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1.  Zinc(II) and Nickel(II) Benzoate Complexes from the Use of 1-methyl-4,5-diphenylimidazole 
Two new complexes, [Zn(O2CPh)2(L)2]·2MeOH (1·2MeOH) and [Ni2(O2CPh))4(L)2]·2MeCN (2·2MeCN), have been synthesized and characterized by X-ray analysis in the course of an ongoing investigation of the MII/X−/L [MII = Co, Ni, Cu, Zn; X− = Cl−, Br−, I−, NCS−, NO3−, N3−, PhCO2−; L = 1-methyl-4,5-diphenylimidazole] reaction system, aiming at understanding and assessing the relative strength and the way in which the intermolecular interactions control the supramolecular organization of these compounds. In the mononuclear complex 1·2MeOH, the benzoate ion acts as a monodentate ligand resulting in a distorted tetrahedral N2O2 coordination environment. Complex 2·2MeCN exhibits a dinuclear paddle-wheel structure; each NiII has a square pyramidal NiNO4 chromophore with four benzoate oxygens in the basal plane and the pyridine-type nitrogen atom of one ligand L at the apex. The structure of 1·2MeOH is stabilized by intramolecular π-π interactions between aromatic rings of adjacent 4,5-diphenylimidazole moieties; it is a feature also evidenced in similar compounds of the type [MX2L2].
PMCID: PMC2927736  PMID: 20811497
2.  Bis(2,2′-bipyridyl-κ2 N,N′)bis­(2-hydroxy­benzoato)-κO 1;κ2 O 1,O 1′-cadmium(II) methanol solvate 
The title compound, [Cd(C7H5O3)2(C10H8N2)2]·CH3OH, contains one monomeric seven-coordinate cadmium complex and one methanol solvate mol­ecule. The CdII atom is coordinated to two 2,2′-bipyridyl ligands via the N atoms and to two salicylate anions (Hsal−) via the carboxyl­ate O atoms, which act as monodentate ligand for the one and bidentate ligand for the second. The CdII atom exhibits a {6 + 1} environment, approximately described as a distorted capped octa­hedron with the apical positions occupied by one of the two N atoms belonging to one bipyridyl ligand and one of the two carboxyl­ate O atoms from the monodentate Hsal− ligand. Two intra­molecular six-membered hydrogen-bonded rings are present, generated from inter­actions between the carboxyl­ate and hydr­oxy groups of the salicylate ligands. There is one inter­molecular hydrogen-bonding inter­action involving the methanol solvent mol­ecule and the carboxyl­ate group from the monodentate Hsal− ligand. The crystal packing is governed by π–π stacking inter­actions [centroid–centroid distance = 3.783 (4) Å] which occur between bipyridyl ligands, by C—H⋯O and C—H⋯π inter­actions and by numerous van der Waals contacts.
PMCID: PMC2979681  PMID: 21579632
3.  Poly[μ-aqua-diaqua(μ3-1H-benzimid­azole-5-carboxylato-κ3 N 3:O,O′)(μ2-1H-benzimidazole-5-carboxylato-κ3 N 3:O:O′)-μ5-sulfato-μ4-sulfato-tri­cadmium] 
The asymmetric unit of the title compound, [Cd3(C8H5N2O2)2(SO4)2(H2O)3]n, contains three CdII ions, two sulfate anions, two 1H-benzimidazole-5-carboxyl­ate (H2bic) ligands and three coordinated water mol­ecules. One CdII ion is six-coordinated and exhibits a distorted octa­hedral geometry, while the other two CdII ions are seven-coordinated, displaying a distorted penta­gonal–bipyramidal geometry. The CdII ions are bridged by two types of sulfate anions, producing inorganic chains along [100]. These chains are further connected by the H2bic ligands, leading to a three-dimensional framework. N—H⋯O and O—H⋯O hydrogen bonds and π–π inter­actions between the imidazole and benzene rings [centroid–centroid distances = 3.953 (2), 3.507 (2), 3.407 (2) and 3.561 (2) Å] further stabilize the crystal structure.
PMCID: PMC3200680  PMID: 22058893
4.  Conformation Preference of a Flexible Cyclohexanetetracarboxylate Ligand in Three New Metal-Organic Frameworks: Structures, Magnetic and Luminescent Properties 
Inorganic chemistry  2009;48(15):7194-7200.
