Structural comparison of group 7 tricarbonyl complexes of 2‐{[2‐(1H‐imidazol‐4‐yl)ethyl]iminomethyl}‐5‐methylphenolate

Two tricarbonyl complexes of rhenium(I) and manganese(I) coordinated by the ligand 2‐{[2‐(1H‐imidazol‐4‐yl)ethyl]iminomethyl}‐5‐methylphenolate are reported, viz. fac‐tricarbonyl(2‐{[2‐(1H‐imidazol‐4‐yl‐κN³)ethyl]iminomethyl‐κN}‐5‐methylphenolato‐κO)rhenium(I) methanol monosolvate, [Re(C₁₆H₁₄N₃O₄)(CO)₃]·CH₃OH, (I), and fac‐tricarbonyl(2‐{[2‐(1H‐imidazol‐4‐yl‐κN³)ethyl]iminomethyl‐κN}‐5‐methylphenolato‐κO)manganese(I), fac‐[Mn(C₁₆H₁₄N₃O₄)(CO)₃], (II), display facial coordination in a distorted octahedral environment. The crystal structure of (I) is stabilized by O—H...O, N—H...O and C—H...O hydrogen‐bond interactions, while that of (II) is stabilized by N—H...O hydrogen‐bond interactions only. These interactions result in two‐dimensional networks and π–π stacking for both structures.     

Three AgI,CuI and CdII coordination polymers based on the new asymmetrical ligand 2‐{4‐[(1H‐imidazol‐1‐yl)methyl]phenyl}‐5‐(pyridin‐4‐yl)‐1,3,4‐oxadiazole: syntheses,characterization and emission properties

The new asymmetrical organic ligand 2‐{4‐[(1H‐imidazol‐1‐yl)methyl]phenyl}‐5‐(pyridin‐4‐yl)‐1,3,4‐oxadiazole ( L , C₁₇H₁₃N₅O), containing pyridine and imidazole terminal groups, as well as potential oxdiazole coordination sites, was designed and synthesized. The coordination chemistry of L with soft Ag^I, Cu^I and Cd^II metal ions was investigated and three new coordination polymers (CPs), namely, catena‐poly[[silver(I)‐μ‐2‐{4‐[(1H‐imidazol‐1‐yl)methyl]phenyl}‐5‐(pyridin‐4‐yl)‐1,3,4‐oxadiazole] hexafluoridophosphate], {[Ag( L )]PF₆}_n, catena‐poly[[copper(I)‐di‐μ‐iodido‐copper(I)‐bis(μ‐2‐{4‐[(1H‐imidazol‐1‐yl)methyl]phenyl}‐5‐(pyridin‐4‐yl)‐1,3,4‐oxadiazole)] 1,4‐dioxane monosolvate], {[Cu₂I₂( L )₂]·C₄H₈O₂}_n, and catena‐poly[[[dinitratocopper(II)]‐bis(μ‐2‐{4‐[(1H‐imidazol‐1‐yl)methyl]phenyl}‐5‐(pyridin‐4‐yl)‐1,3,4‐oxadiazole)]–methanol–water (1/1/0.65)], {[Cd( L )₂(NO₃)₂]·2CH₄O·0.65H₂O}_n, were obtained. The experimental results show that ligand L coordinates easily with linear Ag^I, tetrahedral Cu^I and octahedral Cd^II metal atoms to form one‐dimensional polymeric structures. The intermediate oxadiazole ring does not participate in the coordination interactions with the metal ions. In all three CPs, weak π–π interactions between the nearly coplanar pyridine, oxadiazole and benzene rings play an important role in the packing of the polymeric chains.     

A new one‐dimensional CdII coordination polymer with a two‐dimensional layered structure incorporating 2‐[(1H‐imidazol‐1‐yl)methyl]‐1H‐benzimidazole and benzene‐1,2‐dicarboxylate ligands

The N‐heterocyclic ligand 2‐[(1H‐imidazol‐1‐yl)methyl]‐1H‐benzimidazole (imb) has a rich variety of coordination modes and can lead to polymers with intriguing structures and interesting properties. In the coordination polymer catena‐poly[[cadmium(II)‐bis[μ‐benzene‐1,2‐dicarboxylato‐κ⁴O¹,O^1′:O²,O^2′]‐cadmium(II)‐bis{μ‐2‐[(1H‐imidazol‐1‐yl)methyl]‐1H‐benzimidazole}‐κ²N²:N³;κ²N³:N²] dimethylformamide disolvate], {[Cd(C₈H₄O₄)(C₁₁H₁₀N₄)]·C₃H₇NO}_n, (I), each Cd^II ion exhibits an irregular octahedral CdO₄N₂ coordination geometry and is coordinated by four O atoms from two symmetry‐related benzene‐1,2‐dicarboxylate (1,2‐bdic²⁻) ligands and two N atoms from two symmetry‐related imb ligands. Two Cd^II ions are connected by two benzene‐1,2‐dicarboxylate ligands to generate a binuclear [Cd₂(1,2‐bdic)₂] unit. The binuclear units are further connected into a one‐dimensional chain by pairs of bridging imb ligands. These one‐dimensional chains are further connected through N—H…O hydrogen bonds and π–π interactions, leading to a two‐dimensional layered structure. The dimethylformamide solvent molecules are organized in dimeric pairs via weak interactions. In addition, the title polymer exhibits good fluorescence properties in the solid state at room temperature.     

