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

Vivas, MG; Silva, DL; Rodriguez, RDF; Canuto, S; Malinge, J; Ishow, E; Mendonca, CR; De Boni, L JOURNAL OF PHYSICAL CHEMISTRY C 2015, 119, 12589-12597.

In this present paper, we investigate the relationship between the dynamic first-order hyperpolarizability (DFH, or beta(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 < NO2 < 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 beta(HRS) values exhibited pronounced enhancement from 56 x 10(-30) cm(5)/esu (EWG = CN) up to similar to 400 X 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 (2w = 532 nm) approaches, in energy, the lowest energy band of chromophores. Furthermore, our experimental results suggest that the CF3 group has a significant effect on the beta(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 beta(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).

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Paru le 11 mai 2015

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DOI: 10.1021/acs.jpcc.5b02386