Three novel complexes of formula [Co5(OH)2(cht)2(H2O)10]n · 2nH2O (1) (H4cht = cyclohexane-1,2,4,5-tetracarboxylic acid), [Zn2(cht)(H2O)3]n · nH2O (2), and [Cd2(cht)(H2O)5]n · 2nH2O (3) were synthesized by a hydrothermal reaction of cyclohexane-1,2,4,5-tetracarboxylic acid in the presence of sodium hydroxide with Co(NO3)2 · 6H2O, Zn(NO3)2 · 6H2O, and Cd(NO3)2 · 4H2O, respectively. These complexes were obtained by controlling the molar ratios of starting materials and the pH values of reaction mixtures with an initial pH of 5.87 for 1, 5.50 for 2, and 5.57 for 3, respectively. The single-crystal X-ray investigations reveal that the cht ligands change their conformations exclusively to the a,e,e,a form in all three complexes. Complex 1 features a two-dimensional (2D) metal-organic framework (MOF) with an axis surrounded by two zigzag structures, a rectangular channel surrounded by two a-carboxylate-metal-a-carboxlate and two e-carboxylate-metal-e-carboxylate chains, and two smaller distorted square-pyramidal channels surrounded by hydroxyl oxygen, cyclohexane, and its two a-carboxylates. Each cht ligand connects five cobalt atoms and each cobalt atom is six-coordinated with carboxylate-oxygen, hydroxyl, and water molecules. Complex 2 possesses a three-dimensional (3D) MOF structure that consists of the cht ligands and two types of cobalt; one is four-coordinated with carboxylate-oxygens and the other is six-coordinated with carboxylate-oxygens and water molecules. Each cht ligand is bonded to seven zinc atoms. Complex 3 is also a 2DMOF structure constructed by seven-coordinated cadmium atoms and the cht ligands. The e-carboxylates of two parallel cht ligands are connected to a type of cadmium atoms to form 1D chains, and these chains are further connected through a-carboxylates of the ligands and another type of cadmium atoms to give the 2D structure. Extensive hydrogen bonding interactions involving carboxylate-oxygen atoms and crystallization water molecules afford 3D supramolecular networks in complexes 1 and 2. Magnetic susceptibility measurement of 1 confirmed a six-coordinated high-spin cobalt(II) ion and the presence of magnetic exchange coupling among the three hydroxyl-oxygen bridged cobalt ions. Fluorescent spectra of complexes 2 and 3 show strong fluorescent emissions in the blue region.
PMCID: PMC2760471  PMID: 19586018
5.  Poly[di-μ2-azido-μ3-pyrazine-2-carboxyl­ato-cadmium(II)] 
The title compound, [Cd(C5H3N2O2)(N3)]n, has been pre­pared by the reaction of pyrazine-2-carboxylic acid, cadmium(II) nitrate and sodium azide. In the structure, the CdII atom is six-coordinated by two azide anions and three pyrazine-2-carboxyl­ate ligands. Each pyrazine-2-carboxyl­ate ligand bridges three CdII atoms, whereas the azide ligand bridges two CdII atoms, resulting in the formation of a two-dimensional metal–organic polymer developing parallel to the (100) plane.
PMCID: PMC2977564  PMID: 21583750
6.  Bis(μ-2-hydroxy­benozato)-κ3 O,O′:O′;κ3 O:O,O′-bis­[(2-hydroxy­benozato-κ2 O,O′)(1,10-phenanthroline-κ2 N,N′)cadmium(II)] 
The dinuclear title compound, [Cd2(C7H5O3)4(C12H8N2)2], is located on a crystallographic rotation twofold axis. The two CdII ions are connected by two tridentate bridging 2-hydroxy­benzoate anions. Each CdII ion is seven-coordinated by five O atoms from three 2-hydroxy­benzoate ligands and two N atoms from 1,10-phenanthroline. The 2-hydroxy­benzoate mol­ecules adopt two kinds of coordination mode, bidentate chelating and tridentate bridging–chelating. Intra­molecular hydrogen bonds between hydr­oxy and carboxyl­ate groups from 2-hydroxy­benzoate groups and π–π stacking interactions between parallel 1,10-phenanthroline ligands [centroid–centroid distances = 3.707 (3) and 3.842 (3) Å] are observed. Furthermore, adjacent benzene rings from 2-hydroxy­benzoate ligands are involved in π–π inter­actions with inter­planar distances of 3.642 (3) Å, thereby forming a chain along the a axis direction.
