CHAPTER 7. Nucleobases as Molecular Fossils of Prebiotic Photochemistry: Excited-state Dynamics of C2 and C6 Substituted Purines

The tautomer‐specific excited state dynamics of 2,6‐diaminopurine using resonance‐enhanced multiphoton ionization and quantum chemical calculations

“…11. However, the effects of amino and oxo C2 and C6 substitutions are not additive and the mechanisms for each combination need to be individually described 38 . This conclusion is in line with the work of Martinez‐Fernandez et al 19 .…”

“…However, the effects of amino and oxo C2 and C6 substitutions are not additive and the mechanisms for each combination need to be individually described. 38 This conclusion is in line with the work of Martinez-Fernandez et al 19 who examined how addition of a single amino or oxo group affects photostability and derived a mechanistic understanding of this effect. Their study is limited to purines with a single substituent, as doubly substituted purines further complicate their mechanism.…”

“…Structural motifs do not always predict trends in potential energy surfaces and the effects of substitutions do not necessarily add up 38 . Potential energy surfaces are subtly influenced by molecular structure, and the photochemistry of 2,6‐dAP (see Scheme 1) cannot be simply understood as a combination of the pathways available for 2AP and 6AP.…”

Understanding How a New Hachimoji Nucleobase Alters Photodynamics of Genetic Building Blocks†

“…The internal conversion back to the ground state proceeds through conical intersections, which occur at parts of the potential energy surface with nonequilibrium nuclear coordinates (28). In other words, the process involves deformations of the molecular structure, explaining the exquisite dependence of photostability on even small variations between similar molecules (29,30).…”

“…The internal conversion back to the ground state proceeds through conical intersections, which occur at parts of the potential energy surface with nonequilibrium nuclear coordinates (28). In other words, the process involves deformations of the molecular structure, explaining the exquisite dependence of photostability on even small variations between similar molecules (29,30). This issue's paper by Krul et al examines the excited state dynamics of one of the hajimochi bases, labeled P. With femtosecond transient absorption spectroscopy in different solvents the authors find excited state lifetimes that are 10-30 times longer than those in the closest canonical analog, guanine, and fluorescence quantum yields that are an order of magnitude larger.…”