Template Synthesis of Macrocyclic Compounds
... For some time, semi-and thiosemicarbazones have been a subject of interest to researchers of different profi les. In view of the fact that these organic compounds form with many metals complexes of diverse chemical, physical and structural characteristics, they are of special interest for the specialists in coordination chemistry [1][2][3][4][5]. In addition, many of these organic reagents as well as their metal complexes, have shown a wide spectrum of biological activity, so that they have also become a subject of intense research for pharmacologists [6]. ...
... A number of complexes, primarily of transition metals, involving thiosemicarbazones of different denticity have been prepared and investigated [1][2][3][4][5][6][7][8]. In contrast to thiosemicarbazide fragment, which ones are usualy coordinated via azometinic nitrogene and sulfur atoms, the isothiosemicarbazides and their derivatives, as a rule, involve for coordination the nitrogen atom of the isothioamide group instead of the sulfur [3,9]. ...
... A number of complexes, primarily of transition metals, involving thiosemicarbazones of different denticity have been prepared and investigated [1][2][3][4][5][6][7][8]. In contrast to thiosemicarbazide fragment, which ones are usualy coordinated via azometinic nitrogene and sulfur atoms, the isothiosemicarbazides and their derivatives, as a rule, involve for coordination the nitrogen atom of the isothioamide group instead of the sulfur [3,9]. ...
This work is devoted to the investigation of the template reactions of organic compounds derived from S-alkylisothiosemicarbazide and β-dicarbonylic compounds (acetyl(benzoyl)acetone, 2,6-diformylpyridine, 2,6-diformyl-4-methylphenol, 1-hydroxy-2-naphthaldehyde, sodium nitromalonic dialdehyde, 1,1,3,3-tetraetoxypropane, 3-ethoxyacroleine) in the presence of 3d-metal ions, determination of the structure and properties of the prepared complexes. There were elaborated original methods for synthesis of open-chain or macrocyclic coordination compounds of nickel(II), copper(II), oxovanadium(IV) and cobalt(II) with N4, N3O and N2O2 tetradentate ligands. Two types of hexaazamacrocyclic systems with trans- and cis- arrangement of thiosemicarbazide fragments have been obtained using template condensation of different precursors. The biostimulative properties (biomass accumulation and increasing of enzymatic activity) of complexes have been established. Some complexes of nickel(II) have been studied as coloring agents for plastics.
... So, it is of interest how macrotetracyclic metal chelates with different numbers of atoms in chelate rings, in which 6-membered chelate rings have two shared atoms and which have not yet been considered in terms of the DFT method, would behave in a structural aspect. These metal chelates are exemplified by coordination compounds of general formula I with a "structurally rigid" 17-membered (NNNN)-donor macrocyclic ligand; according to [6,7]; they can be formed upon template synthesis in MCl 2 -1-amino-{2-[(2-aminophenyl)amino]ethyl}aminobenzene-di(2-formylphenyl)amine (M = Cu or Zn) systems by gross scheme (1). We should mention that only the formation of copper (II) and zinc(II) complexes was stated in [6,7]; the possibility for other d elements to form M(II) complexes in similar reactions was not discussed. ...
... These metal chelates are exemplified by coordination compounds of general formula I with a "structurally rigid" 17-membered (NNNN)-donor macrocyclic ligand; according to [6,7]; they can be formed upon template synthesis in MCl 2 -1-amino-{2-[(2-aminophenyl)amino]ethyl}aminobenzene-di(2-formylphenyl)amine (M = Cu or Zn) systems by gross scheme (1). We should mention that only the formation of copper (II) and zinc(II) complexes was stated in [6,7]; the possibility for other d elements to form M(II) complexes in similar reactions was not discussed. No pieces of relevant information can be found in recent publications on the structural chemistry of template complexes either. ...
... First, in order to estimate their degree of non-coplanarity; second, in order to elucidate whether coordination compounds of similar structures can exist for complex-forming M(II) ions of other 3d elements, namely, for Mn(II), Fe(II), Co(II), and Ni(II). Third, it was suggested [6,7] that a donor-acceptor bond occurs between the M atom and the nitrogen atom of the "imine" group NH in these metal chelates, while three fused 5-membered rings and two fused 6-membered rings should exist in these complexes. This conclusion might be doubtful as the structural formula I implies that the distance between those atoms should be too large for a chemical bond to appear between them. ...
... Nickel(II) complexes with S-substituted isothiosemicarbazides (H 2 NNC(SR)NH 2 ) and isothiosemicarbazones (R 1 R 2 C=NNC(SR)NH 2 ) are known for their redox properties. The isothiocarbohydrazides (NH 2 NC(SR) NHNH 2 ) and the isothiocarbohydrazones (R 1 R 2 C=NNC(SR) NHNH 2 ) are closely related derivatives that exhibit redox non-innocent behavior [31,32]. Recently, we have reported several new nickel(II) complexes with 14-and 15-membered octaazamacrocyclic ligands [33]. ...
... In addition, B3LYP calculations with the 6-311G** basis set [27][28][29][30][31][32][33][34] have been taken into account as well as the implicit integral equation formalism polarizable continuum model (IEFPCM) [50,51] of CH 2 Cl 2 to compare with the energetics of the in vacuo B3LYP/6-31G* calculations. Unless otherwise stated, in vacuo B3LYP/6-31G* calculations were reported. ...
The anti (a) to syn (s) isomerization pathway of the deprotonated form of the dimer with two nickel(II) 15-membered octaazamacrocyclic units connected via a carbon–carbon (C–C) σ bond was investigated. For the initial anti (a) structure, a deprotonation of one of the bridging (sp³ hybridized) carbon atoms is suggested to allow for an a to s geometry twist. A 360° scan around the bridging C–C dihedral angle was performed first to find an intermediate geometry. Subsequently, the isomerization pathway was explored via individual steps using a series of mode redundant geometry optimizations (internal coordinates potential energy surface scans) and geometry relaxations leading to the s structure. The prominent geometries (intermediates) of the isomerization pathway are chosen and compared to the a and s structures, and geometry relaxations of the protonated forms of selected intermediates are considered.
Supplementary Information
The online version contains supplementary material available at 10.1007/s00214-024-03100-5.
... The chemistry of polyazamacrocycles (PAMs) is currently one of the most rapidly developing areas of heterocyclic chemistry [1][2][3][4][5][6]. The great interest in PAMs is primarily due to their ability to bind various cations, anions, and neutral molecules [7][8][9][10][11][12][13][14]. ...
... Mp 285.5-286. 5 ...
