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The 3D lanthanum-dicarboxylate MOF [La2(hex)3(H2O)4]3H2O, (1), (hex = trans,trans-muconic acid) has been obtained at 50 °C, in a silica gel column, either via in situ transformation of the 2D MOF [La2(hex)3(H2O)6]9H2O, (2), published previously, or directly. The structure is made up of metal–ligand layers pillared by a ligand dianion. The comparison of the crystal structures of the two MOFs allowed us to propose a possible mechanism of the 2D to 3D transformation. The presence of many short olefinic contacts allowed the formation of three photoproducts at different yields, the major one being the rtct isomer for the 3D MOF and the rttc one for the 2D MOF. In both cases, the three photoreactions proceed with the parallel reaction scheme. The comparison of the crystal structures of 1 and 2 allowed the photoreactivity differences observed to be explained.

A series of Lanthanide MOFs of hydromuconic acid (H2hymuc) with cations of different size (La3+, Ce3+, Gd3+, Y3+) were generated at room temperature, pH = 5.5–5.8, using water as solvent. Two microporous genuine supramolecular isomers were found for the larger cations (La3+, Ce3+) sustained either by discrete (H2O)18 clusters or by infinite water tapes, consisting of fused tetramers, pentamers and hexamers. The smaller cations (Gd3+, Y3+) produced a 2D phase, considered as catenane isomer of previously published lanthanide MOFs with adipic acid. MOFs obtained with Ce3+, Gd3+and Y3+ undergo irreversible solvent-mediated transformation, yielding isomorphous 3D two-fold interpenetrated MOFs. The close structural similarity between the 2D phase and the 3D interpenetrated one indicated a possible mechanism for this transformation.

A 2D lanthanum-dicarboxylate MOF of the formula [La2(hex)3(H2O)6]·9H2O (H2hex = trans,trans-hexadiendioic acid or trans,trans-muconic acid) has been synthesized by the silica gel technique. The structure consists of metal–organic layers separated by a 2D network of water molecules. The metal–organic layers are made up of La3+ arrays linked by the muconate ligands. Within a layer there is an infinite chain of short contacts between olefinic bonds allowing formation, upon UV irradiation, of three photoproducts. One of them was completely unexpected and its formation is explained by complex molecular movements in the solid state. The thermal instability of the MOF allowed isolation of five photochemically active lower hydrates. The rate constants of all hydrates were determined and show significant variations between them, attributable to structural rearrangements within the metal–organic layer brought about upon dehydration.

A series of co-crystals of trans-1,2-bis(4-pyridyl) ethylene (bpe) with aliphatic saturated or unsaturated dicarboxylic acids, of the type [(bpe)(L)] (L = dicarboxylic acid), were prepared and characterized by single crystal X-ray crystallography. In all cases chains of the type acid···bpe···acid were formed via strong O–H···N hydrogen bonds. The chains were further linked between them by weak C–H···O hydrogen bonds, π–π and herringbone interactions to form three-dimensional structures. Thermal analysis showed considerable elevation of the melting/decomposition point of the co-crystals with respect either to both components or to bpe, ascribed to the formation of multiple complementary C–H···O bonds as well as to π–π interactions between the two conformer molecules. When L = fumaric acid, the two components stack separately with their C═C bonds strictly parallel between them at 3.83 A from one another. However, photodimerization reaction takes place only between the olefin bonds of bpe. Photodimerization ...

