The effect of the coordination orientation of N atoms on polymeric structures: synthesis and characterization of one‐ and two‐dimensional CuII coordination polymers based on 4‐amino‐3‐(pyridin‐2‐yl)‐5‐[(pyridin‐3‐ylmethyl)sulfanyl]‐1,2,4‐triazole

Three new one‐ (1D) and two‐dimensional (2D) Cu^II coordination polymers, namely poly[[bis{μ₂‐4‐amino‐3‐(pyridin‐2‐yl)‐5‐[(pyridin‐3‐ylmethyl)sulfanyl]‐1,2,4‐triazole}copper(II)] bis(methanesulfonate) tetrahydrate], {[Cu(C₁₃H₁₂N₅S)₂](CH₃SO₃)₂·4H₂O}_n ( 1 ), catena‐poly[[copper(II)‐bis{μ₂‐4‐amino‐3‐(pyridin‐2‐yl)‐5‐[(pyridin‐4‐ylmethyl)sulfanyl]‐1,2,4‐triazole}] dinitrate methanol disolvate], {[Cu(C₁₃H₁₂N₅S)₂](NO₃)₂·2CH₃OH}_n ( 2 ), and catena‐poly[[copper(II)‐bis{μ₂‐4‐amino‐3‐(pyridin‐2‐yl)‐5‐[(pyridin‐4‐ylmethyl)sulfanyl]‐1,2,4‐triazole}] bis(perchlorate) monohydrate], {[Cu(C₁₃H₁₂N₅S)₂](ClO₄)₂·H₂O}_n ( 3 ), were obtained from 4‐amino‐3‐(pyridin‐2‐yl)‐5‐[(pyridin‐3‐ylmethyl)sulfanyl]‐1,2,4‐triazole with pyridin‐3‐yl terminal groups and from 4‐amino‐3‐(pyridin‐2‐yl)‐5‐[(pyridin‐4‐ylmethyl)sulfanyl]‐1,2,4‐triazole with pyridin‐4‐yl terminal groups. Compound 1 displays a 2D net‐like structure. The 2D layers are further linked through hydrogen bonds between methanesulfonate anions and amino groups on the framework and guest H₂O molecules in the lattice to form a three‐dimensional (3D) structure. Compound 2 and 3 exhibit 1D chain structures, in which the complicated hydrogen‐bonding interactions play an important role in the formation of the 3D network. These experimental results indicate that the coordination orientation of the heteroatoms on the ligands has a great influence on the polymeric structures. Moreover, the selection of different counter‐anions, together with the inclusion of different guest solvent molecules, would also have a great effect on the hydrogen‐bonding systems in the crystal structures.     

The crystal structure,luminescence and nitrobenzene‐sensing properties of a two‐dimensional MnII 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‐κ²N³: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.     

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.     

Synthesis of Bis‐Heterocyclic 1H‐Imidazole 3‐Oxides from 3‐Oxido‐1H‐imidazole‐4‐carbohydrazides

The reaction of 1H‐imidazole‐4‐carbohydrazides 1 , which are conveniently accessible by treatment of the corresponding esters with NH₂NH₂?H₂O, with isothiocyanates in refluxing EtOH led to thiosemicarbazides (=hydrazinecarbothioamides) 4 in high yields (Scheme 2). Whereas 4 in boiling aqueous NaOH yielded 2,4‐dihydro‐3H‐1,2,4‐triazole‐3‐thiones 5 , the reaction in concentrated H₂SO₄ at room temperature gave 1,3,4‐thiadiazol‐2‐amines 6 . Similarly, the reaction of 1 with butyl isocyanate led to semicarbazides 7 , which, under basic conditions, undergo cyclization to give 2,4‐dihydro‐3H‐1,2,4‐triazol‐3‐ones 8 (Scheme 3). Treatment of 1 with Ac₂O yielded the diacylhydrazine derivatives 9 exclusively, and the alternative isomerization of 1 to imidazol‐2‐ones was not observed (Scheme 4). It is important to note that, in all these transformations, the imidazole N‐oxide residue is retained. Furthermore, it was shown that imidazole N‐oxides bearing a 1,2,4‐triazole‐3‐thione or 1,3,4‐thiadiazol‐2‐amine moiety undergo the S‐transfer reaction to give bis‐heterocyclic 1H‐imidazole‐2‐thiones 11 by treatment with 2,2,4,4‐tetramethylcyclobutane‐1,3‐dithione (Scheme 5).     

