Can Anti-Aufbau DFT Calculations Estimate Singlet Excited State Aromaticity? Correspondence on “Dibenzoarsepins: Planarization of 8π-Electron System in the Lowest Singlet Excited State” |
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Authors: | Dr Peter B Karadakov Dr Shohei Saito |
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Institution: | 1. Department of Chemistry, University of York, Heslington, York, YO10 5DD UK;2. Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto, 606-8502 Japan |
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Abstract: | The simple anti-aufbau DFT approach for estimating singlet excited state aromaticity suggested in a recent Communication published in this journal is shown to produce incorrect results because it targets a linear combination of the singlet and triplet configurations involving the HOMO and LUMO rather than the first singlet excited state. If the S1 state of a molecule is dominated by the HOMO→LUMO excitation, a comparably simple but theoretically consistent and qualitatively correct approximation to the S1 wavefunction can be achieved by performing a small “two electrons in two orbitals” CASSCF(2,2) calculation which can be followed by the evaluation of magnetic aromaticity criteria such as NICS. |
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Keywords: | anti-aufbau DFT arsepines Baird's rule excited-state aromaticity NICS |
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