The solid compounds [La(3)(chel)(Hchel)(3)(H(2)O)(8)]center dot H(2)O (1) and [La(Hchel)(H(2)O)(6)](2)[La(2)(Hchel)(4)(H(2)O)(4)]center dot 10H(2)O (2) (H(3)chel = 4-hydroxypyridine-2,6-dicarboxylic acid or chelidamic acid) were isolated from aqueous solutions upon mixing La(3+) cations and chelidamic acid at various pHs (pH 5-10). Compound I is a two-dimensional (213) coordination polymer consisting of La(Hchel)and La(Hchel)(2) units connected bycoordination bonds. Compound 2 is an ion-pair complex made Lip of alternating layers of La(Hchel)(+) and La(2)(Hchel)(4)(2-) ionic units linked between them by lattice water Molecules. The comparison of the two structures showed that the 2D coordination polymer, 1, is formed by a dehydration-condensation reaction between the La(Hchel)(+) and La(2)(Hchel)(4)(2-) units. The relative positions of these units in the crystal lattice suggest that the assembly of 1 takes place by a dehydration-condensation reaction between oligomeric layers of opposite charge and not by reaction between individual ions of opposite charge. Crystal Growth & Design

The reaction of Fe(III) with the substituted salicylaldehydes [X-saloH, where X = 3-OCH3 (L 1 ), 5-CH3 (L 2 ), 5-Cl (L 3 ), 5-NO2 (L 4 )] led to the formation of four new iron(III) hetero-heptanuclear complexes (Fe–Na) under the general formula [Fe2(X-salo)8Νa5] · 3OH · zH2Ο. The two different coordination modes of the ligand, as well as the geometry around the metal ions were deduced by X-ray structure analysis of compound 1, [Fe2(3-OCH3-salo)8Νa5] · 3OH · 8H2Ο. The complexes have also been characterized by physicochemical and spectroscopic (IR, UV–Vis, Mossbauer) methods.

Crystals of a water soluble, potassium(I) complex with the heterocyclic thioamide; 2-mercapto-nicotinic acid (H2mna), of formula {[K(H2mna)2]+ · [K(μ-OH)2]− · 4H2O}n (1) were grown from the filtrate of the reaction between 2-mercapto-nicotinic acid with KOH in a molar ratio 1:1.5 in water. The complex has been characterized by elemental analysis, TG-DTA, 1H NMR and FT-IR spectroscopic techniques and X-ray powder diffraction. The single crystal structure of complex (1) has been determined by X-ray diffraction at ambient conditions. The polymeric structure of the complex is microporous, where water molecules are retained. The water molecules can be reversibly removed. The complex is ionic, containing [S–K+–S] linkages and an infinite ribbon of {[K(μ-OH)2]−}n as a counter anion. Strong hydrogen bonds and π–π interactions stabilize the supramolecular architecture of the inorganic/metal-organic hybrid formed. Heating of (1) at 100 °C for 4 h forms the {[K(H2mna)2]+ · [K(μ-OH)2]−}n (2), which retains the framework structure although the coordinated water molecules were evacuated.

A novel supramolecular structure, [C8H11N2S]2‚(C6Cl2O4), based on hydrogen bonding of the organic S-benzylthiuronium (SBT) cation and the chloranilate dianion, is presented. Chloranilic acid or 2,5dichloro-3,6-dihydroxy-1,4-benzoquinone, is a strong quinoidal diphenic acid (p K1 ) 1.09 and pK2 ) 2.42), with molecular formula C6Cl2O4H2 (H2CA). The CA-dianions and the aromatic rings of the SBTcations form columns along the c-axis giving an ordered pattern of dianions surrounded by densely populated areas of SBT-cations. Each CA-dianion forms eight hydrogen bonds with the amine protons of six SBT-cations, through its oxygen atoms. In this way, an extended H-bond network, containing infinite chains of alternative R 4 2 (8) and R2 2 (9) cyclic patterns, is obtained. The whole arrangement leads to a C2/c space group crystal structure, with unit cell dimensions a ) 15.109 A,b ) 11.606 A, andc ) 14.390 A and with unit cell angles of R) A ) 90°, and ‚ ) 97.01°, and average density of 1.43 g/cm 3 . Dissolution of the crystalline material in DMSO leads to the formation of associated organic ions or charge-transfer complexes as evidenced from the bathochromic shift of the absorption band of chloranilic acid from 420 to 520 nm.

