Spectroscopic study of the interaction of Nd+3 with amino acids: phenomenological 4f-4f intensity parameters

We have studied behaviour of the phenomenological 4f-4f intensity parameters in compounds of the Nd3+ ion with glycine, L-aspartic acid, L-glutamic acid, L-histidine, DL-malic acid and AspartameTM in aqueous solution, as function of the pK values and partial charges on the oxygens of the carboxylate groups of these molecules. The results are discussed and qualitatively interpreted in terms of the forced electric dipole and dynamic coupling mechanisms of the 4f-4f intensities, thus indicating that the forced electric dipole mechanism is dominant. (author)