Photophysical origin of the reduced photodynamic therapy activity of temocene compared to Foscan®: insights from theory

In order to explain the reduced photodynamic (PDT) activity of a recently proposed m-tetra (hydroxyphenyl) porphycene derivative (temocene or THPPo) in terms of singlet oxygen quantum yields compared to porphyrin analogue Foscan (m-THPC), a time dependent DFT investigation has been carried out. Computed electronic transitions, singlet-triplet energy gaps and spin-orbit coupling matrix elements (SOCME) can be related to the reduced PDT activity.