[Cd(phen)2(CA)]n (I, where phen is 1,10-phenanthroline and CA2− is the dianion of 3,6-dichloro-2,5-dihydroxy-1,4-benzoquinone) has been synthesized and its crystal structure has been determined by single-crystal X-ray diffraction at room temperature. The crystal of I is built from infinite chains of chloranilate-bridged cadmium(II) leading to a zig-zag structure, with the phenanthroline ligands being stacked between the chains. These interactions assist the formation of a closely packed 3D structure. The coordination environment of cadmium(II) – very scarce in its chemistry – is square antiprismatic. The polymer was also characterized with spectroscopic (IR, Raman, DRS) and thermogravimetric (TG, DTA) techniques.

Silver(I) bromide reacts with 2-mercapto-3,4,5,6-tetrahydropyrimidine (StpmH2, C4H8N2S) in DMSO with an excess of triethylamine to give a water-insoluble complex of formula [Ag6(μ2-Br)6(μ2-StpmH2)4(μ3-StpmH2)2]n (1), while the reaction of silver(I) nitrate with StpmH2 under the same conditions gives a water-insoluble complex of formula [{Ag4(μ2-StpmH2)6}(NO3)4]n (2). The products were characterized by elemental analyses, and FT-IR far-IR, UV/Vis, 1H and 13C NMR spectroscopy. Crystal structures of complexes 1 and 2 were determined by X-ray diffraction. Complex 1, C24H48Ag6N12S6, crystallizes in the triclinic system space group P , a = 8.041(1) A, b = 12.838(4) A, c = 13.281(2) A, α = 68.40(1)°, β = 72.97(1)°, γ = 87.80(2), Z = 2, forming a one-dimensional infinite ribbon structure by strong interatomic interactions of two μ2-Br bonds with Ag(1). Complex 2, C24H48Ag4N16O12S6, crystallizes in the orthorhombic system, space group Cmc21, and a = 32.148(3) A, b = 9.461(2) A, c = 7.234(1) A, α = β = γ = 90°, Z = 8, forming infinite Ag−S−Ag chains which are bridged to each other by a sulfur atom of μ2-StpmH2 ligands. Complexes 1 and 2 were studied for their cytostatic activity against murine leukemia (L1210) and human T-lymphocyte (Molt4/C8 and CEM) cells and for their antiviral activity against a wide variety of viruses. They are markedly cytostatic at 50% inhibitory concentration (IC50) values ranging from 3 to 17 μg/mL. None of the compounds showed appreciable antiviral activity at subtoxic concentrations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Reaction of 4-formylantipyrine with thiosemicarbazide, N(3)-methylthiosemicarbazide and N(3)-ethylthiosemicarbazide produced the expected thiosemicarbazones, 1, 2 and 3. The three thiosemicarbazones were then reacted with K2PdCl4 to produce [Pd(NS)2] complexes, 4, 5, and 6, respectively, with coordination by the imine nitrogen and thiolate sulfur of the anionic thiosemicarbazone moiety. The thiosemicarbazones and their palladium complexes have been characterized by spectral IR, UV–Vis and 1H, 13C NMR and electrochemical techniques. The crystal structure of 6 has been obtained and found to be highly symmetrical with a trans arrangement of the two bidentate ligands.

Erbium. fumarate [Er-2(fum)(3)(H2O)(4)].8H(2)O, 1, (fum = fumarate dianion) crystallizes at room temperature in a silica gel column. The structure is three-dimensional and consists of layers of erbium fumarate pillared by fumarate dianions acting in the bis-chelating mode. The layers contain arrays of erbium cations bridged by fumarate dianions acting in the bis-bidentate bridging mode. The relatively large channels formed in the direction of the a and c axes are filled by water molecules that form a hydrogen bonded layer, comprising cyclic hexamers with both boat and chair conformations and cyclic decamers with boat-chair-boat conformation. The water molecules are reversibly removed at 90 degreesC. The evacuated metal-organic framework, 2, is stable up to 400 degreesC. Both compounds 1 and 2 exhibit weak antiferromagnetic interactions. Crystal Growth & Design

