STUDY ON FORMATION OF MIXED LIGAND COMPLEXES BETWEEN Er, Tm, Yb WITH L – PHENYLALANINE AND ACETYL ACETONE IN AQUEOUS SOLUTIONS.
Abstract
The stability constants of the mixed ligand complexes and ligand complexes formed between Er3+, Tm3+, Yb3+ with L - phenylalanine and acetyl acetone were determined simple by potentiometric titration in aqueous solution. The reactions were studied at temperature (25 ÷ 450C), ionic strength I = 0,1. The complexes following 1:2 proportion have forms of LnPhe2+, LnAcAc2+, Ln(AcAc)2+, the best formation of complexes occurs in the ranger of pH from 6 to 8; following 1:2:2 proportion have forms of LnPheAcAc+;the best formation of complexes occurs in the range of pH from 7 to 9. The standard thermodynamic parameters (∆G0, ∆H0, ∆S0) were calculated to determine the factors that affect these complexation processes.
