Key Role of Electronic and Structural Properties in Regulating Intersystem Crossing: An In-Depth Investigation on Naphthalene-Diimide Triads for Thermally Activated Delayed Fluorescence Applications
Federico Coppola, Mushraf Hussain, Jianzhang Zhao, Ahmed M. El‐Zohry, Mariachiara Pastore
Abstract
We report an extensive theoretical investigation of the photophysical properties of new carbazole core-substituted naphthalene-diimide dyes to elucidate the effects of different donor–acceptor arrangements on the direct and reverse intersystem crossing rates. These dyes were recently experimentally characterized using steady-state and time-resolved spectroscopy ( J. Phys. Chem. B 2021, 125, 10813). We analyzed the molecular structures of ground states, singlet and triplet excited states, excitation energies, orbital characteristics, and spin–orbit couplings using density functional theory (DFT)/time-dependent DFT calculations to determine the rates of the electronic spin-flip processes. Our findings reveal how different donor–acceptor configurations, by modulating ground and excited state conformational dynamics, may significantly influence the energetic landscape of singlet and triplet electronic states, their nature, and thus the extent of spin–orbit couplings, finally impacting the intersystem crossing rate constants and the reverse ones for thermally activated delayed fluorescence applications.