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A heteronuclear metal organic framework containing erbium(III) and cobalt(II) ion based on a rigid ligand of substituted imidazoledicarboxylic acid has been synthesized and characterized by single-crystal X-ray diffraction analysis (CIF file CCDC no. 1019455). It’s formula is [Er2Co2(μ3-HMimda)2(μ3-Mimda)2 · 4H2O] n · 2nH2O, (H3Mimda = 1-H-2-methyl-4,5-imidazole-dicarboxylic acid). The complex crystallizes in the monoclinic system. It possesses an extended grid-like porous structure constructed from corrugated shaped 2D layer. Direct current magnetic susceptibility measurements for indicated the depopulation of the Stark components at low temperature and possible very weak antiferromagnetic interactions within heteronuclear MOF.

Three three-dimensional polymers, namely, [Zn(bpea)(H2O)]n (1), [Cd(bpea)(H2O)]n (2), and [Ni(bpea)(4,4′-bipyridine)(pyridine)]n (3) have been synthesized by the hydrothermal reaction of ZnII, CdII, or NiII salts with biphenylethene-4,4′-dicarboxylic acid. Complexes 1 and 2 have a 2-fold interpenetrating three-dimensional (3D) structure with Pts topology, and complex 1 exhibits strong fluorescent emission bands at 435 and 459 nm in the solid state at room temperature. Complex 3 is a 3D structure with an unprecedented 9-fold interpenetrated Ths topology.

A nanoparticulate ferric oxide–copper tris(2,4-di-tert-amylphenoxy)-8-quinolinolylphthalocyanine hybrid ultrathin film was constructed from alternate layers by the Langmuir–Blodgett technique. The composition, morphology and structure of the film were studied by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy, atomic force microscopy, small-angle X-ray diffraction, visible spectroscopy and polarized UV-Vis spectroscopy. All the above analyses suggest that the thin film is a kind of one-dimensional superlattice, composed of organic and inorganic components. The XPS data reveal that the nanoparticulate ferric oxide exists as an α-Fe2O3 phase in the films. Gas-sensing measurements show that the hybrid LB film has very fast response-recovery characteristics towards 2 ppm C2H5OH vapor.

In the title complex, {[Ni(C16H10O4)(C12H8N2)(H2O)]·H2O}n, the NiII ion is in a distorted octa­hedral geometry and coordinated by two N atoms of a 1,10-phenanthroline (phen) ligand, three carboxylate O atoms of two different bpea2− ligands and one water mol­ecule. The [Ni(phen)H2O] units are connected by two different 4,4′-(ethene-1,2-di­yl)dibenzoate (bpea2−) bridges, forming a one-dimensional zigzag chain structure. One bpea2− ligand coordinates to Ni in a bis-monodentate fashion, while the other acts as a bis-bidentate chelate.

One of the two independent Zn atoms of the polymeric title compound, [Zn3(C16H10O4)3(C10H8N2)]n, lies on a special position of site symmetry 3 and the other on a special position of site symmetry \overline{3}. The carboxylate ends of the 4,4′-(ethene-1,2-di­yl)dibenzoate dianion, which lies on a special position of site symmetry \overline{1}, each bridge these two independent Zn atoms. The bipyridine-coordinated Zn atom on the threefold axis has a tetra­hedral geometry, whereas the other Zn atom is coordin­ated by the O atoms of six different dianions in an octa­hedral geometry.

In the title complex, [Mn(C4O4)(C12H8N2)(H2O)2]n, each MnII ion is octa­hedrally coordinated by two N atoms of a 1,10-phenanthroline ligand, two carboxylate O atoms of different acetyl­enedicarboxyl­ate (ace2−) ligands and two coordinated water mol­ecules, and the octa­hedral units are connected by ace2− bridges, which adopt a bis-monodentate coordination mode, to form a one-dimensional structure along the [101] direction. A three-dimensional supra­molecular architecture is constructed via hydrogen-bond and π–π inter­actions.

