selectively antibacterial these compounds can be developed into a newer class of therapeutic agents against multi-drug resistant bacterial species.
A new dinuclear Ni(II) complex, [{Ni(L)(C5H5N)}2], has been synthesized with 4-chloro-4′,6′-dibromo-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol (H2L), and characterized by elemental analyses, FT-IR, UV/Vis, molar conductance and X-ray crystallographic analysis. Each Ni(II) atom is located at a N2O2 coordination site of a completely deprotonated (L)²⁻ unit. Two μ-phenoxo oxygen atoms from two [Ni(L)] units and two pyridine nitrogen atoms coordinate with two Ni(II) atoms. The two hexa-coordinated Ni(II) atoms have slightly distorted octahedral geometries. The μ-phenoxo bridges play important roles in assembling Ni²⁺ and (L)²⁻ units. This 2:2 (Ni²⁺:(L)²⁻) structure is different from that of other Salamo-type Ni(II) complexes reported earlier.
Two mono- and dinuclear Ni(II) complexes, [Ni(L³)2]·2H2O (1) (HL³ = 1-(2-{[(E)-3-methoxy-2-hydroxybenzylidene]amino}phenyl)ethanone oxime) and [Ni2(L⁴)2(CH3COO)2] (2) (HL⁴ = 1-(2-{[(E)-2-hydroxybenzylidene]amino}phenyl)ethanone oxime), have been synthesized via complexation of Ni(II) acetate tetrahydrate with HL¹ and HL² (HL¹ = 2-(2-hydroxy-3-methoxyphenyl)-4-methyl-1, 2-dihydroquinazoline 3-oxide, HL² = 2-(2-hydroxyphenyl)-4-methyl-1, 2-dihydroquinazoline 3-oxide) originally. HL¹, HL², and two Ni(II) complexes were characterized by IR, UV-Vis, and fluorescence spectroscopy, as well as by elemental analysis, respectively. The spectroscopic data of two Ni(II) complexes were compared with the ligands HL¹ and HL². The differently geometric features of the obtained complexes 1 and 2 are observed by X-ray crystallography. In the crystal structure, complexes 1 and 2 form an infinite 1-D chain and 2 into 2-D supramolecular frameworks. The electrochemical properties of 1 and 2 were also investigated by cyclic voltammetry. Moreover, thermal property of 1 was also studied. In addition, the antimicrobial activity of HL¹, HL², and complexes 1 and 2 were also investigated.
A new tetranuclear Zn(II) complex, [{Zn(L)(μ-OAc)Zn(H2O)}2], based on an asymmetrical salamo-type bisoxime chelating ligand H3L (6-hydroxy-4′-chloro-2,2′-[ethylenediyldioxybis(nitrilomethylidyne)]diphenol) was synthesized and characterized by elemental analyses, differential thermal methods, single-crystal X-ray crystallography, and IR, UV–vis, and fluorescence spectra. The Zn(II) complex crystallizes in the triclinic system, space group P-1 with cell parameters a = 9.0742(6) Å, b = 11.8225(5) Å, c = 12.4182(8) Å, Z = 2, V = 1212.56(12) Å3 , R 1 = 0.0572, and wR 2 = 0.1734. The environment of the tetranuclear Zn(II) complex is penta-coordinated having a slightly distorted trigonal bipyramidal geometry. Moreover, a 1D chain supramolecular structure is formed along the c-axis by the intermolecular C1–H1B⋯O14 hydrogen bonds; in the same manner, C2–H2C⋯Cg2 functions in the formation of supramolecular structures along the a-axis of the 1D chain. A 2D supramolecular structure along the ac plane extends infinitely under the force of intermolecular hydrogen bonds. Differential scanning calorimetry-thermogravimetry thermal analysis provides evidence of the coordination of Zn(II) atoms to the ligand H3L. The Zn(II) complex shows intense photoluminescence with a maximum emission at ~453 nm upon excitation at 360 nm.
Four 3d–4f heteronuclear complexes, [(ZnL)2La(OAc)2]·ClO4·2CHCl3 (1), [(ZnL)2La(OAc)2]·CF3SO3·H2O (2), [ZnNd(L)(Py)(NO3)3] (3) and [ZnGd(L)(OAc)(NO3)2] (4) (Py = pyridine; H2L = 6,6’-dimethoxy-2,2’-[ethylenedioxybis(nitrilomethylidyne)]diphenol), have been prepared by one-pot reaction of H2L with zinc(II) acetate, lanthanide(III) ions and Py. Although the heterobinuclear complexes 1-4 are prepared in the same reaction condition, the Py does not coordinate to Zn(II) of 1, 2 and 4. Instead, the bridging μ-acetato ligand is present. The coordination of the Py in 3 leads to smaller distortion of square pyramidal coordination site of Zn(II), the higher coplanarity between the planes of ZnO(phenoxo)2 and LnO(phenoxo)2, and the longer Zn···Ln distance compared with 4. The luminescence properties of 1-4 have been discussed. The ligand (L2–) can sensitize NIR luminescence of Nd(III) ions.
