Photonics of UO2 2+ complexes with tryptophan: 1. Influence of anions and temperature on intraspheric deactivation of excited states of UO2 2+ and tryptophan

Quenching of the fluorescence of selectively photoexcited UO 2 2+ and tryptophan (Trp) in the [UO 2 2+ •••Trp] complex and the influence of SO 4 2- and NO 3 - anions and temperature on the electron phototransfer were studied. The fluorescence of selectively photoexcited states of the ligand and metal ion in the [UO 2 2+ •••Trp] complex is quenched by the static mechanism of intraspheric electron transfer. The quenching constants were determined. The influence of complexation and temperature on the electron transfer was studied. The excitation procedure of the ligand and UO 2 2+ crucially affects the electron transfer, although only the electron transfer from tryptophan to UO 2 2+ to form Trp•+ radical cation and uranyl(V) ion is observed at selective photoexcitation in the [UO 2 2+ •••Trp] complex. Quenching of the Trp fluorescence is mainly determined by the factors affecting the stability of the [UO 2 2+ •••Trp] complexes, whereas quenching of the UO 2 2+ fluorescence depends mainly on its acceptor properties in the electronically excited state. © 2006 Nauka/Interperiodica.