We have proved that the first-hyperpolarizabilities β~χ~χ~χ of the four stibazolium-like dyes, which are trans-(N-methylpyrrol-2-yl)- 4-(N-methyl-pyridinio)-stilbazolium iodide (MPPSI), trans-(pyrrol-2- yl)-4-(N-methyl-pyridinio)-stilbazolium iodide (PPSI), trans-(furan-2- yl)-4-(N-methyl-pyridinio)-stilbazolium iodide (FPSI) and trans- (thiophene-2-yl)-4-(N-methyl-pyridinio)-stilbazolium iodide (TPSI), can be linearly correlated with the electron excessivities of donors in fifteen solvents. Then we obtained the linearity correlation between the β~χ~χ~χ of the dyes and the solvents polarity [E~T(30) ]. From the two linearity correlations we obtain three solvent factors η , δ~A and δ~D for describing the solvents effects on the β~χ~ χ~χ : η describes the sensitivity of the intramolecular electron transfer to the solvent polarity, δ~A and δ~D describe the accepting/donating ability of the acceptor/donor effected by the solvent polarity respectively. The δ~A increases linearly, but the δ ~D is decreased linearly with increasing of the E~T(30).

Key words: PYRIDINE P, IODINE COMPOUNDS, SOLVENT EFFECT, POLARIZABILITIES, CHARGE TRANSFER