Three-Dimensional Zinc(II) and Cadmium(II) Coordination Frameworks with N,N,N′,N′-Tetrakis(pyridin-4-yl)methanediamine: Structure, Photoluminescence, and Catalysis

Porous and Nonporous Coordination Polymers Induced by Pseudohalide Ions for Luminescence and Gas Sorption

The three-dimensional (3D) coordination polymers [Cd(tpmd)(NCX)₂]_n [X = O (1), S (2), and BH₃ (3); tpmd = N,N,N',N'-tetrakis(pyridin-4-yl)methanediamine] have been determined to display their network structures through coordinated anionic ligands. Polymers 1 and 2 show nonporous structures, whereas polymer 3 shows a porous coordination framework. On the basis of the Cd(II) network structures, the 3D coordination polymer [Zn(tpmd)(NCBH₃)₂]_n·nMeOH (4) was self-assembled. In the cases of polymers 1 and 2, pseudohalide ions acted to form nonporous network structures; however, in polymers 3 and 4, NCBH₃^- helps to construct porous network structures. Polymers 1-4 show strong ultraviolet luminescence emissions, depending on the pseudohalide ions present, compared to the tpmd ligands. Interestingly, coordination polymers 3 and 4 that possess NCBH₃^- ions exhibit high porosities and gas sorption properties. The polymers appeared to absorb N₂, H₂, CO₂, and CH₄. In the case of polymer 4, the structure is almost identical with that of polymer 3, except for the Cd(II) ion. However, polymer 4 has a larger void volume and higher gas absorption ability for N₂ gas than polymer 3. For the sorption of gases, polymers 3 and 4 showed similar behaviors.

Two-dimensional square-grid iron(ii) coordination polymers showing anion-dependent spin crossover behavior

Two Fe(ii)-based coordination polymers [Fe(tpmd)₂(NCS)₂]·5.5H₂O (1) and [Fe(tpmd)₂(NCSe)₂]·7H₂O (2) with the framework of square-grid type have been assembled from FeSO₄·7H₂O, N,N,N′,N′-tetrakis(pyridin-4-yl)methanediamine (tpmd), and KNCS/KNCSe in methanol and characterized. By utilizing two pyridine groups of a tpmd ligand, 1 and 2 are formed in two-dimensional layered structures through coordination of octahedral iron(ii) ions with the tpmd to NCS⁻/NCSe⁻ ligands in which they have a supramolecular isomorphous conformation. 1 shows a paramagnetic behavior between 2 and 300 K, while 2 exhibits two-step spin crossover (ca. 145 and 50 K) in the temperature range due to the coordination of NCSe⁻ ligands. At 300 K 2 is fully high-spin state. However, at 100 K 2 becomes ca. 50% high spin and 50% low spin iron(ii) ions, which is verified by magnetic moments. In the structural analysis of 2 at 100 K, two different layers are observed with different bond distances around iron(ii) ions in which the layers are stacked alternately.

Two-dimensional Fe-based coordination polymers with square-grid shapes were prepared by self-assembly and exhibited an interesting spin crossover behavior depending on the coordinated counter ions.

Cd(ii) coordination compounds as heterogeneous catalysts for microwave-assisted peroxidative oxidation of toluene and 1-phenylethanol

Cd(ii) compounds as catalysts towards microwave assisted peroxidative oxidation (with tert-butylhydroperoxide, TBHP) of toluene and 1-phenylethanol under heterogeneous conditions are explored.

Synthesis, crystal structure and bovine serum albumin–binding studies of a new Cd(II) complex incorporating 2,2′-(propane-1,3-diyl)bis(1H-imidazole-4,5-dicarboxylate)

