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1.  Poly[μ-aqua-diaqua­(μ2-pyrazine-2,3-dicarboxyl­ato)dilithium(I)] 
The asymmetric unit of the title compound, [Li2(C6H2N2O4)(H2O)3]n, consists of two independent Li+ cations, one pyrazine-2,3-dicarboxyl­ate dianion and three water mol­ecules. One of the Li+ cations has a distorted tetra­hedral geometry, coordinated by one of the carboxyl­ate O atoms of the pyrazine-2,3-dicarboxyl­ate ligand and three O atoms from three water mol­ecules, whereas the other Li+ cation has a distorted trigonal-bipyramidal geometry, coordinated by a carboxyl­ate O atom of a symmetry-related pyrazine-2,3-dicarboxyl­ate ligand, two water mol­ecules and a chelating pyrazine-2,3-dicarboxyl­ate ligand (by utilizing both N and O atoms) of an adjacent mol­ecule. The synthesis of a hydrated polymeric dinuclear lithium complex formed with two pyrazine-2,3-dicarboxylic acid ligands has been reported previously [Tombul et al. (2008a ▶). Acta Cryst. E64, m491–m492]. By comparision to the complex reported here, the dinuclear complex formed with two pyrazine-2,3-dicarboxylic acid ligands differs in the coordination geometry of both Li atoms. The crystal structure further features O—H⋯O and O—H⋯N hydrogen-bonding inter­actions involving the water mol­ecules and carboxyl­ate O atoms.
PMCID: PMC2971803  PMID: 21578706
2.  Poly[di-μ-aqua-μ4-(pyrazine-2,5-dicarboxyl­ato)-dilithium(I)] 
In the title coordination polymer, [Li2(C6H2N2O2)(H2O)2]n the pyrazine-2,5-dicarboxyl­ate dianionic ligand bridges two symmetry-independent Li+ ions using both its N,O-chelating sites. The carboxyl­ate O atom of one of them also bridges to another Li+ ion, while the second O atom of this group is bonded to another Li+ ion. Two symmetry-independent water O atoms participate also in the bridging system, which gives rise to a polymeric three-dimensional framework. Both Li+ ions show distorted trigonal–bipyramidal LiNO4 coordination geometries, with the N atom in an axial site in both cases. The packing is consolidated by O—H⋯O hydrogen bonds, which occur between water mol­ecules as donors and carboxyl­ate O atoms as acceptors.
PMCID: PMC3050281  PMID: 21522570
3.  Crystal structure of 5-{4′-[(2-{2-[2-(2-ammonio­eth­oxy)eth­oxy]eth­oxy}eth­yl)carbamo­yl]-4-meth­oxy-[1,1′-biphen­yl]-3-yl}-3-oxo-1,2,5-thia­diazo­lidin-2-ide 1,1-dioxide: a potential inhibitor of the enzyme protein tyrosine phosphatase 1B (PTP1B) 
A variety of 5-aryl-1,2,5-thia­diazo­lidin-3-one 1,1-dioxides have been developed as inhibitors of the enzyme protein tyrosine phosphatase 1B (PTP1B). For the title compound, there is the expected twisted relationship between the plane of the 1,2,5-thia­diazo­lidin-3-one 1,1-dioxide ring and the aryl ring to which it is attached, although the dihedral angle of 62.87 (8)° is substanti­ally less than that seen in certain protein–ligand structures.
The title compound, C24H32N4O8S, (I), crystallizes as a zwitterion. The terminal amine N atom of the [(2-{2-[2-(2-ammonio­eth­oxy)eth­oxy]eth­oxy}eth­yl)carbamo­yl] side chain is protonated, while the 1,2,5-thia­diazo­lidin-3-one 1,1-dioxide N atom is deprotonated. The side chain is turned over on itself with an intra­molecular N—H⋯O hydrogen bond. The 1,2,5-thia­diazo­lidin-3-one 1,1-dioxide ring has an envelope conformation with the aryl-substituted N atom as the flap. Its mean plane is inclined by 62.87 (8)° to the aryl ring to which it is attached, while the aryl rings of the biphenyl unit are inclined to one another by 20.81 (8)°. In the crystal, mol­ecules are linked by N—H⋯O and N—H⋯N hydrogen bonds, forming slabs lying parallel to (010). Within the slabs there are C—H⋯O and C—H⋯N hydrogen bonds and C—H⋯π inter­actions present.