Synthesis,structure and properties of a new three‐dimensional interpenetrated metal–organic framework with 3,3′‐azodibenzoic acid (H2azdc) and 1,4‐bis(1H‐imidazol‐1‐yl)butane (bimb): {[Cd(azdc)(bimb)2]·H2O}n

A new three‐dimensional interpenetrated Cd^II–organic framework based on 3,3′‐azodibenzoic acid [3,3′‐(diazenediyl)dibenzoic acid, H₂azdc] and the auxiliary flexible ligand 1,4‐bis(1H‐imidazol‐1‐yl)butane (bimb), namely poly[[bis[μ₂‐1,4‐bis(1H‐imidazol‐1‐yl)butane‐κ²N³:N^3′][μ₂‐3,3′‐(diazenediyl)dibenzoato‐κ²O:O′]cadmium(II)] monohydrate], {[Cd(C₁₄H₈N₂O₄)(C₁₀H₁₄N₂)₂]·H₂O}_n, (1), was obtained by a typical solution reaction in mixed solvents (water and N,N′‐dimethylformamide). Each Cd^II centre is six‐coordinated by two O atoms of bis‐monodentate bridging carboxylate groups from two azdc²⁻ ligands and by four N atoms from four bimb ligands, forming an octahedral coordination environment. The Cd^II ions are connected by the bimb ligands, resulting in two‐dimensional (4,4) layers, which are further pillared by the azdc²⁻ ligands, affording a threefold interpenetrated three‐dimensional α‐Po topological framework with the Schläfli symbol 4¹²6³. The thermal stability and solid‐state fluorescence properties of (1) have been investigated.     

A three‐dimensional coordination polymer based on the Zn4(μ3‐OH)2 unit: poly[[(μ4‐benzene‐1,4‐dicarboxylato)bis(μ3‐benzene‐1,4‐dicarboxylato)bis(μ3‐hydroxido)bis(1,10‐phenanthroline‐5,6‐dione)tetrazinc] dihydrate]

The title compound, {[Zn₄(C₈H₄O₄)₃(OH)₂(C₁₂H₆N₂O₂)₂]·2H₂O}_n, has been prepared hydrothermally by the reaction of Zn(NO₃)₂·6H₂O with benzene‐1,4‐dicarboxylic acid (H₂bdc) and 1,10‐phenanthroline‐5,6‐dione (pdon) in H₂O. In the crystal structure, a tetranuclear Zn₄(OH)₂ fragment is located on a crystallographic inversion centre which relates two subunits, each containing a [ZnN₂O₄] octahedron and a [ZnO₄] tetrahedron bridged by a μ₃‐OH group. The pdon ligand chelates to zinc through its two N atoms to form part of the [ZnN₂O₄] octahedron. The two crystallographically independent bdc²⁻ ligands are fully deprotonated and adopt μ₃‐κO:κO′:κO′′ and μ₄‐κO:κO′:κO′′:κO′′′ coordination modes, bridging three or four Zn^II cations, respectively, from two Zn₄(OH)₂ units. The Zn₄(OH)₂ fragment connects six neighbouring tetranuclear units through four μ₃‐bdc²⁻ and two μ₄‐bdc²⁻ ligands, forming a three‐dimensional framework with uninodal 6‐connected α‐Po topology, in which the tetranuclear Zn₄(OH)₂ units are considered as 6‐connected nodes and the bdc²⁻ ligands act as linkers. The uncoordinated water molecules are located on opposite sides of the Zn₄(OH)₂ unit and are connected to it through hydrogen‐bonding interactions involving hydroxide and carboxylate groups. The structure is further stabilized by extensive π–π interactions between the pdon and μ₄‐bdc²⁻ ligands.     

CdII and CoII coordination polymers constructed from benzene‐1,4‐dicarboxylic acid and 2‐(pyridin‐3‐yl)‐1H‐benzimidazole ligands

