Potentiometric investigations of some catechol derivatives of scandium

Abstract

The equilibrium reactions of scandium(III) with some triprotic catechol derivatives (H3L) were studied. The selected ligands that are 2,3-dihydroxybenzoic acid (2,3-DHBA), 3,4-dihydroxybenzoic acid (3,4-DHBA), 3.4-dihydroxyhydrocinnamic acid (3,4-DHHCA), and 3,4-dihydroxyphenylacetic acid (3,4-DHPA) were investigated in aqueous solution by means of potentiometry in 0.1 M ionic medium at 25 degrees C. The stability constants are reported for the ScL and ScL(H2L)(-) mononuclear complexes. 2,3-DHBA can bind to Sc3+ ion strongly and the salicylate mode (COO-, O-) is effective over the acidic pH range. But in higher pH range, 3,4-DHBA, 3,4-DHHCA, and 3,4-DHPA act more efficiently through catecholate groups (O-, O-).