Quantitative Prediction of Aggregation‐Induced Emission: A Full Quantum Mechanical Approach to the Optical Spectra

Full quantum mechanical (FQM) calculation of the excited state of aggregation-induced emission (AIE) materials is highly sought but still a challenging task. Herein, we employed the recently developed electrostatically embedded generalized molecular fractionation (EE-GMF) method, a method based on the systematic fragmentation approach, to predict, for the first time, the spectra of a prototype AIE fluorophore: di( p -methoxylphenyl) dibenzofulvene (FTPE). Compared to the single molecular or QM/MM calculations, the EE-GMF method can significantly improve the accuracy, nearly reproducing the experimental optical spectra of the FTPE in both condensed phases. Importantly, we show that the conventional restriction of intramolecular rotation (RIR) mechanism cannot fully account for AIE, whereas the two-body intermolecular quantum mechanical interaction plays a crucial role in AIE. The success in quantitative predicting optical properties of AIE systems not only validates the FQM fragmentation approach, but also enables more effective design of new AIE materials with novel optical properties.