The photostability of 5-hydroxymethylcytosine, a naturally occurring analogue of cytosine, is investigated by examining the excited state relaxation pathways of the molecule. Stationary points and minimum energy conical intersections are located at the state-averaged complete active space self consistent field (SA-CASSCF) level, and dynamic correlation is recovered using multi-reference perturbation theory (MRMP2) on the structures located with SA-CASSCF. MRMP2 is also used to compute single point energies along the linear least motion (LLM) path connecting the stationary structures. On the ππ* surface, the PES proceeds barrier-less from the Frank-Condon region to the minimum, after which a barrier of approximately 0.27 eV leads to a conical intersection between the ππ* state and the ground state. Deactivation through the nπ* state is also possible but with a much higher barrier. Solvent effects are also examined with the effective fragment potential (EFP) method.

Examining the excited state deactivation pathways of 5-hydroxymethylcytosine

253rd National Meeting (2017)

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