LONG-LIVED PHOTOINITIATED CHARGE SEPARATION IN CAROTENE DIPORPHYRIN TRIAD MOLECULES

被引:129
作者
GUST, D
MOORE, TA
MOORE, AL
GAO, F
LUTTRULL, D
DEGRAZIANO, JM
MA, XCC
MAKINGS, LR
LEE, SJ
TRIER, TT
BITTERSMANN, E
SEELY, GR
WOODWARD, S
BENSASSON, RV
ROUGEE, M
DESCHRYVER, FC
VANDERAUWERAER, M
机构
[1] KATHOLIEKE UNIV LEUVEN,AFDELING ORGAN SCHEIKUNDE,LOUVAIN,BELGIUM
[2] MUSEUM NATL HIST NAT,BIOPHYS LAB,CNRS,ERA 951,F-75231 PARIS 05,FRANCE
[3] ARIZONA STATE UNIV,CTR STUDY EARLY EVENTS PHOTOSYNTH,TEMPE,AZ 85287
关键词
D O I
10.1021/ja00010a002
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
A variety of molecular triads and dyads consisting of covalently linked carotenoid (C) and/or porphyrin (P) moieties have been prepared and studied with transient absorption and time-resolved fluorescence techniques. Diporphyrins of the type P(A)-P(B) and C-P(A)-P(B) triads demonstrate interporphyrin singlet-singlet energy transfer with rate constants ranging from 8.1 x 10(8) to 2.3 x 10(10) s-1. The energy-transfer rates are not in accord with those predicted by the Forster dipole-dipole theory, and it is suggested that energy transfer involves a contribution from an electron-exchange mechanism. Interporphyrin photoinitiated electron transfer is observed in molecules possessing sufficient thermodynamic driving force to produce P(A).+-P(B).- and C-P(A).+-P(B).- charge-separated states. The electron-transfer rate constant increases with increasing reaction free energy change for the molecules studied, and rate constants up to 3.5 x 10(9) s-1 and quantum yields up to 0.68 were measured. The carotenodiporphyrin triad systems undergo a subsequent electron-transfer step to give final C.+-P(A)-P(B).- states. These states are rather long lived (tau-almost-equal-to 250 ns), and the overall quantum yields range up to 0.32.
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页码:3638 / 3649
页数:12
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