Using 3-MeOsalamo H2L (H2L = 1,2-bis(3-methoxysalicylideneaminooxy)ethane) with Zn(OAc)2•2H2O, Ln(NO3)3•6H2O (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd and Tb) and 4,4'-bipy (4,4'-bipyridine) or H2bdc (terephthalic acid), three new families of heteromultinuclear ZnII–LnIII complexes: [{Zn(L)Ln(NO3)3(CH3OH)}2(4,4'-bipy)] (Ln = La (1•2CH3OH) and Ce (2)), [{Zn(L)Ln(NO3)3}2(4,4'-bipy)] (Ln = Pr (3), Nd (4), Sm (5), Eu (6), Gd (7) and Tb(8)), [{(ZnL)2Ln}2(bdc)2]•(NO3)2•2CHCl3 (Ln = Ce (9), Pr (10) and Sm (11•2CH3CH2OH)) and 2∞[Zn(L)Ln(bdc)1.5] (Ln = Eu (12) and Gd (13•2CHCl3)) were obtained, respectively. Complexes 1–8 are heterotetranuclear dimers based on [Zn(L)Ln] moieties which are linked through the exo-dentate 4,4'-bipy having nitrogen-donor atoms. Heterohexanuclear complexes 9–11 constructed from almost linear trinuclear cationic [(ZnL)2Ln] moieties which are linked through the exo-dentate (bdc)2- bearing oxygen-donor atoms. Two 2D coordination polymers 12 and 13 are also assembled by [Zn(L)Ln] units with (bdc)2- linker. Furthermore, the luminescence properties of complexes 1–13 have been studied. An appropriate and selective linker could enhance the construction of a Salamo-type zinc(II)–lanthanide(III) complex possessing efficient luminescent properties.
A novel Schiff-base oxime sensor H2L with the ONON chelating moieties was designed and synthesized based on condensation reaction. Different methods such as elemental analyses, FT-IR, ¹H and ¹³C NMR were fully utilized in characterizing the structure of sensor H2L. The UV–vis spectra of the Zn²⁺ complex exhibit four clear isosbestic points which may be assigned to the ONON moieties binding to Zn²⁺. Sensor H2L operates on the CHEF and PET mechanisms, and the tendency of Zn²⁺ to strongly enhance fluorescence of sensor H2L was explored. Fluorescence measurements show that sensor H2L has excellent fluorescent selectivity for Zn²⁺ over many other metal ions based on intramolecular charge-transfer, and the results demonstrate that the binding between sensor H2L and Zn²⁺ is chemically reversible. The crystal structure of the Zn²⁺ complex has been characterized by X-ray crystallography.
By self-assembly of a Salamo-type ligand H2L [H2L = 1,2-bis(3-methoxysalicylideneaminooxy)ethane] with Ni(OAc)2·4H2O, Ce(NO3)3·6H2O, and H2bdc (H2bdc = terephthalic acid), a novel NiII-CeIII heterometallic complex, [{Ni(L)Ce(NO3)2(CH3OH)(DMF)}2(bdc)], was obtained. Two crystallographically equivalent [Ni(L)Ce(NO3)2(CH3OH)(DMF)] moieties lie in the inversion center, and are linked by one bdc2– ligand leading to a heterotetranuclear dimer, in which the carboxylato group bridges the NiII and CeIII atoms. Moreover, the photophysical properties of the NiII-CeIII complex were studied.
Through the self-assembly of a Salamo-type ligand H2L (H2L = 1,2-bis(3-methoxysalicylideneaminooxy)ethane) with Ni(OAc)2·4H2O, Ln(NO3)3·6H2O (Ln(iii) = La(iii), Gd(iii), Tb(iii) and Dy(iii)) and Py (Py = pyridine) or 4,4′-bipy (4,4′-bipy = 4,4′-bipyridine) or H2bdc (H2bdc = terephthalic acid), nine new Ni(ii)-Ln(iii) heterometallic complexes [Ni(L)La(OAc)(NO3)2(Py)(CH3OH)]·CH3OH (1), [Ni(L)Dy(OAc)(NO3)2(Py)] (2), ¹∞[Ni(L)La(NO3)3(4,4′-bipy)(CH3OH)] (3), ¹∞[Ni(L)Tb(NO3)3(4,4′-bipy)] (4), [Ni(L)Dy(OAc)(NO3)2(4,4′-bipy)] (5), [{Ni(L)Ln(NO3)2(DMF)(CH3OH)}2(bdc)] (Ln = La (6) and Gd (7)) and [{Ni(L)Ln(NO3)2(DMF)}2(bdc)] (Ln = Tb (8) and Dy (9)) were obtained, respectively. The acetato ligand bridges the Ni(ii) and Ln(iii) (Ln = La (1) and Dy (2)) atoms in a μ2 fashion and the Py coordinates to the apical position by a nitrogen atom in the heterobimetallic complexes 1 and 2. Complexes 3 and 4 are 1D coordination polymers constructed from heterobimetallic [Ni(L)Ln] (Ln = La (3) and Tb (4)) units which are connected by the exo-dentate ligand 4,4′-bipy bearing nitrogen-donor atoms, but complex 5 is a heterobimetallic Ni(ii)-Dy(iii) complex which is prepared under the same reaction conditions as complexes 3 and 4. Four heterotetranuclear dimers were constructed from heterobimetallic [Ni(L)Ln] (Ln = La (6), Gd (7)), Tb (8) and Dy (9) units which are connected by the exo-dentate H2bdc ligand with oxygen-donor atoms. Magnetic measurements were performed on the Gd(iii), Tb(iii) and Dy(iii) complexes. © 2016 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
