The spectrochemical properties of bis-(alpha-methioninephosphonato)copper(II) in aqueous solution

The combined results of spectrophotometric measurements and e.s.r. spectra, as well as those obtained from potentiometric titration studies, are used to determine the structure of the individual complex species formed between copper(II) ion and 1-amino-3-methylthiopropane-phosphonic acid (alpha-MetP) in aqueous solution. The e.s.r. parameters are typical for CuN2O2 coordination geometries. The d-d absorption spectrum of [Cu(alpha-MetP)(2)](2-) chromofore in aqueous solution has been treated by the Angular Overlap Model in C-2h symmetry. Low-symmetry splittings of the broad asymmetric absorption band in the measured spectrum were found by Gaussian analysis. The effect of the sigma- and pi-bonding of bidentate ligand upon the central ion d-orbital energies is destribed in a ligand-field framework.