Fluorosolvatochromism of furanyl- and thiophenyl-substituted acetophenones

A series of para-substituted acetophenones bearing a furanyl- or a thiophenyl moiety show a large STOKES-shift which is a function of various solvent properties. Photophysical properties such as emission lifetime of the compounds have been determined using time-correlated-single photon counting to secure the intrinsic fluorescence behaviour. The solvent dependent position of the UV/Vis emission band max, em of the compounds has been measured in 26 various solvents. The influence of the solvent on max, em is of very complex nature and mathematically analysed by multiple square linear solvation energy (LSE)-correlation analysis using CATALÁN`s four solvent parameter set. Solvent acidity has a strong influence on the bathochromic shift of 2,5-disubstituted furan derivatives compared to the non-5-substituted furan and thiophene derivatives which show a contrary behaviour. Therefore, the 5-cyanofuranyl-substituted acetophenone derivative is useful as probe for measuring environment properties by fluorescence spectroscopy.