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In our efforts to investigate the relationships between the structures of ligands and their complexes, two structurally related 3-(2-pyridyl)pyrazole-based ligands, 1-[3-(2-pyridyl)pyrazol-1-ylmethyl]benzene ( L 1 ) and 3-[3-(2-pyridyl)pyrazol-1-ylmethyl]pyridine ( L 2 ), and their two Cu(II) complexes, [Cu( L 1 ) 2 (NO 3 )](NO 3 )(CH 3 CH 2 OH) ( 1 ) and [Cu 2 ( L 2 ) 2 (Cl) 4 ] ( 2 ), were synthesized and structurally characterized by elemental analyses, IR spectra and single crystal X-ray diffraction analysis. Complex 1 has a mononuclear structure, while 2 takes the dinuclear structure, which were further linked into higher-dimensional supramolecular networks by intra- or inter-molecular weak interactions, such as C–H⋯O hydrogen-bonding, C–H⋯π, and π⋯π stacking interactions. The structural differences of 1 and 2 can be attributed to the difference of counter anions and the different pendant aromatic groups of L 1 and L 2 , in which the benzene and pyridine rings act as the directing group for π⋯π stacking and C–H⋯π interactions. Moreover, magnetic properties of 2 have been further investigated in detail.

In our efforts to investigate the influences of different pendant aromatic groups and the spatial position of N donors in 3-(2-pyridyl)pyrazole-based ligands on the structures of their metal complexes, five structurally related ligands: 1-[3-(2-pyridyl)pyrazol-1-ylmethyl]benzene (L1), 1-[3-(2-pyridyl)pyrazol-1-ylmethyl]naphthalene (L2), 8-[3-(2-pyridyl)pyrazol-1-ylmethyl]quinoline (L3), 3-[3-(2-pyridyl)pyrazol-1-ylmethyl]pyridine (L4) and 4-[3-(2- pyridyl)pyrazol-1-ylmethyl]pyridine (L5), have been used to react with AgClO4 to form five Ag(I) complexes, [Ag(L1)2](ClO4) (1), [Ag(L2)2](ClO4) (2), [Ag(L3)(HL3)](ClO4)2(CH3CN) (3), {[Ag(L4)](ClO4)}2 (4), and {[Ag(L5)](ClO4)}∞ (5). The structural differences of these complexes may be attributed to the coordination geometries or N donor position of the pendant aromatic groups in ligands L1–L5. Also, the result reveals that various intra- and/or inter-molecular weak interactions, such as π⋯π stacking, C–H⋯π and C–H⋯O H-bonding interactions, play important roles in the formation of 1–5, especially in the aspect of linking the multi-nuclear discrete subunits or low-dimensional entities into high-dimensional frameworks. Moreover, the coordination behaviors of ligands L1–L5 have been briefly evaluated by DFT calculations.

Crystallization of tetrazole compound, 2-(1 H -tetrazol-5-yl)pyrazine (TZP), from water gives rise to the 2:1 hydrate, TZP·(TZP·H 2 O), with entangled structure involving two-dimensionally distinct strong hydrogen-bonded motifs of 1-D sawtooth chain and 3-D ths net (also called ThSi 2 , (10, 3)-b net). In the former, TZP molecules link each other in an end-to-end mode by N H⋯N(pyrazine) hydrogen bonds (C(6) synthon), while in the latter, both TZP and water molecules assemble through O H⋯N(tetrazol), O H⋯N(pyrazine) and N H⋯O hydrogen bonds with each acting as a 3-connected node. There also exist weak hydrogen bonds of the C H⋯N(tetrazol) between such 1-D chains and the 3-D net, and between adjacent chains, respectively. This result represents a rare example of hydrogen-bonded polythreading organic structure, and further exploits the using of tetrazole compound in hydrogen-bonded crystal engineering.