The transformation of 3-[(ethoxymethylene)amino]-1-methyl-1 H -pyrazole-4-carbonitrile into the 14-membered macrocycle, 2,10-dimethyl-2,8,10,16-tetrahydrodipyrazolo[3,4- e :3',4'- l ][1,2,4,8,9,11]hexaazacyclotetradecine-4,12-diamine, by the reaction with excess hydrazine under various conditions was studied in detail. The reaction proceeded through the initial formation of 4-imino-2-methyl-2,4-dihydro-5 H -pyrazolo[3,4- d ]pyrimidin-5-amine followed by dimerization to give the final macrocycle. A convenient synthesis of the latter starting from 4-imino-2-methyl-2,4-dihydro-5 H -pyrazolo[3,4- d ]pyrimidin-5-amine was developed. A plausible pathway for the macrocycle self-assembly is discussed. Some features of the structure and reactivity of the obtained macrocycle are outlined.
... Reaction of the template synthesis [1] of the boron-capped iron(II) macrobicyclic complexes (clathrochelates [2,3] ) of a general formula FeD 3 (BR) 2 (where D 2À is the alicyclic α-dioximate dianion, R is the apical substituent at a capping boron atom) are known [2] to be the unique objects for studying of the kinetics and thermodynamics of their coordination-driven selfassembly from three chelating and two cross-linking ligand synthons on the iron(II) ion as a matrix. Indeed, the aforementioned reactions proceed in the quantitative yields with respect to Fe 2 + ions at the conditions of kinetic experiments in the solutions (i. ...
... The sample was applied to a steel plate, 2,5-dihydroxybenzoic acid was used as a matrix. The accuracy of measurements was 0.1 %. 1 H and 13 C{ 1 H} NMR spectra of this complex were recorded from its CDCl 3 solution with a Varian Inova 400 spectrometer. The measurements were done using the residual signals of this deuterated solvent. ...
Reaction of the template synthesis of the methylboron‐capped iron(II) tris‐heptoximate clathrochelate on Fe²⁺ ion as a matrix was found to proceed in the quantitative yield in diluted aqueous‐organic solutions. This complex is intensively colored in the visible range, whereas the initial ligand synthons are optically silent, thus allowing to photometric study the kinetics of its synthesis and acidic decomposition reactions. Template condensation of the corresponding chelating and capping ligand synthons gave a solid form of this macrobicyclic complex, which was characterized using modern spectral methods and by the single‐crystal X‐ray diffraction (XRD) experiment. Kinetic schemes and parameters of the aforementioned reactions for the methylboron‐capped clathrochelates, the derivatives of six‐ (H2Nx), seven‐(H2Gx) and eight(H2Ox)‐membered alicyclic α‐dioximes, are dramatically affected by their alicyclic ring size. If the general schemes of their formation persist, those for H2Nx and H2Gx contain a rate‐determining stage, whereas that for H2Ox has three initial consecutive stages with close rates. Passing from H2Nx to H2Gx caused a decrease in the synthesis reaction rates of their macrobicyclic derivatives by approximately three orders of magnitude. These kinetic effects were explained using the XRD data for the initial α‐dioximes and for their methylboron‐capped macrobicyclic derivatives.
... The favourable enthalpy for the formation of the metalligand bonds dominated over the unfavourable entropy from the ordering of the multidentate ligand around the metal ion, thereby enhancing the cyclisation reaction [27]. Hence, the synthesis of macrocyclic compounds through the template effect method is contributed by the combination of pre-ligand and metal ions, as illustrated in Scheme 3 [28]. The macrocyclic product is electrophilically alkylated with 1,2-bis(bromomethyl) benzene, while [Ni(L4)] acts as the template. ...
... The preparation of [Ni(L5)Br2] through kinetic coordination template effect[28] Scheme 4. Demetallation of Ni(II) to obtain metal-free macrocyclic ligand[29] ...
Various methods have been developed for the synthesis of azamacrocyclic ligands and their derivatives, which varies from the selection of amino group, ionic compound, and solvent. Among the popular methods include the rigid group method, high dilution method, and the template metal effect method. Recently, researchers have considered the non-template method as a promising and effective approach to produce a higher yield of metal-free azamacrocyclic ligands compared to the conventional approaches. Hence, this review presented an overview of the synthesis and structure of azamacrocyclic compounds through conventional methods and the newly developed non-template method. The advantages and disadvantages related to each technique were also highlighted.
... Macrocyclic chemistry [1,2] constitutes now a separate area of research which belongs to the more general field of supramolecular chemistry. [3][4][5][6] Macrocycles are well established, very important and multifunctional compounds which have found diverse applications. ...
... The distribution and the number of particular products in such a library can be influenced by the reaction conditions (temperature, kind of solvent, concentration of substrates) and/or by the introduction of a suitable templating agent. [2] Condensation products of 2,6-diformylpyridine (DFP) with trans-1,2-diaminocyclohexane (DACH) [30][31][32][33] or trans-1,2-diaminocyclopentane (DACP) [34][35][36][37][38] may serve as examples of such dynamic libraries. ...
The condensation of enantiopure trans‐1,2‐diaminocyclopentane (DACP) with 2,6‐diformylpyridine (DFP) followed by reduction results in a mixture of 2+2, 3+3, 4+4, and 5+5 macrocyclic amines. The replacement of DACP in this condensation with the 2+1 diamine containing two DACP and one DFP moieties afforded the 4+4 macrocycle as the main product together with a giant 6+6 macrocycle. Conversely, a similar reaction of DACP with the 1+2 dialdehyde, comprising of one DACP and two DFP units, results in the 2+2 macrocycle, whereas the condensation of both 2+1 diamine and 1+2 dialdehyde precursors delivers selectively the 3+3 macrocycle. The formation of larger macrocycles in the condensation of the 2+1 primary diamine with DFP and lack of such preference in the reaction of DACP with the 1+2 dialdehyde was supported by theoretical calculations. The crystal structures of the protonated 2+2, 3+3, 4+4 and 6+6 macrocyclic amines indicate binding of chloride or sulfate anions within the macrocycles.
... 26 The isothiocarbohydrazides (NH 2 NC-(SR)NHNH 2 ) and isothiocarbohydrazones (R 1 R 2 CNNC-(SR)NHNH 2 ) are closely related derivatives and might also exhibit redox noninnocent behavior. 27 Moreover, vanadium-(V) complexes with Schiff bases of carbohydrazone (H 2 NNHCONHNH 2 ) were found to be efficient in peroxidative oxidation of cyclohexane in cyclohexanol and cyclohexanone under solvent-free low-power microwave (MW) irradiation. The key role of the carbohydrazone ligand, which might undergo reduction to an active form of the catalyst, was suggested from density functional theory (DFT) calculations. ...
... Anal. Calcd for C 27 Crystallographic Structure Determination. X-ray diffraction quality single crystals of 3−5 were grown by slow evaporation of chloroform−ethanolic solutions. ...
