Binary Complexes in solution of schiff base ligands, o-hydroxynaphthalidene benzoyl and salicyloyl hydrazone with thorium, uranyl and vanadyl ions and ternary complexes of thorium with aminopolycarboxylic acids as primary ligands

Abstract

Ligand behaviour and aroyl hydrazone Schiff bases, viz., o-hydroxynaphthalidene bezoyl hydrazone (NABHZ) and <em>o</em>-hydroxynaphthalidene salicyloyl hydrazone (NASHZ) have been studied with metal ions (Th⁺⁴, UO₂⁺² and VO⁺²) in dioxane-water medium (75% v/v) at 20ᵒ, 30ᵒ and 40ᵒC with 0.1 <em>M </em>NaCIO₄ salt background. Both the ligands behave as monoprotic and bidentate NO donors. Log<em>β</em>₂values for bis-complexes at 20°C for the ligands, NABHZ and NASHZ ,are 15.05, 14.26; 14.99, 9; 14.12, 13.15; for Th⁺⁴ UO₂⁺², VO⁺² respectively. Complexation is favoured both by enthalpy and entropy changes. Cratic parts of D<em>H </em>are negative and comparatively large indicating greater covalent interaction. Thorium only forms ternary complexes with NTA, HEDTA and EDTA as primary ligands and schiff bases as secondary ligands. The order of stabilities for the ternary step is log <em>K</em><img src='http://www.niscair.res.in/jinfo/equation90.gif' border=0> > log <em>K </em> <img src='http://www.niscair.res.in/jinfo/equation91.gif' border=0> > log <em>K </em><img src='http://www.niscair.res.in/jinfo/equation92.gif' border=0>.