January 2, 2019
Journal Article

Calculations on 1,8-Naphthoquinone Predict that the Ground State of this Diradical Is a Singlet

Weston Borden
David Hrovat
Xue-Bin Wang
(12/12)CASPT2, (16/14)CASPT2, B3LYP, and CCSD(T) calculations have been carried out on 1,8-Naphthoquinone (1,8-NQ), in order 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. In contrast,CCSD(T) finds 3B2 to be the ground state, with 1A1 slightly higher in energy. Based on the comparisons of the singlet-triplet energy differences (?EST), calculated by CASPT2 and by CCSD(T) for two other non-Kekulé quinone diradicals, with the experimental values measured, by negative ion photoelectron spectroscopy (NIPES), it is predicted that NIPES experiments on 1,8-NQ•– will find that 1,8-NQ is a diradical with a singlet ground state.

Published: January 2, 2019

Hrovat D., X. Wang, and W. Borden. 2019. "Calculations on 1,8-Naphthoquinone Predict that the Ground State of this Diradical Is a Singlet." Journal of Computational Chemistry 40, no. 1:119-126. PNNL-SA-135146. doi:10.1002/jcc.25551