Hydrogen bonds not only provide a structural scaffold to assemble donor and acceptor moieties of zinc porphyrin-quinone dyads but also control the photoinduced electron transfer to afford the long-lived charge-separated states.
A series of zinc porphyrin-quinone linked dyads [ZnP-CONH-Q, ZnP-NHCO-Q, and ZnP-n-Q (n = 3, 6, 10)] were designed and synthesized to investigate the effects of hydrogen bonds which can not only provide a structural scaffold to assemble donor and acceptor moieties but also control the photoinduced electron-transfer process. In the case of ZnP-CONH-Q and ZnP-NHCO-Q, the hydrogen bond between the N-H proton and the carbonyl oxygen of Q results in the change in the reduction potential of Q. The strong hydrogen bond between the N-H proton and the carbonyl oxygen of Q*- in ZnP-CONH-Q*-,ZnP-NHCO-Q*-, and ZnP-n-Q*- (n = 3, 6, 10) generated by the chemical reduction has been confirmed by the ESR spectra, which exhibit hyperfine coupling constants in agreement those predicted by the density functional calculations. In the case of ZnP-n-Q (n = 3, 6, 10), on the other hand, the hydrogen bond between two amide groups provides a structural scaffold to assemble the donor (ZnP) and the acceptor (Q) moiety together with the hydrogen bond between the N-H proton and the carbonyl oxygen of Q, leading to attainment of the charge-separated state with a long lifetime up to a microsecond.
Okamoto
Ken
K
Department of Material and Life Science, Graduate School of Engineering, Osaka University, SORST, Japan Science and Technology Agency, Suita, Osaka 565-0871, Japan.
Fukuzumi
Shunichi
S
D016227:Benzoquinones / Q000737:chemistry*; D004583:Electrons; D006860:Hydrogen Bonding; D008027:Light; D008665:Metalloporphyrins / Q000737:chemistry*; D055672:Static Electricity
D016227:Benzoquinones; D008665:Metalloporphyrins; C017802:zinc hematoporphyrin; C004532:quinone