The Origin of the Emission Properties of it-Conjugated Molecules that have an Acid-responsive Benzimidazole Unit
The Origin of the Emission Properties of it-Conjugated Molecules that have an Acid-responsive Benzimidazole Unit
复制标题
具有酸响应性苯并咪唑单元的共轭分子发射特性的起源
DOI：
10.1002/ajoc.201200203
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发表时间：
2013
影响因子：
2.7
通讯作者：
Toshifumi Inouchi
中科院分区：
文献类型：
--
作者：
小宮成義;他;Toshifumi Inouchi
本文研究了具有酸响应性N-甲基苯并咪唑单元的π-共轭分子的电子物理性质，特别是发射性质，并与T-型交叉共轭分子和线性共轭分子进行了比较。X射线晶体结构和基于DFT计算的优化结构表明，即使在质子化后，2-噻吩基-N-苯并咪唑结构也具有平面构象，其中分子内S-N和NH-S相互作用分别负责平面结构的稳定。尽管在基态下是平面的，T形交叉共轭分子表现出响应于质子化的扭曲分子内电荷转移（TICT）发射，而相应的没有水平π系统的线性共轭分子不具有电荷转移状态。HOMO和LUMO的前沿分子轨道的分离的差异和通过DFT计算预测的围绕噻吩基环的旋转的能垒解释了具有质子化苯并咪唑单元的线性和交叉共轭分子之间的发射衰减过程的差异。一个正交分配的π共轭系统似乎是必不可少的质子化后的TICT特征的出现在HOMO和LUMO的分子轨道的分离，以及易于旋转。
The photophysical properties, especially the emission properties, of π‐conjugated molecules with an acid‐responsiveN‐methylbenzimidazole unit have been characterized and compared between T‐shaped cross‐conjugated and linear conjugated molecules. X‐ray crystal structures and optimized structures based on DFT calculations suggest a planar conformation of the 2‐thienyl‐N‐benzimidazole structure even after protonation where intramolecular S–N and NH–S interactions, respectively, are responsible for the stabilization of planar structures. Despite the planarity in the ground state, the T‐shaped cross‐conjugated molecules exhibit the twisted intramolecular charge‐transfer (TICT) emission in response to protonation, whereas the corresponding linear conjugated molecule without a horizontal π‐system does not have a charge‐transfer state. The difference in the separation of frontier molecular orbitals of the HOMO and LUMO and the energy barrier of the rotation about the thienyl ring predicted by the DFT calculations accounts for the difference in the emission decay process between the linear and cross‐conjugated molecules with a protonated benzimidazole unit. An orthogonally allocated π‐conjugated system appears to be essential for the emergence of TICT characteristics upon protonation in terms of the separation of molecular orbitals of the HOMOs and LUMOs, as well as the ease of rotation.