Solvent effects on photophysical properties of merocyanine 540 Original Research Article

Absorption and corrected fluorescence emission spectra of merocyanine 540 (MC 540) were recorded in solvents with different physico-chemical parameters – dielectric constant εr, refractive index n, dipolarity/polarizability π*, hydrogen-bonding ability α. Hypsochromic shifts of their maxima positions did not obey Lippert–Mataga equation. However, a correlation with π* and α was observed. Relative quantum yields φf and rate constants of nonradiative deactivation processes knr of the dye in different solvents based on steady-state measurements were estimated. Dependence on hydrogen-bonding ability was indicated – with increasing α, φf decreased and knr increased. The interaction between MC 540 and solvent molecules is discussed in terms of the different interactions contributing to the solvent stabilization of merocyanine dyes. Our results indicate that hydrogen bonding may contribute to solvent stabilization of MC 540.