Picosecond excited-state dynamics of fixed-distance triads consisting of metalloporphyrin, doubly strapped metal-free porphyrin, and pyromellitimide

Abstract

Upon photoexcitation of fixed-distance triads cosisting of zinc-porphyrin (ZnP) or magnesium-porphyrin (MgP), a doubly strapped metal-free porphyrin (SH 2P), and pyromellitimide (PIm), (ZnP) +SH 2P(PIm) − and (MgP) +SH 2P(PIm) − ion pair states are produced in high yields by two-step electron-transfer reactions: (1) charge separation between 1(SH 2P)* and PIm and (2) hole transfer from (SH 2P) + to the metalloporphyrin. A (MgP) +SH 2P(PIm) − ion pair state is fairly long-lived, while a (ZnP) +SH 2P(PIm) − state is only short-lived due to a decay pathway to the ground state through a reverse hole transfer to give ZnP(SH 2P) +(PIm) − followed by charge recombination.