PMCID: PMC4438830  PMID: 26029383
crystal structure; PTP1B; inhibitor; 1,2,5-thia­diazo­lidin-3-one 1,1-dioxide; hydrogen bonding
4.  Tetra­aqua­tetra­kis{μ3-3,3′-[(E,E)-ethane-1,2-diylbis(nitrilo­methyl­idyne)]benzene-1,2-diolato}octa­zinc(II) N,N-dimethyl­formamide hexa­solvate 
The asymmetric unit of the title compound [Zn8(C16H12N2O4)4(H2O)4]·6C3H7NO, consists of eight ZnII cations, four tetra­valent anionic ligands, L 4− (L 4− = 3,3′-(1E,1′E)-(ethane-1,2-diylbis(azan-1-yl-1-yl­idene))bis­(methan-1-yl-1-yl­idene)dibenzene-1,2-bis­(olate), four coordinated water mol­ecules and six N,N-dimethyl­formamide solvate mol­ecules. The coordination complex comprises an octa­nuclear ZnII unit with its ZnII centers coordinated in two discrete distorted square-pyramidal geometries. Four ZnII atoms each coordinate to two nitro­gen atoms and two phenolate oxygen atoms from an individual L 4− ligand and one coordinated water mol­ecule. The other four ZnII atoms each bind to five phenolate oxygen atoms from three different L 4− ligands. In the crystal structure, the ZnII complex unit, coordinated water mol­ecules and dimethyl­formamide solvate mol­ecules are linked via O—H⋯O and C—H⋯O hydrogen bonds. Mol­ecules are connected by additional inter­molecular O—H⋯O and C—H⋯O hydrogen bonds, forming an extensive three dimensional framework.
PMCID: PMC2972079  PMID: 21578596
5.  catena-Poly[[di­aqua­bis­(μ3-5-carboxyl­ato-1H-pyrazole-3-carb­oxy­lic acid-κ3 O 3:O 3;O 5)dilithium(I)] monohydrate] 
The basic structural unit of the title polymeric ribbon, {[Li2(C5H3N2O2)2(H2O)2]·H2O}n, is a centrosymmetric dinuclear complex in which the two LiI ions are bridged by two carboxyl­ato O atoms, to generate a centrosymmetric Li2O2 core. These are connected into a chain along [01-1] by carboxylic acid–carbonyl-O bonds. The tetra­hedral coordination of the LiI cation is completed by an aqua ligand. The carboxylic acid is involved in an intra-ribbon hydrogen bond. A solvate water molecule showing positional (50:50) disorder is observed. Polymeric ribbons along [01-1] are connected by O—H⋯O, N—H⋯O and O—H⋯N hydrogen bonds into a three-dimensional architecture.
