Hyperpolarizabilities of the m-substituent phenyl amine based chromophores determined from the hyper-Rayleigh scattering and two photon absorption induced fluorescence

Abstract

The technique of hyper‐Rayleigh scattering is used to determine and compare the first hyperpolarizabilities (β) of five structurally similar m‐substituent phenyl‐amine based chromophores using both internal and external standards. Contribution from the two photon absorption induced fluorescence to the observed signal is carefully removed. The chromophores with the m‐substituted phenyl ring, that stabilizes the maximal charge‐transfer state through resonance effect, are found to have larger static β values and redshifted electronic absorption peaks (λ_max) compared with the para‐nitroaniline (pNA) chromophore. The electron‐withdrawing m‐substituent of the chromophore is found to have the effect of reducing both the β and λ_max values. Its effect on β is less pronounced when the π‐electron reservoir is large. The enhancement of β value and the redshift λ_max are observed to be consistent with the extent of the π electron delocalization.