Synthesis, Structural and Magnetic Studies of Dinuclear Complexes with Oxo-Homoscorpionate Borate Ligand

Oxo-homoscorpionate borate ligand, potassium bis(phthalato)borate (KL) has been synthesized as its potassium salt. It was converted into its Co(II), Ni(II) and Cu(II) dinuclear complexes by mixing and stirring with methanol solution of metal chloride. The compositions of ligand and its metal complexes were investigated by elemental analysis in order to ensure their purity and the structural elucidations were based on conductivity measurements, room temperature magnetic susceptibility, thermal and spectral studies (IR, H NMR, UV-Vis and 1 MS-ESI mass spectra). Spectroscopic results support a square planar (SP) geometry in the Cu(II) complex while an octahedral (O ) geometry is suggested in the Ni(II) and Co(II) complexes. Magnetic susceptibility h measurements of complexes reveal that these complexes exhibit antiferromagnetic coupling behavior due to the presence of two metal ions in close proximity. The molar conductance measurement in water shows 1:1 electrolyte natures. The thermal behaviour of compounds was investigated by thermal gravimetrical analysis (TGA), in order to determine their mode of decomposition and thermal stability. All these complexes and ligand show three step loss upon dynamic heating to 1000°C, with of simultaneous loss of both of inorganic and organic fragments exhibiting almost the same mode of decomposition pattern. The residue after heating above 500°C corresponded to metal chlorides, confirmed by microanalysis and IR spectroscopy. It is observed from the results that the thermal stability of the complexes increases in the following sequence: