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

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 (λmax) 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 λmax values. Its effect on β is less pronounced when the π-electron reservoir is large. The enhancement of β value and the redshift λmax are observed to be consistent with the extent of the π electron delocalization.