Mixed-ligand scandium complexes with 4-(2-pyridylazo)resorcinol and monocarboxylic acids

Scandium reacts with 4-(2-pyridylazo)resorcinol in the presence of monocarboxylic acids (X) to form mixed-ligand complexes with a ratio of Sc:PAR:X=1:2:2. The reaction chemism and solvent extraction of the complexes by n-butanol in the presence of diphenyl guanidine were studied. The stability constants and molar absorptivities for the complexes were calculated. The molar absorptivity values decrease in the acid order: CH3COOH > CH2ClCOOH > CCl3COOH. The formation and extraction of the mixed-ligand complexes in the Sc-PAR-X system allow to improve the sensitivity and selectivity of scandium spectrophotometric determination compared with the use of the Sc-PAR complex