PMCID: PMC2959752  PMID: 21580896
7.  catena-Poly[[aqua­(1,10-phenanthroline)cadmium(II)]-μ-benzene-1,4-di­carboxyl­ato] 
The title compound, [Cd(C8H4O4)(C12H8N2)(H2O)]n, is a new coordination polymer of benzene-1,4-dicarboxyl­ate with cadmium(II) and 1,10-phenanthroline. The CdII ion is coordinated by two N atoms from the 1,10-phenanthroline mol­ecule, three O atoms from two crystallographically independent benzene-1,4-dicarboxyl­ate ligands and the O atom of a coordinated water mol­ecule, forming a heavily distorted octa­hedron. The 1,10-phenanthroline ligand is approximately planar within 0.073 (4) Å. The two different benzene-1,4-dicarboxyl­ate ligands each coordinate to two CdII ions in bidentate and monodentate modes, forming an infinite zigzag chain. Adjacent chains are packed tightly by strong π–π inter­actions [centroid–centroid distances = 3.851 (2) and 3.859 (2) Å] between the aromatic rings of the benzene-1,4-dicarboxyl­ate ligand and the 1,10-phenanthroline of a neighboring chain, forming a sheet parallel to (011). Different sheets are linked together via O—H⋯O hydrogen bonds between the coordinated water mol­ecules and the O atoms of the carboxyl­ate groups, forming a three-dimensional network.
PMCID: PMC2967922  PMID: 21581553
8.  Aqua­bis(1H-imidazole-κN 3)bis­(4-methyl­benzoato-κ2 O,O′)cadmium(II) 
In the title compound, [Cd(C8H7O2)2(C3H4N2)2(H2O)], the CdII atom is coordinated by four carboxyl­ate O atoms from two bidentate chelating 4-methyl­benzoate ligands, two N atoms from two imidazole ligands and one water mol­ecule in a distorted penta­gonal bipyramidal geometry. Inter­molecular O—H⋯O hydrogen bonds between the coordinated water mol­ecule and the carboxyl­ate O atoms of 4-methyl­benzoate lead to an infinite chain. These chains are further self-assembled into a two-dimensional layer through N—H⋯O hydrogen bonds between the imidazole ligands and carboxyl­ate groups. One of the imidazole ligands is disordered over two positions with site-occupancy factors of 0.737 (4) and 0.263 (4).
PMCID: PMC2961263  PMID: 21202242
9.  Poly[[aqua­(μ2-4,4′-bipyridine-κ2 N:N′)[μ3-3-bromo-2-(carboxyl­atometh­yl)­benzoato-κ3 O 1:O 1′:O 2]cadmium] monohydrate] 
In the title compound, {[Cd(C9H5BrO4)(C10H8N2)(H2O)]·H2O}n, the CdII atom has a distorted octa­hedral coordination geometry. Two N atoms from two 4,4′-bipyridine (bipy) ligands occupy the axial positions, while the equatorial positions are furnished by three carboxyl­ate O atoms from three 3-bromo-2-(carboxyl­atometh­yl)benzoate (bcb) ligands and one O atom from a water mol­ecule. The bipy and bcb ligands link the CdII atoms into a three-dimensional network. O—H⋯O hydrogen bonds and π–π inter­actions between the pyridine and benzene rings [centroid–centroid distance = 3.736 (4) Å] are present in the crystal.
PMCID: PMC3414131  PMID: 22904738
10.  Bis(μ-4-methyl­benzoato)-κ3 O,O′:O;κ3 O:O,O′-bis­[aqua­(4-methyl­benzoato-κ2 O,O′)(nicotinamide-κN 1)cadmium] 
In the dinuclear centrosymmetric title compound, [Cd2(C8H7O2)4(C6H6N2O)2(H2O)2], the CdII ion is chelated by two carboxyl­ate groups from 4-methyl­benzoate anions, and is further coordinated by one nicotinamide and one water mol­ecule; a carboxyl­ate O atom from an adjacent 4-methyl­benzoate anion bridges to the CdII ion, completing the irregular coordination sphere of the seven ligand atoms. In the crystal, inter­molecular O—H⋯O, N—H⋯O and weak C—H⋯O hydrogen bonds link the mol­ecules into a three-dimensional network. The methyl­benzene moiety of one bridging 4-methyl­benzoate anion is disordered over two orientations of equal occupancy.
