Experimental and theoretical investigation of the first-order hyperpolarizability of a class of triarylamine derivatives

Abstract

This paper reports on the static and dynamic first-order hyperpolarizabilities of a class of push-pull octupolar triarylamine derivatives dissolved in toluene. We have combined hyper-Rayleigh scattering experiment and the coupled perturbed Hartree-Fock method implemented at the Density Functional Theory (DFT) level of theory to determine the static and dynamic (at 1064 nm) first-order hyperpolarizability (βHRS) of nine triarylamine derivatives with distinct electron-withdrawing groups. In four of these derivatives, an azoaromatic unit is inserted and a pronounceable increase of the first-order hyperpolarizability is reported. Based on the theoretical results, the dipolar/octupolar character of the derivatives is determined. By using a polarizable continuum model in combination with the DFT calculations, it was found that although solvated in an aprotic and low dielectric constant solvent, due to solvent-induced polarization and the frequency dispersion effect, the environment substantially affects the first-order hyperpolarizability of all derivatives investigated. This statement is supported due to the solvent effects to be essential for the better agreement between theoretical results and experimental data concerning the dynamic first-order hyperpolarizability of the derivatives. The first-order hyperpolarizability of the derivatives was also modeled using the two- and three-level models, where the relationship between static and dynamic first hyperpolarizabilities is given by a frequency dispersion model. Using this approach, it was verified that the dynamic first hyperpolarizability of the derivatives is satisfactorily reproduced by the two-level model and that, in the case of the derivatives with an azoaromatic unit, the use of a damped few-level model is essential for, considering also the molecular size of such derivatives, a good quantitative agreement between theoretical results and experimental data to be observed.

Photoinduced Intramolecular Charge Transfer and Hyperpolarizability Coefficient in Push‐Pull Pyridinium Salts with Increasing Strength of the Acceptor Group

“…In fact, the β 0 value of 330×10 −30 esu −1 cm 5 derived for A doubles or triples when the N ‐methyl substituent is replaced by the N ‐pyrimidin‐2yl ( B ) or N ‐dinitrophenyl ( C ), respectively (Table ). However, the β 0 values estimated for the present investigated salts resulted high if compared with analogous pyridinium‐based chromophores, and generally comparable with those of systems considered actual NLO materials ,. The significant quadratic NLO activity exhibited by A and particularly by B and C , can be explained taking into account the presence of the very strong electron‐donor piperidine and the positively charged N ‐pyrimidin‐2yl‐ and N ‐dinitrophenyl‐pyridinium as strong electron‐acceptors connected by electron‐rich diene and dithiophenes chain.…”

“…This method allowed the difference between the excited and ground state dipole moment (Δμ) as well as the dynamic (β CT ) and static (β 0 ) hyperpolarizability coefficients to be derived. The β values have been found sizable and comparable to those of systems considered de facto NLO materials ,. The comparison between the A properties and those previously retrieved for the analogous ortho‐substituted salt (namely 1‐methyl‐2‐{( E )‐2‐[5′‐(piperidin‐1‐yl)‐2,2′‐bithiophen‐5‐yl]ethenyl}pyridinium iodide) by the same solvatochromic study, evidenced lower β values for the latter (halved β CT and β 0 reduced by ca .…”

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

“…46 The CF 3 EWG series exhibit a considerable increase in β at 1064 nm (at least, 30% higher) as compared to their homologous tBu·EWG. 46 These observations suggest the effective participation of the CF 3 groups on the charge transfer between the triarylamine core and the EWG group.…”

“…46 The CF 3 EWG series exhibit a considerable increase in β at 1064 nm (at least, 30% higher) as compared to their homologous tBu·EWG. 46 These observations suggest the effective participation of the CF 3 groups on the charge transfer between the triarylamine core and the EWG group. Indeed, CF 3 EWG series exhibit a bathochromic and hypsochromic shift of their UV and visible absorption bands, respectively, corroborating the electronic participation of the CF 3 groups.…”

Não linearidades de segunda e terceira ordem de sistemas moleculares ramificados

“…108 É importante mencionar que a hiperpolarizabilidade de primeira ordem é um parâmetro físico apresentado em moléculas não centrossimétricas, em que a simetria dos estados electrônicos não é bem definida. 109 CN-1 com a CN-3 2CN-1, 2CN-2, 2CN-3 Finalmente, na Fig. 5.6 apresentamos os espectros de A2F para as moléculas do grupo CNO 2 e CNS.…”