Persubstituted Triphenylamine Bearing Zinc Porphyrin to Host Endohedral Fullerene, Sc3N@C80: Formation and Excited State Electron Transfer.

Abstract

A persubstituted porphyrin with eight entities of triphenylamines at the β-pyrrole positions of a zinc tetraphenylporphyrin, 1, was newly synthesized and characterized. Due to the severe nonplanar distortion caused by the peripheral, electron rich substituents, the zinc porphyrin was able to comfortably bind a relatively large endohedral fullerene, Sc3N@C80, to form a new class of donor-acceptor-type host-guest complex. Spectral, computational, and electrochemical studies were systematically performed to evaluate the binding, spatial geometry, and redox properties of the host-guest system. Further, free-energy calculations were performed to seek the thermodynamic feasibility of excited state charge transfer. Finally, transient absorption spectral studies at different time scales were performed to secure evidence and kinetic information on excited state charge transfer leading to the 1•+:Sc3N@C80•- charge separated species. The present unprecedented, highly functionalized material with electron rich substituents carries zinc porphyrin as a photoactive host to large endohedral fullerenes, and its ability to undergo excited state electron transfer opens up new avenues to build photoactive host-guest systems relevant to light energy conversion and optoelectronic applications.