PMCID: PMC3588758  PMID: 23468723
11.  Triaqua­bis{μ-N-[N-(4-meth­oxy-2-oxidobenzyl­idene)glyc­yl]glycinato(3−)}cadmium(II)dicopper(II) dihydrate 
In the title compound, [CdCu2(C12H11N2O5)2(H2O)3]·2H2O, the CuII atoms are in a square plane of N2O2 atoms contributed by the tetra­dentate Schiff base trianion. The CuII atoms are coordinated by one phenolate O atom, one imine N atom, one amido N atom and one carboxyl­ate O atom. The CdII atom is connected via the carboxyl­ate groups, forming a heterotrinuclear CuII–CdII–CuII system. The CdII atom is seven-coordinate in a penta­gonal-bipyramidal geometry with four O atoms from two carboxyl­ate groups and three aqua ligands. The heterotrinuclear mol­ecules are linked to the uncoordinated water mol­ecules by O—H⋯O hydrogen bonds into a three-dimensional framework.
PMCID: PMC2971383  PMID: 21578052
12.  Poly[[(2,2′-bipyridine)(μ 3-7-oxabicyclo­[2.2.1]heptane-2,3-dicarboxyl­ato)cadmium] monohydrate] 
The title compound, {[Cd(C8H8O5)(C10H8N2)]·H2O}n, was obtained by the reaction of cadmium acetate with 2,2′-bi­pyridine and 7-oxabicyclo­(2.2.1)heptane-2,3-dicarb­oxy­lic anhydride. The CdII atom is seven-coordinated in a distorted penta­gonal–bipyramidal configuration, defined by five O atoms from the carboxyl­ate groups of three 7-oxabicyclo­[2.2.1]heptane-2,3-dicarboxyl­ato ligands and two N atoms from the 2,2′-bipyridine ligand. Two O atoms link two CdII atoms, forming a dinuclear center: the Cd—O—Cd bridging angle is 110.19 (6)°. The polymeric structure extends along [100] and is linked by inter­molecular O—H⋯O hydrogen bonds involving the solvent water molecule. Extensive π–π stacking exists between 2,2-bypiridine ligands along [010] with centroid-centroid distance of 3.650 (2) Å
PMCID: PMC3201414  PMID: 22065044
13.  catena-Poly[[aqua­bis­(3-chloro­benzoato-κ2 O,O′)cadmium]-μ-N,N-di­ethyl­nico­tin­amide-κ2 N 1:O] 
In the crystal of the title CdII polymeric complex, [Cd(C7H4ClO2)2(C10H14N2O)(H2O)]n, the CdII cation is chelated by two chloro­benzoate anions and coordinated by two N,N-di­­ethyl­nicotinamide (DENA) ligands and one water mol­ecule in a distorted NO6 penta­gonal–bipyramidal geometry. The CdII cations are bridged by the pyridine N atom and carbonyl O atom of the DENA ligand to form a polymeric chain running along the b axis. Inter­molecular O—H⋯O hydrogen bonds between coordinating water mol­ecules and carboxyl­ate groups link adjacent chains into layers parallel to the bc plane. π–π contacts between benzene rings [shortest centroid–centroid distance = 3.912 (2) Å] further stabilizes the crystal structure. In the mol­ecule, weak C—H⋯O hydrogen bonds occur between the pyridine ring and carboxyl­ate groups; the dihedral angles between the carboxyl­ate groups and adjacent benzene rings are 4.6 (3) and 12.8 (3)°, while the benzene rings are oriented at a dihedral angle of 1.89 (13)°.
PMCID: PMC3793697  PMID: 24109284
14.  Poly[[aqua­(1-naphthyl­acetato)cadmium(II)]-μ3-pyridin-3-olato] 
In the title complex, [Cd(C5H4NO)(C12H9O2)(H2O)]n, each CdII atom is coordinated by two carboxylate O atoms from one 1-naphthyl­acetate ligand, two hydroxyl O atoms from two pyridin-3-olate ligands, one N atom from another pyridin-3-olate ligand and one water mol­ecule, and displays a distorted octa­hedral coordination geometry. The compound forms infinite chains of pyridin-3-olate ligands bridging 1-naphthyl­acetate–CdII units parallel to the b axis, with a Cd⋯Cd separation of 3.578 (2) Å. The chains are further self-assembled into a supra­molecular network through inter­molecular O—H⋯O hydrogen-bonding inter­actions.