PMCID: PMC3884253  PMID: 24454029
6.  Poly[[tetra­aqua-μ4-fumarato-di-μ3-fumarato-dineodymium(III)] trihydrate] 
The title coordination polymer, {[Nd2(C4H2O4)3(H2O)4]·3H2O}, was synthesized by the reaction of neodymium(III) nitrate hexa­hydrate with fumaric acid in a water–methanol (7:3) solution. The asymmetric unit comprises two Nd3+ cations, three fumarate dianions (L 2−), four aqua ligands and three uncoordinated water mol­ecules. The carboxyl­ate groups of the fumarate dianions exhibit different coordination modes. In one fumarate dianion, two carboxyl­ate groups chelate two Nd3+ cations, while one of the O atoms is coordinated to another Nd3+ cation. Another fumarate dianion bridges three Nd3+ cations: one of the carboxyl­ate groups chelates one Nd3+ cation, while the other carboxyl­ate group bridges two Nd3+ cations in a monodentate mode. The third fumarate dianion bridges four Nd3+ cations, where one of the carboxyl­ate groups chelates one Nd3+ cation and coordinates in a monodentate mode to a second Nd3+, while the second carboxyl­ate groups bridges two Nd3+ cations in a monodentate mode and one O atom is coordinated to one Nd3+ cation. The Nd3+ cations are in a distorted tricapped–trigonal prismatic environment and coordinated by seven O atoms from the fumarate ligands and two O atoms from water mol­ecules. The Nd3+ cations are linked by two carboxyl­ate O atoms and two carboxyl­ate groups, generating infinite Nd–O chains to form a three-dimensional framework. There are O—H⋯O and C—H⋯O hydrogen-bonding interactions between the coordin­ated and uncoordinated water mol­ecules and carboxyl­ate O atoms.
PMCID: PMC3238635  PMID: 22199526
7.  catena-Poly[[[aqua­(5-nitro­benzene-1,2,3-tricarboxyl­ato-κO 1)nickel(II)]-di-μ-aqua-[diaqua­sodium]-di-μ-aqua] tetra­hydrate] 
In the title complex, {[NaNi(C9H2NO8)(H2O)7]·4H2O}n, the NiII atom has a distorted octa­hedral coordination, defined by five O atoms from five water mol­ecules and one O atom from one 5-nitro­benzene-1,2,3-tricarboxyl­ate ligand. The Na cation is coordinated by six water O atoms in an irregular trigonal-prismatic geometry. There are seven coordinated water mol­ecules in the asymmetic unit. The Ni and Na atoms are linked by water bridges, forming infinite chains, which are connected by strong O—H⋯O hydrogen bonds involving the coordinated and uncoordinated water mol­ecules into a three-dimensional network.
PMCID: PMC2983560  PMID: 21580274
8.  catena-Poly[[[aqua­(5-nitro­benzene-1,2,3-tricarboxyl­ato-κO 1)copper(II)]-di-μ-aqua-[diaqua­sodium]-di-μ-aqua] tetra­hydrate] 
In the heteronuclear coordination polymer, {[CuNa(C9H2NO8)(H2O)7]·4H2O}n, the CuII atom is coordinated by six O atoms from five water mol­ecules and one 5-nitro­benzene-1,2,3-tricarboxyl­ate ligand in a slightly distorted octa­hedral geometry. The Na+ cation is surrounded by six water mol­ecules in an irregular trigonal-prismatic geometry. The Cu and Na atoms are connected by water bridges, forming an infinite chain. O—H⋯O hydrogen bonds involving the coordinated and uncoordinated water mol­ecules connect the chains into a three-dimensional network.
PMCID: PMC2979819  PMID: 21579616
9.  A novel double-chain silver(I) coordination polymer: catena-poly[[[μ-aqua-aqua­disilver(I)]-bis­(μ3-5-methyl­pyrazine-2-carboxyl­ato)] dihydrate] 
In the title silver(I) coordination polymer, {[Ag2(C6H5N2O2)2(H2O)2]·2H2O}n, the [Ag2(μ2-H2O)(H2O)] cores are extended by anti­parallel 5-methyl­pyrazine-2-carboxyl­ate (L) ligands, forming a novel double-chain structure. Both Ag+ cations show a distorted square-pyramidal coordination. Ag1 is bonded to two water molecules, one L N atom, one N atom and one carboxylate O atom from a neighbouring L, whereas Ag2 is surrounded by two L N atoms, two L carboxylate O atoms and one bridging water molecule. O—H⋯O hydrogen-bonding inter­actions involving water clusters and carboxyl­ate O atoms link the mol­ecules into a three-dimensional supra­molecular architecture, which is further consolidated by weak C—H⋯O inter­actions and π–π stacking inter­actions [centroid–centroid distance 3.643 (5) Å].