In poly[aqua(μ₃‐benzene‐1,4‐dicarboxylato‐κ⁵O¹,O^1′:O¹:O⁴,O^4′)[2‐(pyridin‐3‐yl‐κN)‐1H‐benzimidazole]cadmium(II)], [Cd(C₈H₄O₄)(C₁₂H₉N₃)(H₂O)]_n, (I), each Cd^II ion is seven‐coordinated by the pyridine N atom from a 2‐(pyridin‐3‐yl)benzimidazole (3‐PyBIm) ligand, five O atoms from three benzene‐1,4‐dicarboxylate (1,4‐bdc) ligands and one O atom from a coordinated water molecule. The complex forms an extended two‐dimensional carboxylate layer structure, which is further extended into a three‐dimensional network by hydrogen‐bonding interactions. In catena‐poly[[diaquabis[2‐(pyridin‐3‐yl‐κN)‐1H‐benzimidazole]cobalt(II)]‐μ₂‐benzene‐1,4‐dicarboxylato‐κ²O¹:O⁴], [Co(C₈H₄O₄)(C₁₂H₉N₃)₂(H₂O)₂]_n, (II), each Co^II ion is six‐coordinated by two pyridine N atoms from two 3‐PyBIm ligands, two O atoms from two 1,4‐bdc ligands and two O atoms from two coordinated water molecules. The complex forms a one‐dimensional chain‐like coordination polymer and is further assembled by hydrogen‐bonding interactions to form a three‐dimensional network.     

Poly[aqua[μ2‐1,4‐bis(imidazol‐1‐ylmethyl)benzene‐κ2N3:N3′](μ2‐5‐hydroxybenzene‐1,3‐dicarboxylato‐κ4O1,O1′:O3,O3′)cadmium(II)], a twofold interpenetrated CdSO4‐like metal–organic polymer

In the title cadmium(II) complex, [Cd(C₈H₄O₅)(C₁₄H₁₄N₄)(H₂O)]_n, the 5‐hydroxybenzene‐1,3‐dicarboxylate (5‐OH‐1,3‐bdc) and 1,4‐bis(imidazol‐1‐ylmethyl)benzene (1,4,‐bix) ligands bridge water‐coordinated Cd^II atoms to generate a three‐dimensional network. Two carboxylate groups from different ligands function as O,O′‐chelates, while two imidazole N atoms from different ligands coordinate in a monodentate fashion, and one water molecule completes the seven‐coordinate pentagonal bipyramid around the Cd^II atom, in which the N atoms occupy the axial sites and the O atoms occupy the equatorial sites. The overall architecture is a twofold interpenetrated CdSO₄‐type framework. The two crystallographically equivalent frameworks are linked by O—H...O hydrogen bonds between the water, hydroxy and carboxylate groups.     

A new two‐dimensional CdII coordination polymer based on 2‐(1H‐imidazol‐1‐ylmethyl)‐6‐methyl‐1H‐benzimidazole and benzene‐1,2‐dicarboxylate: synthesis,crystal structure and characterization

In the construction of coordination polymers, many factors can influence the formation of the final architectures, such as the nature of the metal centres, the organic ligands and the counter‐anions. In the coordination polymer poly[aqua(μ‐benzene‐1,2‐dicarboxylato‐κ⁴O ¹,O ^1′:O ²,O ^2′)[μ‐2‐(1H‐imidazol‐1‐ylmethyl)‐6‐methyl‐1H‐benzimidazole‐κ²N ²:N ³]cadmium(II)], [Cd(C₁₂H₁₂N₄)(C₈H₄O₄)(H₂O)]_n or [Cd(immb)(1,2‐bdic)(H₂O)]_n , each Cd^II ion is seven‐coordinated by two N atoms from two symmetry‐related 2‐(1H‐imidazol‐1‐ylmethyl)‐6‐methyl‐1H‐benzimidazole (immb) ligands, by four O atoms from two symmetry‐related benzene‐1,2‐dicarboxylate (1,2‐bdic²⁻) ligands and by one water molecule, leading to a CdN₂O₅ distorted pentagonal bipyramidal coordination environment. The immb and 1,2‐bdic²⁻ ligands bridge Cd^II ions and form a two‐dimensional network structure. O—H…O and N—H…O hydrogen bonds stabilize the structure. In addition, the IR spectroscopic properties, PXRD patterns, thermogravimetric behaviour and fluorescence properties of the title polymer have been investigated.     

Two isomorphous ZnII/CoII complexes with tri‐tert‐butoxysilanethiol and histamine,and (4‐hydroxymethyl‐1H‐imidazole‐κN)bis(tri‐tert‐butoxysilanethiolato‐κ2O,S)zinc(II)

The complexes [2‐(1H‐imidazol‐4‐yl‐κN³)ethylamine‐κN]bis(tri‐tert‐butoxysilanethiolato‐κS)cobalt(II), [Co(C₁₂H₂₇O₃SSi)₂(C₅H₉N₃)], and [2‐(1H‐imidazol‐4‐yl‐κN³)ethylamine‐κN]bis(tri‐tert‐butoxysilanethiolato‐κS)zinc(II), [Zn(C₁₂H₂₇O₃SSi)₂(C₅H₉N₃)], are isomorphous. The central Zn^II/Co^II ions are surrounded by two S atoms from the tri‐tert‐butoxysilanethiolate ligand and by two N atoms from the chelating histamine ligand in a distorted tetrahedral geometry, with two intramolecular N—H...O hydrogen‐bonding interactions between the histamine NH₂ groups and tert‐butoxy O atoms. Molecules of the complexes are joined into dimers via two intermolecular bifurcated N—H...(S,O) hydrogen bonds. The Zn^II atom in [(1H‐imidazol‐4‐yl‐κN³)methanol]bis(tri‐tert‐butoxysilanethiolato‐κ²O,S)zinc(II), [Zn(C₁₂H₂₇O₃SSi)₂(C₄H₆N₂O)], is five‐coordinated by two O and two S atoms from the O,S‐chelating silanethiolate ligand and by one N atom from (1H‐imidazol‐4‐yl)methanol; the hydroxy group forms an intramolecular hydrogen bond with sulfur. Molecules of this complex pack as zigzag chains linked by N—H...O hydrogen bonds. These structures provide reference details for cysteine‐ and histidine‐ligated metal centers in proteins.     

