A higher-order preferential solvation model for the fluorescence of two PRODAN derivatives in toluene-alcohol mixtures

• Fluorescence of two carbonyl-twisted PRODAN derivatives is studied.
• Fluorescence in toluene-alcohol solvents is fit with preferential solvation models.
• Strong quenching behavior with methanol and ethanol involves two H-bonds.
• Quenching shows an energy-gap dependence.

The fluorescence behavior of 3-(dimethylamino)-8,9,10,11-tetrahydro-7H-cyclohepta[α]naphthalen-7-one and 1-(6-(dimethylamino) naphthalen-2-yl)-2,2-dimethylpropan-1-one, both carbonyl-twisted derivatives of PRODAN, in binary mixtures of toluene and an alkanol (methanol, ethanol isopropanol) is fit to a three-step preferential solvation model. The photophysical parameters extracted from the model include the solvatochromic shifts resulting from a single H-bond and the quenching that is due to changes in polarity only. The results confirm that quenching involves two H-bonds. They also show that the H-bond-induced quenching shows an energy-gap dependence.

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