PMCID: PMC2959376  PMID: 21201049
10.  Crystal structure of tetra­aqua­bis(3,5-di­amino-4H-1,2,4-triazol-1-ium)cobalt(II) bis­[bis­(pyridine-2,6-di­carboxyl­ato)cobaltate(II)] dihydrate 
The asymmetric unit of the title compound, [Co(C2H6N5)2(H2O)4][Co(C7H3NO4)2]2·2H2O, features 1.5 CoII ions (one anionic complex and one half cationic complex) and one water mol­ecule. In the cationic complex, the CoII atom is located on an inversion centre and is coordinated by two triazolium cations and four water mol­ecules, adopting an octa­hedral geometry where the N atoms of the two triazolium cations occupy the axial positions and the O atoms of the four water mol­ecules the equatorial positions. The two triazole ligands are parallel offset (with a distance of 1.38 Å between their planes). In the anionic complex, the CoII ion is six-coordinated by two N and four O atoms of the two pyridine-2,6-di­carboxyl­ate anions, exhibiting a slightly distorted octa­hedral coordination geometry in which the mean plane of the two pyridine-2,6-di­carboxyl­ate anions are almost perpendicular to each other, making a dihedral angle of 85.87 (2)°. In the crystal, mol­ecules are linked into a three-dimensional network via C—H⋯O, C—H⋯N, O—H⋯O and N—H⋯O hydrogen bonds.
PMCID: PMC4459343  PMID: 26090171
crystal structure; pyridine-2,6-di­carboxyl­ate; triazolium; CoII complex; hydrogen bonding
11.  Poly[μ3-β-alanine-aqua-μ4-sulfato-dilithium] 
The title compound, [Li2(SO4)(C3H7NO2)(H2O)]n, is a coordination polymer in which the β-alanine residues remain in the zwitterionic form. The crystal structure consists of corrugated sheets of [LiO4] and [SO4] tetra­hedra parallel to (010) with the β-alanine mol­ecules located between the sheets. The two independent Li+ cations are four-coordinated by O atoms in a distorted tetra­hedral geometry. The crystal structure is formed by stacking of alternate organic and inorganic layers along the a axis. The crystal structure is further stabilized by N—H⋯O hydrogen bonds.
PMCID: PMC3274924  PMID: 22346871
12.  Crystal structure of a polymeric calcium levulinate dihydrate: catena-poly[[di­aqua­calcium]-bis­(μ2-4-oxo­butano­ato)] 
The crystal structure of calcium levulinate dihydrate forms a one-dimensional coordination polymer based on a CaO8 complex unit which lies on a twofold rotation axis. This unit comprises two monodentate water O-atom donors and six carboxyl­ate O-atom donors, two of which are also bridging, from the two bidentate chelate levulinate ligands. The complex chains are stabilized by intra- and inter­molecular water O—H⋯O hydrogen bonds, forming an overall three-dimensional structure.
In the title calcium levulinate complex, [Ca(C5H7O3)2(H2O)2]n, the Ca2+ ion lies on a twofold rotation axis and is octa­coordinated by two aqua ligands and six O atoms from four symmetry-related carboxyl­ate ligands, giving a distorted square-anti­prismatic coordination stereochemistry [Ca—O bond-length range = 2.355 (1)–2.599 (1) Å]. The levulinate ligands act both in a bidentate carboxyl O,O′-chelate mode and in a bridging mode through one carboxyl O atom with an inversion-related Ca2+ atom, giving a Ca⋯Ca separation of 4.0326 (7) Å. A coordination polymeric chain structure is generated, extending along the c-axial direction. The coordinating water mol­ecules act as double donors and participate in intra-chain O—H⋯O hydrogen bonds with carboxyl O atoms, and in inter-chain O—H⋯O hydrogen bonds with carbonyl O atoms, thus forming an overall three-dimensional structure.