In the title complex, [Co(C4O4)(C12H8N2)(H2O)2]n, the CoII atom exhibits a slightly distorted octa­hedral coordination geometry involving two N atoms from 1,10-phenanthroline, two O atoms from two acetyl­enedicarboxyl­ate (ace2−) dianions and two water O atoms. The ace2− ligand acts in a bis-monodentate mode to connect two adjacent CoII atoms, forming chains along the b axis. A three-dimensional supra­molecular architecture is constructed via O—H⋯O hydrogen bonds and π–π inter­actions.

In the title coordination polymer, [Ca(2-OPA)2(H2O)2]n [2-OPA− is 2-oxo-1,2-di­hydro­pyridine-1-acetate, C7H6NO3], the Ca atom is eight-coordinated by six O atoms from four 2-OPA− ligands and two water mol­ecules, and displays a dodecahedral coordination geometry. Each 2-OPA− ligand bridges two adjacent Ca atoms, forming a chain along the a-axis direction. The Ca⋯Ca separation within the polymer is 4.1022 (8) A. A two-dimensional supramolecular framework is further constructed by hydrogen bonds and weak π–π stacking interactions.

In the title complex, [Cd2(C9H6O5)2(C7H6N2)4(H2O)2]·2H2O, the CdII atoms are linked by two 3-carboxy­phenoxy­acetate groups into a centrosymmetric dimer. Each CdII atom displays a distorted octa­hedral coordination geometry, with three carboxylate O atoms from different 3-carboxy­phenoxy­acetate groups, two N atoms from two benzimidazole co-ligands and one water mol­ecule. Inter­molecular hydrogen bonding leads to a two-dimensional supramolecular network.

The crystal structure of the title complex, [Co(C9H7O5)2(C10H8N2)2(H2O)2]·4H2O or [Co(4-CPOAH)2(4,4′-bipy)2(H2O)2]·4H2O (4,4′-bipy is 4,4′-bipyridine and 4-CPOAH− is the 4-carboxy­phenoxy­acetate monoanion), consists of two independent mononuclear mol­ecules that inter­act through the uncoordinated water mol­ecules. The CoII atoms lie on inversion centers and display an octa­hedral geometry defined by two oxyacetate O atoms of 4-CPOAH− groups, two N atoms of 4,4′-bipy ligands and two water mol­ecules. A three-dimensional supramolecular network structure is formed through hydrogen-bonding inter­actions.

The title mol­ecule, [Co2(C8H7O2)4(C12H8N2)2(H2O)], is a dinuclear CoII complex which is located on a twofold symmetry axis. Each CoII ion is six-coordinated by three O atoms of different phenyl­acetate ligands, two N atoms of the 1,10-phenanthroline ligands and one O atom of a water mol­ecule, giving a distorted octa­hedral geometry. The two CoII atoms are bridged by two phenyl­acetate groups and the water mol­ecule lying on the twofold axis. The Co⋯Co distance is 3.553 (2) A. A one-dimensional supramolecular chain is constructed by π–π stacking inter­actions between adjacent 1,10-phenanthroline mol­ecules.

In the title coordination polymer, [Zn(C9H6O5)(C8H12N2)]n, the ZnII atom is surrounded by two chelating 3-carboxyl­atophenoxy­acetate (3-CPOA) dianions and one 1,10-phenanthroline (phen) ligand. Adjacent ZnII atoms are bridged by 3-CPOA to form a zigzag chain structure. The polymeric chains are connected via π–π stacking inter­actions.

In the title complex, [Mn(C9H7O5)(C10H8N2)(H2O)3](C9H7O5)·H2O or [Mn(3-CPOAH−)(2,2′-bipy)(H2O)3](3-CPOAH−)·H2O (where 3-CPOAH− is the 3-carboxy­phenoxy­acetate monoanion and 2,2′-bipy is 2,2′-bipyridine), the MnII ion has a distorted octa­hedral geometry involving one O atom of the 3-CPOAH− group, two N atoms of the 2,2′-bipy ligand and three water mol­ecules. A three-dimensional supramolecular network is constructed via O—H⋯O hydrogen-bonding and π–π stacking inter­actions.

