Aggregation-Induced Emission: A Challenge for Computational Chemistry. the Example of TPA-BMO.

A multi-scale and multi-environment computational approach is proposed to study of the modulation of the emission behavior of the triphenylamine (Z)-4-benzylidene-2-methyloxazol-5(4H)-one (TPA-BMO) molecule [Tang et al., J. Phys. Chem. C,119, 21875 (2015)]. Going from (TD-)DFT calculations to classical Molecular Dynamics simulations through the hybrid ONIOM QM/QM’ approach and the in situ chemical polymerization methodology, we have rationalized distinct photophysical phenomena: (1) in low-polar solvents, a polarity-dependent solvatochromic effect as well as a modulation of the emission quantum yield, attributed to possible photophysical energy dissipation caused by low-frequency vibrational modes, (2) in the aggregate, a subtle competition between an excitonic coupling and a restriction of the intramolecular vibrations leading to an Aggregation-Induced Emission behavior, and (3) in the polymer matrix, an antagonist effect between the loss of global flexibility and the presence of vibrational modes similar to those observed in solution, explaining a similar emissive behavior within the polymer.