PMCID: PMC4420067  PMID: 25995864
crystal structure; coordination polymer; calcium levulinate dihydrate; levulinic acid; hydrogen bonding
13.  Tetra­aqua­(2,2′-bipyridine-5,5′-dicarboxyl­ato-κ2 N,N′)nickel(II) dihydrate 
In the title compound, [Ni(C12H6N2O4)(H2O)4]·2H2O, obtained from a basic solution of 2,2′-bipyridine-5,5′-dicarboxyl­ate and nickel(II) chloride in water, the central Ni(II) cation (site symmetry 2) is coordinated by two N atoms from the 2,2′-bipyridine-5,5′-dicarboxyl­ate ligand and four aqua O atoms. The N—Ni—N angle is 78.64 (8)°. Weak but significant π–π stacking inter­actions exist between the pyridine rings with a centroid–centroid distance of 3.652 (8) Å. In addition, four O atoms of the two carboxyl groups form hydrogen bonds with both coordinated and uncoordinated water mol­ecules, forming an infinite three-dimensional network.
PMCID: PMC2970486  PMID: 21577733
14.  Diacetonitrile­tetra­kis{μ2-3-anilinocarbonyl-1-[(5-chloro-2-oxidophen­yl)diazen­yl]-2-naphtholato}tetra­aqua­diiron(III)disodium(I) dihydrate 
The title compound, [Fe2Na2(C23H14ClN3O3)4(C2H3N)2(H2O)4]·2H2O, is a hydrated Fe–azo complex dimer that is used as a charge-control agent in electrophotography. The mol­ecule is a centrosymmetric dimer with two octa­hedral FeIII units linked by two bridging five-coordinate NaI cations. Each FeIII atom is chelated by the N and two O atoms from two 3-anilinocarbonyl-1-[(5-chloro-2-oxidophen­yl)diazen­yl]-2-naph­tholate ligands. The Na+ cation is coordinated by a carbonyl O atom from the two ligands of each octa­hedral FeIII unit, two water mol­ecules and the N atom of an acetonitrile mol­ecule. Two solvent water mol­ecules complete the structure. In the crystal structure, the dimeric mol­ecules are bridged by a pair of discrete inter­molecular O—H⋯O hydrogen bonds, one of which involves a sodium-bound water mol­ecule and a hydrate water, and the other a 5-chloro­phenolate O atom and a water molecule to form an extended chain along b.
PMCID: PMC2915160  PMID: 21200583
15.  Poly[[μ-aqua-tetraaquabis(μ-2-hydroxy-4-oxocyclobut-1-ene-1,3-diolato)strontium] hemihydrate] 
In the title coordination polymer, {[Sr(C4HO4)2(H2O)5]·0.5H2O}n, the Sr2+ ion is coordinated by three monodentate hydrogensquarate (hsq) anions and six aqua ligands in a distorted SrO9 monocapped square-anti­prismatic geometry. The hsq anions and water mol­ecules bridge the metal ions into infinite sheets lying parallel to (100). The O atom of the uncoordinated water mol­ecule lies on a crystallographic twofold axis. The packing is stabilized by numerous O—H⋯O hydrogen bonds.
PMCID: PMC3212191  PMID: 22090893
16.  Aqua­(4,4′-bipyridine-κN)bis­(1,4-dioxo-1,4-dihydronaphthalen-2-olato-κ2 O 1,O 2)zinc 4,4′-bipyridine mono­solvate dihydrate 
The reaction of 2-hy­droxy-1,4-naphtho­quinone and 4,4′-bipyridine with zinc acetate produced the title compound, [Zn(C10H5O3)2(C10H8N2)(H2O)]·C10H8N2·2H2O. The bond lengths and angles around the metal atom indicate a deviation from octa­hedral geometry. The two naphtho­quinone ligands coordinate in a cis fashion, with the 4,4′-bipyridine ligand and the water mol­ecules completing the coordination sphere of the metal atom. The asymmetric unit contains also one free 4,4′-bipyridine mol­ecule and two uncoordinated water mol­ecules. These mol­ecules make contacts with the complex through O—H⋯N and O—H⋯O hydrogen bonds, creating a layer two-dimensional network parallel to (121).