Five heterometallic Co(II)–Ln(III) complexes, a discrete heterodinuclear complex [CoLLa(Py)(NO3)3(CH3OH)] (1) (Py = pyridine), a heterotetranuclear dimer [Co2L2La2(4,4’-bipy)(NO3)6(CH3OH)2] (2) (4,4’-bipy = 4,4’-bipyridine) and three discrete heterodinuclear complexes [CoLLn(OAc)(NO3)2(CH3OH)] (Ln = Gd (3), Tb (4), Dy (5)), were synthesized with a hexadentate bisoxime ligand 1,2-bis(3-methoxysalicylideneaminooxy)ethane (H2L), and characterized by single crystal X-ray diffraction. The complexes 1, 3, 4 and 5 are discrete heterodinuclear structures, but the assembly of two dinuclear units [CoLLa(NO3)3(CH3OH)] and one 4,4’-bipyridine results in a discrete heterotetranuclear dimer 2. The Co(II) and La(III) atoms in the complexes 1 and 2 are penta- and decacoordinated, while the Co(II) and Ln(III) (Ln = Gd, Tb and Dy) atoms in the complexes 3, 4 and 5 are hexa- and nonacoordinated, respectively. Magnetic measurements were performed on the complexes 3, 4 and 5, where an intramolecular ferromagnetic interaction is found in the complex 3.
Employment of a multidentate salicylamide Salen-like ligand, 2-hydroxy-N-(2-(2-hydroxybenzylidene)amino)ethyl)benzamide (H3L), in aid of NO3‒ anions under weak basic conditions in ZnII-LnIII chemistry (Ln = Eu, 1 and Dy, 2 ) led to the isolation of two novel butterfly heterometallic dodecanuclear clusters with six LnIII ions occupying the body position and six ZnII ions the outer wing-tips sites. All of them are fully characterized by elemental analysis, FT-IR spectroscopy, TG analysis, single-crystal X-ray diffraction, and X-ray powder diffraction (XRPD) techniques. Luminescence studies indicate 1 exhibits dual emission, meanwhile 2 exhibit bright blue emission under visible light excitation. Furthermore, Magnetic susceptibility studies carried out for 2 indicate the magnetic exchange between DyIII ions revealed ferromagnetic interactions with interesting slow relaxation of magnetization of the SMM behavior.
Two multinuclear Co(II) complexes, [{Co(L)(i-PrOH)}2Co(H2O)]∙2CH3CN (1) and [{Co(L)(μ-OAc)Co(MeOH)2}2]∙2CH3COCH3 (2), have been synthesized with a new asymmetric Salamo-type ligand (H3L = 6-hydroxy-6′-ethoxy-2,2′-[ethylenediyldioxybis(nitrilomethylidyne)]diphenol). The Co(II) complexes were obtained by different solvents, and the structures are completely different. In the Co(II) complex 1, the ratio of the ligand H3L to Co(II) atom is 2 : 3 and the Co(II) ions are all five-coordinate with trigonal bipyramidal geometries. In the Co(II) complex 2, the ratio of the ligand H3L to Co(II) atom is 2 : 4. Two central Co(II) ions are six coordinate with distorted octahedral geometries and two terminal Co(II) ions are five coordinate with distorted trigonal bipyramidal geometries. Self-assembling of an infinite 1-D supramolecular chain is formed by C–H⋯π interactions in 1. Interestingly, an infinite 2-D-layer plane structure is formed by the self-assembling array of 2 linked by C–H⋯π interactions. 1 and 2 exhibit blue emissions with the maximum emission wavelengths λmax = 403 and 395 nm when excited at 330 nm.
Four new solvent-induced Ni(II) complexes with chemical formulae {[NiL(MeOH)(μ-OAc)]2Ni}·2MeOH (1), {[NiL(EtOH)(μ-OAc)]2Ni} (2), {[NiL(i-PrOH)(μ-OAc)]2Ni} (3) and {[NiL(DMF)(μ-OAc)]2Ni}·2DMF·0.44H2O (4), where H2L = 5-methoxy-4′-chloro-2,2′-[(1,3-propylene)dioxybis(nitrilomethylidyne)]diphenol, have been synthesized and characterized by elemental analyses, 1H NMR, FT–IR, UV–Vis spectra and X-ray crystallography. X-ray crystallographic analyses of the Ni(II) complexes reveal that they crystallize in the triclinic system, space group , and consists of three Ni(II) ions, two deprotonated L2− units, two μ-acetato ligands and two coordinated solvent molecules. In each of the Ni(II) complexes, the Ni(II) ions are hexa-coordinated with a slightly distorted octahedral coordination geometries. Although the molecule structures of the Ni(II) complexes are similar each other, obtained in different solvents, the supramolecular structures are entirely different. The complexes 1 and 3 possess a self-assembled infinite 2D and 1D supramolecular structures via the intermolecular hydrogen bonds, respectively. But the Ni(II) complexes 2 and 4 are formed 0D structures by intramolecular hydrogen bonds. Cyclic voltammetry is used to characterize electrochemical property of the Ni(II) complex 1.
