Excited-State Diproton Transfer in [2,2’-Bipyridyl]-3,3’-diol: the Mechanism Is Sequential, Not Concerted

0329453 - ÚOCHB 2010 RIV US eng J - Journal Article
Plasser, F. - Barbatti, M. - Aquino, A. J. A. - Lischka, Hans
Excited-State Diproton Transfer in [2,2’-Bipyridyl]-3,3’-diol: the Mechanism Is Sequential, Not Concerted.
Journal of Physical Chemistry A. Roč. 113, č. 30 (2009), s. 8490-8499. ISSN 1089-5639. E-ISSN 1520-5215
R&D Projects: GA MŠMT LC512
Grant - others:Austrian Science Fund(AT) P18411-N19
Institutional research plan: CEZ:AV0Z40550506
Keywords : excited-state diproton transfer * on-the-fly dynamics simulations * sequential and concerted mechanisms
Subject RIV: CF - Physical ; Theoretical Chemistry
Impact factor: 2.899, year: 2009

The excited-state mono- and diproton transfer has been investigated in the S1 state RI-CC2 and TDDFT methods. These calculations show that the concerted diproton transfer in S1 proceeds along a ridge thus making this process unlikely. On-the-fly dynamics simulations performed at the RI-CC2 level confirm this picture. The present results shed new light on the interpretation of the experimental results. The simulations show that what has been experimentally determined as concerted transfer is in fact a combination of two sequential proton transfers separated by a small delay below the present experimental resolution. Both the forward and reverse reactions of a mono-/diketo equilibrium were found within the 300 fs period. Environmental effects will lead to a substantial cooling of the initially hot molecule and a concomitant decrease in the monoketo/diketo conversion rates, which will result in the experimentally observed overall time scale of 10 ps for the second proton transfer step.
Permanent Link: http://hdl.handle.net/11104/0005446