ADDUCT FORMATION OF β-DIKETONATO LANTHANOIDS(III) WITH CARBOXYLIC ACIDS HAVING HYDROXYL AND METHOXYL GROUPS

Adduct formation of 2-thenoyltrifluoracetonato(tta) lanthanum(III), europium(III), and ytterbium(III) with alpha-phenyllactic, alpha-methoxy phenylacetic, salicylic, and o-methoxy benzoic acids in chloroform has been studied by solvent extraction technique. It has been found that lanthanoid(III) chelates form more stable adducts with these carboxylic acids in the sequence: Yb(tta)3 < Eu(tta)3 < La(tta)3. The adduct formation constants as well as the separation factors obtained as the ratio of the constants between a pair of metals are the largest for alpha-phenyllactic acid among these acids. The characteristics with alpha-phenyllactic acid would be caused by the action as bidentate unlike benzoic acid derivatives which work as monodentates owing to the internal complexation through hydrogen bonding.