Spectrophotometric study of Bi(III) complexes with oxydiacetic and thiodiacetic acids

Abstract

Complexes of Bi(III) with oxydiacetic and thiodiacetic acids were studied in aqueous solution by UV spectrophotometry. In acidic medium, with oxydiacetic acid 1 : 1, 1 : 2 and 1 : 3 (metal to ligand) mononuclear complexes were found and formation constants calculated at 25°C in 0.5 M (Na, H)ClO 4 medium. By using the protonation constants of the ligand, determined under the same experimental conditions, the following equilibrium constants can be calculated (L 2− is the anion of the acid): Bi 3+ + L 2−⇋BiL + log β 101 = 7.69 Bi 3+ + 2L 2−⇋BiL − 2 log β 102 = 12.73 Bi 3+ + 3L 2−⇋BiL 3− 3 log β 103 = 16.19 With thiodiacetic acid only a 1 : 1 species was found, the stability of which is less than of the corresponding complex with oxydiacetic acid.