In the title coordination polymer, {[Ni(4-CPOA)(phen)(H2O)2]·H2O}n (phen is 1,10-phenanthroline, C12H8N2; 4-CPOA is the 4-carboxy­phenoxy­acetate dianion, C9H6O5), each NiII ion displays a distorted octa­hedral geometry, defined by two carboxyl O atoms from two different 4-CPOA ligands, two N atoms from one phen mol­ecule and two coordinated water mol­ecules. The NiII ions are bridged by carboxyl­ate groups of 4-CPOA to form a chain structure. Adjacent polymeric chains are connected via hydrogen bonds and π–π stacking to construct a three-dimensional supramolecular network.

In the title one-dimensional polymer, {[Zn(3-CPOA)(C3H4N2)2]·3H2O}n (3-CPOA2− is the 3-carboxyl­atophenoxy­acetate dianion, C9H6O5), the Zn atom shows tetra­hedral coordination, as it is linked to two N atoms from two imidazole mol­ecules and two carboxyl­ate O atoms from two different 3-CPOA2− groups. Adjacent Zn atoms are linked by 3-CPOA2− ligands into a helical chain. The chains are linked into a three-dimensional network by hydrogen bonds.

The dinuclear title complex, [Ag2(NO3)2(3-PyOH)4]·2H2O (3-PyOH is 3-hydroxy­pyridine, C5H5NO), situated across a crystallographic inversion centre, can be described as a dimeric structure, in which two [Ag(3-PyOH)2] groups are held together by the Ag⋯Ag inter­action [3.317 (1) A]. Each Ag atom is two-coordinate and exists in an approximately linear geometry. The two NO3− ions inter­act with the AgI atoms in a bridging mode through very weak Ag⋯O inter­actions [Ag⋯O = 2.862 (2) and 2.877 (2) A]. A three-dimensional supramolecular framework is formed by O—H⋯O hydrogen bonds.

In the mononuclear title complex, [Ag(NO3)(3-PyOH)2] (3-PyOH = 3-hydroxy­pyridine, C5H5NO), the AgI atom shows a linear geometry defined by two N atoms of the 3-PyOH ligands, and the NO3− anion inter­acts with the AgI atom in a chelating mode through very weak Ag⋯O bonds. A three-dimensional supramolecular framework is formed by both hydrogen bonds and π–π inter­actions.

In the title coordination polymer, [Cd(4-CPOA)(H2O)3]n (where 4-CPOA2− is the 4-carboxyl­ato­phenoxy­acetate dianion, C9H6O5), the CdII ion is seven-coordinate, involving four O atoms of two different 4-CPOA2− ligands and three water mol­ecules, arranged in a pentagonal–bipyramidal geometry. Adjacent CdII ions are linked by the 4-CPOA2− groups in bidentate mode, giving rise to a zigzag chain with a closest Cd⋯Cd distance of 10.310 (5) A. The chains are further linked by O—H⋯O hydrogen bonds to form a supramolecular three-dimensional network.

The CoII atom in the title coordination polymer, [Co(C9H6O5)(C12H8N2)(H2O)]n, displays a distorted octahedral geometry defined by three carboxyl O atoms from two independent 4-carboxy­phenoxy­acetate groups, two N atoms from one 1,10-phenanthroline mol­ecule and one water mol­ecule. The CoII atoms are bridged by carboxyl­ate groups in monodentate and bidentate modes, forming a chain structure. Adjacent polymeric chains are connected via hydrogen-bond interactions into a double-chain structure. Furthermore, these chains are stacked through π–π interactions to construct a two-dimensional supramolecular network.

The CdII atom in the title coordination polymer, [Cd(4-CPOA)(1,10-phen)(H2O)]n (1,10-phen is 1,10-phenanthroline, C12H8N2, and 4-CPOA2− is the 4-carboxy­phenoxy­acetate dianion, C9H6O5), shows a distorted octahedral geometry, defined by three carboxyl O-atom donors from two independent 4-CPOA2− groups, two N-atom donors from one 1,10-phen ligand, and one water molecule. The CdII ions are bridged by carboxyl­ate groups in mono- and bidentate modes, forming a chain structure. The polymeric chains are connected via O—H⋯O hydrogen bonds and π–π stacking interactions into a two-dimensional layer structure.