A new Cd(II) complex, [Cd(H4pbidc)(H2O)] n (1), incorporating 2,2′-(propane-1,3-diyl)bis(1H- imidazole-4,5-dicarboxylic acid) (H6pbidc) was synthesized and characterized by elemental analysis, infrared spectra and X-ray single-crystal diffraction. In complex 1, each Cd(II) ion is hepta-coordinated, showing a significantly distorted pentagonal-bipyramidal coordination environment. Adjacent Cd(II) ions are alternately joined through two carboxylate oxygen atoms and two bridging water molecules resulting in a one-dimensional chain structure. In the solid state, adjacent chains are further linked by hydrogen bonds, forming a three-dimensional supramolecular architecture. Meanwhile, the interactions of complex 1 with bovine serum albumin were analysed by fluorescence measurements under physiological conditions. The results indicated that the fluorescence intensity of bovine serum albumin was decreased considerably upon the addition of complex 1 through a static quenching mechanism with formation of one binding site. The negative values of the thermodynamic parameters including enthalpy change (Δ H), entropy change (Δ S) and Gibbs free energy change (Δ G) showed that hydrogen bonding and van der Waals forces were the main interactions in the binding of complex 1 to bovine serum albumin, and the binding process is spontaneous in thermodynamics.

Three-dimensional iron(ii) porous coordination polymer exhibiting carbon dioxide-dependent spin crossover

A three-dimensional iron(ii) porous coordination polymer has been observed spin crossover behaviours through the sorption of H₂O and CO₂, respectively.

Sonochemical synthesis and structural characterization of a new nanostructured Co(II) supramolecular coordination polymer with Lewis base sites as a new catalyst for Knoevenagel condensation

A new Co(II) mixed-ligand coordination supramolecular polymer with composition [Co₂(ppda)(4-bpdh)₂(NO₃)₂]_n (1) (where, ppda=p-phenylenediacrylic acid, 4-bpdh=2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene) was synthesized using solvothermal, mechanochemical and sonochemical methods. Compound 1 and the new nanostructure have been characterized by single-crystal X-ray, infrared spectroscopy (IR), powder X-ray diffraction (PXRD) analysis and scanning electron microscopy (SEM). The thermal stability of compound 1 was also studied by thermal gravimetric analysis (TGA). The surface area of these compounds was determined by BET. The single-crystal X-ray data shows a new interesting two-dimensional coordination polymer (CP). In addition, the effect of various sonication concentrations of initial reagents, power of ultrasound irradiation and also the time on the size and morphology of nano-structured coordination polymer 1 were evaluated. Moreover, it has been demonstrated that the nanostructure of the CP1 can be used as a catalyst in Knoevenagel condensation reaction.

A sandwich-shaped M3L2 zinc(ii) complex containing 1,3,5-tris(dimethyl(pyridin-3-yl)silyl)benzene: selective photoluminescence recognition of diiodomethane

Self-assembly of Zn(ClO₄)₂ with 1,3,5-tris(dimethyl(pyridin-3-yl)silyl)benzene (L) as a new C₃-symmetric tridentate N-donor gives rise to a discrete sandwich-shaped M₃L₂ architecture, [Zn₃(μ-OH)₃L₂](ClO₄)₃·4CH₃CN·2H₂O. Its blue photoluminescence is significantly quenched only by CH₂I₂ among the various small molecules, CH₂Cl₂, CH₂Br₂, CHCl₃, 1,2-dichloroethane, EtOH, CH₃CN, benzene, toluene, and phenol.

Enantiomeric two-fold interpenetrated 3D zinc(ii) coordination networks as a catalytic platform: significant difference between water within the cage and trace water in transesterification

Self-assembly of Zn(ClO₄)₂ with 1,1,2,2-tetramethyl-1,2-di(pyridin-3-yl)disilane (L) as a bidentate N-donor gives rise to 3D coordination networks, [Zn(μ-OH)(L)]₃(ClO₄)₃·5H₂O (1·5H₂O), of unique, 10³-a srs net topology. An important feature is that two enantiomeric 3D frameworks, 4¹- and 4³-[Zn(μ-OH)(L)]₃(ClO₄)₃·5H₂O, are interpenetrated to form a racemic two-fold 3D network with cages occupied by two water molecules. Another structural characteristic is a C₃-symmetric planar Zn₃(μ-OH)₃ 6-membered ring with tetrahedral Zn(ii) ions. The steric hindrance of substrates and trace water effects on transesterification catalysis using the network have been scrutinized. The coordination network acts as a remarkable heterogeneous transesterification catalytic system that shows both the significant steric effects of substrate alcohols and momentous water effects. The substrate activity is in the order ethanol > n-propanol > n-butanol > iso-propanol > 2-butanol > tert-butanol. For the reaction system, solvate water molecules within the cages of the interpenetrated 3D frameworks do not decrease the transesterification activity, whereas the trace water molecules in the substrate alcohols act as obvious obstacles to the reaction.