A new one-dimension complex, [Cd(μ2-L)2]n (1, HL=3-(2-pyridyl)pyrazole), has been hydrothermally synthesized and characterized by elemental analysis, IR, TGA, and single-crystal X-ray diffraction analysis. In 1, the L ligand takes tridentate chelating-bridging coordination mode via deprotonation of the pyrazolyl NH group and coordination of the pyrazolyl N atom to a second metal ion. In the solid state, complex 1 shows blue photoluminescent property at room temperature.

Two new Cd(II) complexes with a 3-(2-pyridyl)pyrazole-based ligand, [Cd(L)2(SCN)2] (1) and {[Cd(L)2N3](ClO4)}n (2) (L=3-(2-pyridyl)pyrazol-1-ylmethylbenzene) were synthesized and structurally characterized by elemental analyses, IR and single crystal X-ray diffraction analysis. Complex 1 crystallizes in the monoclinic system, space group C2/c, with a=14.833(3), b=13.790(3), c=15.970(3) A, β=110.89(3)° and Z=4, while 2 crystallizes in the monoclinic system, space group P21/c, with a=13.622(4), b=23.286(7), c=10.547(3) A, β=111.084(6)° and Z=4. In the two complexes, the Cd(II) centers are coordinated by six nitrogen atoms, in which four from two distinct L ligands and two from thiocyanato (1) or azido (2) anions. Complex 1 has a mononuclear structure, whereas 2 has a 1D chain structure bridged by azido anions. In 2, the azido adopts a μ-1,3-trans coordination mode, which is not common in the azide Cd(II) complexes. In addition, in the structure of 2, the 1D chains were further assembled into a quasi-3D supramolecular network by the C–H⋯O hydrogen-bonding interactions. The structural difference of the two complexes is attributable to the different anions, which have different coordination natures.

A new Ni II complex, [Ni( L )(H 2 O) 3 ]·H 2 O ( L =1,10-phenanthroline-2,9-dicarboxylate), has been synthesized and structurally determined by X-ray diffraction analysis. The complex crystallizes in monoclinic system, space group P 2(1)/ c , a =9.667(4), b =21.929(9), c =7.262(3) A, β =95.395(7)° and Z =4. In this complex, each metal center adopts an octahedral geometry formed by two N atoms of a ligand L and four O atoms from three H 2 O molecules and a carboxyl of the ligand. Each ligand adopts N , N , O -tridentate coordination mode with two N atoms and an O atom chelating a Ni II center to form a mononuclear molecule. Intermolecular strong O–H⋯O and weak C–H⋯O hydrogen bonds extend the mononuclear structure into a three-dimensional supramolecular architecture.

Two new coordination polymers, [Eu2(L)3(H2O)2]n 1 and {[Tb2(L)3(H2O)2]·H2O}n 2, (H2L=succinic acid) have been synthesized by the reaction of H2L with nitrate salts of Eu(III) or Tb(III) under hydrothermal conditions. The X-ray diffraction analysis reveals that the two complexes are constructed by L bridging the chains of edge-sharing EuO8(H2O) or TbO8(H2O) polyhedra to form 3D network structure. 1 and 2 possess different topological structures due to the difference in the conformations of L. The solid photoluminescence of 1 and 2 was also investigated in room temperature.

Two new Cu(II) complexes with mixed ligands, [Cu(mal)(L)(H2O)]·H2O (1) and [Cu(phmal)(L)]2 (2) (mal=malonate dianion, phmal=phenylmalonate dianion, L=5,5′-dimethyl-2,2′-bipyridine) have been synthesized and characterized by elemental analyses, IR, UV–vis and X-ray single crystal diffraction. In both complexes the Cu(II) ions take five-coordinated square pyramidal geometry. 1 has a mononuclear structure, and assembles into a 2D supramolecular network by hydrogen bonding. 2 is a dinuclear complex, and also forms 2D framework via π–π interactions. The structural differences of the two complexes may be attributed to the variation of the substituted group of malonate dianion.