A novel single-armed Salamo-type bisoximes (H3L) has been designed and synthesized firstly. A new application of Salamo-type bisoximes in ion recognition is investigated in detail. H3L can act as a relay-sensor for ratiometric recognition of Zn2+/Cu2+ with high selectivity and sensitivity. The Zn2+ and Cu2+ complexes behave successive sensing of H+/OH− through fluorescence intensity increasing (ON) and decreasing (OFF). Meanwhile, the crystal structures of the Zn2+ and Cu2+ complexes based on H3L, [Zn(L)(μ-OAc)Zn] and [Cu(L)(μ-OAc)Cu], have been determined by X-ray crystallographic analyses, respectively.
Three multinuclear complexes, [{Cu(HL)(OAc)Cu}2]·CH3OH, [Zn(HL)(OAc)Zn(CH3CH2OH)] and [{Cd(HL)(OAc)Cd(CH3CH2OH)}2]·2CHCl3, have been synthesized with an asymmetric Salamo-type ligand H4L, and characterized by FT-IR, UV-vis spectra and X-ray crystallography. The Cu(II) complex contains two crystallographically independent but chemically identical dinuclear complexes (molecules 1 and 2). Meanwhile, self-assembled infinite 1D, 2D and 3D structures are formed by intermolecular hydrogen bonds and C–H···π interactions of neighboring complexes in the solid state. The Zn(II) complex also forms a novel dinuclear structure. And a self-assembled infinite 2D structure is formed by C–H···π interaction of neighboring complexes in the solid state. Otherwise, the Cd(II) complex forms an infinite 1D structure by C–H···π interaction of the neighboring complex molecules. In addition, the photophysical properties of the Cu(II), Zn(II) and Cd(II) complexes have also been discussed.
A Schiff base ligand bis(5-methylsalicylaldehyde)-3-oxapentane-1,5-diamine (H2L) has been prepared. Reaction of the shape-specific designed ligand with MnAc2 afforded a new complex, namely, [Mn2L2Ac2] 1. The ligand and complex 1 were characterized by physic-chemical and spectroscopic methods. The crystal structure of complex 1 has been determined by single-crystal X-ray diffraction. It reveals a centrosymmetric binuclear neutral entity, in which Mn(III) ion is bridged by two ligand L and six-coordinated with the coordination surround of distorted octahedron geometry. The antioxidant activities of the ligand and complex 1 were in vitro determined by superoxide and hydroxyl radical scavenging methods, which indicates that the complex 1 exhibits better scavenging activity of hydroxyl radical and superoxide radical than the ligand. Moreover, under the excitation at room temperature, luminescence studies have been carried out on solution-state samples. The result of their fluorescence properties shows that the strong and characteristic luminescence for the ligand and complex. The complex 1 exhibited intense shift in the fluorescence band compare to the ligand attributed to the coupled effect of the metal and the ligand. Copyright © 2015 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany.
A new Co(ΙΙ) complex, [Co2(L)2]·CH3COCH3 based on an asymmetric Salamo-type ligand (H2L, 5-methoxy-4′,6′-dibromo-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol) has been synthesized and characterized structurally by elemental analyses, IR, UV-Vis and fluorescence spectra. The X-ray crystal structure shows the Co(II) ion is pentacoordinated with geometry of a distorted square-pyramidal symetry. The Co(ΙΙ) complex consists of two Co(ΙΙ) ions, two deprotonated L2- units, and one non-coordinated acetone molecule. Each Co(ΙΙ) complex molecule links four other molecules into an infinite 2D supramolecular structure. Meanwhile, the Co(II) complex exhibits emission with the maximum emission wavelength λmax = 432 nm when excited at λex = 349 nm.
Four new polynuclear complexes based on a versatile asymmetric ligand, [Cu2(H2L)2Cl2] (1), [Cu4(H2L)2(L)2]·4CH3OH (2), [MnL]n (3), [Er2(HL)2(NO3)4]·4CH3CN (4), H3L = 2-hydroxy-N-(2-((2-hydroxybenzylidene)amino)ethyl)benzamide], were prepared and structurally characterized. The coordination behavior as well as deprotonation of the H3L in the four complexes reveal considerable variations depending on the metal ions as well as counter anion. The hydroxyl-bridged dinuclear complex 1 with a Cu-O-Cu-O four-membered ring was obtained when copper chloride was used as metal source. The tetranuclear complex 2 with two Cu-O-Cu-O four-membered rings which bridged both through hydroxy and amide group was obtained using copper acetate instead. Reacting the ligand with manganese acetate yielded complex 3 which exhibits 1-D zig-zag chains only bridged through amide group. While complex 4 which holds a dinuclear one by aid of hydroxyl-bridge without nitrogen atom participating in coordination when erbium nitrate was introduced. The experimental magnetic susceptibilities indicate 1, 2 and 4 exhibit antiferromagnetic interactions through hydroxy bridge, while 3 exhibits dominant antiferromagnetic interactions with spin canting through the amido bridge.
