22π‑Electrons [1.1.1.1.1] pentaphyrin as a new photosensitizing agent for water disinfection: experimental and theoretical characterization

In view of their promising photosensitizing features, expanded porphyrins are gaining wide attention for their potential use in both photodynamic therapy (PDT) of cancer or as likely photoactivated agent for water disinfection. Herein, we report a joint experimental and theoretical investigation on the 20-(4’-carboxyphenyl)-2,13-dimethyl-3,12-diethyl-[22]pentaphyrin complex 4. The synthesis, NMR, UV-Vis and mass characterization of the new compound together with a detailed theoretical investigation of the photophysical properties are presented. In particular, type I- and type II- photoreactions have been explored by means of DFT and its TDDFT formulation characterizing the electronic absorption spectra, providing singlet-triplet energy gap, vertical ionization potential and electron affinity. Results show that title compound is able to generate the cytotoxic singlet oxygen species supporting the application of the proposed molecule as a photoactivated agent for water disinfection.