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The Effect of π-Stacking, H-Bonding, and Eectrostatic Interactions on the Ionization Energies of Nucleic Acid Bases Print
Sunday, 14 March 2010 00:00

A combined theoretical and experimental study of the ionized dimers of thymine and adenine, TT, AA, and AT, is presented. Experimentally observed and computed adiabatic and vertical ionization energies (IEs) for monomers and dimers as well as thresholds for the appearance of the protonated species are reported and analyzed. Non-covalent interactions strongly affect the observed IEs. The magnitude and the nature of the effect is different for different isomers of the dimers. The computations reveal that for TT, the largest changes in vertical IEs (0.4 eV) relative to the monomer occur in asymmetric H-bonded and symmetric -stacked isomers, whereas in the lowest-energy symmetric H-bonded dimer the shift in IEs is much smaller (0.2 eV). The origin of the shift and the character of the ionized states is different in asymmetric H-bonded and symmetric stacked isomers. ... Article Link (PDF)