The Coulomb Explosion Imaging Method and Excited–State Proton–Transfer Reactions

Abstract

Conference; The study of the 7-azaindole mol., while not complete, has yielded much information on intermediate states, proton transfer, and solvent effects on reactions. The study of proton-transfer reactions is important since they can provide a solid foundation for the complete understanding of biol. systems. The model base pair, 7- azaindole dimer, gives insight into the behavior of actual base pairs. Solvent-effect expts. are particularly important with regard to the understanding of biol. systems due to the ubiquitous nature of water. Cluster science has long been used to gain insights into condensed-phase properties while investigating gas-phase species. By clustering 7-azaindole with water, information is garnered concerning the role of solvation in proton-transfer reactions. In the case of the 7-azaindole dimer, the addn. of water mols. has been found to result in an increase in the rate of proton transfer. Further solvation of the dimer provides insight as to why the 7-azaindole cannot be studied in polar media. As the solvation is discretely increased, a transition point is reached, at which a conformational change may occur that shifts the planar dimer into a stacked structure. Further solvation may completely isolate the two moieties of the dimer, so as to directly mimic the bulk soln. case. The 7-azaindole dimer also provides an ideal system for the use of the Coulomb explosion imaging method and allows direct evidence of the intermediate state to be garnered. CEIM offers an alternative technique for interrogating the dynamics of various reactions. In reactions where there is a potential for a step-wise vs. a concerted step mechanism, CEIM offers a complementary technique to traditional pump-probe spectroscopy. [on SciFinder (R)]