LAUSR

Abstract To study the relationship between the [2 + 2] photocycloaddition reactivities of 1,4-cyclohexadiene derivatives (1,4-CHDs) and their structures, photophysical properties of a series of 1,4-CHDs were studied experimentally and by performing theoretical calculations. Specifically, UV-Vis absorption spectra of these compounds in diluted solutions were acquired and the theoretical calculations were performed at the density functional theory (DFT) level. Their UV-Vis absorption maxima were found to be related to the substituents on the 1,4-cyclohexadiene ring. To describe the [2 + 2] photocycloaddition reactivities of the 1,4-CHDs, time-dependent density functional theory (TDDFT) was used to optimize their ground- and excited-state structures, and their electronic excitation energies were calculated at the M062X/def-TZVP level. Frontier molecular orbitals and electron-hole distribution analyses were used to illustrate the electron transition modes of the 1,4-CHDs. The differences between the ground- and excited-state structures of the different 1,4-CHDs were characterized by carrying out a root-mean-square-deviation (RMSD) analysis. The results showed that the photophysical properties of 1,4-CHDs are meaningful for explaining their [2 + 2] photocycloaddition reactivities.