A dinuclear CuII complex [Cu2(bpp)2(H2O)2](ClO4)2 (1) with 3,5-bis(2-pyridyl)pyrazole (Hbpp), has been synthesized and characterized by elemental analyses, thermal analysis, conductance, UV–vis and IR spectra. The crystal structure of 1, determined by X-ray diffraction technique, reveals that two centrosymmetric CuII centers are bridged by a pair of tetradentate anionic bpp ligands, adopting a square-pyramidal environment with the water ligand occupying the axial site. An interesting feature of this structure is the formation of a two-dimensional supramolecular network through O–H⋯O hydrogen bonds between the water moieties of the cationic [Cu2(bpp)2(H2O)2]2+ subunits and perchlorate anions. The magnetic properties of 1 have been investigated by variable-temperature magnetic susceptibility and EPR measurements. Very strong antiferromagnetic interaction between the CuII centers (with H=−JS1S2, J=−368.3 cm−1) has been observed, and the magneto-structural correlations was analyzed.

The self-assembly of a flexible disulfoxide ligand, meso-1,2-bis(ethylsulfinyl)ethane (L) with AgClO4 led to the formation of a novel tetra-nuclear complex, {[Ag2(O,O-L)(μ-O-μ-(SO)-L)2(ClO4)]ClO4}2, in which the AgI ions exhibit two kinds of coordination modes: trigonal–bipyramidal and octahedral, and the ligands take bidentate (O,O) chelating and tridentate μ-O-μ-(SO) bridging-chelating coordination modes. Such a ligand coordination mode is unprecedented in the metal-complexes of disulfoxides.

A pentacoordinate monomeric CuII complex, [Cu(H2O)(HL1)(L2)](NO3)(H2O) (1), with the mixed ligands (where H2L1=pyridine-2,6-dicarboxylic acid and L2=3-(2-pyridyl)pyrazole), has been synthesized and characterized by elemental analyses, IR, thermogravimetric analysis and X-ray diffraction techniques. X-ray structural analysis of complex 1 revealed that the CuII center has a CuN3O2 distorted square pyramid environment with three N atoms of two different ligands and an O atom of coordinated water molecule constituting the mean plane, and one O atom of ligand HL1 occupying the axial site. The H2L1 ligand is mono-deprotonated in this structure, and only one oxygen atom of the carboxylate group coordinates to the CuII center. A striking structural feature of complex 1 is the three-dimensional supramolecular architecture formed through intermolecular C–H⋯O, O–H⋯O and N–H⋯O hydrogen-bonding interactions. The IR and ESR spectra, and thermogravimetric analysis of complex 1 have been further investigated.

A novel CuII complex with a pyridyl dithioether ligand [Cu(L)Cl2]2 (1) [L=1,3-bis(2-pyridylthio)propane], has been synthesized and structurally characterized by X-ray diffraction analysis. Complex 1 crystallizes in monoclinic system, space group P2(1)/n, a=14.208(5), b=8.586(3), c=14.309(5) A, β=116.787(6)° and Z=4. In this complex, the ligand adopts N,N-bidentate coordination mode with two pyridine nitrogens in syn-form, and two ligands equivalently bridge two CuII centers to form a 20-membered macrometallacyclic structure. Each CuII center is four-coordinated by two nitrogen donors from two distinct L ligands and two chloride anions in trans-form. In addition, the weak C–H⋯Cl hydrogen-bonding interactions link these dimeric units into a three-dimensional supramolecular architecture.