Silver(I) chloride reacts with 2-mercapto-nicotinic acid (H(2)mna, C6H5NO2S) in the presence of an excess of triethylamine in DMSO to form a hexanuclear, water soluble, cluster of formula {[Ag-6(mu(3)-Hmna)(4)(mu(3)-mna)(2)](2-) (.)[(Et3NH)(+)](2)(.)(DMSO)(2)(.)(H2O)} (1). The complex 1 was characterized by elemental analyses, and FT-IR, UV-Vis and H-1 NMR spectroscopy. Crystal structures of complex 1 and the ligand, 2-mecapto-nicotinic acid (2), have been determined by X-ray diffraction. Compound 1, C52H68Ag6-N8O15S8, is monoclinic with a space group P2(1)/c (No. 14) and a = 11.7080(10), b = 16.2920(10), c = 18.3010(10) Angstrom, beta = 91.350(10)degrees, Z = 4. The entire molecule is ionic and consists of a double anionic hexa-nuclear cluster and two protonated triethylamine counter cations while it is solvated by two DMSO and one water molecule. The 2-mercapto-nicotinic acid (2), C6H5NO2S, is orthorhombic (space group Pna2(1) (No. 33), a = 8.3910(10), b = 13.2720(10), c = 5.892 Angstrom, Z = 4). An extended inter-molecular hydrogen bonding via (OH)-H-...-N contacts (O(1)H-...(5)[N(5)] = 1.8998, O(1)N-...(5) = 2.8049 Angstrom) links the molecules forming a supramolecular two-dimensional network. Complex 1, was evaluated for anti-HIV-RT activity. It was found to inhibit the human immunodeficiency viral replication reverse transcriptase (HIV-RT) with calculated inhibiting concentration (IC50) 0.01275 +/- 0.00115 mg ml(-1). (C) 2002 Elsevier Science B.V. All rights reserved. Inorganica Chimica Acta

Single crystals of [Cd(terephthalate)(H2O)3].4H2O (1), triaquo(1,4-benzenecarboxylato-κO)cadmium tetrahydrate, are grown in a silica gel column. Crystal structure analysis shows that (1) is a polymer with metal-organic chains stacked along the a axis forming layers parallel to the ab plane. These layers are linked by an unusual hydrogen-bonded network formed by the water molecules (both `free' and coordinated ones) and the carboxylate O atoms. This network comprises tridymite-like O8 cages which `propagate' in the direction of the a axis, mimicking the way they `propagate' along the c axis in hexagonal ice.

The reaction of a lanthanide(III) nitrate (Ln = Pr, Nd) with the base 2, 2′-dipyridylamine (dpamH) afforded two very stable microcrystalline compounds. These compounds were characterized as complex salts with the general formula [Ln(NO3)6]·3[dpamH-H+]·H2O, where the dpamH ligand is not coordinated, but exists in its protonated form serving as counterion (dipyridylammonium cation), as it was revealed by single-crystal X-ray diffraction studies. Each one of the nitrate ions is coordinated, however, in a bidentate manner with the lanthanide(III) ion, which obtains coordination number twelve. All organic dpamH-H+ cations are arranged in two columns parallel to the a axis of the cell forming pairs of almost parallel cationic molecules at a distance of about 3.5 A. Inside each pair the molecules interact by strong π–π interactions. The water molecules, arranged between the inorganic anions [Ln(NO3)6]3–, bridge them by strong hydrogen bonds, involving the water proton and one nitrate oxygen. The lattice can be described as made from successive organic and inorganic alternating parallel columns interacting between them with strong hydrogen bonds. The thermal stability and decomposition mode of the two lanthanide compounds were studied by the simultaneous TG/DTG-DTA technique and compared with the starting hexahydrate lanthanide(III) salts and the dipyridylamine.

