Complex formation of curium(III) with amino acids of different functionalities: L-threonine and O -phospho-L-threonine

Abstract

The speciation of curium(III) with L-threonine and O-phospho-L-threonine was determined by time-resolved laser-induced fluorescence spectroscopy (TRLFS) at trace Cm(III) concentrations (3 × 10−7 M). Curium species of the type MpHqLr were identified in the L-threonine- and O-phospho-L-threonine system. These complexes are characterized by their individual luminescence spectra and luminescence lifetimes. The following formation constants were determined (a) for L-threonine: log β101 = 6.72 ± 0.07, log β102 = 10.22 ± 0.09, and log β1–22 =−(7.22 ± 0.19) at ionic strength I = 0.5 M and (b) for O-phospho-L-threonine: log β121 = 18.03 ± 0.13 and log β111 = 14.17 ± 0.09 at ionic strength I = 0.154 M. Possible structures of the identified curium species are discussed on the basis of the luminescence lifetime measurements and the magnitude of the formation constants.