A one‐dimensional zigzag coordination polymer of di­aqua­(pyridine‐2,3‐di­carboxyl­ato)­cobalt(II)

The asymmetric unit of the title one‐dimensional coordination polymer, catena‐poly­[[μ‐pyridine‐2,3‐di­carb­oxyl­ato‐1κO:2κ²N,O′‐bis­[di­aqua­cobalt(II)]]‐μ‐pyridine‐2,3‐di­carboxyl­ato‐1κ²N,O:2κO′:1′κO′], [Co(C₇H₃NO₄)(H₂O)₂]_n, is composed of a cobalt(II) ion, a pyridine‐2,3‐di­carboxyl­ate dianion and two water mol­ecules. The polymer has a zigzag structure consisting of a chain of edge‐fused rings, and the polymer chains are linked by O—H⃛O hydrogen bonds into a three‐dimensional framework.     

Two cobalt(II) supramolecular isomers based on N,N′‐bis(pyridin‐3‐yl)oxalamide induced by the molecular orientation of lattice DMF molecules

Supramolecular isomerism for coordination networks refers to the existence of different architectures having the same building blocks and identical stoichiometries. For a given building block, different arrangements can lead to the formation of a series of supramolecular isomers. Two one‐dimensional Co^II coordination polymers based on N,N′‐bis(pyridin‐3‐yl)oxalamide (BPO), both catena‐poly[[[dichloridocobalt(II)]‐bis[μ‐N,N′‐bis(pyridin‐3‐yl)oxalamide‐κ²N:N′]] dimethylformamide disolvate], {[CoCl₂(C₁₂H₁₀N₄O₂)₂]·2C₃H₇NO}_n, have been assembled by the solvothermal method. Single‐crystal X‐ray diffraction analyses reveal that the two compounds are supramolecular isomers, the isomerism being induced by the orientation of the dimethylformamide (DMF) molecules in the crystal lattice.     

Synthesis and characterization of a cadmium(II)–organic supramolecular coordination compound based on the multifunctional 2‐amino‐5‐sulfobenzoic acid ligand

Much attention has been paid by chemists to the construction of supramolecular coordination compounds based on the multifunctional ligand 5‐sulfosalicylic acid (H₃SSA) due to the structural and biological interest of these compounds. However, no coordination compounds have been reported for the multifunctional amino‐substituted sulfobenzoate ligand 2‐amino‐5‐sulfobenzoic acid (H₂asba). We expected that H₂asba could be a suitable building block for the assembly of supramolecular networks due to its interesting structural characteristics. The reaction of cadmium(II) nitrate with H₂asba in the presence of the auxiliary flexible dipyridylamide ligand N,N′‐bis[(pyridin‐4‐yl)methyl]oxamide (4bpme) under ambient conditions formed a new mixed‐ligand coordination compound, namely bis(3‐amino‐4‐carboxybenzenesulfonato‐κO¹)diaquabis{N,N′‐bis[(pyridin‐4‐yl)methyl]oxamide‐κN}cadmium(II)–N,N′‐bis[(pyridin‐4‐yl)methyl]oxamide–water (1/1/4), [Cd(C₇H₆NO₅S)₂(C₁₄H₁₄N₄O₂)₂(H₂O)₂]·C₁₄H₁₄N₄O₂·4H₂O, (1), which was characterized by single‐crystal and powder X‐ray diffraction analysis (PXRD), FT–IR spectroscopy, thermogravimetric analysis (TG), and UV–Vis and photoluminescence spectroscopic analyses in the solid state. The central Cd^II atom in (1) occupies a special position on a centre of inversion and exhibits a slightly distorted octahedral geometry, being coordinated by two N atoms from two monodentate 4bpme ligands, four O atoms from two monodentate 4‐amino‐3‐carboxybenzenesulfonate (Hasba⁻) ligands and two coordinated water molecules. Interestingly, complex (1) further extends into a threefold polycatenated 0D→2D (0D is zero‐dimensional and 2D is two‐dimensional) interpenetrated supramolecular two‐dimensional (4,4) layer through intermolecular hydrogen bonding. The interlayer hydrogen bonding further links adjacent threefold polycatenated two‐dimensional layers into a three‐dimensional network. The optical properties of complex (1) indicate that it may be used as a potential indirect band gap semiconductor material. Complex (1) exhibits an irreversible dehydration–rehydration behaviour. The fluorescence properties have also been investigated in the solid state at room temperature.     