Nickel(II) complexes with 15-membered (1-5) and 14-membered (6) octaazamacrocyclic ligands derived from 1,2- and 1,3-diketones and S-methylisothiocarbohydrazide were prepared by template synthesis. The compounds were characterized by elemental analysis, electrospray ionization mass spectrometry, IR, UV-vis, 1H NMR spectroscopies, and X-ray diffraction. The complexes contain a low-spin nickel(II) ion in a square-planar coordination environment. The electrochemical behavior of 1-6 was investigated in detail, and the electronic structure of 1e-oxidized and 1e-reduced species was studied by electron paramagnetic resonance, UV-vis-near-IR spectroelectrochemistry, and density functional theory calculations indicating redox noninnocent behavior of the ligands. Compounds 1-6 were tested in the microwave-assisted solvent-free oxidation of cyclohexane by tert-butyl hydroperoxide to produce the industrially significant mixture of cyclohexanol and cyclohexanone (i.e., A/K oil). The results showed that the catalytic activity was affected by several factors, namely, reaction time and temperature or amount and type of catalyst. The best values for A/K oil yield (23%, turnover number of 1.1 × 102) were obtained with compound 6 after 2 h of microwave irradiation at 100 °C.
... The soft and hard base containing thiosemicarbazone ligand has the diversity to coordinate with metal. So, attention is grown to these compounds day by day [24][25][26][27][28][29]. The ligand exhibits flexible coordination only by two coordinating sites, although it has three available options. ...
... By the beginning of the 21st century, the number of publications on the synthesis and study of the physicochemical properties of macrocyclic metal complexes was already in the thousands; at the same time, they included not only original articles and reviews, but also special monographs (see, in particular, refs. [3][4][5][6]). In this connection, it should be noted that the vast majority of these compounds (both open-and closed-loop) contain d-metal ions and polydentate organic ligands with donor nitrogen, oxygen and sulfur atoms. ...
The concept of “macrocyclic compounds” combines very different classes of chemicals that contain nine or more atoms in the macrocycle; macroheterocyclic compounds, the macrocycle of which contains at least one heteroatom, are also distinguished among them [...]
... [1][2][3][4][5] In the template synthesis of macrocyclic oligomers signicant progress has been made since the pioneering work of Pederson. [6][7][8][9][10][11][12][13] Templating the synthesis of linear oligomers involves an additional level of challenge, because the product contains reactive terminal groups that are not present in the corresponding macrocycles. Further oligomerisation of linear products must therefore be blocked by controlling the reaction time or concentration, or by using end-capping reagents. ...
Sandwich complexes formed by two zinc porphyrins and a diamine ligand (DABCO) have been used as a supramolecular template to direct the synthesis of triazole oligomers. Monomer units equipped with two polymerizable functional groups, an alkyne and an azide, were attached to the template via ester bonds between a phenol unit on the monomer and benzoic acid units on the porphyrin. Self-assembly of the zinc porphyrins by addition of DABCO led to a supramolecular complex containing four of the monomer units, two on each porphyrin. CuAAC oligomerisation was carried out in the presence of a chain capping agent to prevent intermolecular reactions between the templated products, which carry reactive chain ends. The templated-directed oligomerisation resulted in selective formation of a duplex, which contains two identical chains of triazole oligomers connecting the porphyrin linkers. The effective molarity for the intramolecular CuAAC reactions on the template is 3-9 mM, and because the triazole backbone has a direction, the product duplex was obtained as a 4 : 1 mixture of the parallel and antiparallel isomers. Hydrolysis of the ester bonds connecting the oligomers to the template gave a single product, the phenol 2-mer, in excellent yield. The introduction of a supramolecular element into the template considerably broadens the scope of the covalent template-directed oligomerisation methodology that we previously developed for the replication of sequence information in synthetic oligomers.
... At the same time, open-chain aliphatic tetraamines like L (L = 1,4,8,11-tetraazaundecane, C 7 H 20 N 4 ), which is the closest structural and electronic analogue of cyclam, are practically unexploited in this respect and only one work dealing with the crystal structures of MOFs formed by the [Ni(L)] 2+ cation with tris(4carboxylatobenzyl)amine has been reported to date (Jiang et al., 2012). Besides, the [M(L)] synthons (M = Cu II , Ni II ) are convenient precursors for the one-pot template preparation of corresponding metal complexes of 14-membered azacyclam macrocycles (azacyclam = 1,4,8,11,13-pentaazacyclotetradecane) (Rosokha et al., 1993;Gerbeleu et al., 1999) and some complexes of this type functionalized at the N 13 position of the macrocyclic backbone have been structurally characterized by our group (Andriichuk et al., 2019;Tsymbal et al., 2010Tsymbal et al., , 2021. Herein, we report the syntheses and crystal structure of the product of the reaction of CuCl 2 , L and the isophthalate anion (ip 2À ) as its sodium salt, namely, trans-diaqua (1,4,8,11-tetraazaundecane-4 N 1 ,N 4 ,N 8 ...
In the title hydrated molecular salt, [Cu(C7H20N4)(H2O)2](C8H4O4)·H2O, the metal ion is coordinated by the two primary and two secondary N atoms of the amine ligand and the mutually trans O atoms of the water molecules in a tetragonally distorted octahedral geometry. The average equatorial Cu—N bond lengths (2.013 and 2.026 Å for Cu—Nprim and Cu—Nsec, respectively) are substantially shorter than the average axial Cu—O bond length (2.518 Å). The tetraamine ligand adopts its energetically favored conformation with its five- and six-membered chelate rings in gauche and chair conformations, respectively. In the crystal, the N—H donor groups of the tetraamine, the acceptor carboxylate groups of the isophthalate dianion and both the coordinated water molecules and the water molecule of crystallization are involved in numerous N—H⋯O and O—H⋯O hydrogen bonds, resulting in the formation of electroneutral layers oriented parallel to the ac plane.
... [7][8][9][10][11] Indeed, macrocyclic compounds based on crown ethers proved to be interested in "host-guest" chemistry, biochemistry, phase transfer catalysis, sensor as well as in the design and synthesis of various oriented compounds with specific properties and applications. [3,[12][13][14][15] The biological properties of crown compounds are also explored. The most important properties of crown-based macrocycles are the ability to chelate with metal leading to increase of metal salt solubility and anion reactivity in non-aqueous solvents, enabling transport through the cell membrane. ...
