Nonlinear optical properties for a class of hexa-peri-hexabenzocoronenechromophores: a computational investigation

Abstract

The systematic investigation of the linear and nonlinear optical properties on such a class of hexa-peri-hexabenzocoronene (HBC) chromophores is of significance for rationally designing two-photon absorption (TPA) materials. The results indicate that increasing the strength of electron-donating or accepting terminal groups leads to bathochromic-shift of the absorption band and enhancement of the TPA cross section (δ_max). For the molecules with fluorinated methylene and cyano substituents, replacement of a double bond by a triple bond in the conjugated linker produces the increase of δ_max, owing to the lower bond-length alternation and better rigidity of phenylene–ethynylene. In contrast, for the molecules with nitro groups, the similar replacement results in a slight decrease of δ_max because N-HBC-E-NO2 has excellent planarity architecture and effective electronic coupling. The TPA spectra are red-shifted and the δ_max values are enhanced as the number of branches increases. Thus, a solvatochromism effect has a positive influence on the TPA response of the nitryl compounds due to larger polarization of the nitro moiety. We have shed light on the linear relationship between the first hyperpolarizability and δ_max. These HBC derivatives hold potential as high-performance nonlinear optical materials.