A 1,2,4‐Triazole‐based Polynuclear Mixed‐valence MnIIMnIII Complex: Synthesis,Characterization, and Magnetic Property

A mixed‐valence Mn complex {[Mn^IIMn^III(HL)₂(4,4′‐bpy)(H₂O)₂] · (ClO₄)(DMF)₃(4,4′‐bpy)_0.5}_n ( 1 ) [H₂L = 3‐(2‐phenol)‐5‐(pyridin‐2‐yl)‐1,2,4‐triazole] was synthesized and characterized by X‐ray single‐crystal structure analysis and magnetic susceptibility. Single‐crystal X‐ray analysis revealed that complex 1 has a dinuclear core, in which adjacent central Mn^III atoms are linked by 4,4′‐bipyridine to form an infinite one‐dimensional (1D) molecular configuration. According to the Mn surrounding bond lengths and bond valence sum (BVS) calculations, we demonstrated that the Mn atom coordinated to the pyridine N atoms is in the +2 oxidation state, while another Mn atom coordinated to the phenolic oxygen atoms is in the +3 oxidation state. Magnetic susceptibility data of the complex 1 indicate that the ferromagnetic interaction dominates in this complex.     

Tetrakis(μ‐2,3‐dimethoxybenzoato)bis[(2,2′‐bipyridine)(2,3‐dimethoxybenzoato)lanthanum(III)]

The title compound, tetrakis(μ‐2,3‐di­methoxy­benzoato)‐κ⁴O:O′;κ⁶O,O′:O′‐bis[(2,2′‐bi­pyridine‐N,N′)(2,3‐di­methoxy­benzoato‐O,O′)lanthanum(III)], [La₂(2,3‐DMOBA)₆(2,2′‐bpy)₂], where 2,3‐DMOBA is 2,3‐di­methoxy­benzoate (C₉H₉O₄) and 2,2′‐bpy is 2,2′‐bi­pyridine (C₁₀H₈N₂), is a dimer with a centre of inversion between the La atoms bridged by four carboxyl­ate ligands. The central La atom is ennea‐coordinated and has a distorted monocapped square‐antiprism geometry.     

Three zinc(II) and cadmium(II) complexes containing 4‐amino‐3,5‐bis(pyridin‐2‐yl)‐1,2,4‐triazole and polynitrile ligands: synthesis,molecular and supramolecular structures,and photoluminescence properties

Three photoluminescent complexes containing either Zn^II or Cd^II have been synthesized and their structures determined. Bis[4‐amino‐3,5‐bis(pyridin‐2‐yl)‐1,2,4‐triazole‐κ²N ¹,N ⁵]bis(dicyanamido‐κN ¹)zinc(II), [Zn(C₁₂H₁₀N₆)₂(C₂N₃)₂], (I), bis[4‐amino‐3,5‐bis(pyridin‐2‐yl)‐1,2,4‐triazole‐κ²N ¹,N ⁵]bis(dicyanamido‐κN ¹)cadmium(II), [Cd(C₁₂H₁₀N₆)₂(C₂N₃)₂], (II), and bis[4‐amino‐3,5‐bis(pyridin‐2‐yl)‐1,2,4‐triazole‐κ²N ¹,N ⁵]bis(tricyanomethanido‐κN ¹)cadmium(II), [Cd(C₁₂H₁₀N₆)₂(C₄N₃)₂], (III), all crystallize in the space group P , with the metal centres lying on centres of inversion, but neither analogues (I) and (II) nor Cd^II complexes (II) and (III) are isomorphous. A combination of N—H…N and C—H…N hydrogen bonds and π–π stacking interactions generates three‐dimensional framework structures in (I) and (II), and a sheet structure in (III). The photoluminescence spectra of (I)–(III) indicate that the energies of the π–π* transitions in the coordinated triazole ligand are modified by minor changes of the ligand geometry associated with coordination to the metal centres.     

