pH-metric and Thermodynamic Studies on Metal Chelates of Al(III), Cr(III) and Fe(III) Ions with Tridentate Biprotic Ligands

Abstract

The pH-metric studies on the metal chelates of trivalent AI (III), Cr(III)
and Fe(III) ions with the tridentate biprotic ligands derived from dibenzoylmethane
with  o-aminobenzoic acid- (H₂BB) and 2-aminopropanoic acid
(H₂BP), respectively, have been carried out by employing Calvin-Bjerrum
pH-titration technique at 25°, 35° and 45 ± 0.1 °C (μ= 0.01.0.05 and
0.1 M NaCIO₄) in aqueous media The dissociation constants (pK₁ and
pK₂),  θ^o and pk_m^h  value of the ligands have been evaluated. The stability
constants have been determined and these values follow the Irving-William
order. The thermodynamic parameters (ΔG^o, ΔH^o and ΔS^o) of the chelation
have been evaluated and discussed.