Theoretical and Experimental Studies on the Ground- and Excited-State Dipole Moments of 1,4-Naphthoquinone and Its Derivatives

Abstract

Abstract The dipole moments of the ground- and excited-states of 1,4-naphthoquinone (1), 2-chloro-1,4-naphthoquinone (2), 2-bromo-1,4-naphthoquinone (3), 2-methyl-1,4-naphthoquinone (4), 2,3-dichloro-1,4-naphthoquinone (5), 2,3-dibromo-1,4-naphthoquinone (6), 2-hydroxy-1,4-naphthoquinone (7), 3-chloro-2-hydroxy-1,4-naphthoquinone (8), 3-bromo-2-hydroxy-1,4-naphthoquinone (9), and 2-hydroxy-3-methyl-1,4-naphthoquinone (10) were studied from both experimental and theoretical perspectives. For the ground states, the dipole moments of compounds 5, 8, and 9 were determined experimentally in dilute solutions (via Debye’s method), and compared with those of the other compounds 1–4, 6, 7, and 10 which we had already determined. The density functional theory calculations were also performed, revealing a positive correlation with the experimental results. For the excited states, however, the dipole moments of the excited states of compounds 1–10 have not yet been studied. In this work, we determined the dipole moments of some of the lower excited states of these compounds using the spectroscopic method. Results revealed the determined excited-state dipole moments exceeded those of the ground state, a finding also supported by the configuration interaction involving one-electron excitations only.