The asymmetric unit of the title one-dimensional coordination polymer, {[Co(C10H8N2)(H2O)4](C9H6O5)·H2O}n, comprises two half-cations, [Co(4,4′-bipy)(H2O)4]22+ (4,4′-bipy is 4,4′-bi­pyridine), one 3-carboxyl­ato­phenoxy­acetate (3-CPOA2−) dianion and one non-coordinated water mol­ecule. The CoII ions, both of which are located on inversion centres, have approximately octahedral geometries, involving two N atoms of the centrosymmetric 4,4′-bipy ligand and four water mol­ecules. Adjacent CoII atoms are linked by 4,4′-bipy ligands into a chain, the shortest Co⋯Co separation within the polymeric chain being 11.456 (2) A. The chains are further linked by hydrogen-bonding and π–π stacking interactions, generating a three-dimensional network.

In the title two-dimensional coordination polymer, [Cu(C9H6O5)(C7H6N2)]n, each CuII atom exists in a distorted square-pyramidal coordination environment, defined by one N atom from the terminal benz­imidazole mol­ecule and four carboxyl O atoms derived from three different 3-carboxyl­ato­phenoxy­acetate (3-CPOA) dianions. The tetradentate 3-CPOA ligand forms three bonds to adjacent Cu atoms to form chains that are linked to neighboring chains, via a fourth Cu—O bond, so as to form a layer structure that is further stabilized by hydrogen bonds.

In the title coordination polymer, [Cu(HIDC)(1,10-phen)]n (HIDC2− is the 4-carboxy­imidazole-5-carboxyl­ate dianion, C5H2N2O42−, and 1,10-phen is 1,10-phenanthroline, C12H8N2), the CuII atom shows a distorted octahedral coordination configuration, defined by two N atoms from a terminal 1,10-phen mol­ecule, two N atoms and two O atoms from two individual HIDC2− groups. Adjacent CuII atoms are bridged by HIDC2− groups, forming a one-dimensional chain structure. The Cu⋯Cu separation within the polymer is 6.132 (4) A. The chains are linked into a two-dimensional supramolecular network via π–π stacking interactions.

Each seven-coordinate CdII atom in the title coordination polymer, poly­[[bis(1H-imidazole-κN3)­cadmium(II)]-μ3-m-phenyl­enebis­(oxy­acetato)], [Cd(1,3-BDOA)(C3H4N2)2]n (1,3-BDOA2− is the benzene-1,3-dioxy­acetate dianion, C10H8O6), displays a distorted monocapped octahedral coordination geometry, defined by two N atoms from the imidazole ligands and five O atoms from three 1,3-BDOA2− anions. Adjacent CdII atoms are bridged by two 1,3-BDOA2− ligands, forming a one-dimensional double-chain structure, with Cd⋯Cd separations of 4.014 (3) A across the double chain and 13.105 (2) A along the chain. A network of N—H⋯O interchain hydrogen bonds is also present.

In the title coordination polymer, [Zn(C9H6O5)(C10H8N2)(H2O)]n, the ZnII ion displays a distorted octahedral coordination configuration, defined by two N atoms from the 2,2′-bi­pyridine ligand, three carboxyl­ate O atoms from two 4-carboxyl­ato­phenoxy­acetate dianions and one water mol­ecule. Adjacent ZnII atoms are linked by carboxyl­ate groups into zigzag chains with a Zn⋯Zn separation of 9.710 (3) A across the chains. Intermolecular hydrogen bonds serve to assemble the chains into a double-chain structure.