The mononuclear CuII complex [CuL(H2O)]·2H2O (1) with a diazamesocyclic ligand bearing two functional carboxylic donor groups, 1,5-diazacyclooctane-N,N′-diacetate acid (H2L), has been synthesized and characterized by elemental analyses, thermal analyses and IR spectrum. The crystal structure of 1 has been determined by X-ray diffraction analysis, which revealed that the CuII center coordinates to the tetradentate chelated ligand L and an axial water molecule, and the 1,5-diazacyclooctane (DACO) moiety adopts a boat/chair conformation that inhibits the axial coordination at the metal center to form this penta-coordinated pyramidal (CuN2O3) complex. The most striking feature of this structure is the formation of a novel two-dimensional joint-ladder like architecture through multiple inter- and intramolecular O–H⋯O hydrogen bonds. The solution behaviors of 1 have been further investigated by conductance, UV–Vis and ESR techniques.

The reactions of CoCl 2 salt and piperazine ( L ) in the presence of different organic acid mediums afford a series of cobalt(II) complexes, the solid structures (determined by X-ray diffraction techniques) of which are controlled by the nature of the specific acid. When terephthalic acid was used, a novel mononuclear molecule [Co(H L ) 2 Cl 3 ]·Cl·(H 2 O) ( 1 ) was obtained [orthorhombic, Pnma , a =24.604(16) A, b =9.882(7) A, c =6.609(4) A, Z =4], in which the Co II center takes the unusual compressed trigonal-bipyramidal coordination geometry (CoN 2 Cl 3 ) and multiple hydrogen-bonding interactions extend this structure into a three-dimensional supramolecular network. However, with the replacement of terephthalic acid with malonic acid in the above reaction, a one-dimensional coordination polymer [Co L Cl 2 ] n ( 2 ) was obtained [monoclinic, P 2 1 / n , a =6.363(3) A, b =10.244(5) A, c =12.124(5) A, β =103.560(8)°, Z =4], in which the tetrahedral Co II centers (CoCl 2 N 2 ) are linked by the bidentate-coordinated piperazine molecules to form a zigzag chain array and these coordination chains are further expanded to a three-dimensional hydrogen-bonding architecture. In addition, a mononuclear complex [Co(gly) 3 ]·(H 2 O) ( 3 ) [monoclinic, P 2 1 / c , a =6.261(5) A, b =14.280(9) A, c =12.182(8) A, β =101.450(14)°, Z =4] was yielded when glycine was used in the similar procedure. A three-dimensional framework is also observed through the hydrogen-bonding interactions between [Co(gly) 3 ] moieties, in which the guest water molecules are included. These results unequivocally indicate that the nature of the organic acid templates play the key role in formation of these complexes.

A four-coordinated monomeric Ni II complex with a new tetradentate diazamesocyclic ligand funtionalized by oxime donor pendants,[Ni(HL)]ClO 4 (1), where H 2 L ¼ N,N 0 -bis(acetophenoneoxime)-1,5-diazacyclooctane, has been synthesized and characterized by elementalanalyses, IR, UV–vis and X-ray diffraction techniques. The crystal structure of complex 1 reveals that the Ni II center has a NiN 4 distortedplanar environment and the 1,5-diazacyclooctane ring takes the unusual boat–boat configuration. The oxime groups exhibit the only N-binding mode with Ni II ion. A striking structural feature of complex 1 residues in the formation of a two-dimensional (2D) hydrogen-bondingsupramolecular architecture with (6,3) topology through intermolecular C–H···O interactions, in which both ClO 42 counter anions and thecoordination cations act as 3-connected nodes. The spectral properties of the title complex have been further analyzed in detail.q 2003 Elsevier B.V. All rights reserved. Keywords: Ni

A bis-substituent diazamesocyclic compound containing bulky phenolic donor pendants, 1,4-bis(3-tert-butyl-5-methyl-2hydroxybenzyl)-1,4-diazacycloheptane, has been prepared from 1,4-diazacycloheptane (DACH) and 2-tert-butyl-4methylphenol by the Mannich reaction, and structurally characterized by NMR, IR and X-ray diffraction techniques. The crystal structure of the title compound reveals that 1,4-diazacycloheptane (DACH) ring is folded up into unusual chair configuration, and the two phenol pendants of the compound are in unexpected trans positions, which is different from those in the transition metal complexes of DACH and its derivatives. There exist intra-molecular O‐ H· · ·N hydrogen bonds between the phenolic O atoms and the DACH N donors which stabilize the crystal structure. q 2003 Elsevier Science B.V. All rights reserved.