New derivatives of thiacrown ethers were synthesized based on the domino reaction of 1,5‐bis(2‐formylphenthio)‐3‐oxapentane with ketones containing active methylene group and ammonium acetate. After 24 hours at moderate temperature, the reaction afforded new substances containing both polyether chain S(CH2)2−O−(CH2)2−S and heterocyclic piperidone. Particularly when benzyl acetoacetate was used, the three ‐ component reaction provided a final tetrahydropyridine derivative product containing enamine fragment instead of piperidone as expected. Physico‐chemical methods of analyses including IR, ¹H &¹³C‐NMR and HRMS were used to clarify these structures. Subsequently, the cytotoxicity of five novel derivatives were evaluated on four cancer cells including HeLa (HeLa cervical cancer), Hep‐G2 (human hepatocellular carcinoma), MCF7 (human breast adenocarcinoma), Lu‐1 (human lung adenocarcinoma) and Vero cell. The result showed the potential application of these compounds in terms of biological activity.
... It is known from [1][2][3][4][5][6] that the heterometallic complex compounds in solid compressed state have a wide range of electrically-conductive properties, which depend on features of a central atom, a heteroatom and chelating and bridging ligands and vary widely from dielectric to low impedance. In practical applications, the compounds can be used as semiconductor material for the thermistor manufacture. ...
A new material of strontium tetraaquad[N, N'-bis(salicylidene)semicarbazidatocobalt(II)] dihydrate (I) with the following composition: Sr[CoL'(Н2О)2]22Н2О, where H3L = N,N'-bis(salicylidene)semicarbazide was synthesized. The molar mass of the extracted and dehydrated complex compound Sr[Co (C15H14N3O5)]2 is 838.07 g/mol, and the number of valence electrons in one molecule is 256. A cylindrical sample with a mass of 0.09 g and a volume of 17.67∙10-9 m3 was utilized for experimental studies. Experimental measurements and theoretical calculations for the main physical parameters of the synthesized material were performed. Such quantities were calculated: the substance density, the molecule mass, the number of molecules in the test cylindrical sample, the number of valence electrons, the bandgap. Dependences of specific conductivity, current density, resistance, the Hall coefficient, and charge carrier concentration on temperature were obtained.
... Thus, template condensation could be used to prepare complexes of the ligands which could not be obtained with a simple condensation. These reactions mainly work with the directing effect of the metal ion and this function of the metal ion is coined as "template effect" [34]. ...
2,2′ -Dihydroxybenzophenone-S-methyl-thiosemicarbazone and 3-methoxy-salicylaldehyde were reacted in the presence of oxovanadium(IV) or nickel(II) ions to yield the N2O2-type-chelate complex. The synthesized complexes were characterized by employing elemental analysis, electronic and infrared spectra, 1H NMR spectra, magnetic measurements, and thermogravimetric analyses. The expected structures of oxovanadium(IV) and nickel(II) complexes were confirmed by using the single-crystal X-ray diffraction method. The presence of π-π stacked dimeric structures provided stronger crystalline formations. The optimized geometries and vibrational frequencies of the compounds were obtained using the DFT/ωB97XD method with the 6-31G (d,p) basis set and compared with the experimental data. The electrochemical characterization of the oxovanadium(IV) and nickel (II) complexes were carried out by using the cyclic voltammetry (CV) method. The oxovanadium(IV) complex gives a ligand-centered oxidation and a metal-centered one electron reduction and oxidation peaks corresponding to the VIV/IIIO and VIV/VO, respectively. The nickel(II) complex gives a ligand-centered oxidation and metal-centered (NiII/I) reduction peaks in a dimethyl sulfoxide (DMSO) solution. The redox potentials were calculated in terms of Gibbs free energy change of the redox reaction at the theory level of M06-L/LANL2DZ/ PCM. In addition, the energy gap, HOMO and LUMO distributions were calculated. The total antioxidant capacities of the compounds were determined by using cupric reducing antioxidant capacity (CUPRAC) method, in
which the oxovanadium(IV) complex was found to be powerful as an antioxidant agent.
... The chemistry of macrocyclic Schiff base complexes have been reviewed in several excellent papers. [1][2][3][4][5][6][7][8][9][10] Macrocyclic Schiff bases have been widely studied because they can selectively chelate certain metal ions depending on the number, type and position of their donor atoms, the ionic radius of the metal center, and coordinating properties of counterions. Interest in exploring metal ion complexes with macrocyclic ligands has been continuously increasing owing to the recognition of the role played by these structures in metalloproteins. ...
A series of discrete heterodinuclear lanthanide(dinuclear complexes have been prepared in situ from their corresponding mononuclear complexes without isolation. The phenolate oxygen atom of the binucleating ligands behaves as a bridging group between two metals. The complexes have been characterized by elemental analysis, IR, NMR, UV, ESI, MALDI-TOF spectra and magnetic studies. The yield of these complexes increases from lighter lanthanides to heavier lanthanides. The electrochemical studies carried out for Eu(III)-Ni(II) complexes exhibit two reduction waves and two oxidation waves. The fluorescence studies were carried out for europium and terbium complexes. The results of elemental analysis of the complexes are in good agreement with the theoretical values. Conductivity studies reveal that all the complexes are 1:1 electrolytes.
... A s seen in DNA-replication, the template effect 1,2 is a powerful strategy for efficient synthesis of assemblies whose building blocks are well arranged, such as macrocycles [3][4][5][6][7][8][9] , cages 10,11 , interlocked and knotted molecules [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] , and submicrometer-sized materials [28][29][30][31][32][33][34] . Basically, this effect makes the interconnection of the building blocks feasible by their preorganization by binding to the template molecule(s). ...
The template effect is a key feature to control the arrangement of building blocks in assemblies, but its kinetic nature remains elusive compared to the thermodynamic aspects, with the exception of very simple reactions. Here we report a kinetic template effect in a self-assembled cage composed of flexible ditopic ligands and Pd(II) ions. Without template anion, a micrometer-sized sheet is kinetically trapped (off-pathway), which is converted into the thermodynamically most stable cage by the template anion. When the template anion is present from the start, the cage is selectively produced by the preferential cyclization of a dinuclear intermediate (on-pathway). Quantitative and numerical analyses of the self-assembly of the cage on the on-pathway revealed that the accelerating effect of the template is stronger for the early stage reactions of the self-assembly than for the final cage formation step itself, indicating the kinetic template effect. Thermodynamic template effects are widely used in supramolecular assembly, but kinetic template effects are less well understood. Here the contributions of thermodynamic and kinetic template effects in the self-assembly of palladium metallocages are disentangled using QASAP methodology.
... Of particular interest is the study of reduction capabilities of polyazamacrocyclic nickel(II) complexes based on diketones and Smethylisothiosemicarbazide or S-methylisothiocarbohydrazide as new platforms for catalysis [22,23]. It was shown that the catalytic activity of these complexes decreases with the decrease of reduction potential. ...
