Interpreting the First-Order Electronic Hyperpolarizability for a Series of Octupolar Push–Pull Triarylamine Molecules Containing Trifluoromethyl

In this present paper, we investigate the relationship between the dynamic first-order hyperpolarizability (DFH, or β HRS ) of a triarylamine core bearing two 3,3′-bis(trifluoromethyl)phenyl arms and the nature of a third group containing distinct electron-withdrawing strength (H < CN < CHO < NO 2 < Cyet < Vin). For that, we have combined hyper-Rayleigh scattering (HRS) experiments with picosecond pulse train at 1064 nm and quantum chemical calculations at the density functional theory (DFT) level. The β HRS values exhibited pronounced enhancement from 56 × 10 –30 cm 5 /esu (EWG = CN) up to ∼400 × 10 –30 cm 5 /esu (EWG = Vin) due to the increase in the degree of donor–acceptor charge transfer concomitant with the intensification of the resonance enhancement effect observed when the scattered photon (2ω = 532 nm) approaches, in energy, the lowest energy band of chromophores. Furthermore, our experimental results suggest that the CF 3 group has a significant effect on the β HRS, since we observed a considerable increase in this parameter (at least 30% higher) for CF 3 EWG molecules as compared to their homologous tBu·EWG derivatives, recently investigated. Finally, the β HRS results were compared with theoretical results provided by the coupled perturbed Hartree–Fock method implemented at the DFT level of theory and combined with a polarizable continuum model to take into account the solvent environment. The theoretical results allowed us to evaluate the effects of solvent-induced polarization and frequency dispersion on the first-order hyperpolarizability of the molecules and their molecular anisotropy (or dipolar/octupolar contributions).