Spin Orbit Coupling in Charge Transfer States

Researchers from the University of Amsterdam investigated the effects of twisting an electron donor-acceptor molecule. The conformational dependence of the matrix element for spin–orbit coupling (SOCME) and of the electronic coupling for charge separation are determined for an electron donor–acceptor system containing a pyrene acceptor and a dimethylaniline donor. All ADF input files (in a repository) and three YouTube lectures on this work will help researchers to use a similar approach for their own work.

Thermally activated delayed fluorescence (TADF), photodynamic therapy, triplet light emitting diodes are all controlled by spin orbit coupling. Different kinetic and energetic aspects that play a role in the spin–orbit charge transfer intersystem crossing (SOCT-ISC) mechanism are discussed. This includes parameters related to initial charge separation and the charge recombination pathways using the Classical Marcus Theory of electron transfer. The spin–orbit coupling, which plays a significant role in charge recombination to the triplet state, can be probed by (TD)DFT, using the latter as a tool to understand and predict the SOCT-ISC mechanism. The matrix elements for spin–orbit coupling for acetone and 4-thio-thymine are used for benchmarking. (Time Dependent) Density Functional Theory (DFT and TDDFT) calculations have been performed with Amsterdam Density Functional (ADF).

spin-orbit coupling controlled ISC angle twist

Videos explaining SOCT-ISC in detail

Check out the following YouTube videos for more details and background!

Institutional lecture by René Williams
Literature Thesis presentation by Davita van Raamsdonk, see SI of manuscript
MSc Internship presentation by Shivan Bissesar

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Bissesar, D. M. E. van Raamsdonk, D. J. Gibbons, R. M. Williams, Spin Orbit Coupling in Orthogonal Charge Transfer States: (TD-)DFT of Pyrene—Dimethylaniline. Molecules 2022, 27 (3), 891.

Key concepts