PMCID: PMC2914920  PMID: 21200605
15.  Poly[bis­(μ2-pyrazine-2-carboxyl­ato)-κ3 N 1,O:O′;κ3 N 1,O:O-cadmium(II)] 
In the structure of the title compound, [Cd(C5H3N2O2)2]n, the CdII ion is six-coordinated by two N atoms and four O atoms from three different pyrazine-2-carboxyl­ate ligands. One N atom and one O atom of the carboxyl­ate group in the ligand coordinate to the metal center, forming a five-membered chelate ring. The carboxyl­ate anion adopts two types of bridging modes, viz. μ2-O and syn–anti. Two CdII ions form a centrosymmetric dimer via a μ2-O bridge, and the dimers are linked through the syn–anti carboxyl­ate functional group, forming a two-dimensional polymeric structure extending along (100).
PMCID: PMC2980228  PMID: 21579983
16.  Diaqua­bis­(2-oxo-2H-chromene-3-carboxyl­ato-κ2 O 2,O 3)cadmium 
In the title mononuclear cadmium complex, [Cd(C10H5O4)2(H2O)2], the CdII atom, located on a crystallographic inversion center, exhibits a slightly distorted octa­hedral geometry and is six-coordinated by two O atoms from water mol­ecules in the axial positions and four O atoms from two deprotonated coumarin-3-carb­oxy­lic acid ligands in the equatorial plane. Angles around the CdII atom vary between 81.00 (5) and 99.00 (0)°. The Cd—O bond lengths vary between 2.1961 (13) and 2.3360 (13) Å. O—H⋯O hydrogen bonds between the H atoms of coordinated water mol­ecules and the O atoms of carboxyl­ate groups link the complex mol­ecules into layers parallel to the ab plane.
PMCID: PMC3050216  PMID: 21522537
17.  Poly[[μ4-tartrato-cadmium(II)] 0.167-hydrate] 
The title compound, {[Cd(C4H4O6)]·0.167H2O}n, adopts a three-dimensional network structure in which each CdII ion is chelated by two pairs of carboxyl­ate and hydroxyl O atoms from two tartrate anions, and is additionally linked to two O atoms of two carboxyl­ate groups that are not involved in chelation. The asymmetric unit has four independent cadmium atoms, two of which lie on special positions of 2 site symmetry. The tartrate anions all lie on general positions. All hydroxyl groups are engaged in O—H⋯O hydrogen-bonds, one of which is also bifurcated. The non-coordinating water molecule is situated on a site with half-occupation.
PMCID: PMC2969599  PMID: 21582997
18.  Poly[(μ2-quinoline-3-carboxyl­ato-κ2 N:O)(μ2-quinoline-3-carboxyl­ato-κ3 N:O,O′)cadmium] 
In the title compound, [Cd(C10H6NO2)2]n, the CdII atom is coordinated by three O atoms and two N atoms from four quinoline-3-carboxyl­ate (L −) ligands, leading to a distorted trigonal–bipyramidal geometry. The L − ligands link the CdII atoms into a plane parallel to (100), with one ligand being tridentate, coordinating via the N atom and chelating a second Cd atom, and the other being bidentate, bridging two Cd atoms via the N and one O atom.. This two-dimensional network extends into a double-layer network by π–π inter­actions, with centroid–centroid distances of 3.680 (2) and 3.752 (2) Å. Another type of π–π inter­action between pyridine rings [centroid–centroid distance = 3.527 (2) Å] leads to a three-dimensional supra­molecular architecture.
