化学学报 ›› 2016, Vol. 74 ›› Issue (11): 902-909.DOI: 10.6023/A16080452 上一篇    下一篇

研究论文

有机分子聚集体中振动分辨光谱的激子耦合效应

李文强a, 彭谦b, 谢育俊c, 张天a, 帅志刚a   

  1. a 清华大学化学系 北京 100084;
    b 中国科学院化学研究所 北京 100190;
    c 武汉大学化学系 武汉 430072
  • 收稿日期:2016-08-30 出版日期:2016-11-15 发布日期:2016-11-24
  • 通讯作者: 彭谦, 帅志刚 E-mail:qpeng@iccas.ac.cn;zgshuai@tsinghua.edu.cn
  • 基金资助:

    项目受科技部973计划(013CB834703,2015CB65502,2013CB933503),国家自然科学基金(21473214,21290191,91233105)及中国科学院战略性先导科技专项(XDB12020200)资助.

Effect of Intermolecular Excited-state Interaction on Vibrationally Resolved Optical Spectra in Organic Molecular Aggregates

Li Wenqianga, Peng Qianb, Xie Yujunc, Zhang Tiana, Shuai Zhiganga   

  1. a Department of Chemistry, Tsinghua University, Beijing 100084;
    b Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190;
    c Department of Chemistry, Wuhan University, Wuhan 430072
  • Received:2016-08-30 Online:2016-11-15 Published:2016-11-24
  • Supported by:

    Project supported by the Ministry of Science and Technology of China through the 973 program (Grants 2013CB834703, 2015CB65502 and 2013CB933503), the National Natural Science Foundation of China (Grants 21473214, 21290191 and 91233105), and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant XDB12020200).

光谱是探究分子间相互作用及发光机理的有效手段.本工作采用Frenkel激子模型和量子力学/分子力学(QM/MM)方法系统研究了一系列聚集诱导发光(AIE)体系和传统荧光(非AIE)体系晶态下的吸收、发射光谱.结果表明,分子内电声子耦合(λ)与分子间激子耦合(J)竞争决定了晶态聚集体的光谱特性.在室温下,当J/λ值大于约0.17时,有机分子聚集体光谱的激子耦合效应将表现明显.例如,对于面对面排列的H聚集体,只有考虑激子耦合效应的理论计算光谱才与其实验光谱吻合很好,即相较于单分子光谱的吸收蓝移、发射减弱并红移.对于AIE体系,因为其J/λ值均小于0.17,AIE聚集体光谱特征主要是由分子内电声子耦合所主导,激子耦合可以忽略不计.

关键词: 有机分子聚集体, Frenkel激子模型, 电声子耦合, 激子耦合效应, QM/MM方法

The optical spectra are effective means to reveal the molecular interactions and the luminescent mechanism of the organic molecules in aggregates. Herein, we systematically investigate the crystalline state vibrationally resolved absorption and emission spectra for a series of AIEgens and non-AIEgens by considering intermolecular excited state interaction by using Frenkel-exciton model coupled with quantum mechanics and molecular mechanics (QM/MM) calculations. It is found that the competition between the intramolecular vibronic coupling (λ) and the intermolecular exciton coupling (J) governs the crystalline aggregate spectral characters. At room temperature, when J/λ value is larger than a critical value (ca. 0.17), the exciton coupling would have a large effect on the optical spectra. For face-to-face H-aggregates, only when both intermolecular electrostatic and excitonic couplings are considered, can one obtain calculated vibrationally resolved spectra and well reproduce the experimental results, namely, remarkable blue-shift in absorption but much less red-shift in emission when compared with the gas-phase. The optical spectra of the AIE-active aggregates are determined by the intramolecular vibronic coupling because the ratio J/λ is less than the critical value.

Key words: organic molecular aggregate, Frenkel exciton model, intramolecular vibronic coupling, intermolecular exciton coupling, QM/MM