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Download file# Investigating the Nonradiative Decay Pathway in the Excited State of Silepin Derivatives: A Study with Second-Order Multireference Perturbation Wavefunction Theory

journal contribution

posted on 2021-01-08, 17:11 authored by Naoto Inai, Daisuke Yokogawa, Takeshi YanaiThe fluorescence quantum yield for fluorescent organic molecules
is an important molecular property, and tuning it up is desired for
various applications. For the computational estimation of the fluorescence
quantum yield, the theoretical prediction of the nonradiative decay
rate constant has become an attractive subject of study. The rate
constant of thermally activated nonradiative decay is related to the
activation energy in the photoreaction; thus, the accuracy and reliability
of the excited-state potential energies in the quantum chemical computation
are critical. In this study, we employed a second-order multireference
perturbation wavefunction theory for studying the thermally activated
decay via conical intersection (CI) of 1,1-dimethyldibenzo[

*b*,*f*]silepin derivatives. The correlation between the computed activation energy to reach the CI geometry in the S_{1}state and the experimentally determined fluorescence quantum yield implied that silepins nonradiatively decay via the CI triggered by the twisting of the central C–C bond. Geometry optimization of the transition state using multireference perturbation theory drastically reduced the estimated activation energy. Our computation gave reasonable predictions of the activation free energies of photoexcited 1,1-dimethyldibenzo[*b*,*f*]silepin. The energy profiles and geometry optimizations using proper quantum chemical methods played a critical role in reliable estimation of the rate constant and fluorescence quantum yield.