The conformation of title compounds has been determined in the solid state by X-ray crystallography and in solution by nmr spectroscopy. MM2 and molecular dynamics calculations were used to determine the conformation of one of these compounds in vacuo and in solution

The molecular bilayer motif reported here is formed by trimesic acid and Cd2+. The ligand acts as a three-connected node while the metal is a simple spacer. The assembly of these motifs into a three-dimensional structure forms cavities into which coordinated and lattice water molecules are located.

A water-mediated transformation reversibly converts the neutral 3D microporous coordination polymers [Ln(2)(adipate)(3)(-)(H(2)O)(4)]center dot 6H(2)O (Ln(3+) = Pr(3+)) and [Ln(2)(adipate)(3)(H(2)O)(4)]xH(2)O (Ln(3+) = Gd(3+), Sm(3+)), into the ionic 1D polymer [Ln(adipate)(H(2)O)(5)]XH(2)O (with X = NO(3)(-), Cl(-) and Ln(3+) = Pr(3+), Gd(3+), Sm(3+)). The 1D polymer consists of positively charged hydrogen-bonded lanthanide-adipate chains enclathrating NO(3)(-) or Cl(-) anions acting as templates. The hydrogen bonds linking the chains between them are so strong, that it is possible to exchange NO(3)(-) for Cl(-) and vice versa in a crystal-to-crystal manner. The anion exchange reactions were directly observed oil crystals by Using Raman microprobe spectroscopy, single-crystal X-ray diffraction, and scanning electron microscopy. Crystal Growth & Design

For the understanding of the influence of organic complexing additives on crystal growth, we studied the habit modification of Ni(β-ala)2·2H2O crystals in the presence of glycine. We show that the mixed complex Ni(β-ala)(gly)·2H2O is formed on the crystal surface and causes disruption of one hydrogen bond in the 1[⦶1]0 direction, accounting for the observed habit modification.

Organotin(IV) complexes with the formulas [(C(6)H(5))(3)Sn(mbzt)] (1), [(C(6)H(5))(3)Sn(cmbzt)] (3), and [(C(6)H(5))(2)Sn(cmbzt)(2)] (4) (Hmbzt = 2-mercaptobenzothiazole and Hcmbzt = 5-chloro-2-mercaptobenzothiazole) have been synthesized and characterized by elemental analysis; FT-IR, Raman, (1)H, (13)C, and (119)Sn NMR, and Mossbauer spectroscopic techniques; and X-ray crystallography at various temperatures. The crystal structures of complexes 1, 3, and 4 were determined by X-ray diffraction at room temperature [295(1) or 293(2) K]. The complexes [(C(6)H(5))(3)Sn(mbzo)] (2) and [(n-C(4)H(9))(2)Sn(cmbzt)(2)] (5) (Hmbzo = 2-mercaptobenzoxazole) were synthesized by new improved methods, and their structures were determined at low temperature [100(1) K] and compared to those solved at room temperature. Comparison with {(CH(3))(2)Sn(cmbzt)(2)]} (6), already reported, was also attempted. The influence of temperature on the geometry of the complexes is discussed. In the cases of complexes 1-3, three carbon atoms from phenyl groups and one sulfur atom and one nitrogen atom from thione ligands form a tetrahedrally distorted trigonal-bipyramidal geometry around the five-coordinate tin(IV) ion. In complexes 4-6, two carbon atoms from aryl groups and two sulfur atoms and two nitrogen atoms from thione ligands form a distorted tetrahedral geometry, tending toward octahedral, around the six-coordinate tin(IV) ions, with trans-C(2), cis-N(2), and cis-S(2) configurations. Although the C-Sn and S-Sn bond distances are found to be constant in compounds 1-6, their N-Sn bond lengths vary significantly (from 2.635 to 3.078 angstrom), with the longer distances found in the cases of five-coordinate complexes 1-3. Inorg Chem

