Determination of the molecular first-order hyperpolarizabilities of six stilbazolium-like dyes in solid state and the solvent effects

By using the solvatochromism, we have studied the solvent effects on the molecular first-order hyperpolarizabilities of six stilbazolium-like dyes: trans-4-( N, N-dimethylamino)-(4-N-methylpyridinio)- stilbazolium iodide (DAPSI), trans-( N-methylpyrrol-2-yl)-4-( N-methyl-pyridinio)-stilbazolium iodide(MPPSI), trans-(pyrrol-2-yl) -4-(N-methyl-pyridinio) -stilbazolium iodide (FPSI), trans-(furan-2-yl)-4-( N-methyl-pyridinio)- stilbazolium iodide (FPSI) and trans- (thiophene-2-yl)-4( N-methyl-pyridinio)-stilbazolium iodide (TPSI), and trans-(4-methyl-pyridinio)-stilbazolium iodide (pSI), and obtained the results that the molecular hyperpolarizabilities are in linear correlation with the solvent polarity, E-T(30), and introduced the concept that the effects on the energy levels of the compound by the solvent is equavalent to those by the surrounding molecules of the compound itself, from which we calculated the molecular first-order hyperpolarizabilities beta(xxx)(s) of the six dyes in pure solid state, as -46, 7, - 7. 1, - 6. 7, - 3. 1, - 2. 2, and 0. 55 x 10-(27)esu for DAPSI, MPPSI, PPSI, FPSI, TPSI and PSI, respectively. And we also obtained the perfect linearity relationship between the beta(xxx)(s) and the electron excessivities of the donor for the latter five dyes.