An unexpected dinuclear Cu(II) complex, [Cu2(L2)2], has been synthesized via complexation of Cu(II) acetate monohydrate with a bis(Salamo) ligand H2L1. Catalysis of Cu(II) ions results in unexpected cleavage of two N-O bonds in H2L1, giving a dialkoxo-bridged dinuclear Cu(II) complex. Each Cu(II) complex possesses a Cu-O-Cu-O four-membered ring instead of the usual bis(Salamo) [Cu2L1] complex with H2L1. The H2L1 molecule is stabilized by intramolecular O1-H1···N1 hydrogen bonds and π···π stacking interactions linking adjacent molecules into a 1D infinite zigzag chain. In the structure of the Cu(II) complex, intermolecular hydrogen bonds have stabilized the Cu(II) complex to form a self-assembling infinite 1D linear chain. Furthermore, the H2L1 ligand shows intense photoluminescence with two emissions at ca. 370 and 464 nm upon excitation at 310 nm. The Cu(II) complex shows photoluminescence with maximum emission at ca. 423 nm upon excitation at 370 nm.
A new pentadentate chelate-bridging ligand possessing an inner N2O3 coordination site with one amide, one imine, and two phenoxo functions, 2-hydroxy-N-(2-(((3-hydroxynaphthalen-2-yl)methylene)amino)ethyl)benzamide (H3L), was synthesised. Reaction it with Mn(OAc)2⋅4H2O yielded a novel zigzag penta-coordinated Mn(III) coordination polymer, [MnL]n, due to the bridging ability of the amide function. The crystal structure of [MnL]n has been determined at 293 K which crystallizes in the monoclinic space group P21/c (No. 14): a = 16.0601(12) Å, b = 8.4048(6) Å, c = 12.7168(10) Å, β = 112.395(9), V = 1606.0(2) Å3, Z = 4. The experimental magnetic susceptibilities indicates the Mn(III) coordination polymer exhibits dominant antiferromagnetic interactions between the manganese centers through the amido bridge, and spin canting is observed with a ferromagnetic transition occurring at 8.5 K.
Novel ligands 1,2-bis(salicylideneaminooxy)ethanes were synthesized. They were much more stable against exchange reactions of aldehyde units than the corresponding salen derivatives. They form stable complexes with a copper(II) ion, whose structures were crystallographically determined. Spectroscopic and electrochemical studies indicated that the complexes have lower LUMO levels than salen analogues.
A pentadentate Schiff base bis(N-salicylidene)-3-oxapentane-1,5-diamine (H2L) and its lanthanide(III) complexes, [GdL(NO3)(DMF)(H2O)] (1) and [Dy2L2(NO3)2]·2H2O (2), have been synthesized and characterized by physical, chemical, and spectroscopic methods. Single crystal X-ray structure reveals that 1 is a discrete mononuclear species with nine-coordinate Gd(III) in a distorted mono-capped square antiprism geometry. Complex 2 is a centrosymmetric binuclear neutral entity, in which Dy(III) is eight-coordinate in a distorted square antiprism. Electronic absorption titration spectra, ethidium bromide competitive experiments, and viscosity measurements indicate that both the ligand and complexes bind calf thymus DNA, presumably via groove binding. Investigations of antioxidant activities show that both complexes have some scavenging effects for hydroxyl and superoxide radicals.
A new mononuclear Cu(II) complex, [Cu(L)2]·CH3OH·H2O, has been synthesized by the complexation of copper(II) acetate monohydrate with a new oxime-type ligand (HL = 1-(4-{[(E)-3-ethoxyl-2-hydroxybenzylidene]amino}phenyl)ethanone oxime) in methanol/acetone solution. The Cu(II) atom is four-coordinated by the phenolate O atoms and imine N atoms from two oxime-type ligands, in a distorted square-planar geometry. The O- and N-donor atoms are mutually cis and the dihedral angle between the two coordination plane (Cu1N2O2 and Cu1N4O5) is 48.06(3)°. In the crystal structure, each molecule links four other adjacent molecules into an infinite two-dimensional layer supramolecular structure through intermolecular O‒H···O hydrogen bonds.
