DETERMINATION OF THE FIRST HYPERPOLARIZABILITIES OF OCTUPOLAR MOLECULAR-IONS MADE FROM SYMMETRICAL CYANINE DYES

Symmetric cyanine dyes of the kind Me(2)N(+)=CH-(CH=CH)(n)-NMe(2) norm ally exhibit no first hyperpolarizabilities beta but have relatively l ong absorption wavelengths. Therefore they are not suitable NLO chromo phores for second-order applications. However, if these chromophores a re converted into octupolar molecules either by coupling an extra aldi minium group onto the dye molecule or by grafting three vinamidinium u nits onto a benzene ring, NLO chromophores with considerable first hyp erpolarizabilities are obtained. To prove this, the beta values of bot h kinds of octupoles have been determined via hyper-Rayleigh scatterin g in solution at 1064 nm.