PMCID: PMC3274893  PMID: 22346840
19.  catena-Poly[[aqua­bis­(4-formyl­benzoato-κ2 O 1,O 1′)cadmium]-μ-pyrazine-κ2 N:N′] 
The polymeric title compound, [Cd(C8H5O3)2(C4H4N2)(H2O)]n, contains two 4-formyl­benzoate (FB) anions, one pyrazine mol­ecule and one coordinating water mol­ecule; the FB anions act as bidentate ligands. The O atom, the aldehyde H atom and the benzene ring of one of the FB anions are disordered over two positions. The O atoms were freely refined [refined occupancy ratio 0.79 (2):0.21 (2)], while the aldehyde H atoms and the benzene ring atoms were refined with fixed occupancy ratios of 0.8:0.2 and 0.5:0.5, respectively. In the ordered FB anion, the carboxyl­ate group is twisted away from the attached benzene ring (A) by 22.7 (8)°. In the disordered FB anion, the corresponding angles are 15.6 (10) and 11.4 (11)° for rings B and B′, respectively. Benzene rings A and B are oriented at a dihedral angle of 24.2 (7), A and B′ at 43.0 (8)°. The pyrazine ring makes dihedral angles of 67.5 (4), 89.6 (7) and 86.2 (7)°, respectively, with benzene rings A, B and B′. The pyrazine ligands bridge the CdII cations, forming polymeric chains running along the b-axis direction. In the crystal, O—Hwater ⋯ Ocarboxyl­ate hydrogen bonds link adjacent chains into layers parallel to the bc plane. These layers are linked via C—Hpyrazine ⋯ Oform­yl hydrogen bonds, forming a three-dimensional network. π–π interactions [centroid–centroid distances = 3.870 (11)–3.951 (5) Å] further stabilize the crystal structure. There is also a weak C—H⋯π inter­action present.
PMCID: PMC3998250  PMID: 24764811
20.  Di-μ-nicotinamide-κ2 N 1:O;κ2 O:N 1-bis­[aqua­bis­(3-chloro­benzoato-κ2 O,O′)cadmium] 
In the centrosymmetric dinuclear title compound, [Cd2(C7H4ClO2)4(C6H6N2O)2(H2O)2], the CdII atom is coord­inated by one N atom from one bridging nicotinamide ligand and one O atom from another symmetry-related bridging nicotinamide ligand, four O atoms from two 3-chloro­benzoate ligands and one water mol­ecule in an irregular geometry. The dihedral angles between the carboxyl­ate groups and the adjacent benzene rings are 6.98 (12) and 2.42 (13)°, while the benzene rings are oriented at a dihedral angle of 4.33 (6)°. Inter­molecular O—H⋯O, N—H⋯O and weak C—H⋯O hydrogen bonds link the mol­ecules into a three-dimensional network. π–π inter­actions, indicated by short centroid–centroid distances [3.892 (1) Å between the pyridine rings and 3.683 (1) Å between the benzene rings] further stabilize the structure.
PMCID: PMC3772423  PMID: 24046566
21.  catena-Poly[[[aqua­(1,10-phenan­throline)cadmium(II)]-μ-benzene-1,4-dicarboxyl­ato] benzene-1,4-dicarboxylic acid hemisolvate] 
A new cadmium(II) coordination polymer, {[Cd(C8H4O4)(C12H8N2)(H2O)]·0.5C8H6O4}n, has been synthesized under hydro­thermal conditions. The asymmetric unit contains one CdII atom, one benzene-1,4-dicarboxyl­ate anion, one 1,10-phenanthroline ligand, one coordinated water mol­ecule and half of an uncoordinated benzene-1,4-dicaboxylic acid solvent mol­ecule. The CdII atom is in the centre of a monocapped distorted octa­hedron made up of four O atoms of two chelating benzene-1,4-dicarboxyl­ate anions, one water O atom and two 1,10-phenanthroline N atoms. The metal centres are connected via bis-chelating benzene-1,4-dicarboxyl­ate anions into a zigzag chain structure along [001]. These chains are further connected by O—H⋯O hydrogen bonds between the water mol­ecules and adjacent carboxyl­ate O atoms. Additional O—H⋯O hydrogen bonding between the uncoordinated benzene-1,4-dicaboxylic acid mol­ecules along [010] consolidates the structure.
PMCID: PMC2968137  PMID: 21581788
22.  Crystal structure of catena-poly[[cadmium(II)-di-μ2-bromido-μ2-l-proline-κ2 O:O′] monohydrate] 
In the title salt, crystalline water mol­ecules serve as donors for the weak inter­molecular O—H⋯O and O—H⋯Br hydrogen bonds which link adjacent polymeric chains.