In the title compound, poly­[cadmium(II)-μ4-m-phenyl­enebis­(oxy­acetato)], [Cd(C10H8O6)]n, the CdII atom exists in a distorted monocapped octahedral coordination environment with seven O atoms from four carboxyl­ate groups. The Cd atoms are bridged by benzene-1,3-dioxy­acetate dianions with tridentate and tetradentate modes of the oxy­acetate groups, leading to a two-dimensional layer structure parallel to (001).

In the asymmetric unit of the title compound, [Mn(C10H8O6)(H2O)3]n, the two half-MnII atoms lie on inversion centres. One MnII atom is in an octahedral configuration, defined by two O atoms from two monodentate carboxyl­ate groups and four water mol­ecules, and the other MnII atom exists in a different octahedral coordination environment, defined by four O atoms from four monodentate carboxyl­ate groups and two water mol­ecules. The MnII atoms are bridged by a benzene-1,3-dioxy­acetate dianion in monodentate and bridging-bidentate modes, forming a two-dimensional layer structure.

In the title one-dimensional coordination polymer, {[Co(4-CPOA)(3-PyOH)2(H2O)2]·H2O}n [4-CPOA2− is the 4-carboxy­phenoxy­acetate dianion (C9H6O52−) and 3-PyOH is 3-hydroxy­pyridine (C5H5NO)], the CoII atom has a distorted octahedral coordination geometry, defined by two carboxyl O-atom donors from two 4-CPOA2− groups, two N-atom donors from two 3-PyOH co-ligands and two water mol­ecules. The CoII atoms are bridged by bis-monodentate carboxyl­ate groups, forming a one-dimensional chain structure. The Co⋯Co separation within the polymer is 10.862 (3) A. The chains are linked into a three-dimensional supramolecular network via O—H⋯O hydrogen bonds.

In the title complex {systematic name: aqua­[p-phenyl­enebis­(dioxy­acetato)-κO]­tetrakis(1H-imidazole-κN3)­nickel(II) mono­hydrate}, [Ni(C10H8O6)(C3H4N2)4(H2O)]·H2O, the NiII atom shows a distorted octahedral configuration, defined by one carboxyl O atom of the benzene-1,3-dioxy­acetate group, four N atoms from four imidazole ligands and one water mol­ecule. A three-dimensional supramolecular network is constructed by hydrogen-bonding and π–π stacking interactions.

In the title complex, [Zn(H2IDC)2(H2O)2] (where H2IDC− is the 5-carboxy-1H-imidazole-4-carboxyl­ate monoanion, C5H3N2O4), the ZnII atom is located on an inversion centre, is trans-coordinated by two N,O-bidentate H2IDC− ligands and two water mol­ecules and shows an approximately octahedral configuration. A three-dimensional supramolec­ular architecture is formed via hydrogen-bond interactions.

In the title one-dimensional coordination polymer, [Cd(HIDC)(1,10-phen)]n (where HIDC2− is the imidazole-4,5-di­carboxyl­ate dianion, C5H2N2O42−, and 1,10-phen is 1,10-phenanthroline, C12H8N2), the CdII atom has a distorted octahedral coordination geometry, defined by two N donors from a chelating 1,10-phen mol­ecule, two N-atom donors and two O-atom donors from two individual HIDC2− groups. Adjacent CdII ions are bridged by HIDC2− groups, resulting in a one-dimensional chain structure. The Cd⋯Cd separation within the polymer is 6.661 (2) A. The chains are linked into a two-dimensional supramolecular network via π–π stacking interactions.

The title complex crystallizes as a methanol solvate, [Cu2(C16H14O4N2)2(C5H5N)2]·2CH4O. The dinuclear complex is generated from the atoms of the asymmetric unit by inversion symmetry, resulting in a Cu⋯Cu separation of 3.497 (3) A. The copper(II) species has a square-pyramidal geometry, with the basal plane defined by two O atoms and one N atom from the hydrazone ligand and a pyridine N atom. The apical site is occupied by a phenolate O atom in the symmetry-generated hydrazone ligand, which also bonds to the second Cu atom. Intramolecular O—H⋯N hydrogen bonds are formed between the methanol solvent mol­ecules and the uncoordinated N atoms of the hydrazone ligand.

