Photo-rearrangement of N-substituted pyridinium and meta-alkoxypyridinium ions

Document Type

Article

Abstract

A computational study of the minimum-energy structures and transition states relevant to the photo-initiated rearrangement of N-substituted pyridinium and meta-alkoxypyridinium ions is reported. Density Functional Theory in the form of 6-31G(d) B3LYP computations has been used to determine the relative energies of the significant stationary points on the ground state potential energy surfaces, including the global minima, the bicyclic (prefulvene-like) and tricyclic (benzvalene-like) intermediates, and the connecting transition states. The S0, S1, and S2 potential energy surfaces have been mapped along a reaction path from the C2v-symmetry minimum on S1 to the bicyclic intermediate on S0 with multi-reference self-consistent-field computations. Two conical intersections are located along this path, the first occurs as the open-shell electron configuration becomes the ground state, and the second occurs as the closed-shell electron configuration of the bicyclic intermediate becomes the ground state. The impact of various N-substituents on the relative energies of the intermediates is also explored. Previously, experimental X-ray structures have firmly established the exo nature of the photohydration of N-substituted pyridinium and alkylpyridinium ions, however, endo solvation has been claimed for the photoaddition of alcohols to meta-alkoxypyridinium ions. The intermediate structures and energies reported here suggest that exo solvation should also be operative in the case of meta-alkoxypyridinium ions. © 2006 Elsevier B.V. All rights reserved.

Department(s)

Chemistry

Publication Title

Journal of Molecular Structure: THEOCHEM

Volume

807

Issue

1-3

First Page

25

Last Page

32

Publication Date

4-1-2007

DOI

10.1016/j.theochem.2006.12.001

ISSN

01661280

Comments

Student author: Kerri Grove, Chemistry

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