title: Theoretical insights into the aggregation-induced emission by hydrogen bonding: a QM/MM study.
abstract: We investigate the excited-state decay processes for the 3-(2-cyano-2- phenylethenyl-Z)-NH-indole (CPEI) in the solid phase through combined quantum mechanics and molecular mechanics (QM/MM) and vibration correlation formalisms for radiative and nonradiative decay rates, coupled with time-dependent density functional theory (TDDFT). By comparing the isolated CPEI molecule and the molecule-in-cluster, we show that the molecular packing through intermolecular hydrogen-bonding interactions can hinder the excited-state nonradiative decay and thus enhance the fluorescence efficiency in the solid phase. Aggregation effect is shown to block the nonradiative decay process through hindering the low-frequency vibration motions. The fluorescence quantum yields for both isolated molecule and aggregation are predicted to be insensitive to temperature due to the hydrogen-bonding nature, and their values at room temperature are consistent with the experiment.
authors.affiliation: MOE Key Laboratory of Organic OptoElectronics and Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing 100084, People's Republic of China.
authors.forename: Qunyan
authors.initials: Q
authors.lastname: Wu
authors.forename: Qian
authors.initials: Q
authors.lastname: Peng
authors.forename: Yingli
authors.initials: Y
authors.lastname: Niu
authors.forename: Xing
authors.initials: X
authors.lastname: Gao
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Shuai