title: Ab initio insight into ultrafast nonadiabatic decay of hypoxanthine: keto-N7H and keto-N9H tautomers.
abstract: Nonadiabatic dynamics simulations at the SA-CASSCF level were performed for the two most stable keto-N7H and keto-N9H tautomers of hypoxanthine in order to obtain deep insight into the lifetime of the optically bright S1((1)ππ*) excited state and the relevant decay mechanisms. Supporting calculations on the ground-state (S0) equilibrium structures and minima on the crossing seams of both tautomers were carried out at the MR-CIS and CASSCF levels. These studies indicate that there are four slightly different kinds of conical intersections in each tautomer, exhibiting a chiral character, each of which dominates a barrierless reaction pathway. Moreover, both tautomers reveal the ultrafast S1→ S0 decay, in which the S1 state of keto-N9H in the gas phase has a lifetime of 85.5 fs, whereas that of keto-N7H has a longer lifetime of 137.7 fs. An excellent agreement is found between the present results and the experimental value of 130 ± 20 fs in aqueous solution (Chen and Kohler, Phys. Chem. Chem. Phys., 2012, 14, 10677-10689).
authors.affiliation: State Key Laboratory for Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, PR China.
authors.forename: Xugeng
authors.initials: X
authors.lastname: Guo
authors.forename: Zhenggang
authors.initials: Z
authors.lastname: Lan
authors.forename: Zexing
authors.initials: Z
authors.lastname: Cao
mesh_terms: D005740:Gases / Q000737:chemistry; D006859:Hydrogen / Q000737:chemistry; D019271:Hypoxanthine / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D005740:Gases; D019271:Hypoxanthine; D006859:Hydrogen