PMCID: PMC3246923  PMID: 22219743
17.  catena-Poly[[[diaqua­cobalt(II)]-μ-(3,5-dinitro-2-oxidobenzoato)-κ3 O 1,O 2:O 1′-[tetra­aqua­cobalt(II)]-μ-(3,5-dinitro-2-oxidobenzoato)-κ3 O 1:O 1′,O 2] dihydrate] 
In polymeric title compound, {[Co2(C7H2N2O7)2(H2O)6]·2H2O}n, obtained from the reaction of 3,5-dinitro­salicylic acid with cobalt(II) acetate, both CoII atoms are located on inversion centres and exhibit a distorted octahedral coordination geometry. The coordin­ation sphere about one CoII atom comprises four O-atom donors from two bidentate chelate (Ophenolate and Ocarbox­yl) and bridging dianionic ligands and two water mol­ecules [Co—O range = 2.0249 (11)–2.1386 (14) Å], while that about the second CoII atom has four water mol­ecules and two bridging carboxyl­ate O-donor atoms [Co—O range = 2.0690 (14)–2.1364 (11) Å]. The coordinated water mol­ecules as well as the water mol­ecules of solvation give O—H⋯O water–water and water–carboxyl hydrogen-bonding inter­actions in the three-dimensional framework structure.
PMCID: PMC3050395  PMID: 21522530
18.  Poly[di-μ2-aqua-μ4-chlorido-μ4-(2-mercaptopyrimidine-4,6-diolato-κ4 O:O:O′:O′)-disodium(I)] 
In the title coordination polymer, [Na2(C4H3N2O2S)Cl(H2O)2]n, the NaI ion lies on a twofold rotation axis and the chloride anion on an inversion center. The NaI ion is six-coordinated by two O atoms from two zwitterionic 2-mercaptopyrimidine-4,6-diolate ligands (mm2 symmetry), two water O atoms (m symmetry) and two Cl atoms in a distorted octa­hedral geometry. Adjacent NaI ions are bridged by an olate group, a water mol­ecule and a chloride anion into a three-dimensional network. The crystal structure is further stabil­ized by N—H⋯Cl, O—H⋯O and O—H⋯S hydrogen bonds.
PMCID: PMC3011735  PMID: 21589240
19.  Tetra­aqua­bis(isonicotinamide-κN 1)nickel(II) bis­(4-formyl­benzoate) dihydrate 
The asymmetric unit of the title complex, [Ni(C6H6N2O)2(H2O)4](C8H5O3)2·2H2O, contains one-half of the complex cation with the NiII atom located on an inversion center, a 4-formyl­benzoate (FB) counter-anion and an uncoordinated water mol­ecule. The four O atoms in the equatorial plane around the Ni atom form a slightly distorted square-planar arrangement and the slightly distorted octa­hedral coordination is completed by the two N atoms of the isonicotinamide (INA) ligands at a sligthly longer distance in the axial positions. The dihedral angle between the carboxyl­ate group and the attached benzene ring is 8.14 (11)°, while the pyridine and benzene rings are oriented at a dihedral angle of 3.46 (6)°. In the crystal structure, O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds link the mol­ecules into a three-dimensional network. π–π Contacts between the benzene and pyridine rings [centroid–centroid distance = 3.751 (1) Å] may further stabilize the crystal structure.