2,6‐Bis(1‐benzyl‐1H‐1,2,3‐triazol‐4‐yl)pyridine and its octahedral copper complex

In the tridentate ligand 2,6‐bis(1‐benzyl‐1H‐1,2,3‐triazol‐4‐yl)pyridine, C₂₃H₁₉N₇, both sets of triazole N atoms are anti with respect to the pyridine N atom, while in the copper complex aqua[2,6‐bis(1‐benzyl‐1H‐1,2,3‐triazol‐4‐yl)pyridine](pyridine)(tetrafluoroborato)copper(II) tetrafluoroborate, [Cu(BF₄)(C₅H₅N)(C₂₃H₁₉N₇)(H₂O)]BF₄, the triazole N atoms are in the syn–syn conformation. The coordination of the Cu^II atom is distorted octahedral. The ligand structure is stabilized through intermolecular C—H...N interactions, while the crystal structure of the Cu complex is stabilized through water‐ and BF₄‐mediated hydrogen bonds. Photoluminiscence studies of the ligand and complex show that the ligand is fluorescent due to triazole–pyridine conjugation, but that the fluorescence is quenched on complexation.     

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)‐κ⁴O¹,O^1′:O⁴,O^4′;κ²O¹:O⁴‐bis{μ₂‐2‐[(1H‐1,2,4‐triazol‐1‐yl)methyl‐κN⁴]‐1H‐benzimidazole‐κN³}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 bdic²⁻ ligands [bdic²⁻(A) and bdic²⁻(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 bdic²⁻(A) ligands, forming a two‐dimensional network structure. The two‐dimensional layers are further connected by bdic²⁻(B) ligands, resulting in a three‐dimensional framework with the topological notation 6⁶. 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.     

Synthesis,Structure, and Magnetic Characterization of a Series of Iron(II) Coordination Frameworks with 2, 6‐Bis(1, 2,4‐triazole‐4‐yl)pyridine

Based on the bis‐triazole ligand 2, 6‐bis(1, 2,4‐triazole‐4‐yl)pyridine (L), the triazole‐iron(II) complexes [Fe(L)₂(dca)₂(H₂O)₂] · 2H₂O ( 1 ) (Nadca = sodium dicyanamide), {[Fe(μ₂‐L)₂(H₂O)₂]Cl₂}_n ( 2 ), and {[Fe(μ₂‐L)₂(H₂O)₂](ClO₄)₂ · L · H₂O}_n ( 3 ) were isolated by solvent diffusion methods. When iron(II) salts and Nadca were used, compound 1 was isolated, which contains mononuclear Fe(L)₂(dca)₂(H₂O)₂ units. When FeCl₂ or FeClO₄ were used, one‐dimensional (1D) cation iron(II) chains ( 2 ) and two‐dimensional (2D) cation iron(II) networks ( 3 ) were isolated indicating anion directing structural diversity. Moreover, variable‐temperature magnetic susceptibility data of 1 – 3 were recorded in the temperature range 2–300 K. The magnetic curve of complex 2 was fitted by using the classical spin Heisenberg chain model indicating anti‐ferromagnetic interactions (J = –5.31 cm^–1). Obviously complexes 1 – 3 show no detectable thermal spin crossover behaviors, the lack of spin‐crossover behavior may be correlated with FeN₄O₂ coordination spheres in 1 – 3 .     

Construction of (3,8)‐connected three‐dimensional cobalt(II) and copper(II) coordination polymers with 1,3‐bis[(1,2,4‐triazol‐4‐yl)methyl]benzene and benzene‐1,3,5‐tricarboxylate ligands

