Intersystem crossing dynamics in thiobases studied by time-resolved photoelectron spectroscopy: tautomer aspects

Sulfur substitution of an oxygen atom in the canonical nucleobases deactivates ultrafast internal conversion pathways back to the ground state and instead triplet states are populated with high quantum yields. To date gas-phase studies into the photophysics of thiobases have primarily focused on thiouracils and revealed a central role of the thiocarbonyl group in mediating the electronic relaxation dynamics. Extending this work to thiocytosine, which exists purely in its thiol form in a gas-phase environment, we investigate the photophysics of a thiobase from a different tautomer perspective.