Studies on kinetics of complexation of lanthanide α-hydroxycarboxylates with 1,10-phenanthroline

• Published in: Polyhedron 1997-01, Vol.16 (24), p.4229-4232
• Main Authors: Yanping, Ren, Li, Zhang, Liufang, Wang, Yu, Liu
• Format: Article
• Language: English
• Subjects: 1,10-phenanthroline; coordination reaction; kinetics; lanthanide α-hydroxycarboxylates; linear free energy relationship; rate constant
• ISSN: 0277-5387
• DOI: 10.1016/S0277-5387(97)00232-5

Kinetics of the coordination reaction of lanthanide (La III, Eu III) α-hydroxycarboxylates [LnL 3(H 2O) 2] with 1,10-phenanthroline (phen) in methanol-water ( v/v, 3:2) were studied at 25°C by calorimetric titration. A one-step reaction process in accordance with the rate law has been suggested. The reaction is found to be first order for both lanthanide α-hydroxycarboxylates and phen. We have evaluated rate constants of the reactions. It is found that a linear free energy relationship exists between the stability constants of the lanthanide-α-hydroxycarboxylate-phen ternary complex and the rate constants. It is also found that a linear free energy relationship exists between the rate constants of La-hydroxycarboxylate with phen and the acid strength of α-hydroxy-acid as primary ligand, but the linear free energy relationship does not exist in the Eu-α-hydroxycarboxylate-phen ternary complex. The influence of other factors upon the reaction rate constants was also discussed.