Two new structure-related pyrazolone-type Salen ligands, N,N′-ethylamine bis[1-(4-methoxy-phenyl)-3-methyl-4-benzoylimino-2-pyrazoline-5-ol](H2LI) and N,N′-ethylamine bis[1-(4-methoxy-phenyl)-3-methyl-4-acetylimino-2-pyrazoline-5-ol](H2LII) have been designed and synthesized with the ultimate aim of self-assembling novel Zn(II) compounds with interesting fluorescence properties. Reactions of Zn(OAc)2 with the two ligands led to the formation of two new Zn(II) complexes with the formulae of [ZnLI(CH3OH)] (1) and [Zn2LII2] (2), which have been characterized by single-crystal X-ray diffraction, powder X-ray diffraction, elemental analysis, IR spectroscopy and thermal gravimetric analysis. Mononuclear complex 1 with the pentacoordinated zinc(II) ion hosted into the N2O3 compartment crystallized in the monoclinic space group P21/c, while the hydroxyl-bridged dinuclear [Zn2LII2] complex (2) with the pentacoordinated zinc(II) ion hosted into the N2O2 compartment crystallized in the monoclinic space group C2/c and had a Zn–O–Zn–O four-membered ring. The structure determinations show that substituted group at the 4,4′-position of the this kind of Salen ligands are important factors influencing the crystalline array. The fluorescent properties of the two compounds at ambient temperature both in solid state and solution were also investigated. The results provided interesting insights into ligand effects on the structures and fluorescent properties of zinc(II) coordination complexes.
A Schiff base bis(N-salicylidene)-3-oxapentane-1,5-diamine (H2L) and its Cu(II) complex, [Cu2(L)2]CHCl3, have been synthesized and characterized by physicochemical and spectroscopic methods. Single-crystal X-ray analysis revealed that the complex is a centrosymmetric binuclear neutral entity, in which Cu(II) is a five-coordinate in a distorted trigonal bipyramidal geometry. The DNA-binding properties of the free ligand and the complex have been investigated by electronic absorption, fluorescence, and viscosity measurements. The results suggest that the H2L and the complex to DNA via the intercalation mode and the binding affinity of the complex were higher than that of the H2L. The intrinsic binding constants K b of the ligand and the complex are 2.2 × 104 and 2.7 × 104 M−1, respectively. Antioxidant assay in vitro shows the Cu(II) complex possesses significant antioxidant activities and better scavenging activity than the H2L and other antioxidants.
The Schiff base N,N′-bis(salicylidene)-1,5-diamino-3-oxapentane (H2L) and its lanthanide(III) complexes, PrL(NO3)(DMF)(H2O) (1) and Ho2L2(NO3)2·2H2O (2), were synthesized and characterized by physicochemical and spectroscopic methods. Single crystal X-ray structure analysis revealed that complex 1 is a discrete mononuclear species. The PrIII ion is nine-coordinate, forming a distorted capped square antiprismatic arrangement. Complex 2 is a centrosymmetric dinuclear neutral entity in which the HoIII ion is eight-coordinate with distorted square antiprismatic arrangement. The DNA-binding properties of H2L and its LnIII complexes were investigated by spectrophotometric methods and viscosity measurements. The results suggest that the ligand H2L and its LnIII complexes both connect to DNA in a groove binding mode; the complexes bind more strongly to DNA than the ligand. Moreover, the antioxidant activities of the LnIII complexes were in vitro determined by superoxide and hydroxyl radical scavenging methods, which indicate that complexes 1 and 2 have OH· and O2–· radical scavenging activity.
Three copper(II) ternary complexes with the V-shaped ligand bis(2-benzimidazolylmethyl)amine (bba), with composition [Cu(bba)(crotonate)]·ClO4 (1), [Cu(bba)(methacrylate)]·ClO4 (2) and [Cu(bba)(acrylate)(CH3OH)]·NO3·H2O (3), have been synthesized and characterized by elemental analyses, molecular conductivities, IR, UV spectra and X-ray single crystal diffraction. The copper ions in these three complexes have a similar coordination mode, which can be described as a five-coordinated tetragonal pyramid geometry. The interaction of the ligand bba and copper(II) complexes with calf thymus DNA was investigated by electronic absorption, fluorescence spectroscopy and viscosity measurements. The experimental results suggest that the ligand bba and copper(II) complexes bind to DNA in an intercalation mode, and their binding affinity for DNA follows the order 2 > 1 > 3 > bba. The main reason for the DNA-binding behaviors can be attributed to the large coplanar aromatic rings in the V-shaped ligand. Such a trend in the DNA-binding affinities of the bba ligand and copper(II) complexes binding to DNA can be reasonably explained by the change of the electron density, the V-shaped angle (αV) and the value of τ. Moreover, the antioxidant assay in vitro also shows that the copper(II) complexes possess significant antioxidant activities.
A new Salen-type bisoxime ligand, 2,2'-[ethylenedioxybis(nitrilomethylidyne)]dinaphthol (H2L) and its corresponding cobalt(II) and nickel(II) complexes, [{CoL(DMF)}2(OAC)2Co] and [{NiL(H2O)}2(OAc)2Ni]⋅2C2H5OH have been synthesized, and characterized by elemental analyses, IR spectra, UV-vis spectra, TG-DTA and molar conductance measurements, etc. The X-ray crystal structure studies reveal that the cobalt(II) and nickel(II) complexes are symmetric trinuclear structures. All of the M(II) (Co(II) or Ni(II)) ions for the cobalt(II) or nickel(II) complexes are six-coordinated and have slightly distorted octahedral coordination geometries.