... Thiosemicarbazone Schiff base compounds have soft sulfur and hard nitrogen as well hard oxygen atoms (Mohamed et al., 2009). These Schiff base compounds are of special interest because of their diversity in coordinating to hard and soft metals using the hard and soft coordinating sites such as NSO (Arion et al., 2001;Leovac & Č ešljević, 2002;Chandra & Sangeetika, 2004;Singh et al., 2000;Gerbeleu et al., 2008;Mohamed et al., 2009). Many Schiff base compounds and their complexes with transition metals have wide biological and pharmaceutical applications (Padhyé & Kauffman, 1985;Salam et al., 2012b). ...
The asymmetric unit of the title compound, C 15 H 21 N 3 OS, comprises of two crystallographically independent molecules ( A and B ). Each molecule consists of a cyclohexane ring and a 2-hydroxy-3-methylbenzylidene ring bridged by a hydrazinecarbothioamine unit. Both molecules exhibit an E configuration with respect to the azomethine C=N bond. There is an intramolecular O—H...N hydrogen bond in each molecule forming an S (6) ring motif. The cyclohexane ring in each molecule has a chair conformation. The benzene ring is inclined to the mean plane of the cyclohexane ring by 47.75 (9)° in molecule A and 66.99 (9)° in molecule B . The mean plane of the cyclohexane ring is inclined to the mean plane of the thiourea moiety [N—C(=S)—N] by 55.69 (9) and 58.50 (8)° in molecules A and B , respectively. In the crystal, the A and B molecules are linked by N—H...S hydrogen bonds, forming `dimers'. The A molecules are further linked by a C—H...π interaction, hence linking the A – B units to form ribbons propagating along the b -axis direction. The conformation of a number of related cyclohexanehydrazinecarbothioamides are compared to that of the title compound.
... which are hard atoms (Mohamed, Omar, & Ibrahim, 2009). These Schiff base compounds are of special interest because of their diversity in coordinating to hard and soft metals using the hard and soft coordinating sites (Arion et al., 2001;Chandra & Sangeetika, 2004;Gerbeleu, Arion, & Burgess, 2008;Leovac & Cešljevi c, 2002;Mohamed et al., 2009;Singh, Srivastava, Sodhi, & Ranjan, 2000). ...
The bidentate N‐cyclohexyl‐2‐(3‐hydroxy‐4‐methoxybenzylidene)hydrazine‐1‐carbothioamide Schiff base ligand (HL) was coordinated to divalent nickel, palladium and platinum ions to form square planar complexes. The nickel and palladium complexes, [NiL2], [PdL2] form square planar complexes with 2:1 ligand to metal ratio. The platinum complex, [PtL(dmso)Cl] formed a square planar complex with 1:1 ligand to metal ratio. Platinum undergoes in situ reaction with DMSO before complexing with the ligand in solution. The cytotoxicity of HL, [NiL2], [PdL2], and [PtL(dmso)Cl] were evaluated against human colon cancer cell line (HCT‐116), human cervical cancer (Hela) cell line, melanoma (B16F10) cells, and human normal endothelial cell lines (Eahy926) by MTT assay. The [NiL2] complex displayed selective cytotoxic effect against the HCT 116 cancer cell line with IC50 of 7.9 ± 0.2 μM. However, HL, [PdL2], and [PtL(dmso)Cl] only exhibited moderate cytotoxic activity with IC50 = 75.9 ± 2.4, 100.0 ± 1.8, and 101.0 ± 3.6 μM, respectively. The potent cytotoxicity of [NiL2] was characterized using Hoechst and Rhodamine assays. The nickel complex, [NiL2], caused remarkable nuclear condensation and reduction in mitochondrial membrane potential. In addition, molecular docking studies confirms that [NiL2] possesses significant binding efficiency with Tyrosine kinase. Altogether, the results revealed that [NiL2] exhibits cytotoxicity against the cancer cells via Tyrosine kinase‐induced proapoptosis pathway. This study demonstrates that the [NiL2] complex could be a promising therapeutic agent against colorectal carcinoma.
... This would be a favorable geometry for the attack of the C1' atom by the pyrophosphate group. Therefore, we propose that disruption of the conventional magnesium geometry is used in a template effect chemical reaction, to initiate the reverse enzymatic reaction (26,27). We put forward the following mechanism for the reverse reaction (Fig. 6b). ...
The reversible adenine phosphoribosyltransferase enzyme (APRT) is essential for purine homeostasis in prokaryotes and eukaryotes. In humans, APRT (hAPRT) is the only enzyme known to produce AMP in cells from dietary adenine. APRT can also process adenine analogs, which are involved in plant development or neuronal homeostasis. However, the molecular mechanism underlying substrate specificity of APRT and catalysis in both directions of the reaction remains poorly understood. Here we present the crystal structures of hAPRT complexed to three cellular nucleotide analogs (Hypoxanthine, IMP and GMP) that we compare to the phosphate-bound enzyme. We established that binding to hAPRT is substrate-shape-specific in the forward reaction, while it is base-specific in the reverse reaction. Furthermore, a quantum mechanics/molecular mechanics (QM/MM) analysis suggests that the forward reaction is mainly a nucleophilic substitution of type 2 (SN2) with a mix of SN1-type molecular mechanism. Based on our structural analysis, a magnesium-assisted SN2-type mechanism would be involved in the reverse reaction. These results provide a framework for understanding the molecular mechanism and substrate discrimination in both directions by APRTs. This knowledge can play an instrumental role in the design of inhibitors, such as antiparasitic agents, or adenine-based substrates.
... The coordination properties of N-functionalized macrocycles have been extensively studied in recent years. The application of polyaza macrocycle precursors in the synthesis of transition metal complexes stems mainly from their use as models for protein-metal binding sites in the biological systems [1][2][3][4][5][6][7] and as selective complexing agents for metal ions [8][9][10]. The biological activity of this class of compounds is associated with the formation of chelates with essential metal ions bonding through nitrogen as well as sulphur/oxygen donor atoms [11,12]. ...
Complexes of Ni(II), Pd(II), Pt(IV) and Cu(II) with a novel azamacrocyclic ligand viz. 5,7,12,14-tetramethyl-1,2,4,8,10,11-hexaazacyclotetradeca-4,7,11,14-tetraene-3,9-dione (L) were synthesized and characterized by elemental analysis, molar conductance, magnetic susceptibitity, mass spectra, ¹H NMR (L), FT-IR and electronic spectral studies. In molecular modeling, the geometry of ligand (L) was fully optimized with respect to the energy using the 6-31g(d,p) basis set. On the basis of these spectral studies a distorted octahedral geometry was assigned for Ni(II) complex, square planar for Pd(II), octahedral and tetragonal geometry for Pt(IV) and Cu(II) complexes respectively. The ligand and its metal complexes were screened in vitro against some species of bacteria and plant pathogenic fungi. Electrochemical behaviour of nickel and copper complexes were studied by cyclic voltammetry.
