AbstractA set of six new two-photon engineered diethylamino-substituted styryl pyrazine (DEASP) dyes have been developed as chemically responsive chromophores. This work employs UV/Vis spectroscopy to draw structure-optical property relationships and to quantify the solvatochromic effect observed for these dyes. Absorbance profiles for each of these dyes have been measured in 22 solvents ranging from very nonpolar (TMS) to very polar (water). Absorbance maxima of the longest wavelength π→π transitions have been correlated to nine empirical scales of solvent polarity, and a comparative analysis is presented. Dimroth & Reichardt's and Kamlet & Taft's single parameter scales have been recalculated with spectral data obtained for the six DEASP dyes. The correlation of these established and recalculated scales are shown and discussed. DEASP chromophores are found to exhibit high sensitivity to their chemical environment and exceptional range as solvatochromic probes. Current models of solvatochromism, based on dipolar probes, cannot account for the solvatochromism observed in our quadrupolar dyes, and fail to describe the effect of the chemical environment on this family of twophoton dyes. The need to develop a more universal model of solvation incorporating higher order moment contributions is apparent.
