Can subpyriporphyrin and its boron complex be proposed as photosensitizers in photodynamic therapy ? A first principle time dependent study.

Density functional theory (DFT) and its time-dependent approach (TDDFT) in conjunction with the PBE0 exchange-correlation functional have been employed to characterize the structural and electronic properties of a new synthesized homologue of a triphyrin, in which a pyrrole ring has been substituted with a pyridine moiety, and its boron complex. Absorption spectra have been computed for different isomers of the free compound as well as for the corresponding boron containing system. The solvent effects have been evaluated through the polarizable continuum model (PCM). Triplet energies have been computed in order to verify whether these systems should be proposed as photosensitizers in photodynamic therapy. Results show that the employed tool is able to correctly reproduce the absorption spectra and to contribute to better assign the electronic transitions explaining their origin and that the examined boron complex has a triplet energy that, in principle, can activate the singlet O(2) reactive species.