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Purine Nucleobases: The Relationship Between Structure and Dynamics

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A lasting effort of our group has been to elucidate the relationship between structure and dynamics of the purine canonical and alternative nucleobases. There are only slight structural differences distinguishing the two yet drastic differences in lifetimes and excited state decay pathways are seen. For the canonical nucleobases have extremely fast excited state lifetimes while the alternative forms have much slower relaxation pathways. The base chromophore purine itself has a long lifetime so it is only through structural additions that a fast lifetime can be achieved. Our focus has centered only on amino- and oxo- substitutions at the 2 and 6 position. Fast relaxation dynamics often rely on a conical intersection to quickly relax out of an excited state and conical intersections require a deformation in the molecular structure which most often happens around the 2 or 6 position. Adding substituents to those positions greatly affects the accessibility of the conical intersections, consequently determining the lifetime.  While molecules like adenine, 2-AP, guanine and purine have been well studied both experimentally and theoretically. Isoguanine has been studied recently. We are focusing on adding data concerning the other alternative nucleobases to see what patters emerge between structure and dynamics.

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