The anti ( a ) to syn ( s ) isomerization pathway of the deprotonated form of the carbon-carbon (C-C) σ dimer complex with two nickel(II) 15-membered octaazamacrocyclic units was investigated. For the initial anti ( a ) structure, a deprotonation of one of the bridging (sp ³ hybridized) carbon atoms is suggested to allow for an a to s geometry twist. A 360° scan around the bridging C-C dihedral angle was performed first to find an intermediate geometry. Subsequently, the isomerization pathway was explored via individual steps using a series of mode redundant geometry optimizations and geometry relaxations leading to the s structure. The prominent geometries (intermediates) of the isomerization pathway are chosen and compared to the a and s structures. Finally, geometry relaxations of the protonated forms of selected intermediates are considered. It is shown that albeit the reaction barrier appears to be higher than that obtained in the experiment, the DFT series of mode redundant geometry optimizations and geometry relaxations proves itself useful in the exploration of the isomerization pathway of the chosen diastereomeric dinickel(II) bis(octaazamacrocyclic) complex.
Modified crown ethers are fundamental building blocks in supramolecular chemistry, with applications in phase transfer catalysis, metal extraction, smart materials, and molecular machines. Here we report on a one‐pot highly chemo‐ and regioselective photocatalytic fluoroalkylation protocol for the mono‐functionalization of benzo substituted crown ethers. For this important class of macrocycles, the method described here represents one of the few late‐stage functionalization procedures that is both high yielding and scalable. Because of its breadth of scope and substrate tolerance, the devised approach can be applied to a wide range of aromatic crown ethers (18 examples, up to 99 % yield), including those engaged in mechanically interlocked molecules.
Template condensation between pentane-1,5-dial and triethylenetetramine in the presence of divalent metal salts in methanolic solution resulted in mononuclear 15-membered tetraazamacrocyclic Schiff base metal complexes, [M(C11H22N4)X2], where M = Co(II), Ni(II) and Cu(II), X = Cl⁻ and C11H22N4 is the tetradentate macrocyclic ligand. The bonding and overall geometry of the complexes are inferred through elemental analysis, FT-IR, UV–vis, ¹H/¹³C NMR, ESI-mass, molar conductance, magnetic susceptibility and TG measurements. On the basis of the absorption bands in UV–vis spectra and magnetic moment analyses, a six-coordinate octahedral geometry is proposed for all the metal complexes. The formulation of the metal chelates is compatible with the thermal decomposition profiles. Photocatalytic efficiency of the macrocyclic Ni(II) complex was studied using solar water-splitting. The in vitro antimicrobial activity of metal complexes has been tested against certain bacterial and fungal species. The scavenging ability of DPPH free radicals was used to test the antioxidant activity of the complexes. In addition, MTT assay was used to assess the cytotoxicity of Cu(II) chloro complex against L929 mouse fibroblast cell lines.
Two improved routes to synthesize 1-benzyl-1,4,7,10-tetraazacyclododecane (6) and 1,4,7,10- tetraazacyclododecane-1-acetic acid ethyl ester (11) are described as well as the synthesis of 1-{2-[4-(maleimido-N-propylacetamidobutyl)amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane- 4,7,10-triacetic acid (17) and its Y, Ho, Tm, and Lu complexes. The ¹H and ¹³C NMR spectra of the new compounds as well as the single crystal X-ray structure analyses of the intermediates 4-benzyl-1,7-bis(p-toluenesulfonyl)diethylenetriamine (3) and 1,4,7-tris(p-toluenesulfonyl)diethylenetriamine (7) are reported and discussed. The rare earth complexes of 17 have been characterized by ¹H NMR spectroscopy and MALDI-TOF mass spectrometry.
A novel synthetic strategy for large macrocyclic molecules using boroxine formation was developed. For this, the threefold intramolecular olefin metathesis of 3,5-bis(alkenyloxy)phenylboroxines with various lengths of alkenyl chains, formed by the dehydration of the corresponding boronic acid substrates, together with treatment with pinacol, was used to produce 39-, 45-, and 51-membered macrocyclic compounds with three boronate units. The boroxine moiety functions as a covalent template but can also be used to postmodify the macrocycle. Boroxine-templated macrocyclization implemented in this way does not require the addition of template molecules and simplifies the synthetic procedure.
Functionalized macrocycles and medium‐sized rings have important applications in countless applied scientific fields, but they can be challenging to make using traditional synthetic methods. In this chapter, we provide an overview and perspective on current strategies for the synthesis of heterocyclic macrocycles and medium‐sized rings. We start by summarizing the state of the art in high dilution and pseudo‐high dilution methods. We then go on to detail methods for which high dilution is not required that take advantage of conformational and/or template effects. Ring‐expansion methods are also covered, and finally, medium‐sized ring synthesis is treated separately.
A general and stereoselective five-step approach to 14-membered cyclic bis-semicarbazones, 5,12-diaryl-7,14-dimethyl-1,2,4,8,9,11-hexaazacyclotetradeca-7,14-diene-3,10-diones, starting from aldehyde semicarbazones has been developed. The key intermediates, 4-(3-oxobut-1-yl)semicarbazones, were prepared by BF3-catalyzed amidoalkylation of 2-(trimethylsilyloxy)propene with 4-[(aryl)(methoxy)methyl]- or 4-[(aryl)(tosyl)methyl]semicarbazones. Treatment of these intermediates with excess of hydrazine gave hydrazones of 4-(3-oxobut-1-yl)semicarbazones or 4-(3-oxobut-1-yl)semicarbazides, which in the presence of TsOH were converted into the target macrocycles. All steps of this approach could be scaled up easily to the multi-gram level.
Schiff base macrocycles play a remarkable role in the advancement of modern coordination chemistry in light of their importance to various multidisciplinary research fields. Bioinorganic chemistry has grown tremendously and provides opportunities to use macrocyclic Schiff base metal complexes as therapeutic agents. Macrocyclic Schiff base complexes have been studied on account of their ability to coordinate a variety of metal ions, preparative accessibility and growing applicability in numerous fields. In view of their pharmacological or biological properties, metal complexes of Schiff base macrocycles opened up a new vista of prospects in synthetic organic chemistry. Various methods were embraced to develop macrocyclic Schiff base metal complexes, along with their pharmacological properties. One of the simplest and effective methods for macrocyclic synthesis is an in-situ approach where the appearance of a metal ion in the cyclization reaction increases the yield of the macrocyclic product. This review focuses on the one-pot synthesis of biologically significant Schiff base macrocyclic metal complexes reported from 2005-2021.
