Conformations and Photophysics of a Stilbene Dimer.
Conformations and Photophysics of a Stilbene Dimer.
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二苯乙烯二聚体的构象和光物理学。
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
V. Sundström
中科院分区：
文献类型：
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作者：
A. Ruseckas;E. Namdas;J. Lee;S. Mukamel;Shujun Wang;G. Bazan;V. Sundström
在四氢呋喃溶液中，准对二苯基[2.2]对环番烷的光物理研究表明，基态至少存在两种构象。光学间隙最小为3 eV的构象A的辐射寿命较短，为3.3 ns，而光学间隙约为0.3 eV的构象B在溶液中含量较高，辐射寿命约为B的10倍。从头算结果表明，基态能量相对于苯乙烯侧基团和对环烷基核在零位置附近的扭转角有一个浅的极小值，在扭转角为-21°时能量构象最小。在此基础上，将A和B分别指定为平面构象和扭曲构象。构象B表现出激发态吸收和荧光的部分衰减，时间常数从5到30ps，取决于激发光子的能量。我们将这归因于二苯乙烯部分的异构化，它最初将共轭保持在基态。异构化产物寿命长，易在溶液中积累。
Photophysical studies of pseudo-p-distyryl[2.2]paracyclophane, a model molecule of a stilbene dimer arranged in a brick-wall geometry, in tetrahydrofurane solution indicate the existence of at least two conformers in the ground state. The conformer A with the smallest optical gap of 3 eV has a short radiative lifetime of 3.3 ns, while the conformer B with an optical gap about 0.3 eV larger is much more abundant in solution and its radiative lifetime is about 10 times longer. Ab initio calculations show that the ground-state energy has a shallow minimum with respect to the torsional angle between the styryl side group and the paracyclophane core around the zero position, with the lowest energy conformation at a torsional angle of -21°. On this basis, A and B are assigned to flat and twisted conformations, respectively. Conformer B shows a partial decay of excited-state absorption and fluorescence with a time constant ranging from 5 to 30 ps, depending on excitation photon energy. We attribute this to isomerization of the stilbene moiety, which initially keeps conjugation in the ground state. The isomerization product is long-lived and tends to accumulate in solution.