Theoretical study of photophysical properties of bisindolylmaleimide derivatives.
Theoretical study of photophysical properties of bisindolylmaleimide derivatives.
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DOI：
10.1021/jp9043489
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发表时间：
2009-07
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影响因子：
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通讯作者：
Kenichiro Saita;Manabu Nakazono;K. Zaitsu;S. Nanbu;H. Sekiya
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作者：
Kenichiro Saita;Manabu Nakazono;K. Zaitsu;S. Nanbu;H. Sekiya
用从头算和多参考微扰理论研究了3，4-二（3-吲哚基）-1H-吡咯-2，5-二酮（arcyriarubin A）和吲哚并[2，3-a]吡咯并[3，4-c]咔唑-5，7-（6 H）-二酮（arcyriaflavin A）的分子物理性质.这些化合物被认为是从吲哚NH基团在非质子极性溶剂中去质子化的单价阴离子。分子轨道的分析表明，S（1）和S（2）态的电子结构是由吲哚部分和马来酰亚胺部分上的分子轨道之间的单电子或双电子激发所描述的。这表明，分子内电荷转移（ICT）转移可能发生的光激发。Arcyriarubin A阴离子的最低能量结构是扭曲的;吲哚和马来酰亚胺环之间的二面角分别为83.4度和20.2度，对于S（1）和S（0）状态。通过对最小能量路径沿着扭转角坐标的分析，探讨了S（1）态的发射过程。结果表明，随着扭转角的增加，斯托克斯位移的幅度增加，但振子强度降低。有人认为，实验观察到的荧光出现在S（1）态的能量最小值的道路上。在S（2）态激发后，通过S（1）-S（0）电子弛豫，得到了该化合物的斯托克斯位移发射。
The photophysical properties of two bisindolylmaleimide derivatives, 3,4-bis(3-indolyl)-1-H-pyrrole-2,5-dione (arcyriarubin A) and indolo[2,3-a]pyrrolo[3,4-c] carbazole-5,7-(6 H)-dione (arcyriaflavin A), are investigated by using ab initio molecular orbital (MO) and multireference perturbation theory. These compounds are suggested to exist as monovalent anions deprotonated from an indole NH group in aprotic polar solvents. The analysis of MOs shows that the electronic structures of the S(1) and S(2) states are described by the single- or double-electron excitation between the naturally localized MOs on an indole moiety and on the maleimide part. This indicates that the intramolecular charge transfer (ICT) transfer may occur by photoexcitation. The minimum-energy structure of the arcyriarubin A anion is twisted; the dihedral angles between the indole and maleimide rings are 83.4 degrees and 20.2 degrees for the S(1) and S(0) states, respectively. The analysis of the minimum energy path along the coordinate of the twist angle is performed to explore the emission process from the S(1) state. It has been shown that the magnitude of the Stokes shift increases with increasing the twist angle, but the oscillator strength decreases. It has been suggested that the experimentally observed fluorescence arises on the way toward the energy minimum of the S(1) state. The Stokes-shifted emission of arcyriaflavin A is contributed by the S(1)-S(0) electronic relaxation after the excitation in the S(2) state.