ABSTRACT
The stability constants of the lanthanide ions [La, Ce, Pr, Nd, Sm, Gd, Dy, Er and Yb]; Sc, Y, Th and UO22+ ions with some hydroxy nitrosocoumarins were determined in 40% ethanol-water mixture at 25 degree and 0.1 ionic strength. It was found that the stability constants of the complexes increased with increasing ionic radii, from Y to Sm. The so called Gadolinium break was observed with heavier lanthanides. Sc and Th complexes possessed the highest stability constants. The potentiometric measurements and conductimetric titrations showed that 1: 1 and 1: 2 [M: L] complexes were invariably formed
Subject(s)
Metals, Rare Earth/chemistry , Hydroxides/chemistry , Nitroso Compounds/chemistry , Scandium/chemistry , Yttrium/chemistry , Thorium/chemistry , Uranium/chemistry , Chelating Agents/chemistryABSTRACT
The UV and visible absorption spectra of some hydroxy nitrosocoumarins have been studied in organic solvents of varying polarities. The dependence of the band shift on the nature of substituent, dielectric effect and specific solvation was studied. The acid dissociation constants of the different ionizable groups were determined using the half- height and the modified limiting absorbance methods. The observed transition energy and oscillator strengths were correlated with those calculated from the SCF PPP CI method for molecular orbitals