The self-assembly of four symmetrically substituted tri-aryl-benzene derivatives of formula C24H15X3, where X = H (1), Cl (2), COOMe (3), and COOH (4), was studied as a function of the substituent X. Crystal packing analysis of compounds 1-3 showed that in 1, there are no strong face-to-face stacking interactions, whereas in both compounds 2 and 3, molecular columns were formed, held by numerous "lateral" C-H center dot center dot center dot Cl and C-H center dot center dot center dot O hydrogen bonds, respectively. However, strong intermolecular face-to-face aromatic interactions, appropriate for excimer formation, were observed only in 3, in line with results obtained by fluorescence spectroscopy. The pi-pi aromatic interactions are significantly stronger in the case of the triacid 4, but a lack of adequate single crystals of this compound prevented any detailed study for correlating crystal architecture with fluorescence emission observed. However, FT-IR and TEM experiments showed the existence of dimeric H-bonds and short (0.35 nm) distances between the phenyl rings. Crystal Growth & Design

Two isostructural coordination polymers of formula [Ln(2)(ADC)(3)(H2O)(6)]center dot 2H(2)O, (ADC = acetyledicarboxylato dianion, Ln(3+) = La3+ or Ce3+) have been prepared at room temperature. The structure is three-dimensional, possessing one-dimensional channels filled with lattice and coordinated water molecules. The presence of three water molecules in the coordination sphere of the metal creates a dense hydrogen-bonded network. The lattice water molecules were removed from the cerium compound at 100 T with retention of the structure. This transformation was also possible in a crystal-to-crystal manner. The structure of the dehydrated solid was determined and found to present only minor modifications compared to the parent structure. The departure of the coordinated water molecules is carried out in three steps, with retention of the structure up to 150 degrees C. Beyond this temperature, dehydration is accompanied by polymerization, due to the existence of an infinite chain of short acetylene-acetylene contacts. Crystal Growth & Design

The synthesis and characterization of copper(II) complexes with a potent non-steroidal anti-inflammatory drug, tolfenamic acid, Htolf, with formula [Cu(tolf)(2)L](2) (where L is H2O or DMF, N,N-dimethylformamide) were investigated. The crystal-and molecular structure Of [Cu(tolf)(2)(DMF)](2) was reported. Crystallographic data are as follows: monoclinic system, space group P2(1)/n with cell constants a = 9.068(2) Angstrom, b = 14.514(3) Angstrom, c = 22.826(4) Angstrom, V = 2948.9(10) Angstrom(3) and Z = 2. The crystal structure consists of binuclear, quadruply bridged neutral molecule with a Cu-Cu bond length of 2.6075(19) Angstrom. The complex is self-assembled via C-H-pi intermolecular stacking interactions. Spectroscopic and electrochemical studies were reported. The superoxide dismutase activity is measured and compared with those of superoxide dismutase enzyme, SOD, the free ligand and related copper complexes with nonsteroidal anti-inflammatory drugs, NSAIDs. IC50 value was measured by the Fridovich test (1.97 +/- 0.17 muM), which showed that [Cu(tolf)(2)L](2) is a good superoxide scavenger. (C) 2003 Elsevier Inc. All rights reserved. J Inorg Biochem

Reaction of H2PtCl4 and K2PdCl4 with 2-hydroxyacetophenone N(4)-ethylthiosenticarbazone, H(2)Ap4Et, afforded [Pt(Ap4Et)(H(2)Ap4Et)] and [Pd(Ap4Et)(H(2)Ap4Et)]. Their crystal and molecular structures are reported and represent the first 1:2 thiosemicarbazone complexes with ligands having both different formal charge and denticity. The dianion, Ap4Et(2-), coordinates in a planar conformation to palladium(II) or platinum(II) via the phenolato 0, imine N and thiolato S atoms, while the neutral molecule exhibits monodentate coordination by the thione S atom. Intra-, intermolecular hydrogen bonds and C-H... pi contacts lead to aggregation and a supramolecular assembly. Electronic, IR, and NMR spectral data, as well as electrochemical measurements, are included. The pK(a) values of the poorly water soluble H2Ap4Et were obtained spectrophotometrically in aqueous solutions of constant ionic strength. (C) 2004 Elsevier B.V. All rights reserved. Inorganica Chimica Acta