The new semirigid exo-bidentate ligand incorporating furfurysalicylamide terminal groups, namely, 1,4-bisf[(2 '-furfurylaminoformyephenoxyllmethyl}-2,5-bismethylbenzene (L) was synthesized and used as building blocks for constructing lanthanide coordination polymers with luminescent properties. The series of lanthanide nitrate complexes have been characterized by elemental analysis, IR spectroscopy, and X-ray diffraction analysis. The semirigid ligand L, as a bridging ligand, reacts with lanthanide nitrates forming three distinct structure types: chiral noninterpenetrated two-dimensional (2D) honeycomblike (6,3) (hcb, Schlafli symbol 6(3), vertex symbol 6 6 6) topological network as type I, 1D zigzag chain as type II and 1D trapezoid ladder-like chain as type III. The structural diversities indicate that lanthanide contraction effect played significant roles in the structural self-assembled process. The luminescent properties of Eu-III, Tb-III and Dy-III complexes are discussed in detail. Due to the good match between the lowest triplet state of the ligand and the resonant energy level of the lanthanide ion, the lanthanide ions in Eu-III, Tb-III and Dy-III complexes can be efficiently sensitized by the ligand.
A new mononuclear CdII complex, [CdL(H2O)2], with halogen-substituted Salen-type bisoxime ligand (H2L = 4,4′-dibromo- 6,6′-dichloro-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol), was synthesized and structurally characterized. The CdII complex crystallizes in the monoclinic system, space group C2/c. The CdII center exhibits a slightly distorted octahedral geometry with halogen-substituted Salen-type bisoxime ligand forming the basal N2O2 coordination plane and two oxygen atoms from the coordinated water molecules in the axial position. An infinite 1D metal-water chain is formed by intermolecular hydrogen-bonding and π-π stacking interactions of neighboring benzene rings.Supplemental materials are available for this article. Go to the publisher's online edition of Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry to view the supplemental file.
An unexpected mononuclear Ni(II) complex, [Ni(L2)2]·CH3OH (HL2 = 1-(2-{[(E)-3,5-dichloro-2-hydroxybenzylidene]amino}phenyl)ethanone oxime), has been synthesized via complexation of Ni(II) acetate tetrahydrate with HL1. HL1 and its corresponding Ni(II) complex were characterized by IR, 1H-NMR spectra, HRMS, as well as by elemental analysis, UV–vis, and emission spectroscopy. The crystal structure of the complex has been determined by single-crystal X-ray diffraction. Each complex links two other molecules into an infinite 1-D chain via intermolecular hydrogen bonds. Moreover, the electrochemical properties of the nickel complex were studied by cyclic voltammetry. Superoxide dismutase-like activities of HL1 and Ni(II) complex were also investigated.
A supramolecular CoII complex, [CoL(H2O)2], bearing Salen-type bisoxime chelate ligand 4,4′,6,6′-tetrachloro-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol (H2L), has been synthesized and structurally characterized by elemental analyses, IR spectra, UV–vis spectra, and X-ray diffraction techniques. The crystal structure of [CoL(H2O)2] indicates that the CoII complex consists of one CoII atom, one L2– unit, and two coordinated water molecules. The CoII complex exhibits slightly distorted octahedral geometry with the Salen-type bisoxime ligand forming the basal N2O2 coordination plane and two oxygen atoms from the coordinated water molecules in the axial positions. An infinite 1D metal–water chain and 2D supramolecular network structure were formed by intermolecular O-H···O, O-H···Cl, and C-H···O hydrogen bonding and π-π stacking interactions.Supplemental materials are available for this article. Go to the publisher's online edition of Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry to view the supplemental file.
A new Cu(II) complex, [Cu(L)2], has been synthesized via the complexation of copper(II) acetate monohydrate with a new oxime-type ligand (HL = 1-(3-{[(E)-3-bromo-5-chloro-2-hydroxybenzylidene]amino}phenyl)ethanone oxime). X-ray crystallographic analysis reveals that the complex is a mononuclear complex. The Cu(II) atom is four-coordinated by the phenolate O atoms and imine N atoms from two oxime-type ligands, in a square-planar geometry in which the dihedral angle of two coordination plane (Cu1N1O1 and Cu1N#1O#1) is 0°. The crystal packing of the Cu(II) complex shows that a notable feature of this structure resides in the formation of a novel 3D supramolecular networks through intermolecular O–H···N, C–H···O, and C–H···π interactions.Supplemental materials are available for this article. Go to the publisher's online edition of Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry to view the supplemental file.
A Schiff base ligand bis(N-salicylidene)-3-oxapentane-1,5-diamine H2L have been prepared. Reaction of the shape-specific designed ligand with Ln(NO3)3⋅6H2O afforded three novel complexes, namely, Sm(L)(NO3)(DMF)(H2O) 1, [Eu(H2L)2(NO3)3]n2 and Tb2(L)2(NO3)23. The ligand and complexes were characterized by elemental analysis, UV–Vis, IR, NMR spectroscopy and X-ray crystallography. It is noteworthy that the complexes demonstrate three different types of the structure which changed according to the charge density and acidity of the lanthanide. Complex 1 is a discrete mononuclear species that Sm(III) ion is nine-coordinated in the structure and forming a distorted tricapped trigonal prism geometry. Complex 2 is possessed a 1-D ribbon framework constructed from an extended array of ten-coordinated Eu³⁺ centers and the Schiff base ligands. Complex 3 is revealed as a centrosymmetric binuclear neutral entity, in which Tb(III) ion is eight-coordinated with the coordination surround of distorted square antiprism geometry. In order to explore the relationship between the structure and biological properties, the DNA-binding properties have been investigated by electronic absorption, fluorescence, and viscosity measurements. The results suggest that the ligand and complexes bind to DNA via groove modes. The intrinsic binding constants Kb of the complexes 1–3 are (1.19 ± 0.112) × 10⁵, (4.22 ± 0.086) × 10⁴ and (3.89 ± 0.104) × 10⁴ M⁻¹ respectively. Moreover, the antioxidant activity experiments show that these compounds also exhibit good antioxidant activities against OH and O2⁻ in vitro studies.
