Dynamical Excimer Formation in Rigid Carbazolophane via Charge Transfer State
Dynamical Excimer Formation in Rigid Carbazolophane via Charge Transfer State
复制标题
通过电荷转移态在刚性卡巴唑啉中动态形成准分子
作者：
Tamai;Y.; Ohkita;H.; Shimada;J.; Benten;H.; Ito;S.; Yamanaka;S.; Hisada;K.; Tani;K.; Kubono;K.; Shinmyozu;T.
用时间分辨光谱方法和计算方法研究了二氧杂[3.3](3，6)咔唑罗番分子内准分子的形成动力学。在基态下，CZOCz中最稳定的构象是两个咔唑环反平行排列的反构象。即使在溶液加热到150℃后，也没有观察到其他异构体，尽管通过分子力学计算发现了三个特征异构体：第一个是反构象，第二个是两个咔唑环沿同一方向堆积的同位异构体，第三个是整形异构体，其中两个咔唑环以边对面的几何形状排列。由于反构象的存在，在基态下CZOCz的发色相互作用可以忽略不计。尽管如此，分子内准分子是在乙腈(MeCN)溶液中动态形成的，这表明在激发态下发生了强烈的发色间相互作用和反式构象的异构化。CZOCz中准分子的形成在极性溶剂中比在弱极性溶剂中更有效，这表明电荷转移(CT)态对准分子形成的贡献。通过两个咔唑环之间的分子轨道相互作用讨论了激发态的稳定性。根据分子内构象的CT特征，讨论了溶剂-极性诱导的准分子的形成。
Formation dynamics of intramolecular excimer in dioxa[3.3](3,6)carbazolophane (CzOCz) was studied by time-resolved spectroscopic methods and computational calculations. In the ground state, the most stable conformer in CzOCz is theanti-conformation where two carbazole rings are in antiparallel alignment. No other isomers were observed even after the solution was heated up to 150 °C, although three characteristic isomers were found by the molecular mechanics calculation: the first is theanti-conformer, the second is thesyn-conformer where two carbazole rings are stacked in the same direction, and the third is theint-conformer where two carbazole rings are aligned in an edge-to-face geometry. Because of theanti-conformation, the interchromophoric interaction in CzOCz is negligible in the ground state. Nonetheless, the intramolecular excimer in CzOCz was dynamically formed in an acetonitrile (MeCN) solution, indicating strong interchromophoric interaction and the isomerization from theanti- tosyn-conformation in the excited state. The excimer formation in CzOCz is more efficient in polar solvents than in less polar solvents, suggesting the contribution of the charge transfer (CT) state to the excimer formation. The stabilization in the excited state is discussed in terms of molecular orbital interaction between two carbazole rings. The solvent-polarity-induced excimer formation is discussed in terms of the CT character in theint-conformation.