Excited State Energetics and Proton Transfer Barriers in Malonaldehyde

Document Type

Article

Journal/Book Title

Journal of Physical Chemistry

Publication Date

1994

Publisher

American Chemical Society

Volume

98

Issue

14

First Page

3582

Last Page

3587

Abstract

The ground and first four excited electronic states of malonaldehyde are examined by ab initio methods, using a variety of basis sets including 4-31G, 6-311G**, and 6-31+G**. The lowest-energy excited state is found to be ~T-T*, followed in order by 3n-~*, In**, and IT-*. At the CIS level, the proton-transfer barriers in the excited states are all higher than the ground-state barrier; the exception is IT-* for which the barrier is lower. An inverse correlation is noted between the height of each barrier and the strength of the intramolecular H bond. Correlation, when added via second-order Maller-Plesset perturbation theory, reduces the excitation energy of each state. As is typical of the ground state, electron correlation lowers the proton-transfer barrier in the excited states as well. Their correlated barriers are all smaller than that in the ground state. Indeed, in a number of excited states, the transfer potential is likely to contain only a single symmetric minimum.

Comments

Originally published by American Chemical Society in the Journal of Physical Chemistry.

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