文摘
Calculations on donor-acceptor molecular pairs of tetraalkylammonium halide/carbon tetrabromide complexesare provided to investigate structure/property-related linear and nonlinear optical properties by using the time-dependent density functional theory technique coupled with the sum-over-states method. The calculated energiesof the first allowed electronic transition decrease, and the nonresonant third-order polarizabilities at the THG,EFISHG, and DFWM optical processes increase progressively from [DBU-H+Br-·CBr4] to [NPr4Br·CBr4]to [NMe4Br·CBr4]. The obtained electronic absorption spectra show a progressive red shift with increasingdonor strength from Cl to I for [NR4h·CBr4] (h = Cl, Br, and I). The charge transfers from the halogen donorto the carbon tetrabromide acceptor make significant contributions to the electronic absorption spectra in thelow-energy zone and the third-order polarizabilities in the nonresonant frequency region. The counterionindirectly affects the electronic absorption and third-order polarizability spectra through the interactions betweenthe donor and acceptor.