The novel one-dimensional coordination polymer [Cd(ADC)(H2O)(3)] H2O, where ADC(2-) = acetylenedicarboxylate dianion, was synthesized and characterized by single-crystal X-ray diffraction. The titled compound crystallizes in the monoclinic system, P2(1)/n, a = 6.908(1) Angstrom, b = 7.946(1) Angstrom, c = 16.390(1) Angstrom, beta = 100.21(1)degrees, V = 885.4(2) Angstrom(3), and Z = 4. The structure is made up of metal-organic chains linked by hydrogen bonds to form channels along the b axis. The carbon-carbon triple bonds are in close proximity (3.27 Angstrom) along the a axis. This induces, upon heating, polymerization with formation of conjugated polycarboxylic chains. Detailed EPR studies have been performed in order to understand the polymerization process. Chemistry of Materials

The crystal structures have been determined and the magnetic properties investigated for four novel [M-II(A)(H2O)(m)](n) polymeric complexes, where M-II=Cd-II, Cu-II or Ni-II, m=2-4 and A=adipate dianion. In [Cd(A)(H2O)(2)](n) 1, [Cu(A)(H2O)(2)](n) 2 and [Ni(A)(H2O)(4)](n) 4 the combination of the metal cation with the dicarboxylate ligand leads to the formation of infinitive chains; still the co-ordinated water molecules and the carboxylate oxygen atoms collaborate to hydrogen-bond the chains into 3-D structures. Each cadmium(II) and nickel(II) ion in 1 and 4 is coordinated in an octahedral geometry to carboxylate and water molecules. The coordination sphere around copper(II) ions in 2 is square planar. The structure of 3, [Cu-3(A)(2)(OH)(2)(H2O)(4)](n), is made up of ribbons linked to neighboring ones by hydrogen bonds. Each ribbon is composed of 2 crystallographically independent metal centers, Cu(1) and Cu(2), which exhibit octahedral and square pyramidal coordination geometries, respectively. Weak antiferromagnetic interactions were observed for 2, and 3 (singlet-triplet energy gap values of -2.3 and -54.5 cm(-1), respectively) and isolated nickel(II) ions for 4. An interpretation of the magnetic behavior was attempted. The strategy for the assembly of 1-D metal-organic chains into 3-D structures, with the use of coordinated water molecules as hydrogen bond donors and carboxylate oxygens as hydrogen bond acceptors, is also discussed. Journal of the Chemical Society-Dalton Transactions

The structure of the gel-grown coordination polymer Ag-4 (2,2-dimethylglutarate)(2) was determined by X-ray crystallography. It crystallizes in the monoclinic space group P2(1)/a, with a = 10.67(1) Angstrom, b = 6.334(6) Angstrom, c = 13.32(1) Angstrom, beta = 96.34(4)degrees, V = 895(2) Angstrom(3) and Z = 4. The structure is based on an unusual oligomeric unit, which was first found in silver(I) glutarate, and consists of a planar, centrosymmetric, tetranuclear silver cluster coordinated by two bridging ligands disposed at both sides of the metal plane. Additional Ag-O coordination bonds link the units together in a 2-D framework. Short metal-metal contacts in the range 2.81-3.40 Angstrom, are observed within the layers, suggesting that d(10)-d(10) interactions contribute to the stabilization of the structure. (C) 1997 Academic Press. Journal of Solid State Chemistry

Silver(I) glutarate is a 2D polynuclear polymer whose repeat unit consists of a tetranuclear silver cluster coordinated by two bridging glutarate anions; these units are organised, through additional metal–oxygen linkages, in layers parallel to the ac plane, in which uncommon metal–metal contacts (3.14–3.43 A) are observed.

[Ni-3(trim)(2)(H2O)(14)]. 4H(2)O (trim = trimesate trianion), a self-complementary molecule organised In tapes using aqua ligands as hydrogen bond donors and carboxylate groups as hydrogen bond accepters, is synthesised and the structure confirmed by X-ray crystallography. Journal of Chemical Research-S