Helicity of single-helical metal complexes, [(LZn3La)-Zn-1](3+) and [(LZn2La)-Zn-2](3+), was dynamically controlled by coordination of chiral carboxylate ions such as mandelate ion. Spectroscopic investigation indicated that two chiral carboxylate ions contribute to the dynamic helicity control. In addition, the coordination of the carboxylate ions resulted in a nonlinear response in the dynamic helicity control. (c) 2014 Elsevier Ltd. All rights reserved.
A new complex of ytterbium(III) nitrate with bis(N-salicylidene)-3-oxapentane-1,5-diamine (H2L), with the composition Yb2(L)2(NO3)2·2H2O, was synthesized and characterized by physic-chemical and spectroscopic methods. The crystal structure of the ytterbium(III) complex has been determined by single-crystal X-ray diffraction. It reveals a centrosymmetric binuclear neutral entity where Yb(III) metal centers are bridged by two phenoxo oxygen atoms. Electronic absorption titration spectra, ethidium bromide displacement experiments, and viscosity measurements indicate that both the ligand and the Yb(III) complex can bind calf thymus DNA, presumably via a groove binding mechanism. Furthermore, the antioxidant activities of the Yb(III) complex were determined by a superoxide and hydroxyl radical scavenging method in vitro, which indicates that it is a scavenger for OH and O2− radicals.
Development of artificial helical molecules that can undergo responsive helicity inversion has been a challenging research target in functional molecular chemistry. However, most of reported helicity inversions are based on a single-mode transition, i.e., the conversion between right- and left-handed states. We report here the first molecular system that allows the stepwise multi-sequential helicity inversion utilizing metal exchange of helical complexes derived from a hexaoxime ligand H6L1. The ligand H6L1 underwent a four-step conversion (H6L1 → L1Zn3 → L1Zn5 → L1Zn3Ba → L1Zn3La) upon sequential metal addition (Zn2+, Ba2+, then La3+). Associating with the conversion, three-step helicity inversion took place (L1Zn3, right-handed → L1Zn5, left-handed → L1Zn3Ba, right-handed → L1Zn3La, left-handed). This is the first example of stepwise multi-mode helicity inversion of a discrete molecule, which could be useful as a platform for construction of dynamic regulation systems with multiple asymmetric functions.
A new dinuclear Cu complex, [Cu2(3-MeOSalamo-2)(H2O)3]·2pic·CH3COCH3·H2O, has been synthesized by the reaction of copper(II) picrate tetrahydrate with H2(3-MeOSalamo-n) (n = 2). X-ray crystallographic analysis reveals that the complex is a dinuclear structure when the O-alkyl chain length is relatively short (two CH2 groups), while a tetranuclear structure is obtained when the O-alkyl chain length becomes longer (four CH2 groups). In the complex, the μ-phenoxo bridging, picratol, and intermolecular hydrogen bonds play important roles in assembling Cu ions and ligands. Interestingly, the complex not only has a helical chain, but has an infinite metal–water chain supramolecular structure.
A supramolecular Cu complex, [Cu(L)(H2O)] (H2L: 4,4′,6,6′-tetrachloro-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol), has been synthesized and structurally characterized. X-ray crystallographic analysis shows that the complex is a centrosymmetric mononuclear Cu complex, and the Cu atom is penta-coordinated by two phenolic O atoms and two oxime N atoms from the deprotonated Salen-type ligand, and one oxygen atom from the coordinated water molecule. A self-assembling continual supramolecular structure is formed by intermolecular O3-H3···O2 and O3-H3···Cl1 hydrogen bonds.
An unexpected dinuclear Cu(II) complex, [Cu2(L)2] (H2L= 3-methoxysalicylaldehyde O-(2-hydroxyethyl)oxime), has been synthesized via complexation of Cu(II) acetate monohydrate with H4L. Catalysis by Cu(II) results in unexpected cleavage of two N–O bonds in H4L, giving a dialkoxo-bridged dinuclear Cu(II) complex possessing a Cu–O–Cu–O four-membered ring core instead of the usual bis(salen)-type tetraoxime Cu3–N4O4 complex. Every complex links six other molecules into an infinite-layered supramolecular structure via 12 intermolecular C–H ··· O hydrogen bonds. Furthermore, Cu(II) complex exhibits purple emission with maximum emission wavelength λmax = 417 nm when excited with 312 nm.