Syntheses,structures and characterization of isomorphous CoII and NiII coordination polymers based on 2‐[(1H‐imidazol‐1‐yl)methyl]‐6‐methyl‐1H‐benzimidazole and benzene‐1,4‐dicarboxylate

Careful choice of the organic ligands is one of the most important parameters in the rational design and synthesis of coordination polymers. Aromatic polycarboxylates have been widely used in the preparation of metal–organic polymers since they can utilize various coordination modes to form diverse structures and can act as hydrogen‐bond acceptors and donors in the assembly of supramolecular structures. Nitrogen‐heterocyclic organic compounds have also been used extensively as ligands for the construction of polymers with interesting structures. In the polymers catena‐poly[[[diaquabis{2‐[(1H‐imidazol‐1‐yl)methyl]‐6‐methyl‐1H‐benzimidazole‐κN ³}cobalt(II)]‐μ₂‐benzene‐1,4‐dicarboxylato‐κ²O ¹:O ⁴] dihydrate], {[Co(C₈H₄O₄)(C₁₂H₁₁N₄)₂(H₂O)₂]·2H₂O}_n , (I), and catena‐poly[[[diaquabis{2‐[(1H‐imidazol‐1‐yl)methyl]‐6‐methyl‐1H‐benzimidazole‐κN ³}nickel(II)]‐μ₂‐benzene‐1,4‐dicarboxylato‐κ²O ¹:O ⁴] dihydrate], {[Ni(C₈H₄O₄)(C₁₂H₁₁N₄)₂(H₂O)₂]·2H₂O}_n , (II), the Co^II or Ni^II ion lies on an inversion centre and exhibits a slightly distorted octahedral coordination geometry, coordinated by two N atoms from two imidazole rings and four O atoms from two monodentate carboxylate groups and two water molecules. The dicarboxylate ligands bridge metal ions forming a polymeric chain. The 2‐[(1H‐imidazol‐1‐yl)methyl]‐6‐methyl‐1H‐benzimidazole ligands coordinate to the Co^II or Ni^II centres in monodentate modes through an imidazole N atom and are pendant on opposite sides of the main chain. The two structures are isomorphous. In the crystal, the one‐dimensional chains are further connected through O—H…O, O—H…N and N—H…O hydrogen bonds, leading to a three‐dimensional supramolecular architecture. In addition, the IR spectroscopic properties, PXRD patterns, thermogravimetric behaviours and fluorescence properties of both polymers have been investigated.     

A three‐dimensional CdII coordination polymer constructed from 1,1′‐biphenyl‐2,2′,5,5′‐tetracarboxylate and 1,4‐bis(1H‐imidazol‐1‐yl)benzene ligands

The title coordination polymer, poly[[aqua(μ₅‐1,1′‐biphenyl‐2,2′,5,5′‐tetracarboxylato)bis[μ₂‐1,4‐bis(1H‐imidazol‐1‐yl)benzene]dicadmium(II)] dihydrate], {[Cd₂(C₁₆H₆O₈)(C₁₂H₁₀N₄)₂(H₂O)]·2H₂O}_n, was crystallized from a mixture of 1,1′‐biphenyl‐2,2′,5,5′‐tetracarboxylic acid (H₄bpta), 1,4‐bis(1H‐imidazol‐1‐yl)benzene (1,4‐bib) and cadmium nitrate in water–dimethylformamide. The crystal structure consists of two crystallographically independent Cd^II cations, with one of the Cd^II cations possessing a slightly distorted pentagonal bipyramidal geometry. The second Cd^II centre is coordinated by carboxylate O atoms and imidazole N atoms from two separate 1,4‐bib ligands, displaying a distorted octahedral CdN₂O₄ geometry. The completely deprotonated bpta⁴⁻ ligand, exhibiting a new coordination mode, bridges five Cd^II cations to form one‐dimensional chains viaμ₃‐η¹:η²:η¹:η² and μ₂‐η¹:η¹:η⁰:η⁰ modes, and these are further linked by 1,4‐bib ligands to form a three‐dimensional framework with a (4².6⁴)(4.6²)(4³.6⁵.7²) topology. The structure of the coordination polymer is reinforced by intermolecular hydrogen bonding between carboxylate O atoms, aqua ligands and crystallization water molecules. The solid‐state photoluminescence properties were investigated and the complex might be a candidate for a thermally stable and solvent‐resistant blue fluorescent material.     