The title complex, [Co(2-OPA)2(H2O)4] [2-OPA− = (2-oxo-1,2-dihydropyridin-1-yl)­acetate, C7H6NO], is a neutral mononuclear compound. The CoII atom, located on an inversion center, has an octahedral coordination geometry involving two carbonyl O atoms of different 2-OPA− ligands and four water mol­ecules. A layer structure is formed via O—H⋯O intermolecular hydrogen bonds.

In the title complex, [Zn(1,4-BDOA)(H2O)4]n or [Zn(C10H8O6)(H2O)4]n (where 1,4-BDOA2− is the benzene-1,4-dioxy­acetate dianion), the ZnII atom and the 1,4-BDOA2− ligand build up a one-dimensional polymer chain along c. The ZnII atom, located on an inversion center, shows an octahedral coordination geometry, defined by two carboxyl O atoms of different benzene-1,4-dioxy­acetate ligands and four water mol­ecules. Adjacent ZnII atoms are bridged by bis-monodentate carboxyl­ate groups of the centrosymmetric 1,4-BDOA2− ligands, to furnish the one-dimensional chain along the c axis; the Zn⋯Zn separation within the polymer is 14.717 (3) A. A hydrogen-bonded supramolecular architecture is formed via O—H⋯O intermolecular hydrogen bonds.

The hydro­xide group in the centrosymmetric title complex, {[Zn4(C9H6O5)3(OH)2(C10H8N2)2]·2H2O}n, which adopts a three-dimensional network structure, bridges three Zn atoms. One of the symmetry-independent di­carboxyl­ate groups chelates to a Zn—OH—Zn unit through the carboxyl group on the aromatic ring, while its other oxy­acetate arm uses only one O atom for binding. The other di­carboxyl­ate dianion is disordered over a center of inversion and functions as a chelating ligand to two Zn—OH—Zn units. The modes of coordination by the hydro­xide, heterocycle and di­carboxyl­ate ligands give rise to tetrahedral coordination for one Zn atom and octahedral coordination for the other.

The Zn atom in the title mononuclear complex, [Zn(C2H3O3)2(C12H8N2)]·2H2O, exists in an octahedral coord­ination environment defined by two hydroxy O atoms, two carboxyl­ate O atoms from different glycolate (hydroxy­acetate) ligands and two N atoms from one phenanthroline (phen) ligand. The Zn atom occupies a special position with twofold symmetry. A layer structure is formed via O—H⋯O hydrogen bonds involving the water molecules.

In the title coordination polymer, [Cd(1,4-BDOA)(C3H4N2)3]n (1,4-BDOA2− is benzene-1,4-dioxy­acetate, C10H8O6), each CdII atom exists in a distorted octahedral coordination sphere, involving three carboxyl O atoms from different 1,4-BDOA2− groups and three N atoms from the imidazole co-ligands. The CdII ions are linked by carboxyl­ate groups into a one-dimensional infinite chain. The Cd⋯Cd separation within the polymer is 15.009 (2) A. N—H⋯O hydrogen bonds help to establish the crystal packing.

In the title coordination polymer, also called catena-poly­[[aqua­bis(1H-imidazole-κN3)copper(II)]-μ-phenyl­ene­dioxy­diacetato-κ2O:O′], [Cu(1,4-BDOA)(C3H4N2)2(H2O)]n (where 1,4-BDOA2− is benzene-1,4-dioxy­acetate, C10H8O6), the CuII atom is five-coordinate involving two O atoms of the 1,4-BDOA ligand, two N atoms of imidazole ligands and one water mol­ecule, displaying a distorted square-pyramidal coordination geometry. The CuII atoms are bridged by carboxyl­ate groups, forming a one-dimensional zigzag chain. The adjacent Cu⋯Cu distance is 12.656 (5) A. Furthermore, such chains are linked by hydrogen-bond interactions, resulting in a three-dimensional network.

