Increasing the lifetimes of charge separated states in porphyrin-fullerene polyads

摘要

Two linear polyads were designed using zinc(II) porphyrin, [ZnP], and N-methyl-2-phenyl-3,4-fulleropyrrolidine (C-60) where C-60 is dangling either at the terminal position of [ZnP]-C6H4-R-C6H4-[ZnP]-C-60 (1) or at the central position of [ZnP]-C6H4-R-C6H4-[ZnP(C-60)]-C6H4-R-C6H4-[ZnP] (2) in order to test whether the fact of having one or two side electron donors influences the rate of electron transfer, k(et). These polyads were studied using cyclic voltammograms, DFT computations, steady state and timeresolved fluorescence spectroscopy, and femtosecond transient absorption spectroscopy (fs-TAS). Photo-induced electron transfer confirmed by the detection of the charge separated state [ZnP center dot+]/C-60(center dot-) from fs-TAS occurs with rates (k(et)) of 3-4 x 10(10) s(-1) whereas the charge recombinations (CRs) are found to produce the [ZnP] ground state via two pathways (central [(ZnP center dot+)-Zn-1]/C-60(center dot-) (ps) and terminal central [ZnP center dot+]/C-60(center dot-) (ns) producing [(ZnP)-Zn-1] (ground state) and [(ZnP)-Zn-3*]). The formation of the T1 species is more predominant for 2.