Thermodynamics of gallium(III) and indium(III) monoazide complexes in dimethyl sulphoxide solutions

Abstract

The stability constants of gallium(III) and indium(III) monoazide complexes in DMSO solution at 25 °C have been determined spectrophotometrically using equimolar mixtures of gallium(III)–iron(III) or indium(III)-iron(III) perchlorates as constant ionic-strength media. Formation heats of both complexes have been studied calorimetrically. The thermodynamic functions for gallium and indium monoazide complex formation are, respectively: ΔG⁰_Ga=–27.18 ± 0.23 kJ mol^–1, ΔH⁰_Ga=–6.68 ± 0.11 kJ mol^–1, ΔS⁰_Ga= 68.8 ± 1.1 J K^–1 mol^–1, ΔG⁰_ln=–33.99 ± 0.11 kJ mol^–1, ΔH⁰_ln=–13.19 ± 0.17 kJ mol^–1, ΔS⁰_ln= 70.0 ± 0.9 J K^–1 mol^–1. The thermodynamic parameters are discussed in terms of hard and soft acceptor–donor interactions.