A new dithioether palladium(II) complex {Pd[PhS(CH 2 ) 5 SPh]Cl 2 } n ( 1 ) has been prepared by the reaction of PdCl 2 and bis(phenylthio)pentane [PhS(CH 2 ) 5 SPh, bptf] in acetonitrile/chloroform (1:1), and structurally characterized by X-ray crystallography. It crystallized in orthorhombic system, space group Pbcn , with a =9.744(3), b =14.452(4), c =27.393(8) A, and Z =8. There are two palladium(II) ions in the same structure unit and each is coordinated by two chloride anions and two sulfur atoms of two distinct ligands in trans positions, forming a rhombic planar geometry. The flexible bptf ligand acts as bridge to link palladium(II) ions to form a coordination polymer with one-dimensional chain structure.

A series of four-coordinated monomeric Cu II , Co II , and Ni II complexes of a tetradentate diazamesocyclic ligand containing bulky phenolate donor pendants, [Cu L ] ( 1 ), [Cu( HL )]ClO 4 ( 2 ), [Co L ] ( 3 ), and [Ni L ] ( 4 ), where H 2 L =1,4-bis-(3- tert -butyl-5-methyl-2-hydroxybenzyl)-1,4-diazacycloheptane, have been synthesized and characterized by elemental analyses, IR, UV–vis and ESR spectra. The crystal structure of complex 1 has been determined by X-ray diffraction analysis.

A novel phenoxo-bridged dinuclear Co II complex with a diazamesocyclic ligand bearing one additional phenol functional donor group, [CoLCl] 2 ·2C 3 H 6 O ( 1 ) (where HL=1-(2-hydroxybenzyl)-1,5-diazacyclooctane), has been synthesized and characterized by elemental analyses, conductance, thermal analyses, IR and UV–vis spectra. The crystal structure of complex 1 has been determined by X-ray diffraction technique, which reveals that it is a neutral complex and resides on a crystallographic inversion center. The two Co II centers bridged by the phenoxo groups are penta-coordinated, taking a coordination sphere in the midst of the ideal square-pyramid and trigonal bipyramid. 1,5-Diazacyclooctane of the ligand takes a boat / chair conformation and an H atom from it effectively blocks the axial coordination site opposite the Cl − ligand to form CoN 2 O 2 Cl geometry. The crystal structure is stabilized by the N–H⋯O hydrogen bond between the amino group and the acetone molecule.

A new potential tetradentate ligand, 1,4-bis(N-1-methylimidazol-2-ylmethyl)-1,4-diazacycloheptane ( l ), together with its CuII complex [Cu l Cl]ClO4 (1), has been reported. The crystal structure of 1, determined by single-crystal X-ray analysis, shows that it is in chiral P212121 space group. The CuII centre is penta-coordinated in square pyramidal geometry and the diazacycloheptane (DACH) ring adopts normal boat configuration. The most striking feature of this complex is the formation of a 3D network bridged through the C–H⋯Cl hydrogen bonds with the perchlorate anions in the cavities, and stabilized via π–π stacking interactions along the a-direction. The solution behaviour of 1 has been further investigated by UV/Vis and ESR techniques.

A series of penta-coordinated CoII complexes of 1,4-diazacycloheptane (DACH) functionalized by additional imidazole or pyridine donor pendants, [CoL1Cl](ClO4)·H2O (1), [CoL2Cl](ClO4) (2) and [CoL3Cl](ClO4)·CH3OH (3), where L1=1,4-bis(imidazole-4-ylmethyl)-DACH, L2=1,4-bis(N-1-methylimidazol-2-ylmethyl)-DACH and L3=1,4-bis(pyridyl-2-ylmethyl)-DACH have been synthesized and characterized by elemental analyses, IR and UV–Vis spectra. In all the mononuclear complexes, each CoII center is penta-coordinated to four nitrogen donors of the ligand and one axial chloride anion. The crystal structure of complex 2 has been determined by X-ray diffraction analysis, which forms a one-dimensional linear structure through inter-molecular C–H⋯Cl and C–H⋯O hydrogen-bonding.

