Y. Hasegawa et al., THERMODYNAMIC PARAMETERS OF COMPLEXATION OF LANTHANOIDS(III) BY ALPHA-SUBSTITUTED CARBOXYLATE ANIONS, Radiochimica Acta, 61(3-4), 1993, pp. 191-194
The protonation enthalpy of alpha-hydroxyphenylacetate, alpha-phenylla
ctate, and alpha-methoxyphenylacetate anions and the complexation enth
alpy of lanthanoid(III) with these carboxylate ions have been measured
by calorimetric technique in 0.1 mol/dm3 (NaClO4) at 25-degrees-C. Th
e results are compared to those of the phenylacetate complexation. The
low protonation enthalpy of alpha-hydroxycarboxylate relative to othe
r monocarboxylates is attributed to intra hydrogen-bond formation. The
difference between DELTAH101 of alpha-hydroxycarboxylates of light la
nthanoid(III) and those of the heavy ions is smaller than the correspo
nding difference for complexation by phenylacetate. By contrast, the d
ifference in DELTAS101 for complexation of light and heavy ions by the
two ligands is similar. Complexation by alpha-methoxyphenylacetate, h
owever did not follow either pattern.