Acetylation makes the difference: a joint experimental and theoretical study on low-lying electronically excited states of 9H-adenine and 9-acetyladenine.

Vibronic spectra of 9H-adenine, 9-acetyladenine and several alkyladenines have been recorded by resonant two-photon ionization spectroscopy of the laser-desorbed molecules, entrained in a molecular beam. While adenine and the alkyladenines exhibit similar electronic spectra, 9-acetyladenine behaves considerably different. Theoretical absorption spectra of 9H-adenine and 9-acetyladenine were calculated using the combined density functional theory/multi-reference configuration interaction approach and using second order coupled cluster theory, in order to explain striking differences in the experimental spectra. The major differences between the 9H-adenine and the 9-acetyladenine absorption spectra can be traced back to the different configurations, which contribute to the excitations, both of the lowest ππ* and the nπ* states. While the excitations in 9H-adenine are localized in the chromophore, they show considerable charge transfer character from the chromophore to the acetyl group in the case of 9-acetyladenine.

Citation

Gernot Engler, Kai Seefeld, Michael Schmitt, Jörg Tatchen, Oliver Grotkopp, Thomas J J Müller, Karl Kleinermanns. Acetylation makes the difference: a joint experimental and theoretical study on low-lying electronically excited states of 9H-adenine and 9-acetyladenine. Physical chemistry chemical physics : PCCP. 2013 Jan 21;15(3):1025-31

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PMID: 23223195

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