Two mononuclear RuII complexes of polypyridyl ligands, cis-[Ru(bpy)2(4,4′-bpy)Cl](PF6)·H2O (1) and cis-[Ru(phen)2(CH3CN)2](PF6)2 (2) (bpy=2,2′-bipyridyl, 4,4′-bpy=4,4′-bipyridyl, and phen=1,10-phenanthroline), have been synthesized and characterized by elemental analyses, IR and UV–vis spectra. The crystal structures of both complexes have been determined by X-ray diffraction, indicating that each RuII center is hexa-coordinated (RuN5Cl for 1 and RuN6 for 2) and takes a distorted octahedral geometry. The favored feature of both complexes is that they are quite useful complex precursors for further constructing new functional architectures.

Two three-dimensional (3D) supramolecular compounds of the general formula [M(L) 2 (NCS) 2 (H 2 O) 2 ], where M is Mn II or Co II and L is 2,5-bis(4-pyridyl)-1,3,4-oxadiazole), have been synthesized and structurally determined by X-ray diffraction analyses. The crystal structures of both complexes reveal that they are isomorphic neutral molecules and the metal ions are at the center of symmetry. Each metal center is six-coordinated and the MN 4 O 2 coordination sphere can be considered as an octahedron. The most striking feature of both complexes resides in the formation of a 3D network through hydrogen bonds and π–π stacking co-effection.

Two new platinum(II) complexes with dithioether ligands, cis-[Pt(L1)Cl2] (1) and cis-[Pt(L2)Cl2]2 (2), where L1=1,3-bis(phenylthio)propane and L2=1,5-bis(n-propylthio)pentane, have been synthesized and structurally characterized by X-ray diffraction analyses. In 1, the Pt(II) center is four-coordinated and forms a six-membered chelated ring with L1, while 2 exhibits a unique di-nuclear structure containing a 16-membered metallomacrocyles with chair-shaped conformation, in which each Pt(II) center is coordinated by two chloride anions and two sulfur-donors from two L2 ligands.

With the aim of examining the metal-assisted rearrangement behaviors of 2,2′-pyridil (L), its reactions with M(ClO4)2·6H2O (M=CoII, NiII and CuII) were considered. X-ray diffraction analyses of the products reveal the formation of complexes containing 2,2′-pyridilate anion (L1) or picolinate anion (L2) as arrangement products of 2,2′-pyridil, induced by different metal ions. [CoIII(L1)2](ClO4)·CH3OH (1) and [NiII(L1)2]·2H2O (2) have similar mononuclear structures, and it should be noted that the CoII ion is unstable to oxidation in this process. However, [CuII(L2)2]·2H2O (3) forms a one-dimensional linear complex via Cu–O weak interactions.

The cis-dioxo-molybdenum(V) complex anion [(MoO2)-O-(V)(C6H4O2)(2)](3-) was obtained by the reaction of tetra-butyl ammonium beta -octamolybdate with catechol and ethylenediamine in the mixed solvent of CH3OH and CH3CN, and characterized by IR, NM, UV, EPR spectroscopy and X-ray diffraction with its discrete (NH2CH2CH2NH3)(+) cations. The determination of single crystal X-ray analysis revealed that the metal center exhibits distorted octahedral co-ordination with cis dioxo catechol. The result of essentially the same of EPR spectra shown by the complex and flavoenzyme suggests that the title complex anion and flavoenzyme have related structure feature. (C) 2001 Elsevier Science B.V. All rights reserved.