Construction of noninterpenetrating and interpenetrating Co(ii) networks with halogenated carboxylate modulated by auxiliary N-donor co-ligands: structural diversity, electrochemical and photocatalytic properties

Six Co(ii) complexes with 2,5-dichloroterephthalate and bis(benzimidazole) were synthesized and characterized, which manifest photocatalytic activities.

A new three-dimensional zinc(II) coordination polymer involving 2-[(1H-1,2,4-triazol-1-yl)methyl]-1H-benzimidazole and benzene-1,4-dicarboxylate ligands

Metal-organic frameworks (MOFs) based on multidentate N-heterocyclic ligands involving imidazole, triazole, tetrazole, benzimidazole, benzotriazole or pyridine present intriguing molecular topologies and have potential applications in ion exchange, magnetism, gas sorption and storage, catalysis, optics and biomedicine. The 2-[(1H-1,2,4-triazol-1-yl)methyl]-1H-benzimidazole (tmb) ligand has four potential N-atom donors and can act in monodentate, chelating, bridging and tridentate coordination modes in the construction of complexes, and can also act as both a hydrogen-bond donor and acceptor. In addition, the tmb ligand can adopt different coordination conformations, resulting in complexes with helical structures due to the presence of the flexible methylene spacer. A new three-dimensional coordination polymer, poly[[bis(μ2-benzene-1,4-dicarboxylato)-κ(4)O(1),O(1'):O(4),O(4');κ(2)O(1):O(4)-bis{μ2-2-[(1H-1,2,4-triazol-1-yl)methyl-κN(4)]-1H-benzimidazole-κN(3)}dizinc(II)] trihydrate], {[Zn(C8H4O4)(C10H9N5)]·1.5H2O}n, has been synthesized by the reaction of ZnCl2 with tmb and benzene-1,4-dicarboxylic acid (H2bdic) under solvothermal conditions. There are two crystallographically distinct bdic(2-) ligands [bdic(2-)(A) and bdic(2-)(B)] in the structure which adopt different coordination modes. The Zn(II) ions are bridged by tmb ligands, leading to one-dimensional helical chains with different handedness, and adjacent helices are linked by bdic(2-)(A) ligands, forming a two-dimensional network structure. The two-dimensional layers are further connected by bdic(2-)(B) ligands, resulting in a three-dimensional framework with the topological notation 6(6). The IR spectra and thermogravimetric curves are consistent with the results of the X-ray crystal structure analysis and the title polymer exhibits good fluorescence in the solid state at room temperature.

Comparative structure activity relationship for heterogeneous phosphatase-like catalytic activities of one-dimensional Cu(ii) coordination polymers

A structure activity relationship for heterogeneous phosphatase-like activities of one-dimensional Cu(ii) coordination polymers, has been studied. Complex 1 exhibits maximum activity due to coordinated water molecules, shorter metal–metal distance and exposed metal centers.

A two-dimensional layered Cd(II) coordination polymer with a three-dimensional supramolecular architecture incorporating mixed multidentate N- and O-donor ligands

The combination of N-heterocyclic and multicarboxylate ligands is a good choice for the construction of metal-organic frameworks. In the title coordination polymer, poly[bis{μ2-1-[(1H-benzimidazol-2-yl)methyl]-1H-tetrazole-κ(2)N(3):N(4)}(μ4-butanedioato-κ(4)O(1):O(1'):O(4):O(4'))(μ2-butanedioato-κ(2)O(1):O(4))dicadmium], [Cd(C4H4O4)(C9H8N6)]n, each Cd(II) ion exhibits an irregular octahedral CdO4N2 coordination geometry and is coordinated by four O atoms from three carboxylate groups of three succinate (butanedioate) ligands and two N atoms from two 1-[(1H-benzimidazol-2-yl)methyl]-1H-tetrazole (bimt) ligands. Cd(II) ions are connected by two kinds of crystallographically independent succinate ligands to generate a two-dimensional layered structure with bimt ligands located on each side of the layer. Adjacent layers are further connected by hydrogen bonding, leading to a three-dimensional supramolecular architecture in the solid state. Thermogravimetric analysis of the title polymer shows that it is stable up to 529 K and then loses weight from 529 to 918 K, corresponding to the decomposition of the bimt ligands and succinate groups. The polymer exhibits a strong fluorescence emission in the solid state at room temperature.

