Solvent effects on the electronic absorption and fluorescence emission spectra of merocyanine 540 - A biological probe

Abstract

The electronic absorption and fluorescence spectra of merocyanine 540 (MC-540) were determined at 298 K in several solvents of different polarity (dioxane, toluene, triethylamine, diethyl ether, chloroform, methyl acetate, pyridine, acetone, ethanol, methanol, nitromethane, acetonitrile, and dimethyl sulfoxide). For the first time, the ground-state dipole moment of MC-540 was measured in dioxane-dimethylformamide (15 : 1, v/v) at 298 K. Solvent effects were evaluated using the solvatochromic shift method (Bakhshiev and Kawski-Chamma-Viallet correlations). The spectral blue shifts observed with increasing solvent polarity indicate a slightly lower value of the dipole moment in the first excited singlet state as compared with the ground-state dipole moment. The application of the Kamlet-Abboud-Taft polarity parameters to the electronic spectral data of MC-540 is discussed.