Coordination polymers (CPs) have been widely studied because of their diverse and adjustable topologies and wide‐ranging applications in luminescence, chemical sensors, magnetism, photocatalysis, gas adsorption and separation. In the present work, two coordination polymers, namely poly[(μ₅‐benzene‐1,3,5‐tricarboxylato‐κ⁶O¹:O^1′:O³:O³:O⁵,O^5′){μ₃‐1,3‐bis[(1,2,4‐triazol‐4‐yl)methyl]benzene‐κ³N:N′:N′′}di‐μ₃‐hydroxido‐dicobalt(II)], [Co₂(C₉H₃O₆)(OH)(C₁₂H₁₂N₆)]_n or [Co₂(btc)(OH)(mtrb)]_n, (1), and poly[[diaquabis(μ₃‐benzene‐1,3,5‐tricarboxylato‐κ³O¹:O³:O⁵)bis{μ₃‐1,3‐bis[(1,2,4‐triazol‐4‐yl)methyl]benzene‐κ³N:N′:N′′}tetra‐μ₃‐hydroxido‐tetracopper(II)] monohydrate], {[Cu₄(C₉H₃O₆)₂(OH)₂(C₁₂H₁₂N₆)₂(H₂O)₂]·H₂O}_n or {[Cu₄(btc)₂(OH)₂(mtrb)₂(H₂O)₂]·H₂O}_n, (2), were synthesized by the hydrothermal method using 1,3‐bis[(1,2,4‐triazol‐4‐yl)methyl]benzene (mtrb) and benzene‐1,3,5‐tricarboxylate (btc^3?). CP (1) exhibits a (3,8)‐coordinated three‐dimensional (3D) network of the 3,8T38 topological type, with a point symbol of {4,5,6}₂{4²·5⁶·6¹⁶·7²·8²}, based on the tetranuclear hydroxide cobalt(II) cluster [Co₄(μ₃‐OH)₂]. CP (2) shows a (3,8)‐coordinated tfz‐d topology, with a point symbol of {4₃}₂{4⁶·6¹⁸·8⁴}, based on the tetranuclear hydroxide copper(II) cluster [Cu₄(μ₃‐OH)₂]. The different (3,8)‐coordinated 3D networks based on tetranuclear hydroxide–metal clusters of (1) and (2) are controlled by the different central metal ions [Co^II for (1) and Cu^II for (2)]. The thermal stabilities and solid‐state optical diffuse‐reflection spectra were measured. The energy band gaps (E_g) obtained for (1) and (2) were 2.72 and 2.29 eV, respectively. CPs (1) and (2) exhibit good photocatalytic degradation of the organic dyes methylene blue (MB) and rhodamine B (RhB) under visible‐light irradiation.     

Copper(II) and cadmium(II) isothiocyanate coordination polymers with 4,4′‐bi‐1,2,4‐triazole

The coordination polymers catena‐poly[[[(4,4′‐bi‐1,2,4‐triazole‐κN¹)bis(thiocyanato‐κN)copper(II)]‐μ‐4,4′‐bi‐1,2,4‐triazole‐κ²N¹:N^1′] dihydrate], {[Cu(NCS)₂(C₄H₄N₆)₂]·2H₂O}_n, (I), and poly[tetrakis(μ‐4,4′‐bi‐1,2,4‐triazole‐κ²N¹:N^1′)bis(μ‐thiocyanato‐κ²N:S)tetrakis(thiocyanato‐κN)tricadmium(II)], [Cd₃(NCS)₆(C₄H₄N₆)₄]_n, (II), exhibit chain and two‐dimensional layer structures, respectively. The differentiation of the Lewis acidic nature of Cu^II and Cd^II has an influence on the coordination modes of the triazole and thiocyanate ligands, leading to topologically different polymeric motifs. In (I), copper ions are linked by bitriazole N:N′‐bridges into zigzag chains and the tetragonal–pyramidal CuN₅ environment is composed of two thiocyanate N atoms and three triazole N atoms [basal Cu—N = 1.9530 (18)–2.0390 (14) Å and apical Cu—N = 2.2637 (15) Å]. The structure of (II) contains two types of crystallographically unique Cd^II atoms. One type lies on an inversion center in a distorted CdN₆ octahedral environment, with bitriazole ligands in the equatorial plane and terminal isothiocyanate N atoms in the axial positions. The other type lies on a general position and forms centrosymmetric binuclear [Cd₂(μ‐NCS‐κ²N:S)₂(NCS)₂] units (tetragonal–pyramidal CdN₄S coordination). N:N′‐Bridging bitriazole ligands link the Cd centers into a flat (4,4)‐network.     

Hexaaquacobalt(II) and hexaaquanickel(II) bis(μ‐pyridine‐2,6‐dicarboxylato)bis[(pyridine‐2,6‐dicarboxylato)bismuthate(III)] dihydrate

