Spin-restricted descriptions of singlet oxygen reactions from XMS-CASPT2 benchmarks

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Winslow, M., Hazelby, A. and Robinson, D. ORCID: 0000-0003-2760-7163, 2024. Spin-restricted descriptions of singlet oxygen reactions from XMS-CASPT2 benchmarks. The Journal of Physical Chemistry A. ISSN 1089-5639

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Official URL: https://doi.org/10.1021/acs.jpca.4c00744

Abstract

Reactions of singlet oxygen are numerous, some of which are desired but many are unwanted. Therefore, the ability to correctly predict and interpret this reactivity for complex molecular systems is essential to our understanding of singlet oxygen reactions. DFT is widely used for predicting many reactions but is not suited to degenerate electronic structures; application to isolated singlet oxygen often uses the spin-unrestricted formalism, which results in severe spin contamination. In this work, we demonstrate that spin-restricted DFT can correctly describe the reaction pathway for four prototypical singlet oxygen reactions. By careful benchmarking with XMS-CASPT2, we show that, from the first transition state onward, the degeneracy of the 1Δg state is broken due to differing interactions of the (degenerate) π* orbitals with the organic substrate; this result is well replicated with DFT. These findings demonstrate the utility of using spin-restricted DFT to explore reactions, opening the way to confidently use this computationally efficient method for molecular systems of medium to large organic molecules.

Item Type:

Journal article

Publication Title:

The Journal of Physical Chemistry A

Creators:

Winslow, M., Hazelby, A. and Robinson, D.

Publisher:

American Chemical Society

Date:

13 May 2024

ISSN:

1089-5639