This article is dedicated to the history of apparition and development of Coordination chemistry in Moldova.The main scientific centres are characterized, as well as their main research directions. The most valuable results in fundamental and applicative research are described, obtained in the field of coordination chemistry in the republic.
This communication deals with the appearance and development of the research in the field of chemistry in the Republic of Moldova; at the beginning - in chemistry sections of Moldovan Branch of the USSR Academy of Sciences and then - at the Institute of Chemistry, founded in 1959. The dynamics of changes in the structure and research subjects is traced. Data are presented concerning the research results in the fi eld of the chemistry of coordination compounds, fine organic synthesis, natural products chemistry, physicochemical analysis, quantum chemistry, mineral resources, chemistry of natural water and purifi cation of waste water, the preparation and utilization of active carbons, and ecological chemistry. A detailed account both of basic research and applied investigation is given. The collaboration of our scientists with their colleagues from abroad is considered. Information is presented related to the scientific schools at our institute, its guidance and laboratory′s leaders. The scientific equipment of the institute is mentioned. The relationship of the institute with higher schools, as well as training of young researchers will be presented.
We have researched the color properties of coordination compounds synthesized by us previously [1] (8-(1',2'-naphthyl)-1-R3-methyl-6-thiomethyl-4,5,7-triazaocta-1,3,5,7-tetraenato-1,1'-diolato(-)O, O', N4, N7-M(II), where R=CH3, C6H5, M=Ni, Co, Cu), which can be used for coloring thermoplastic masses. They meet the requirements for use as a pigment for coloring thermoplastic masses.
Nickel(II), copper(II), and palladium(II) complexes ML
H
, where M = Ni (1), Cu (2), Pd (3), and ML
OMe
, where M = Ni (4), Cu (5), Pd (6), have been prepared by reactions of NiCl2·6H2O, Cu(OAc)2·H2O, and PdCl2(MeCN)2 with 14-membered bis-semicarbazide hexaazamacrocycles H
2
L
H
and H
2
L
OMe
in dimethylformamide (DMF). The compounds were characterized by elemental analysis, ESI mass spectrometry, IR, UV-vis, and 1D (1H, 13C) and 2D (1H-1H COSY, 1H-1H TOCSY, 1H-1H NOESY, 1H-13C HSQC, 1H-13C HMBC) NMR spectra (1, 3, 4, and 6), and X-ray diffraction (2, 4-6). The complexes with MIIN4 coordination environment have S = 0, 1/2, 0 ground states for Ni, Cu, and Pd, respectively. The electrochemical behavior of 1-6 was investigated in detail. The electronic structures of 1e-oxidized species were studied by EPR, UV-vis-NIR spectroelectrochemistry, and DFT calculations, indicating the redox-noninnocent behavior of the ligands. Compounds 1-6 were tested in the oxidation of styrene and C-C coupling (Henry and Knoevenagel condensations). Compounds 2 and 5 selectively catalyze the microwave-assisted oxidation of neat styrene to benzaldehyde (up to 88% yield), whereas the 1 and 4 catalytic systems afforded up to 99% β-nitroethanol yield with an appreciable diastereoselectivity toward the formation of the anti isomer.
The synthesis and structure of the new organic proligand 2-formylpyridine S-methyl-isothiosemicarbazone in a bi-protonated form (HL.2HCl) and its coordination compounds with Mn(II) - [Mn(HL)·Cl2], Co(III) - [CoL2]·ClO4, Ni(II) - [Ni(HL)2]·2ClO4, Cu(II) - [Cu(HL)Cl2]·(H2O), Zn(II) - [Zn(HL)2]·2(ClO4)·(H2O) and Pd(II) - [Pd(HL)·Cl]·Cl are reported. According to the X-ray investigation, the ligand has the molecular form of HL in the case of Mn(II), Cu(II), Zn(II) and Pd(II) compounds, and the deprotonated form L⁻ in case of the Co(III) complex. The ligand coordinates to the metal ions via a N,N,N set of donors atoms in case of Zn(II), Cu(II) and Co(III). For Mn(II), the ligand coordinates via N,N donor atoms, whereas in the case of Pd(II) metal ions, the coordination sphere is N,N,S. This latter coordination mode (via S(CH3)) has been previously reported in case of salicylaldehyde S-alkyl-isothiosemicarbazones.
Herein we report an aqueous polymerization strategy, assisted by dual-purpose supramolecular templates, for the formation of polyhydrazones and their subsequent hydrogelation. In this approach, donor-acceptor charge transfer interactions between small molecule templates and bipyridinium-based dialdehyde monomers facilitated monomer-monomer and polymer-monomer preorganization. The template-assisted polymerizations thus experienced augmented Mw and Mn values by up to 68 and 84% respectively as compared to the untemplated protocol. In this capacity, the presence of the templates and the increased molecular weight of the polymers effectively decreased the minimum monomer concentration needed for hydrogelation, enhanced the mechanical strength of the hydrogel microstructure, and increased the recovery velocity of the gel following shear-induced breakdown. The hydrogels were processed into colored films and highly crystalline ultra-light aerogels with a sheet-like morphology, as revealed by cross-polarized light, scanning electron, and transmission electron microscopies. The aerogels exhibited the ability to uptake gaseous iodine and iodine from solution with removal efficiencies and uptake capacities up to 91% and 363 wt% respectively.
Herein, we report the synthesis of a novel family of constrained pseudopeptidic macrocyclic compounds containing the hexahydropyrrolo[3,4-f]isoindolocyclophane scaffold and involving four coupled substitution reactions in the macrocyclization process. Although the increase in the number of steps involved in the macrocyclization could lead to a larger number of possible side products, the optimization of the methodology and the study of the driving forces, has made possible to obtain the desired macrocycles in excellent yields. A thorough computational study has been carried out to understand the macrocyclization process and the results obtained nicely agree with experimental data. Moreover, bromide anion had a clear catalytic template effect in the macrocyclization reaction, and surprisingly the chloride anion had a negative template effect in opposition to the results obtained for analogous macrocycles. The parameters responsible of the specific kinetic template effect observed have been studied in detail.
Covalent macrocycles and three-dimensional cages were prepared by the self-assembly of di- or tri-topic anilines and 2,6-diformylpyridine subcomponents around palladium(II) templates. The resulting 2,6-bis(imino)pyridyl-PdII motif contains a tridentate ligand leaving a free coordination site on the PdII centers, which points inward. The binding of ligands to the free coordination sites in these assemblies was found to alter the product stability, and multi-topic ligands could be used to control product size. Multi-topic ligands also bridged metallomacrocycles to form higher-order supramolecular assemblies, which were characterized via NMR spectroscopy, mass spectrometry and X-ray crystallography. An efficient method was developed to reduce the imine bonds to secondary amines, leading to fully organic covalent macrocycles and cages, which were inaccessible through other means.
