HYPERPOLARIZABILITIES OF THE M-SUBSTITUENT PHENYL AMINE BASED CHROMOPHORES DETERMINED FROM THE HYPER-RAYLEIGH SCATTERING AND 2-PHOTON ABSORPTION INDUCED FLUORESCENCE

The technique of hyper-Rayleigh scattering is used to determine and co mpare the first hyperpolarizabilities (beta) of five structurally simi lar m-substituent phenyl-amine based chromophores using both internal and external standards. Contribution from the two photon absorption in duced fluorescence to the observed signal is carefully removed. The ch romophores with the m-substituted phenyl ring, that stabilizes the max imal charge-transfer state through resonance effect, are found to have larger static beta values and redshifted electronic absorption peaks (lambda(max)) compared with the para-nitroaniline (pNA) chromophore. T he electron-withdrawing m-substituent of the chromophore is found to h ave the effect of reducing both the beta and lambda(max) values. Its e ffect on beta is less pronounced when the pi-electron reservoir is lar ge, The enhancement of beta value and the redshift lambda(max) are obs erved to be consistent with the extent of the pi electron delocalizati on. (C) 1996 American Institute of Physics.