Octanuclear Zinc(II) and Cobalt(II) Clusters Produced by Cooperative Tetrameric Assembling of Oxime Chelate Ligands

Synthesis and characterization of heterotrinuclear bis(μ2-chlorido)dicopper (II) mono zinc(II) complexes derived from succinoyldihydrazones

Three new zinc (II)-copper (II) heterometallic trinuclear complexes of the composition [ZnCu2(L(n))(μ2-Cl)2(H2O)6]⋅2H2O (H4L(n)=H4L(1), H4L(2), H4L(3)) have been synthesized from substituted succinoyldihydrazones (H4L(n)) in methanol medium. The composition of the complexes has been established on the basis of data obtained from analytical, mass spectral studies and molecular weight determinations in DMSO. The structure of the ligand H4L(2) has been established by X-ray crystallography. The structure of the complexes has been discussed in the light of molar conductance, magnetic moment, electronic, EPR, IR and FT-IR spectral studies. The molar conductance values for the complexes fall in the region 1.2-1.7 ohm(-1) cm(2) mol(-1) in DMSO solution indicating that all of these are non-electrolyte. The magnetic moment values suggest weak M-M interaction in the structural unit of the complexes. The dihydrazone ligand is present in enol form in all of the complexes. Copper centre has tetragonally distorted octahedral stereochemistry. The EPR parameters of the complexes indicate that the copper centre has doublet state as the ground state. The electron transfer reactions of the complexes have been investigated by cyclic voltammetry.

A family of polynuclear cobalt complexes upon employment of an indeno-quinoxaline based oxime ligand

The employment of an indeno-quinoxaline based oxime ligand in cobalt chemistry afforded a new family of polynuclear cobalt clusters.

Synthesis and Structure of a Penta- and Hexa-Coordinated Tri-Nuclear Cobalt(II) Complex

The tri-nuclear cobalt(II) complex, [(CoL)2(μ-OAc)2Co]·2CHCl3 (H2L = 5,5'-dimethoxy-2,2'-[(ethylene)dioxybis(nitrilome thylidyne)]diphenol), has been synthesised. Its X-ray structure shows it to contain two acetate ions coordinating to the three cobalt(II) atoms through Co–O–C–O–Co bridges, and four μ-phenoxo-oxygen atoms from two [CoL] chelates also coordinating to the central cobalt(II) atom. The complex possesses two penta- and one hexa-coordinated cobalt atoms. The crystal packing of the CoII complex shows that a 2D-layer supramolecular network parallel to the ab-plane is formed through intermolecular C–H···O and C–H···Cl hydrogen bonding interactions.

Syntheses, Structures and Photoluminescence of a Series of Transition Metal-Cyanopyridine Polymers

A series of transition metal- n cyanopyridines ( i.e. pyridine- n-carbonitrile; n = 2, 3, 4) complexes with one-dimensional (1-D) structures, [CuCl2(pyridine-3-carbonitrile)2] n, [CuCl2(pyridine-4-carbonitrile)2] n and [CoCl2(pyridine-4-carbonitrile)2] n, have been synthesised via hydrothermal reactions and structurally characterised by single-crystal X-ray diffraction. All these complexes feature infinite 1-D chain-like structures. Photoluminescent investigation reveals that the title complexes display strong emissions which may originate from π→π* charge-transfer interaction of the ligands.

Synthesis, structure and spectroscopic properties of two new trinuclear nickel(II) clusters possessing solvent effect

Two solvent-induced trinuclear nickel(II) clusters, [{NiL(CH(3)OH)}(2)(OAc)(2)Ni].2CH(3)OH (I) and [{NiL(C(2)H(5)OH)}(2)(OAc)(2)Ni].2C(2)H(5)OH (II), have been synthesized by the reaction of a new Salen-type bisoxime chelating ligand of 5,5'-di(N,N'-diethylamino)-2,2'-[(1,3-propylene)dioxybis(nitrilomethylidyne)]diphenol (H(2)L) with nickel(II) acetate tetrahydrate in different solvents. Clusters I and II were characterized by elemental analyses, IR spectra, UV-vis absorption spectra, TG-DTA and X-ray diffraction methods. In clusters I (or II), there are two ligand moieties (which provide N(2)O(2) donors), two acetate ions, two coordinated methanol (or ethanol) molecules and two crystallizing methanol (or ethanol) molecules, which result in the formation of three slightly distorted octahedral geometries around Ni(II) ions. Interestingly, nickel(II) ions in the structures of clusters I and II are all six-coordinated geometry, but clusters I and II are grown up in different solvent. Right because of this, solvent effect cause to their different crystal structures.

New templating strategies with salen scaffolds (Salen=N,N'-bis(salicylidene)ethylenediamine dianion)

Templated approaches towards selective organic synthesis is a common feature in nature in which nucleic acid templated synthesis plays a crucial role in various fundamental biological processes. The key feature that allows control over the amazing selectivity found in natural processes is evidently the effective molarity of the reaction partners that is mediated by the macromolecular templation event. An ongoing challenge within many chemical sciences is to exploit similar templating principles and make use of synthetic systems that are designed for specific chemical conversions. Here, we describe the recent developments that involve (metallo)salen scaffolds that are used for diverse templating events (salen=N,N'-bis(salicylidene)ethylenediamine dianion).

Synthesis, structure and spectroscopic behaviors of a five- and six-coordinated tri-cobalt(II) cluster: [(CoL)2(OAc)2Co].2C2H5OH

A tri-nuclear cobalt(II) cluster, [(CoL)2(OAc)2Co].2C2H5OH, has been synthesized by the reaction of cobalt(II) acetate tetrahydrate with a novel Salen-type bisoxime chelating ligand, 3,3'-dimethoxy-2,2'-[ethylenedioxybis(nitrilomethylidyne)]diphenol (H2L), and characterized by elemental analyses, IR spectra, TG-DTA and molar conductances. UV-vis spectroscopic titration in methanol solution clearly indicated the exclusive formation of the 3:2 [Co3L2]2+ cluster. The single-crystal X-ray diffraction determination of the Co(II) cluster shows that there are two acetate ions coordinate to three cobalt(II) ions through Co-O-C-O-Co bridges, and quadruple mu-phenoxo oxygen atoms from two [CoL] chelates also coordinate to cobalt(II) ions. Interestingly, different conformational central ions: five- and six-coordinated geometries were found in the cluster.