The title compound, C16H16N2O 4·H2O, crystallizes as a monohydrate in which the water molecule forms bifurcated hydrogen bonds to the hydroxyl and methoxy O atoms of the methoxysalicyldehyde portion of the Schiff base. The molecule is approximately planar; hydrogen-bonding interactions involving the amino group and the water molecule give rise to a layer structure. © 2004 International Union of Crystallography Printed in Great Britain - all rights reserved.

In the crystal structure of the title 1:1 co-crystal, C7H8NO3+·NO3−·C7H7NO3, two cations inter­act with two zwitterions to form a hydrogen-bonded ring, the nitrate anions being located outside of the ring.

In the title one-dimensional coordination polymer {systematic name: catena-poly­[[[aqua(1,10-phenanthroline-κ2N,N′)­copper(II)]-μ-phenyl­enebis­(oxy­acetato)-κ2O:O′] dihydrate]}, {[Cu(C10H8O6)(C12H8N2)(H2O)]·2H2O}n, the CuII atom has a distorted square-pyramidal coordination geometry, defined by two carboxyl O-atom donors from two benzene-1,3-dioxy­acetate groups, two N-atom donors from the 1,10-phenanthroline ligand and one water mol­ecule. The CuII ions are bridged by benzene-1,3-dioxy­acetate dianions (1,3-BDOA2−), resulting in a one-dimensional chain structure. The intrachain Cu⋯Cu separation is 9.769 (4) A. The chains are linked into a three-dimensional supramolecular network via hydrogen bonds and π–π stacking interactions.

In the title complex, [CoCl2(C5H5NO)4], the Co atom is in an elongated octahedral environment, defined by two Cl− ions and four N atoms of 3-hydroxy­pyridine ligands. The Co atom lies on a special position with crystallographic twofold rotation symmetry. Individual mol­ecules are linked by intermolecular O—H⋯Cl hydrogen bonds into a layer structure.

In the title centrosymmetric dinuclear complex, [Cu2(C2H3O2)4(C5H5NO)2], the two CuII atoms are bridged by four atetate groups, the Cu⋯Cu separation being 2.6468 (7) A. Each CuII atom exists in a square-pyramidal coordination environment defined by four carboxyl acetate O atoms and one 4-pyridone O atom. Intermolecular hydrogen bonds give rise to a two-dimensional layer structure.

In the title complex, [Co(NO3)(C5H5NO)2(H2O)2](NO3), the Co atom exists in an octahedral environment, defined by four O atoms of two 4-pyridone ligands and a chelating nitrate ion, as well as two water mol­ecules. The Co atom and two nitrate ions lie on special positions with twofold rotation symmetry. A three-dimensional network structure is formed by intermol­ecular hydrogen bonds and π–π interactions.

The title compound, expected to be a betaine, 4-hydroxy­pyridinio­acetate, HOC5H4N+CH2CO2− or C7H7NO3, on the basis of its synthesis by the nucleophilic displacement of chloride from the chloro­acetate ion in water, exists as (4-oxo-1,4-di­hydro­pyridin-1-yl)­acetic acid. The acid H atom interacts with the oxo O atom of an adjacent molecule to form a linear helical chain [O⋯O = 2.451 (3) A].

The title complex, tetraaquabis[(2-oxo-1,2-dihydropyridin-1-yl)acetato]magnesium(II), [Mg(C7H6NO3)2(H2O)4], is a neutral mononuclear mol­ecule consisting of an MgII ion, two (2-oxo-4H-pyridin-1-yl)­acetate ligands and four coordinated water mol­ecules. The MgII atom, located on a symmetry center, has octahedral coordination involving two carbonyl O atoms of different (2-oxo-4H-pyridin-1-yl)­acetate ligands and four water mol­ecules. O—H⋯O intermolecular hydrogen bonds form a layer structure.

In the title compound, [Zn(C2H3O2)(C11H12N3O2)(C3H4N2)], the Zn atom is five-coordinate in a ZnN3O2 trigonal-bipyramidal enviroment. Adjacent mol­ecules are linked by an intermolecular hydrogen bond into a chain running along the a axis of the monoclinic cell.