Excited State Behavior of Uranyl Complexes with Salophen and Oxine as Chromophoric Ligands

Abstract

Abstract The electronic spectra and the photochemistry of the uranyl complexes UO2 (salophen) and UO2 (oxinate)2 with H2salophen = N,N´-bis(salicylidene)-o-phenylenediamine and oxine = 8- hydroxyquinoline were studied. The excited state behavior of both complexes is determined by a low-energy salophen2- / oxinate- to U(VI) ligand-to-metal charge transfer (LMCT) state which is not luminescent but can be reactive. In the case of UO2 (oxinate)2 the photolysis leads to the formation of free oxine with ϕ = 3.6 x 10-3 at λirr = 366 nm in CHCl3. It is suggested that various redox processes with the participation of the solvent are involved in product formation. UO2 (salophen) is not light sensitive since the primary electron transfer is followed by recombination which is facilitated by the rigid UO2(salophen) structure.