Synthetic strategies, structures and properties of di and polynuclear cobalt complexes with H2salen type Schiff bases and their reduced analogues

Formation of H-bonding networks in the solid state structure of a trinuclear cobalt(iii/ii/iii) complex with N2O2 donor Schiff base ligand and glutaric acid as bridging co-ligand: synthesis, structure and DFT study

A trinuclear linear mixed-valence centrosymmetric cobalt(iii)-cobalt(ii)-cobalt(iii) complex, [CoII{(μ-L)(μ-Hglu)CoIII(OH2)}2](ClO4)2·6H2O has been synthesized during tetradentate N2O2 donor 'Schiff base' ligand, H2L {N,N'-bis(salicylidene)-1,3-diaminopropane} and glutaric acid (H2glu) as anionic co-ligand. The complex has been characterized by spectroscopic measurements and its solid state structure has been determined by single crystal X-ray diffraction analysis. The supra-molecular assembly formed by the hydrogen bonding interactions in the solid state of the complex has been analysed using DFT calculations.

Application of a distinctly bent, trinuclear, end-to-end azide bridged, mixed valence cobalt(iii/ii/iii) complex in the fabrication of photosensitive Schottky barrier diodes

A mixed-valence trinuclear cobalt(iii)-cobalt(ii)-cobalt(iii) complex, [(μ-1,3-N3)Co3L(N3)3]·MeOH has been synthesized using a tetradentate N2O2 donor 'reduced Schiff base' ligand, H2L {1,3-bis(2-hydroxybenzylamino)2,2-dimethylpropane} and azide as anionic co-ligand. The complex has been characterised by elemental analysis, IR, UV-vis spectroscopy and single-crystal X-ray diffraction studies etc. The cobalt(iii)-cobalt(ii)-cobalt(iii) skeleton in the complex is non-linear and non-centrosymmetric. The redox behavior of the complex was studied by using Cyclic Voltammetry (CV). The complex is found to be a semiconductor material as confirmed by determining the band gap of this complex by experimental as well as theoretical studies. The band gap in the solid state has been determined experimentally. The conductivity of the synthesized complex based device improves considerably in illumination conditions from the non-illuminated conditions. The complex has also been used to fabricate Schottky barrier diodes.

A mixed-valence [CoII4CoIII2] cluster with defect disk-shaped topology

The employment of the new Schiff base ligand 2-[(4-chloro-2-hydroxybenzylideneamino)methyl]phenol (H2L) bearing O2N donors for the preparation of a novel Co6 cluster is reported. The hexanuclear cobalt complex, namely, di-μ2-acetatotetrakis{μ2-2-[(4-chloro-2-oxidobenzylideneamino)methyl]phenolato}tetra-μ3-methanolato-tetracobalt(II)dicobalt(III), [CoII4CoIII2(C14H10ClNO2)4(CH3COO)2(CH3O)4], was obtained using Co(CH3COO)2·4H2O and H2L as starting materials in MeOH under solvothermal conditions. The six metal ions are linked together by the μ3-O atoms of four deprotonated MeOH molecules, two CH3COO- units and six phenolate O atoms of four L2- ligands to form a defect disk-shaped topology. DC magnetic susceptibility investigations revealed the existence of antiferromagnetic interactions in the Co6 cluster.