Photoacoustic spectra of complexes of phenylalanine with La3+, Nd3+, Sm3+ and Tb3+

Crystals of complexes Ln(Phe)Cl-3.5H(2)O (Phe: phenylalanine; Ln: La3+, Nd3+, Sm3+, and Tb3+) were synthesized and their photoacoustic (PA) spectra in the UV-Vis region were recorded. PA intensities of central lanthanide ions are interpreted in terms of the probability of non-radiative transitions. It is found that PA intensity of the ligand phenylalanine bears a relation to the energy transfer processes. Different PA intensities of the ligand are interpreted by comparison with the fluorescence spectra. The relaxation process model is also studied based on their PA and fluorescence spectra. Co-fluorescence effect of co-precipitates Tb(0.8)Ln(0.2)(Phe)Cl-3.5H(2)O (Ln: La3+, and Nd3+) are firstly reported. PA intensity of the ligand increases for Tb0.8La0.2(Phe)Cl-3.5H(2)O, Tb(Phe)Cl-3.5H(2)O and Tb0.8Nd0.2(Phe)Cl-3.5H(2)O, respectively. The changes of fluorescence spectra turn out to be complementary to the PA spectra. The intramolecular energy transfer and intermolecular energy transfer processes in the co-precipitates are discussed in depth from two aspects: radiative and non-radiative relaxations. (C) 2003 Elsevier Science B.V. All rights reserved.