لیتیم یکی از ارزشمندترین عناصر فلزی است که بهطور گسترده در زمینههای مختلف ازجمله الکترولیتهای لیتیمی (LiOH) باطریهای نوع دوم، داروهای لیتیمی، روغنهای روان کننده بر پایهی لیتیم و تصفیهی گاز تنفسی در فضاپیماها و زیردریاییها (به فرم LiOH) استفاده میشود. به همین دلیل بازیابی و جداسازی لیتیم از محلولهای حاوی لیتیم ازجمله آب دریا (غلظت mg/lit ۱۷/0)، محلولهای آلوده به سدیم ناشی از نشت آب به محلول لیتیمبرماید در چیلرهای جذبی و بازیابی لیتیم از باطریهای لیتیمی بازیافتی دارای اهمیت زیادی است. بسیاری از منابع لیتیمی از جمله آب دریا ، ذخایر شورابه و محلول آلوده شده لیتیم برماید در چیلر های جذبی دارای یون های مشابه لیتیم از جمله سدیم است، به علت شباهت شیمیایی و ساختاری زیاد این یونها، جداسازی با روشهای متداول مثل ترکیب، واکنش، ترسیب و سانتریفیوژ کردن مقدور نیست. در این پژوهش مطالعات و تحقیقات گذشته در زمینه جداسازی انتخابی یون لیتیم از منابع مختلف لیتیم و مقایسه روش های مطرح شده، انجام شده است.
Template‐mediated synthesis is a powerful approach to build a variety of functional materials and complex supramolecular systems. However, the systematic study of how templates structurally evolve from basic building blocks, and then affect the templated self‐assembly, is critical to understanding and utilizing the underlying mechanism, to work towards designed assembly. Here we describe the templated self‐assembly of a series of gigantic Mo Blue (MB) clusters 1–4 using l‐ornithine as a structure‐directing ligand. We show that by using l‐ornithine as a structure director, we can form new template⊂host assemblies. Based on the structural relationship between encapsulated templates of {Mo8} (1), {Mo17} (2) and {Mo36} (4), a pathway of the structural evolution of templates is proposed. This provides insight into how gigantic Mo Blue cluster rings form and could lead to full control over the designed assembly of gigantic Mo‐blue rings.
Gigantische Molybdänblau‐Cluster mit ligandendirigierten Templat⊂Wirt‐Architekturen werden über eine aniontemplatierte Selbstorganisation mit l‐Ornithin als strukturdirigierendem Agens aufgebaut. Basierend auf der strukturellen Beziehung zwischen verkapselten Templaten von {Mo8}, {Mo17} und {Mo36} kann ein Weg für die Strukturevolution der Template postuliert werden.
Abstract
Template‐mediated synthesis is a powerful approach to build a variety of functional materials and complex supramolecular systems. However, the systematic study of how templates structurally evolve from basic building blocks, and then affect the templated self‐assembly, is critical to understanding and utilizing the underlying mechanism, to work towards designed assembly. Here we describe the templated self‐assembly of a series of gigantic Mo Blue (MB) clusters 1–4 using l‐ornithine as a structure‐directing ligand. We show that by using l‐ornithine as a structure director, we can form new template⊂host assemblies. Based on the structural relationship between encapsulated templates of {Mo8} (1), {Mo17} (2) and {Mo36} (4), a pathway of the structural evolution of templates is proposed. This provides insight into how gigantic Mo Blue cluster rings form and could lead to full control over the designed assembly of gigantic Mo‐blue rings.
The self-assembly of macrocyclic tetranuclear 3d-4f single-molecule magnet (SMM) building blocks, [CuII3TbIII(LPr)(NO3)2(H2O)]NO3 (1), with K3[MIII(CN)6] linkers, where M = Fe, Cr, or Co, results in a range of discrete (monomer and dimer) and one-dimensional (1D) chain (coordination polymer) supramolecular architectures, which have been structurally and magnetically characterized. The outcome of reactions of 1 with an excess of K3[Fe(CN)6] has been probed in detail. It was found to be dependent on several factors, resulting in five distinctly different compounds, all of which have the same 1:1 ratio of [Cu3Tb(LPr)]3+ to [Fe(CN)6]3-, but which differ in structural type, solvent content, and magnetic behavior. Three are discrete complexes: monomeric {[Cu3Tb(LPr)(H2O)5][Fe(CN)6]·(H2O)3·(MeCN)]} (2) and [Cu3Tb(LPr)Fe(CN)6(H2O)4(MeCN)]·(H2O)2·(MeCN) (3) plus dimeric {[Cu3Tb(LPr)Fe(CN)6(H2O)4]·(H2O)6.75}2 (4), while two are 1D chains (coordination polymers): {[Cu3Tb(LPr) cis-Fe(CN)6(H2O)3(MeOH)]·(H2O)3.75·(MeOH)0.75} n (5) and {[Cu3Tb(LPr) trans-Fe(CN)6(H2O)4]·(H2O)5·(DMF)5]} n (6). When K3[Cr(CN)6] or K3[Co(CN)6] are used in place of K3[Fe(CN)6], a discrete dimer {[Cu3Tb(LPr)Cr(CN)6(H2O)4]·(H2O)2.75}2 (7) and a 1D chain coordination polymer {[Cu3Tb(LPr)Co(CN)6(H2O)3(MeOH)]·(H2O)4·(MeOH)} n (8) are obtained, respectively, which are isomorphous with 4 and 5, respectively. Magnetic studies reveal the paramagnetism of these compounds down to 1.8 K, except for 7, which displays an ordered antiferromagnetic ground state with metamagnetic behavior. The 1D-coordination polymers (5, 6, and 8) do not exhibit single-chain magnet properties, because of the very weak interbuilding block magnetic interactions. For chain 8, below 2.8 K, a clear nonzero out-of-phase signal is seen, similar to that seen for the building block 1, so the magnetism of 8 is governed by that of these SMM building blocks (1).
Open‐chain vs. hemiaminal and macrocycle forms of the condensation product of 2,6‐diformylpyridine and opposite enantiomers of trans‐1,2‐diaminocyclopentane have been studied using DFT methods to reveal that the macrocycle (with a water molecule co‐product) is the thermochemically preferred form. The mechanistic picture of formation of [[2+2]] Schiff base macrocycle from its chain precursor has been supplemented with the electron localization function analysis revealing the crucial electronic aspects underlying the covalent bonds evolution. The macrocycle formation may proceed along two paths, through two distinct diastereoisomerc hemiaminal intermediates. The reaction rate limiting water elimination step exhibits the considerably lower and unusually flat energy barrier for the path involving S hemiaminal due to the strong decoupling of the CO bond cleavage from the proton migration to form the water molecule.
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