Synthesis, characterization and toxicity of lanthanide complexes with Schiff bases derived from S-benzoyl dithiocarbazate and aldehydes

Abstract

New O:N:S and N:S donor ligands namely, S-benzoyl-N-(<em>o</em>-hydroxybenzaldehyde) dithiocarbazate, S-benzoyl-N-(N ,N-dimethylaminobenzaldehyde) dithiocarbazate, S-benzoyl-N(N-thiophene- 2-aldehyde) dithiocarbazate and their complexes with La(III), Ce(III), Pr(III), Nd(III), Sm(III), Gd(III), Tb(III), Dy(III), Ho(III), Er(III), Yb(III) and Lu(III) have been synthesized and characterized on the basis of elemental analysis, IR, NMR and electronic spectroscopy. The nephelauxetic effect (l-<img src="http://www.niscair.res.in/jinfo/equation121.gif" alt="" border="0" >) bonding parameter, <img src='http://www.niscair.res.in/jinfo/equation121.gif' border=0>, <em>b</em>^1/2 and Sinha covalency⁹ parameter δ, have been calculated. Their positive values indicate covalent nature of metal-ligand bond which is also supported by their molar conductances measured in nitrobenzene. Magnetic moment values exhibit paramagnetic nature of the complexes. Log <em>K, G</em>, <img src='http://www.niscair.res.in/jinfo/delta.gif' border=0><em>H </em>and <img src='http://www.niscair.res.in/jinfo/delta.gif' border=0><em>S</em> values have also been calculated. Toxicity of the compounds has been evaluated against cockroaches and fungi (<em>Aspergillus flavus </em>and <em>A. niger</em>)<em>. </em>The LD₅₀ and % inhibition values demonstrate greater efficacy of the complexes than that of the free bases.