Two threefold interpenetrated two‐dimensional frameworks based on a flexible imidazole‐containing ligand and benzene‐1,4‐dicarboxylate

The open‐chain polyether‐bridged flexible ligand 1,2‐bis[2‐(1H‐1,3‐imidazol‐1‐ylmethyl)phenoxy]ethane (L) has been used to create two two‐dimensional coordination polymers under hydrothermal reaction of L with Cd^II or Co^II, in the presence of benzene‐1,4‐dicarboxylic acid (H₂bdc). In poly[[(μ₂‐benzene‐1,4‐dicarboxylato){μ‐1,2‐bis[2‐(1H‐1,3‐imidazol‐1‐ylmethyl)phenoxy]ethane}cadmium(II)] dihydrate], {[Cd(C₈H₄O₄)(C₂₂H₂₂N₄O₂)]·2H₂O}_n, (I), and the cobalt(II) analogue {[Co(C₈H₄O₄)(C₂₂H₂₂N₄O₂)]·2H₂O}_n, (II), the Cd^II and Co^II cations are six‐coordinated by four carboxylate O atoms from two different bdc²⁻ dianions in a chelating mode and two N atoms from two distinct L ligands. The metal ions, bdc²⁻ dianions and L ligands each sit across crystallographic twofold axes. The bdc²⁻ coordination mode and the coordinating orientation of the L ligand play an important role in constructing the novel two‐dimensional framework. Complexes (I) and (II) are threefold interpenetrated two‐dimensional frameworks; their structures are almost isomorphous, while the bond lengths, angles and hydrogen bonds are different in (I) and (II).     

A one‐dimensional lead(II) coordination polymer with terminal and bridging 5‐carboxy‐2‐(pyridin‐3‐yl)‐1H‐imidazole‐4‐carboxylate ligands

In the coordination polymer catena‐poly[[[diaqua[5‐carboxy‐2‐(pyridin‐3‐yl)‐1H‐imidazole‐4‐carboxylato‐κ²N³,O⁴]lead(II)]‐μ‐5‐carboxy‐2‐(pyridin‐3‐yl)‐1H‐imidazole‐4‐carboxylato‐κ³N³,O⁴:N²] dihydrate], {[Pb(C₁₀H₆N₃O₄)(H₂O)₂]·2H₂O}_n, the two 5‐carboxy‐2‐(pyridin‐3‐yl)‐1H‐imidazole‐4‐carboxylate ligands have different coordination modes, one being terminal and the other bridging. The bridging ligand links Pb^II cations into one‐dimensional coordination polymer chains. The structure is also stabilized by intra‐ and interchain π–π stacking interactions between the pyridine rings, resulting in the formation of a two‐dimensional network. Extensive hydrogen‐bonding interactions lead to the formation of a three‐dimensional supramolecular network.     

A three‐dimensional ZnII coordination network based on 5,5′‐methylenebis(2,4,6‐trimethylisophthalic acid) and 2,7‐bis(1H‐imidazol‐1‐yl)fluorene: synthesis,structure and luminescence properties

In recent years, coordination polymers constructed from multidentate carboxylate ligands and N‐containing ligands have attracted much attention since these ligands can adopt a rich variety of coordination modes which can lead to crystalline products with intriguing structures and interesting properties. A new coordination polymer, namely poly[[diaqua[μ‐2,7‐bis(1H‐imidazol‐1‐yl)fluorene‐κ²N³:N^3′][μ‐5,5′‐methylenebis(3‐carboxy‐2,4,6‐trimethylbenzoato)‐κ²O¹:O^1′]zinc(II)] hemihydrate], {[Zn(C₂₃H₂₂O₈)(C₁₉H₁₄N₄)(H₂O)₂]·0.5H₂O}_n, 1 , was prepared by the self‐assembly of Zn(NO₃)₂·6H₂O with 5,5′‐methylenebis(2,4,6‐trimethylisophthalic acid) (H₄BTMIPA) and 2,7‐bis(1H‐imidazol‐1‐yl)fluorene (BIF) under solvothermal conditions. The structure of 1 was determined by elemental analysis, single‐crystal X‐ray crystallography, powder X‐ray diffraction, IR spectroscopy and thermogravimetric analysis. Each Zn^II ion is six‐coordinated by two O atoms from two H₂BTMIPA^2? ligands, by two N atoms from two BIF ligands and by two water molecules, forming a distorted octahedral ZnN₂O₄ coordination geometry. Adjacent Zn^II ions are linked by H₂BTMIPA^2? ligands and BIF ligands, leading to the formation of a two‐dimensional (2D) (4,4)‐ sql network, and intermolecular hydrogen‐bonding interactions connect the 2D layer structure into the three‐dimensional (3D) supramolecular structure. Each 2D layer contains two kinds of helices with the same direction, which are opposite in adjacent layers. The luminescence properties of complex 1 in the solid state have also been investigated.     

