Photoinduced energy transfer in truxene-linked zinc porphyrin–fullerene-corrole tetrad and its application in triplet−triplet annihilation upconversion

Abstract

Triplet photosensitizers (PSs) have attracted widespread interest due to their application in photocatalytic organic reactions, photodynamic therapy (PDT), photoinduced hydrogen production from water splitting, and triplet–triplet annihilation (TTA) upconversion. Herein, the triad T-P-Co and tetrad T-C60-P-Co were synthesized, characterized, and applied in triplet–triplet annihilation (TTA) upconversion. The photophysical processes were investigated with steady-state UV–visible absorption and fluorescence spectroscopies, nanosecond time-resolved transient absorption spectroscopy and electrochemical characterization. T-P-Co and T-C60-P-Co show efficient intramolecular singlet–singlet energy transfer from the porphyrin moiety to corrole/fullerene moiety. The energy transfer efficiency is nearly 100% for T-P-Co and 69.4% for T-C60-P-Co, respectively. Electrochemical investigation shows that the photo-induced intramolecular electron transfer of the excited triad T-P-Co and tetrad T-C60-P-Co is thermodynamically prohibited in toluene due to the positive ΔGCS for charge-separation. Nanosecond time-resolved transient difference absorption spectra indicate that the triplet excited states of T-P-Co and T-C60-P-Co are both distributed on the corrole moiety. The triplet lifetimes of T-P-Co and T-C60-P-Co are 86.9 μs and 73.3 μs, respectively. The triad T-P-Co and tetrad T-C60-P-Co were used as triplet photosensitizers for TTA upconversion, and upconversion quantum yields of 0.76% and 0.84% were observed, respectively.