The crystal structure, luminescence and nitrobenzene-sensing properties of a two-dimensional Mn(II) coordination polymer based on 2,6-bis(imidazol-1-yl)pyridine

A two-dimensional Mn(II) coordination polymer (CP), poly[bis[μ2-2,6-bis(imidazol-1-yl)pyridine-κ(2)N(3):N(3')]bis(thiocyanato-κN)manganese] [Mn(NCS)2(C11H9N5)2]n, (I), has been obtained by the self-assembly reaction of Mn(ClO4)2·6H2O, NH4SCN and bent 2,6-bis(imidazol-1-yl)pyridine (2,6-bip). CP (I) was characterized by FT-IR spectroscopy, elemental analysis and single-crystal X-ray diffraction. The crystal structure features a unique two-dimensional (4,4) network with one-dimensional channels. The luminescence and nitrobenzene-sensing properties were explored in a DMF suspension, revealing that CP (I) shows a strong luminescence emission and is highly sensitive for nitrobenzene detection.

A one-dimensional zinc(II) coordination polymer based on mixed multidentate N- and O-donor ligands

In the title coordination polymer, catena-poly[[bis[{1-[(1H-benzimidazol-2-yl-κN(3))methyl]-1H-tetrazole}zinc(II)]-bis(μ4-pentane-1,5-dioato-1:2:1':2'κ(4)O(1):O(1'):O(5):O(5'))] methanol disolvate], {[Zn(C5H6O4)(C9H8N6)]·CH3OH}n, each Zn(II) ion is five-coordinated by four O atoms from four glutarate ligands and by one N atom from a 1-[(1H-benzimidazol-2-yl)methyl]-1H-tetrazole (bimt) ligand, leading to a slightly distorted square-pyramidal coordination environment. Two Zn(II) ions are linked by four bridging glutarate carboxylate groups to generate a dinuclear [Zn2(CO2)4] paddle-wheel unit. The dinuclear units are further connected into a one-dimensional chain via the glutarate ligands. The bimt ligands coordinate to the Zn(II) ions in a monodentate mode and are pendant on both sides of the main chain. In the crystal, the chains are linked by O-H···O and N-H···O hydrogen bonds into a two-dimensional layered structure. Adjacent layers are further packed into a three-dimensional network through van der Waals forces. A thermogravimetric analysis was carried out and the photoluminescent behaviour of the polymer was investigated.

Potassium induced stitching of a flexible tripodal ligand into a bi-metallic two-dimensional coordination polymer for photo-degradation of organic dyes

A novel strategy for the stitching of a flexible tripodal ligand into a bimetallic two-dimensional coordination polymer was developed for photo-degradation of dyes.

Diverse zinc(ii) coordination assemblies built on divergent 4,2′:6′,4′′-terpyridine derivatives: syntheses, structures and catalytic properties

Diverse Zn(ii) metal–organic assemblies of 4,2′:6′,4′′-terpyridine derivatives were structurally characterized and applied for catalytic transesterification of phenyl acetate with alcohols.

Luminescent group 12 metal tetracarboxylate networks as probe for metal ions

Hydrothermalin situdecomposition of DMF generated three [NH₂(CH₃)₂]⁺templated anionic zinc and cadmium terphenyl-3,2′′,5′′,3′-tetracarboxylate frameworks, which show tunable luminescence in the presence of metal ions. In particular,1could be a luminescent sensor for selectively detecting traces of Ca²⁺ions at ppm level in a pyridine suspension.

Coordination polymers of a multipyridyl and pyrazolyl ligand with conformational flexibility: syntheses, structures and luminescence

Eight novel coordination polymers were obtained by the coordination of a multipyridyl and pyrazolyl ligand, which shows rich conformational changes.

Halogen effects on photoluminescence and catalytic properties: a series of spatially arranged trimetallic zinc(ii) complexes

Halogen effects of a unique columnar ensemble of discrete trimetallic zinc(ii) complexes formed via π⋯π interactions and hydrogen-bonds were investigated.