Determination of the energy levels of radical pair states in photosynthetic models oriented in liquid crystals with time-resolved electron paramagnetic resonance

被引:54
作者
Levanon, H [1 ]
Galili, T
Regev, A
Wiederrecht, GP
Svec, WA
Wasielewski, MR
机构
[1] Hebrew Univ Jerusalem, Dept Phys Chem, IL-91904 Jerusalem, Israel
[2] Hebrew Univ Jerusalem, Farkas Ctr Light Induced Proc, IL-91904 Jerusalem, Israel
[3] Argonne Natl Lab, Div Chem, Argonne, IL 60439 USA
[4] Northwestern Univ, Dept Chem, Evanston, IL 60208 USA
关键词
D O I
10.1021/ja980409c
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
We report the results of time-resolved electron paramagnetic resonance (TREPR) studies of photoinduced charge separation in a series of biomimetic supramolecular compounds dissolved in oriented liquid crystal solvents. The molecules contain a chlorophyll-like (zinc 9-desoxomethylpyropheophorbide a) electron donor, D (ZC), and two electron accepters with different reduction potentials, i.e., pyromellitimide, A(1) (PI), and 1,8:4,5-naphthalenediimide, A(2) (NI). The compounds investigated are ZCPI, ZCNI, and ZCPINI, and they have small but well-defined differences of their ion-pair energies. Temperature-dependent TREPR studies on this series of compounds permit the determination of the radical pair energy levels as the solvent reorganization energy increases from the low-temperature crystalline phase, through the soft glass phase, to the nematic phase of the liquid crystal. As the temperature is increased, the radical pair with the lowest energy is the first to exhibit triplet-initiated charge separation as the solvent reorganization energy increases in the liquid crystal. The energy levels of the radical pairs and the solvent reorganization energy are determined by using the known singlet: and triplet excited state energy levels of ZC, the electrochemically determined relative energies between the radical ion pairs in polar isotropic solvents, and the TREPR data. All these yield information about the ordering of the radical ion pair energy levels relative to the excited-state energy levels of ZC.
引用
收藏
页码:6366 / 6373
页数:8
相关论文
共 30 条
[21]   THE PHOTOEXCITED TRIPLET-STATE AS A PROBE OF DYNAMICS AND PHASE MEMORY IN A MULTIPHASE LIQUID-CRYSTAL - TIME-RESOLVED ELECTRON-PARAMAGNETIC RESONANCE SPECTROSCOPY [J].
REGEV, A ;
GALILI, T ;
LEVANON, H .
JOURNAL OF CHEMICAL PHYSICS, 1991, 95 (11) :7907-7916
[22]   DYNAMIC SOLVENT EFFECTS ON OUTER-SPHERE ELECTRON-TRANSFER [J].
RIPS, I ;
JORTNER, J .
JOURNAL OF CHEMICAL PHYSICS, 1987, 87 (04) :2090-2104
[23]  
RIPS I, 1987, CHEM PHYS LETT, V13, P3411
[24]  
TANG J, 1994, CHEM PHYS LETT, V219, P283, DOI 10.1016/0009-2614(94)87059-4
[25]   Separation of the exchange and dipolar contributions to the spin-spin coupling in the donor-acceptor complex TAPD-ZnP-NQ [J].
van der Est, A ;
Fuechsle, G ;
Stehlik, D ;
Wasielewski, MR .
APPLIED MAGNETIC RESONANCE, 1997, 13 (3-4) :317-335
[26]  
WASIELEWSKI MR, 1992, N-HOLLAND D, P87
[27]   PHOTOINDUCED ELECTRON-TRANSFER IN SUPRAMOLECULAR SYSTEMS FOR ARTIFICIAL PHOTOSYNTHESIS [J].
WASIELEWSKI, MR .
CHEMICAL REVIEWS, 1992, 92 (03) :435-461
[28]   CHLORIN-BASED SUPRAMOLECULAR ASSEMBLIES FOR ARTIFICIAL PHOTOSYNTHESIS [J].
WASIELEWSKI, MR ;
WIEDERRECHT, GP ;
SVEC, WA ;
NIEMCZYK, MP .
SOLAR ENERGY MATERIALS AND SOLAR CELLS, 1995, 38 (1-4) :127-134
[29]   Ultrafast photoinduced electron transfer in a chlorophyll-based triad: Vibrationally hot ion pair intermediates and dynamic solvent effects [J].
Wiederrecht, GP ;
Niemczyk, MP ;
Svec, WA ;
Wasielewski, MR .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1996, 118 (01) :81-88
[30]   Differential control of intramolecular charge separation and recombination rates using nematic liquid crystal solvents [J].
Wiederrecht, GP ;
Svec, WA ;
Wasielewski, MR .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1997, 119 (26) :6199-6200