The title complexes, hexaaquacobalt(II) bis(μ‐pyridine‐2,6‐dicarboxylato)bis[(pyridine‐2,6‐dicarboxylato)bismuthate(III)] dihydrate, [Co(H₂O)₆][Bi₂(C₇H₄NO₄)₄]·2H₂O, (I), and hexaaquanickel(II) bis(μ‐pyridine‐2,6‐dicarboxylato)bis[(pyridine‐2,6‐dicarboxylato)bismuthate(III)] dihydrate, [Ni(H₂O)₆][Bi₂(C₇H₄NO₄)₄]·2H₂O, (II), are isomorphous and crystallize in the triclinic space group P. The transition metal ions are located on the inversion centre and adopt slightly distorted MO₆ (M = Co or Ni) octahedral geometries. Two [Bi(pydc)₂]⁻ units (pydc is pyridine‐2,6‐dicarboxylate) are linked via bridging carboxylate groups into centrosymmetric [Bi₂(pydc)₄]²⁻ dianions. The crystal packing reveals that the [M(H₂O)₆]²⁺ cations, [Bi₂(pydc)₄]²⁻ anions and solvent water molecules form multiple hydrogen bonds to generate a supramolecular three‐dimensional network. The formation of secondary Bi...O bonds between adjacent [Bi₂(pydc)₄]²⁻ dimers provides an additional supramolecular synthon that directs and facilitates the crystal packing of both (I) and (II).     

Amide hydrogen bonding: control of the molecular and extended structures of two symmetrical pyridine‐2‐carboxamide derivatives

The crystal structures of two symmetrical pyridine‐2‐carboxamides, namely N,N′‐(propane‐1,3‐diyl)bis(pyridine‐2‐carboxamide), C₁₅H₁₆N₄O₂, (I), and N,N′‐(butane‐1,4‐diyl)bis(pyridine‐2‐carboxamide), C₁₆H₁₈N₄O₂, (II), exhibit extended hydrogen‐bonded sequences involving their amide groups. In (I), conventional bifurcated amide–carbonyl (N—H)...O hydrogen bonding favours the formation of one‐dimensional chains, the axes of which run parallel to [001]. Unconventional bifurcated pyridine–carbonyl C—H...O hydrogen bonding links adjacent one‐dimensional chains to form a `porous' three‐dimensional lattice with interconnected, yet unfilled, voids of 60.6 (2) ų which combine into channels that run parallel to, and include, [001]. 4% of the unit‐cell volume of (I) is vacant. Compound (II) adopts a Z‐shaped conformation with inversion symmetry, and exhibits an extended structure comprising one‐dimensional hydrogen‐bonded chains along [100] in which individual molecules are linked by complementary pairs of amide N—H...O hydrogen bonds. These hydrogen‐bonded chains interlock viaπ–π interactions between pyridine rings of neighbouring molecules to form sheets parallel with (010); each sheet is one Z‐shaped molecule thick and separated from the next sheet by the b‐axis dimension [7.2734 (4) Å].     

Synthesis,Characterization, and Properties of Four Metal Complexes with Mulitdentate N‐Acyl‐Salicylhydrazide Ligands

The reactions of the new nitrilotriacetic acid N′,N′,N′‐tri(salicyloyl)trihydrazide (Ntash) with the corresponding metal salts gave four new complexes [Pb₄(bshz)₂] · 2DMF ( 1 ), [Co₂(bshz)(C₅H₅N)₆] · 2ClO₄ · (C₅H₅N) · 2H₂O ( 2 ), [Cu₃(fshz)₂(C₅H₅N)₂] ( 3 ), and [Zn₃(fshz)₂(C₅H₅N)₃]_n · 2DMF ( 4 ), in which two multidentate ligands, namely N,N′‐disalicyloylhydrazine (H₄bshz) and N‐formylsalicylhydrazide (H₃fshz) were generated in situ from Ntash. The structures of these complexes were determined by single‐crystal X‐ray diffraction analysis. Complex 1 presents a novel tetranuclear lead(II) cluster structure with the four lead(II) cations in “hemidirected” coordination spheres. The neighboring tetranuclear clusters of 1 are connected by DMF molecules through weak Pb–O bonds, forming one‐dimensional ribbons. Complexes 2 and 3 show dinuclear and linear trinuclear structures with the corresponding Co^III and Cu^II ions in distorted octahedral and square‐planar coordination environments, respectively. Complex 4 exhibits a one‐dimensional zigzag chain structure. The magnetic properties of 3 and the photoluminescent properties of 4 were also investigated.     