A two‐dimensional cadmium(II) coordination polymer constructed from 4‐carboxy‐1‐(4‐carboxylatobenzyl)‐2‐propyl‐1H‐imidazole‐5‐carboxylate and 1‐(4‐carboxylatobenzyl)‐2‐propyl‐1H‐imidazole‐4‐carboxylate ligands

Crystals of poly[[aqua[μ₃‐4‐carboxy‐1‐(4‐carboxylatobenzyl)‐2‐propyl‐1H‐imidazole‐5‐carboxylato‐κ⁵O¹O^1′:N³,O⁴:O⁵][μ₄‐1‐(4‐carboxylatobenzyl)‐2‐propyl‐1H‐imidazole‐4‐carboxylato‐κ⁷N³,O⁴:O⁴,O^4′:O¹,O^1′:O¹]cadmium(II)] monohydrate], {[Cd₂(C₁₅H₁₄N₂O₄)(C₁₆H₁₄N₂O₆)(H₂O)]·H₂O}_n or {[Cd₂(Hcpimda)(cpima)(H₂O)]·H₂O}_n, (I), were obtained from 1‐(4‐carboxybenzyl)‐2‐propyl‐1H‐imidazole‐4,5‐dicarboxylic acid (H₃cpimda) and cadmium(II) chloride under hydrothermal conditions. The structure indicates that in‐situ decarboxylation of H₃cpimda occurred during the synthesis process. The asymmetric unit consists of two Cd²⁺ centres, one 4‐carboxy‐1‐(4‐carboxylatobenzyl)‐2‐propyl‐1H‐imidazole‐5‐carboxylate (Hcpimda²⁻) anion, one 1‐(4‐carboxylatobenzyl)‐2‐propyl‐1H‐imidazole‐4‐carboxylate (cpima²⁻) anion, one coordinated water molecule and one lattice water molecule. One Cd²⁺ centre, i.e. Cd1, is hexacoordinated and displays a slightly distorted octahedral CdN₂O₄ geometry. The other Cd centre, i.e. Cd2, is coordinated by seven O atoms originating from one Hcpimda²⁻ ligand and three cpima²⁻ ligands. This Cd²⁺ centre can be described as having a distorted capped octahedral coordination geometry. Two carboxylate groups of the benzoate moieties of two cpima²⁻ ligands bridge between Cd2 centres to generate [Cd₂O₂] units, which are further linked by two cpima²⁻ ligands to produce one‐dimensional (1D) infinite chains based around large 26‐membered rings. Meanwhile, adjacent Cd1 centres are linked by Hcpimda²⁻ ligands to generate 1D zigzag chains. The two types of chains are linked through a μ₂‐η² bidentate bridging mode from an O atom of an imidazole carboxylate unit of cpima²⁻ to give a two‐dimensional (2D) coordination polymer. The simplified 2D net structure can be described as a 3,6‐coordinated net which has a (4³)₂(4⁶.6⁶.8³) topology. Furthermore, the FT–IR spectroscopic properties, photoluminescence properties, powder X‐ray diffraction (PXRD) pattern and thermogravimetric behaviour of the polymer have been investigated.     

Two new isomeric zinc(II) metal–organic frameworks based on 1,5‐bis(2‐methyl‐1H‐imidazol‐1‐yl)pentane and 5‐methylisophthalate ligands

Many factors, such as temperature, solvent, the central metal atom and the type of coligands, may affect the nature of metal–organic frameworks (MOFs) and the framework formation in the self‐assembly process, which results in the complexity of these compounds and the uncertainty of their structures. Two new isomeric Zn^II metal–organic frameworks (MOFs) based on mixed ligands, namely, poly[[μ‐1,5‐bis(2‐methyl‐1H‐imidazol‐1‐yl)pentane‐κ²N ³:N ^3′](μ‐5‐methylisophthalato‐κ²O ¹:O ³)zinc(II)], [Zn(C₉H₆O₄)(C₁₃H₂₀N₄)]_n , (I), and poly[[μ‐1,5‐bis(2‐methyl‐1H‐imidazol‐1‐yl)pentane‐κ²N ³:N ^3′](μ₃‐5‐methylisophthalato‐κ³O ¹:O ^1′:O ³)(μ₃‐5‐methylisophthalato‐κ⁴O ¹:O ^1′:O ³,O ^3′)dizinc(II)], [Zn₂(C₉H₆O₄)₂(C₁₃H₂₀N₄)]_n , (II), have been synthesized under hydrothermal conditions and characterized by single‐crystal X‐ray diffraction, IR spectroscopy, elemental analysis and thermogravimetric analysis. Complex (I) displays a two‐dimensional layer net, while complex (II) exhibits a twofold interpenetrating three‐dimensional framework. Both complexes show high stability and good fluorescence in the solid state at room temperature.     

