Desenvolvimento de um novo marcador luminescente para Microcistina-LR : um estudo teórico

Abstract

In this work we describe a theoretical study of lanthanide complexes with macrocyclic ligands. Spectroscopic properties of the cryptate [EuÌ(bipy)2py(CO2Et)2]3+.2H2O were investigated with semiempirical methodologies such as Sparkle, INDO/S-CIS, Judd- Ofelt model as well as Malta s models implemented in LUMPAC (Luminescence Package). This computational package has turned viable the purely theoretical design of highly luminescent lanthanide complexes. We initially looked for a calculation method that better reproduced the absorption spectrum of the cryptate, finding out that AM1-p was the best candidate. This method used Sparkle/AM1 together with INDO/S-CIS. In the sequence we tested LUMPAC s efficacy using a series of trisbipyridines and observed that the theoretical results were in good agreement to the experimental ones. Finally, we studied the cryptate EuÌ(bipy)2py(CO2Et)2]3+.2H2O and its derivatives. The theoretical intensity parameters (= 2, 4, 6) of the cryptates revealed that Eu3+ ion lies in a weakly polarizable environment. The transfer rates clearly indicated that the energy transfer occurs predominantly from the ligand s triplet state to 5D1 and 5D0 levels belonging to Eu3+ ion. The low quantum yield values observed for all cryptates were probably due to a poor resonance between the ligand s triplet state and the emitting level from Eu3+. The most promising substituted cryptate was found to be [EuÌ3]3+, however the calculation of a cryptate conjugated with microcystin-LR did not show better results. In summary the results as a whole evidenced that the methodology employed is promising in predicting spectroscopic properties of lanthanide complexes.