Two new CoII coordination polymers with multifunctional 5‐amino‐2,4,6‐tribromoisophthalic acid and flexible isomeric bis(imidazole) ligands: preparation,crystal structure and characterization

Two new Co^II coordination polymers (CPs), namely, catena‐poly[[[(5‐amino‐2,4,6‐tribromobenzene‐1,3‐dicarboxylato‐κO)aquacobalt(II)]‐bis[μ‐1,3‐bis(imidazol‐1‐ylmethyl)benzene‐κ²N:N′]] 4.75‐hydrate], {[Co(C₈H₂Br₃NO₄)(C₁₄H₁₄N₄)₂(H₂O)]·4.75H₂O}_n, (1), and poly[(μ‐5‐amino‐2,4,6‐tribromobenzene‐1,3‐dicarboxylato‐κ²O¹:O³)[μ‐1,2‐bis(imidazol‐1‐ylmethyl)benzene‐κ²N:N′]cobalt(II)], [Co(C₈H₂Br₃NO₄)(C₁₄H₁₄N₄)]_n, (2), have been synthesized successfully by the assembly of multifunctional 5‐amino‐2,4,6‐tribromoisophthalic acid (H₂ATBIP) and Co^II ions in the presence of the flexible isomeric bis(imidazole) ligands 1,3‐bis(imidazol‐1‐ylmethyl)benzene (mbix) and 1,2‐bis(imidazol‐1‐ylmethyl)benzene (obix). The isomeric mbix and obix ligands have a big influence on the structures of CPs (1) and (2). CP (1) is composed of chains of nanometre‐sized elliptical rings, in which the Co^II atom exhibits a distorted octahedral coordination geometry and ATBIP²⁻ acts as a monodentate ligand. Two adjacent chains are interlinked by π–π stacking interactions and hydrogen bonds, resulting in a supramolecular double chain. Hydrogen‐bonded R₈⁶(16) rings extend adjacent supramolecular double chains into a two‐dimensional supramolecular layer. Halogen bonding and a hydrogen‐bonded R₄²(8) ring further link the two‐dimensional supramolecular layers, leading to the formation of a three‐dimensional supramolecular network. The Co^II ion in CP (2) is tetracoordinated, exhibiting a distorted tetrahedral configuration. The ATBIP²⁻ ligand exhibits a bis(monodentate) coordination bridging mode, linking adjacent Co^II ions into zigzag chains, which are further bridged by the auxiliary bridging obix ligand, resulting in a two‐dimensional (4,4) topological network. Interlayer hydrogen and halogen–halogen bonding further extend the two‐dimensional layers into a three‐dimensional supramolecular network. A detailed analysis of the solid‐state UV–Vis–NIR diffuse‐reflectance spectra of (1) and (2) indicates that a wide optical band gap exists in both (1) and (2). CP (1) exhibits an irreversible dehydration–rehydration behaviour.     

One‐dimensional copper(II) coordination polymers based on 1,3‐bis(pyridin‐4‐yl)propane and diimine ligands

Two one‐dimensional (1D) coordination polymers (CPs), namely catena‐poly[[[aqua(2,2′‐bipyridine‐κ²N,N′)(nitrato‐κO)copper(II)]‐μ‐1,3‐bis(pyridin‐4‐yl)propane‐κ²N:N′] nitrate], {[Cu(NO₃)(C₁₀H₈N₂)(C₁₃H₁₄N₂)(H₂O)]·NO₃}_n ( 1 ), and catena‐poly[[[aqua(nitrato‐κO)(1,10‐phenanthroline‐κ²N,N′)copper(II)]‐μ‐1,3‐bis(pyridin‐4‐yl)propane‐κ²N:N′] nitrate], {[Cu(NO₃)(C₁₂H₈N₂)(C₁₃H₁₄N₂)(H₂O)]·NO₃}_n ( 2 ), have been synthesized using [Cu(NO₃)(NN)(H₂O)₂]NO₃, where NN = 2,2′‐bipyridine (bpy) or 1,10‐phenanthroline (phen), as a linker in a 1:1 molar ratio. The CPs were characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis and single‐crystal X‐ray structure determination. The 1,3‐bis(pyridin‐4‐yl)propane (dpp) ligand acts as a bridging ligand, leading to the formation of a 1D polymer. The octahedral coordination sphere around copper consists of two N atoms from bpy for 1 or phen for 2 , two N atoms from dpp, one O atom from water and one O atom from a coordinated nitrate anion. Each structure contains two crystallographically independent chains in the asymmetric unit and the chains are linked via hydrogen bonds into a three‐dimensional network.