Calculations on 1,8-naphthoquinone predict that the ground state of this diradical is a singlet

Abstract

(12/12)CASPT2, (16/14)CASPT2, B3LYP, and CCSD(T) calculations have been carried out on 1,8-Naphthoquinone (1,8-NQ), to predict the low-lying electronic states and their relative energies in this non-Kekulé quinone diradical. CASPT2 predicts a 1A1 ground state, with three other electronic states—3B2, 3B1, and 1B1—within about 10 kcal/mol of the ground state in energy. On the basis of the results of these calculations, it is predicted that NIPES experiments on 1,8-NQ•– will find that 1,8-NQ is a diradical with a singlet ground state. © 2018 Wiley Periodicals, Inc.