2014, Bekçioǧlu, G., Allolio, C., Ekimova, M., Nibbering, E.T.J., Sebastiani, D.

We investigate the acid-base proton exchange reaction in a microsolvated bifunctional chromophore by means of quantum chemical calculations. The UV/vis spectroscopy shows that equilibrium of the keto-and enol-forms in the electronic ground state is shifted to the keto conformation in the excited state. A previously unknown mechanism involving a hydroxide ion transport along a short water wire is characterized energetically, which turns out to be competitive with the commonly assumed proton transport. Both mechanisms are shown to have a concerted character, as opposed to a step-wise mechanism. The alternative mechanism of a hydrogen atom transport is critically examined, and evidence for strong solvent dependence is presented. Specifically, we observe electrostatic destabilization of the corresponding πσ* state by the aqueous solvent. As a consequence, no conical intersections are found along the reaction pathway.

2013, Greve, C., Preketes, N.K., Costard, R., Koeppe, B., Fidder, H., Nibbering, E.T.J., Temps, F., Mukamel, S., Elsaesser, T.

We characterize diagonal and off-diagonal anharmonicities of N-H stretching vibrations in adenosine and thymidine monomers and in A•T-base pairs in chloroform solution, showing the important role of coupling between vibrationally excited N-H stretching states.

2013, Ghosh, H.N., Adamczyk, K., Verma, S., Dreyer, J., Nibbering, E.T.J.

Femtosecond infrared absorption studies strongly suggest that photoexcited 9-anthranol takes part in an ultrafast electron transfer (ET) reaction in electron-donating triethylamine solvent, but that ultrafast proton coupled electron transfer (PCET) occurs in diethylamine solvent.

2013, Prémont-Schwarz, M., Xiao, D., Sekharan, S., Batista, V.S., Nibbering, E.T.J.

We characterize the transient solvent-dependent OH-stretching frequency shifts of photoacid 2-naphthol hydrogen-bonded with CH3CN in the S0- and S1-states using a combined experimental and theoretical approach, and disentangle specific hydrogen-bonding contributions from nonspecific dielectric response.