STUDIES ON SOME LANTHANIDE COMPLEXES OF HIGHER COORDINATION NUMBER - SYNTHESIS AND CHARACTERIZATION

摘要

Lanthanum(III), cerium(III), praseodymium(III), neodymium(III), samarium(III) and europium(III) form complexes in 1:1, 1:2 and 1:3 stoichiometric ratios with the ligands 2-thiophenealdehyde salicyloylhydrazone (tash) and indole-3-aldehyde semicarbazone(iasc). The complexes have been characterised on the basis of elemental analyses, spectral, magnetic and thermal data. tash is a tetradentate ligand forming complexes upto maximum coordination number of twelve for the lanthanide ion whereas the iasc behaves as bidentate and the other coordination sites are occupied by aqua/or acido ions. The spectral parameters bonding (b(1/2)), covalency angular overlap(eta), Sinha's covalency (delta), have been calculated and indicate partial covalent bonding developing between the lanthanide metal and ligand in these complexes. Higher (mu)RT values for Sm(III) and Eu(III) complexes along with structural characteristics of the lanthanide complexes are discussed. [References: 41]