PMCID: PMC2970033  PMID: 21577450
20.  4,4′-Bipyridinium bis­(μ-4-oxo-1,4-dihydropyridine-2,6-dicarboxyl­ato)bis­[aqua­hydroxido­anti­monate(III)] dihydrate 
The title compound, (C10H10N2)[Sb2(C7H2NO5)2(OH)2(H2O)2]·2H2O, consists of a binuclear anion, a diprotonated 4,4′-bipyridinium cation and two uncoordinated water mol­ecules. Each SbIII atom is six-coordinated by one chelating 4-oxidopyridine-2,6-dicarboxyl­ate ligand, one water mol­ecule, one OH group and one bridging O atom from a neighboring carboxyl­ate group in a distorted penta­gonal-pyramidal geometry, with the OH group at the apical position. The two pyridine rings in the bipyridinium cation are twisted with respect to each other, making a dihedral angle of 22.7 (1)°. The cations are connected to the anions by N—H⋯O hydrogen bonds, forming a chain. The coordinated water mol­ecules form hydrogen bonds with the oxido O atoms of the anion, building a two-dimensional sheet, which is further connected into a three-dimensional structure by O—H⋯O and C—H⋯O hydrogen bonds and C=O⋯π inter­actions [O⋯centroid distances = 3.1785 (17), 3.4737 (19) and 3.5685 (19) Å].
PMCID: PMC2983914  PMID: 21580551
21.  Aqua­bis(2,2′-bipyridine-κ2 N,N′)(1H-indole-2-carboxyl­ato-κO)nickel(II) 1H-indole-2-carboxyl­ate dihydrate 
The hydro­thermal reaction of Ni2(OH)2CO3 with 2,2′-bipyridine and 2-indolyl-formic acid in CH3OH/H2O at 423 K for 7 d produced the novel NiII complex [Ni(C9H6NO2)(C10H8N2)2(H2O)](C9H6NO2)·2H2O. The asymmetric unit of the title compound consists of a monovalent [Ni(L)(bpy)2(H2O)]+ cation (bpy is 2,2′-bipyridine and L is 1H-indole-2-carboxyl­ate), an L anion and two solvent water mol­ecules. In the [Ni(L)(bpy)2(H2O)]+ cations, the Ni atom coordinates to four N atoms from the two bpy ligands and two O atoms, one from a L anion and the other from a water mol­ecule to complete an significantly distorted NiN4O2 octa­hedron. The coordinated and solvate water mol­ecules form an extensive series of O—H⋯O hydrogen bonds. N—H⋯O and C—H⋯O hydrogen bonds are also present and the mol­ecules are inter­linked, forming a three-dimensional network.
PMCID: PMC2967892  PMID: 21581519
22.  Poly[triaquabis­(μ2-3-carboxy­pyrazine-2-carboxyl­ato)dilithium(I)] 
In the title compound, [Li2(C6H3N2O4)2(H2O)3]n, the coordination number for both independent Li+ cations is five. One of the Li+ ions has a distorted trigonal–bipyramidal geometry, coordinated by one of the carboxyl O atoms of a 3-carboxy­pyrazine-2-carboxyl­ate ligand, two O atoms from two water mol­ecules, and an N and a carboxyl­ate O atom of a second 3-carboxy­pyrazine-2-carboxyl­ate ligand. The other Li+ ion also has a distorted trigonal–bipyramidal geometry, coordinated by one water mol­ecule and two 3-carboxy­pyrazine-2-carboxyl­ate ligands through an N and a carboxyl­ate O atom from each. One of the carboxyl groups of the two ligands takes part in an intra­molecular O—H⋯O hydrogen bond. The stabilization of the crystal structure is further assisted by O—H⋯O, O—H⋯N and C—H⋯O hydrogen-bonding inter­actions involving the water mol­ecules and carboxyl­ate O atoms.
PMCID: PMC2960851  PMID: 21201874
23.  Poly[[di­aqua­deca-μ2-cyanido-κ20 C:N-hexa­cyanido-κ6 C-bis­(μ2-5-methyl­pyrimidine-κ2 N:N′)bis­(5-methyl­pyrimidine-κN)tricopper(II)ditungstate(V)] dihydrate] 
In the title complex, {[Cu3[W(CN)8]2(C5H6N2)4(H2O)2]·2H2O}n, the coordination polyhedron of the eight-coordinated WV atom is a bicapped trigonal prism, in which five CN groups are bridged to CuII ions, and the other three CN groups are terminally bound. Two of the CuII ions lie on a centre of inversion and each of the three independent CuII cations is pseudo-octahedrally coordinated. In the crystal structure, cyanido-bridged-Cu—W—Cu layers are linked by pillars involving the third independent CuII ion, generating a three-dimensional network with non-coordinating water mol­ecules and 5-methyl­pyrimidine mol­ecules. O—H⋯O and O—H⋯N hydrogen bonds involve the coordinating and non-coordin­ating water mol­ecules, the CN groups and the 5-methyl­pyrimidine mol­ecules.
PMCID: PMC3998256  PMID: 24764817
24.  Poly[[tetra­aqua­bis­(μ3-1H-imidazole-4,5-dicarboxyl­ato)tetra­kis­(μ2-1H-imidazole-4,5-dicarboxyl­ato)tricobalt(II)diytterbium(III)] dihydrate] 
The asymmetric unit of the title compound, {[Co3Yb2(C5H2N2O4)6(H2O)4]·2H2O}n, contains one YbIII ion, two CoII ions (one situated on an inversion centre), three imidazole-4,5-dicarboxyl­ate ligands, two coordinated water mol­ecules and one uncoordinated water mol­ecule. The YbIII ion is seven-coordinated, in a monocapped trigonal prismatic coordination geometry, by six O atoms from three imidazole-4,5-dicarboxyl­ate ligands and one water O atom. Both CoII ions are six-coordinated in a slightly distorted octa­hedral geometry. The CoII ion that is located on an inversion center is coordinated by two O atoms from two water mol­ecules, as well as two O atoms and two N atoms from two imidazole-4,5-dicarboxyl­ate ligands. The second CoII ion is bonded to four O atoms and two N atoms from four imidazole-4,5-dicarboxyl­ate ligands. These metal coordination units are connected by bridging imidazole-4,5-dicarboxyl­ate ligands, generating a three-dimensional network. The crystal structure is further stabilized by N—H⋯O, O—H⋯O and C—H⋯O hydrogen-bonding inter­actions involving the water mol­ecules and the imidazole-4,5-dicarboxyl­ate ligands.
PMCID: PMC3212186  PMID: 22090888
25.  Tetra­aqua­(2,2′-bipyridine-κ2 N,N′)manganese(II) di-μ-aqua-bis­[aqua­(2,2′-bipyridine-κ2 N,N′)(5-sulfonatoisophthalato-κO)manganate(II)] tetra­hydrate 
The crystal structure of the title salt, [Mn(C10H8N2)(H2O)4][Mn2(C8H3O7S)2(C10H8N2)2(H2O)4]·4H2O, consists of mononuclear manganese(II) cations, dinuclear manganate(II) dianions and uncoordinated water mol­ecules. The dianion is located about an inversion center; the MnII atom is coordinated by a 2,2′-bipyridine ligand, a sulfonatoisophthalate group, a water mol­ecule along with two bridging water mol­ecules in an octa­hedral geometry. The cation lies on a twofold rotation axis; the MnII atom is coordinated by four water mol­ecules and a chelating 2,2′-bipyridine ligand in a distorted octa­hedral geometry. A partially overlapped arrangement between the bipyridine ligands and the aromatic ring of the sulfoisophthalate group of adjacent anions is observed; the distance (3.357 Å) indicates π–π stacking. Hydrogen bonds, with the water mol­ecules serving as hydrogen-bond donors, lead to a three-dimensional network architecture.
PMCID: PMC2961927  PMID: 21202998

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