Complex Formation of Europium(III) with Photoditazine According to Luminescence and IR Spectroscopy

Abstract

Europium(III) complexation with photoditazine, a photosensitizer for photodynamic therapy, was studied using luminescence and IR spectroscopy. The luminescence spectra of europium–photoditazine solutions and solid complex show emission bands in the 400–700 nm range, typical of both Eu³⁺ complexes and photoditazine. It was shown that Eu³⁺ luminescence intensity in the red region increases upon complex formation with photoditazine. Since the luminescence bands of solutions at 400–700 nm overlap with photoditazine absorption bands, the addition of europium chloride enhances the excitation energy transfer to photoditazine. A medication comprising a europium salt and photoditazine as a photosensitizer could serve for the targeted delivery of light radiation to photoditazine at UV excitation, which would result in more efficient formation of reactive oxygen species and can be promising for external photodynamic therapy.