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Can Anti‐Aufbau DFT Calculations Estimate Singlet Excited State Aromaticity? Correspondence on “Dibenzoarsepins: Planarization of 8π‐Electron System in the Lowest Singlet Excited State”
Author(s) -
Karadakov Peter B.,
Saito Shohei
Publication year - 2020
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.202001934
Subject(s) - chemical mechanical planarization , excited state , singlet state , aromaticity , state (computer science) , singlet fission , atomic physics , physics , computational chemistry , chemistry , materials science , quantum mechanics , molecule , computer science , nanotechnology , algorithm , layer (electronics)
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 S 1 state of a molecule is dominated by the HOMO→LUMO excitation, a comparably simple but theoretically consistent and qualitatively correct approximation to the S 1 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.