Three novel topologically different metal–organic frameworks built from 3‐nitro‐4‐(pyridin‐4‐yl)benzoic acid

The design and synthesis of metal–organic frameworks (MOFs) have attracted much interest due to the intriguing diversity of their architectures and topologies. However, building MOFs with different topological structures from the same ligand is still a challenge. Using 3‐nitro‐4‐(pyridin‐4‐yl)benzoic acid (HL) as a new ligand, three novel MOFs, namely poly[[(N,N‐dimethylformamide‐κO)bis[μ₂‐3‐nitro‐4‐(pyridin‐4‐yl)benzoato‐κ³O,O′:N]cadmium(II)] N,N‐dimethylformamide monosolvate methanol monosolvate], {[Cd(C₁₂H₇N₂O₄)₂(C₃H₇NO)]·C₃H₇NO·CH₃OH}_n, ( 1 ), poly[[(μ₂‐acetato‐κ²O:O′)[μ₃‐3‐nitro‐4‐(pyridin‐4‐yl)benzoato‐κ³O:O′:N]bis[μ₃‐3‐nitro‐4‐(pyridin‐4‐yl)benzoato‐κ⁴O,O′:O′:N]dicadmium(II)] N,N‐dimethylacetamide disolvate monohydrate], {[Cd₂(C₁₂H₇N₂O₄)₃(CH₃CO₂)]·2C₄H₉NO·H₂O}_n, ( 2 ), and catena‐poly[[[diaquanickel(II)]‐bis[μ₂‐3‐nitro‐4‐(pyridin‐4‐yl)benzoato‐κ²O:N]] N,N‐dimethylacetamide disolvate], {[Ni(C₁₂H₇N₂O₄)₂(H₂O)₂]·2C₄H₉NO}_n, ( 3 ), have been prepared. Single‐crystal structure analysis shows that the Cd^II atom in MOF ( 1 ) has a distorted pentagonal bipyramidal [CdN₂O₅] coordination geometry. The [CdN₂O₅] units as 4‐connected nodes are interconnected by L^? ligands to form a fourfold interpenetrating three‐dimensional (3D) framework with a dia topology. In MOF ( 2 ), there are two crystallographically different Cd^II ions showing a distorted pentagonal bipyramidal [CdNO₆] and a distorted octahedral [CdN₂O₄] coordination geometry, respectively. Two Cd^II ions are connected by three carboxylate groups to form a binuclear [Cd₂(COO)₃] cluster. Each binuclear cluster as a 6‐connected node is further linked by acetate groups and L^? ligands to produce a non‐interpenetrating 3D framework with a pcu topology. MOF ( 3 ) contains two crystallographically distinct Ni^II ions on special positions. Each Ni^II ion adopts an elongated octahedral [NiN₂O₄] geometry. Each Ni^II ion as a 4‐connected node is linked by L^? ligands to generate a two‐dimensional network with an sql topology, which is further stabilized by two types of intermolecular OW—HW…O hydrogen bonds to form a 3D supramolecular framework. MOFs ( 1 )–( 3 ) were also characterized by powder X‐ray diffraction, IR spectroscopy and thermogravimetic analysis. Furthermore, the solid‐state photoluminescence of HL and MOFs ( 1 ) and ( 2 ) have been investigated. The photoluminescence of MOFs ( 1 ) and ( 2 ) are enhanced and red‐shifted with respect to free HL. The gas adsorption investigation of MOF ( 2 ) indicates a good separation selectivity (71) of CO₂/N₂ at 273 K (i.e. the amount of CO₂ adsorption is 71 times higher than N₂ at the same pressure).     

Synthesis,crystal structure and characterization of a three‐dimensional CdII coordination polymer constructed from 2,5‐bis(1H‐1,2,4‐triazol‐1‐yl)terephthalate

Bifunctional organic ligands are very popular for the design of coordination polymers because they allow the formation of a great diversity of structures. In the title coordination polymer, the new bifunctional inversion‐symmetric ligand 2,5‐bis(1H‐1,2,4‐triazol‐1‐yl)terephthalic acid (abbreviated as H₂bttpa) links Cd^II cations, giving rise to the three‐dimensional Cd^II coordination polymer catena‐poly[diaqua[μ₄‐2,5‐bis(1H‐1,2,4‐triazol‐1‐yl)terephthalato‐κ⁴O¹:O⁴:N⁴:N^4′]cadmium(II)], [Cd(C₁₂H₆N₆O₄)(H₂O)₂]_n or [Cd(bttpa)(H₂O)₂]_n. The asymmetric unit consists of half a Cd^II cation, half a bttpa²⁻ ligand and one coordinated water molecule. The Cd^II cation is located on a twofold axis and is hexacoordinated in a distorted octahedral environment of four O and two N atoms. Four different bttpa²⁻ ligands contribute to this coordination, with two carboxylate O atoms in trans positions and two triazole N atoms in cis positions. Two aqua ligands in cis positions complete the coordination sphere. The fully deprotonated bttpa²⁻ ligand sits about a crystallographic centre of inversion and links two Cd^II cations to form a chain in a μ₂‐terephthalato‐κ²O¹:O⁴ bridge. This chain extends in the other two directions via the triazole heterocycles, producing a three‐dimensional framework. O—H…O hydrogen bonds and weak C—H…N interactions stabilize the three‐dimensional crystal structure. The FT–IR spectrum, X‐ray powder pattern, thermogravimetric behaviour and solid‐state photoluminescence of the title polymer have been investigated. The photoluminescence is enhanced and red‐shifted with respect to the uncoordinated ligand.     

