Stability investigations of medically relevant complexes by the simultaneous analysis of series of spectrophotometric titrations

This contribution presents a selection of results obtained using spectrophotometric titrations and subsequent second-order global analysis of the data. For several reasons the investigated equilibria present particular challenges to traditional analysis techniques. Equilibrium constants and UV absorption spectra for differently protonated ligand and complex species in the complexation of Eu3+ with PDA (1,10-phenanthroline-2,9-dicarboxylic acid) and with FNAC (4,4,4-trifluoro-1-(2'-naphthyl)-1,3-butanedione) are reported. Additionally, in order to investigate the stability of the complex between In3+ and DTPA (diethylenetriamine-pentaacetic acid), the absorbing auxiliary ligand HEED (N,N'-di(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid) was employed in a ligand competition study. Equilibrium constants and UV absorption spectra are reported for HEED protonated species, and In(III)-HBED and In(III)-DTPA complex species. (C) 1999 Elsevier Science Ltd. All rights reserved.