Thermodynamic and kinetic stability of cerium(IV) complexes with a series of aminopolyacetic acids

摘要

The compositions, stability constants, and rate constants of intramolecular redox decomposition of cerium(IV) complexes with anions of aminoacetic (H2NCH2COOH), iminodiacetic HN(CH2COOH)(2), nitrilotriacetic N(CH2COOH)(3), ethylenediaminetetraacetic (CH2COOH)(2)N(CH2)(2)N(CH2COOH)(2), and hexamethylenediaminetetraacetic (CH2COOH)(2)N(CH2)(6)N(CH2COOH)(2) acids were determined by potentiometric, spectrophotometric, and kinetic methods at pH in the range 1.3-2.0 in perchlorate and nitrate media at an ionic strength I = 0.1 and a temperature of 298.15 K. Direct linear correlation between the logarithms of the stability constants of the complexes, log beta(101), and logarithms of the cumulative protonation constants, log D' (m+k) (k = 1-2), of aminopolyacetic acid anions L (m-), and inverse linear correlation between log beta(101) and logarithms of the rate constants of intramolecular redox decomposition of the complexonates CeL(4-m) (m = 1-4), log k (n=1), were found.