Ultrafast excited-state dynamics of isocytosine

摘要: The alternative nucleobase isocytosine has long been considered as a plausible component of hypothetical primordial informational polymers. To examine this hypothesis we investigated the excited-state dynamics two most abundant forms in gas phase (keto and enol). Our surface-hopping nonadiabatic molecular simulations employing algebraic diagrammatic construction to second order [ADC(2)] method for electronic structure calculations suggest that both tautomers undergo efficient radiationless deactivation ground state with time constants which amount τketo = 182 fs τenol 533 fs. dominant photorelaxation pathways correspond ring-puckering (ππ* surface) CO stretching/N–H tilting (nπ* enol keto respectively. Based on these findings, infer is relatively photostable compound terms resembles biologically relevant nucleobases. estimated S1 T1 intersystem crossing rate constant 8.02 × 1010 s−1 suggests triplet states might also play an important role overall tautomer. reliability ADC(2)-based was tested against multireference quantum-chemical potential limitations employed ADC(2) approach are briefly discussed.