Heteroaryl oxenium ions have diverse and unusual low-energy electronic states.
Title | Heteroaryl oxenium ions have diverse and unusual low-energy electronic states. |
Publication Type | Journal Article |
Year of Publication | 2012 |
Authors | Hanway, Patrick J., and Winter Arthur H. |
Journal | The journal of physical chemistry. A |
Volume | 116 |
Issue | 37 |
Pagination | 9398-403 |
Date Published | 2012 Sep 20 |
ISSN | 1520-5215 |
Abstract | The electronic state orderings and energies of heteroaryl oxenium ions were computed using high-level CASPT2//CASSCF computations. We find that these ions have a number of diverse, low-energy configurations. Depending on the nature of the heteroaryl substituent, the lowest-energy configuration may be open-shell singlet, closed-shell singlet, or triplet, with further diversity found among the subtypes of these configurations. The 2- and 3-pyridinyl oxenium ions show small perturbations from the phenyl oxenium ion in electronic state orderings and energies, having closed-shell singlet ground states with significant gaps to an n,π* triplet state. In contrast, the 4-pyridinyl oxenium ion is computed to have a low-energy nitrenium ion-like triplet state. The pyrimidinyl oxenium ion is computed to have a near degeneracy between an open-shell singlet and triplet state, and the pyrizidinyl oxenium ion is computed to have a near-triple degeneracy between a closed-shell singlet state, an open-shell singlet state, and a triplet state. Therefore, the ground state of these latter heteroaryl oxenium ions cannot be predicted with certainty; in principle, reactivity from any of these states may be possible. These systems are of fundamental interest for probing the spin- and configuration-dependent reactivity of unusual electronic states for this important class of reactive intermediate. |
DOI | 10.1021/jp306817j |
Alternate Journal | J Phys Chem A |