Formation constants of lanthanide metal chelates with 8-formyl-7-hydroxy-4-methyl-2H-(1)-benzopyran-2-one and its anils

Proton-ligand and metal-ligand formation constants of 1:1, 1:2 and 1:3 binary chelates of 8-formyl-7-hydroxy-4-methyl-2H-(1)-benzopyran-2-one (FHMB) and its anils (derived from 4-methyl-, 4-chloro- and 4-nitro-anilines) with Sm(III), Dy(III), Gd(III), Nd(III), Pr(III), Ce(III) and La(III) have been determined pH-metrically in 70 per cent (v/v) dioxane-water medium at 30degC and I=0.1M(NaClO4). The order of stabilities with respect to (i) metal ions is in the order of increasing Z2/γ values of Ln(III) ions and (ii) the ligands (Me-FHMBANIL>FHMBANIL>FHMB>Cl-FHMBANIL> NO2-FHMBANIL) is in accordance with the relative basicities of the ligands. 3 tables, 6 refs. (author)