Construction and photocatalytic properties of two metal‐mediated coordination polymers based on benzene‐1,3,5‐tricarboxylic acid and trans‐1‐(pyridin‐3‐yl)‐2‐(pyridin‐4‐yl)ethene

With the rapid development of modern industry, water pollution has become an intractable environmental issue facing humans worldwide. In particular, the organic dyes discharged into natural water from dyestuffs, dyeing and the textile industry are the main sources of pollution in wastewater. To eliminate these types of pollutants, degradation of organic contaminants through a photocatalytic technique is an effective methodology. To exploit more crystalline photocatalysts for the degradation of organic dyes, two coordination polymers, namely catena‐poly[[(3,5‐dicarboxybenzene‐1‐carboxylato‐κO ¹)silver(I)]‐μ‐trans‐1‐(pyridin‐3‐yl)‐2‐(pyridin‐4‐yl)ethene‐κ²N :N ′], [Ag(C₉H₅O₆)(C₁₂H₁₀N₂)]_n or [Ag(H₂BTC)(3,4′‐bpe)]_n , (I), and poly[[(μ₃‐5‐carboxybenzene‐1,3‐dicarboxylato‐κ⁴O ¹,O ^1′:O ³:O ³)[μ‐trans‐1‐(pyridin‐3‐yl)‐2‐(pyridin‐4‐yl)ethene‐κ²N :N′ ]cadmium(II)] monohydrate], {[Cd(C₉H₄O₆)(C₁₂H₁₀N₂)]·H₂O}_n or {[Cd(HBTC)(3,4′‐bpe)]·H₂O}_n , (II), have been prepared by the hydrothermal reactions of benzene‐1,3,5‐tricarboxylic acid (H₃BTC) and trans‐1‐(pyridin‐3‐yl)‐2‐(pyridin‐4‐yl)ethene (3,4′‐bpe) in the presence of AgNO₃ or Cd(NO₃)₂·4H₂O, respectively. These two title compounds have been structurally characterized by IR spectroscopy, elemental analysis, single‐crystal X‐ray diffraction and powder X‐ray diffraction. In (I), the Ag^I ions and organic ligands form a one‐dimensional coordination chain, and adjacent coordination chains are connected by Ag…O interactions to give rise to a two‐dimensional supramolecular network. Each two‐dimensional network is entangled with other equivalent networks to generate an infrequent interlocked 2D→3D (2D and 3D are two‐ and three‐dimensional, respectively) supramolecular framework. In (II), the Cd^II ions are bridged by the HBTC²⁻ and 3,4′‐bpe ligands, which lie across centres of inversion, to give a two‐dimensional coordination network. The thermal stabilities and photocatalytic properties of the title compounds have also been studied.     

Two new cadmium(II) coordination polymers based on bis(1,2,4‐triazol‐1‐yl)alkane ligands and pyrazine‐2,3‐dicarboxylic acid

Assemblies of pyrazine‐2,3‐dicarboxylic acid and Cd^II in the presence of bis(1,2,4‐triazol‐1‐yl)butane or bis(1,2,4‐triazol‐1‐yl)ethane under ambient conditions yielded two new coordination polymers, namely poly[[tetraaqua[μ₂‐1,4‐bis(1,2,4‐triazol‐1‐yl)butane‐κ²N⁴:N^4′]bis(μ₂‐pyrazine‐2,3‐dicarboxylato‐κ³N¹,O²:O³)dicadmium(II)] dihydrate], {[Cd₂(C₆H₂N₂O₄)₂(C₈H₁₂N₆)(H₂O)₄]·2H₂O}_n, (I), and poly[[diaqua[μ₂‐1,2‐bis(1,2,4‐triazol‐1‐yl)ethane‐κ²N⁴:N^4′]bis(μ₃‐pyrazine‐2,3‐dicarboxylato‐κ⁴N¹,O²:O³:O^3′)dicadmium(II)] dihydrate], {[Cd₂(C₆H₂N₂O₄)₂(C₆H₈N₆)(H₂O)₂]·2H₂O}_n, (II). Complex (I) displays an interesting two‐dimensional wave‐like structure and forms a distinct extended three‐dimensional supramolecular structure with the help of O—H...N and O—H...O hydrogen bonds. Complex (II) has a three‐dimensional framework structure in which hydrogen bonds of the O—H...N and O—H...O types are found.