In the title coordination polymer, {[CdBr2(C5H9NO2)]·H2O}n, the CdII ion is coordinated by four bromido ligands and two carboxyl­ate oxygen atoms of two symmetry-related proline ligands, which exist in a zwitterionic form, in a distorted octa­hedral geometry. There is an intra­molecular N—H⋯O hydrogen bond between the amino group and the carboxyl­ate fragment. Each coordinating ligand bridges two CdII atoms, thus forming polymeric chains running along the c-axis direction. The water mol­ecules of crystallization serve as donors for the weak inter­molecular O—H⋯O and O—H⋯Br hydrogen bonds that link adjacent polymeric chains, thus forming a three-dimensional structure. N—H⋯O and N—H⋯Br hydrogen bonds also occur.
PMCID: PMC4384587  PMID: 25878823
crystal structure; l-proline cadmium bromide; cadmium coordination polymer; N/O—H⋯Br/O hydrogen bonds; distorted octa­hedral geometry.
23.  catena-Poly[[bis­(pyridine-κN)cadmium]-di-μ2-thio­cyanato-κ2 N:S;κ2 S:N] 
The asymmetric unit of the title compound, [Cd(NCS)2(C5H5N)2]n, consists of two crystallographically independent CdII cations, four thio­cyanato anions and four pyridine ligands. The CdII atoms are each coordinated by four N atoms from two pyridine ligands and two thio­cyanato anions, each in a mutually cis orientation, and by two S atoms from two adjacent thio­cyanato anions within a slightly distorted octa­hedral coordination environment. The CdII atoms are μ-1,3-bridged via the thio­cyanato anions into polymeric chains parallel to [001]. The CdII⋯CdII intra­chain separations range between 5.9688 (6) and 6.0195 (6) Å, whereas the shortest CdII⋯CdII inter­chain separations are 7.8272 (7) and 8.6312 (6) Å.
PMCID: PMC3099960  PMID: 21753993
24.  Poly[[tetra­aqua­bis­(μ3-5-carboxybenzene-1,2,4-tri­carboxyl­ato)tricadmium] tetra­hydrate] 
There are three independent CdII ions in the title complex, {[Cd3(C10H3O8)2(H2O)4]·4H2O}n, one of which is coordinated by four O atoms from three 5-carboxybenzene-1,2,4-tri­carboxyl­ate ligands and by two water mol­ecules in a distorted octa­hedral geometry. The second CdII ion is coordinated by five O atoms from four 5-carboxybenzene-1,2,4-tri­carboxyl­ate ligands and by one water mol­ecule also in a distorted octa­hedral geometry while the third CdII ion is coordinated by five O atoms from three 5-carboxybenzene-1,2,4-tri­carboxyl­ate ligands and by one water mol­ecule in a highly distorted octa­hedral geometry. The 5-carboxybenzene-1,2,4-tri­carboxyl­ate ligands bridge the CdII ions, resulting in the formation of a three-dimensional structure. Intra- and inter­molecular O—H⋯O hydrogen bonds are present throughout the three-dimensional structure.
PMCID: PMC3379128  PMID: 22719349
25.  Poly[[(μ2-benzene-1,3-di­carboxyl­ato){μ2-1,4-bis­[(1H-imidazol-1-yl)meth­yl]benzene}­cadmium] di­methyl­formamide monosolvate] 
The title coordination polymer, {[Cd(C8H4O4)(C14H14N4)]·C3H7NO}n, was synthesized by solvothermal reaction of metallic cadmium with the semi-rigid neutral ligand 1,4-bis­[(1H-imidazol-1-yl)meth­yl]benzene (bix) and the V-shaped benzene-1,3-di­carb­oxy­lic acid (m-H2bdc). The structure exhibits a pseudo-C-centring which is almost fulfilled by the polymeric metal complex but not by the solvent dimethylform­amide (DMF) mol­ecules. The asymmetric unit contains two independent CdII ions, two m-bdc2− ligands, one and two half bix ligands, and two solvent DMF mol­ecules. The CdII ions are both five-coordinated by three O atoms from two different m-bdc2− ligands and two N atoms from two different bix ligands in a distorted square-pyramidal geometry. The m-bdc2− ligands adopt a chelate-monodentate coordination mode, connecting neighboring CdII ions into a zigzag chain parallel to [110]. Adjacent chains are further cross-linked by bix ligands, giving rise to a puckered sheet nearly perpendicular to the chain direction. Thus, each CdII ion is connected to four neighboring CdII ions through two m-bdc2− anions and two bix ligands, giving rise to the final non-inter­penetrating uninodal layer with sql (4,4) topology.
PMCID: PMC3884267  PMID: 24454043

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