Py and BPe solvent polarity scales: effect of temperature on pyrene and benzo[ghi]perylene fluorescence spectra

Abstract

The Py and BPe solvent polarity scales are based on the photophysical properties of pyrene and benzo[ghi]perylene dissolved in a fluid solution. The ratio of the fluorescence emission intensities for bands I and III serve as a quantitative measure of solvent polarity. Intensity ratios are reported for pyrene dissolved in butyl acetate, dibutyl ether, isobutyl methyl ketone (IBMK), octan-1-ol, dimethyl sulphoxide (DMSO), propylene carbonate and several water-organic mixtures as a function of temperature. The intensity ratios for benzo[ghi]perylene in butyl acetate, dibutyl ether, IBMK, dimethylformamide dimethyl acetal and an aqueous DMSO mixture were also determined. The results of these measurements indicate that numerical Py values vary with temperature, particularly for the more polar solvents. In comparison the BPe solvent polarity scale appears to be nearly independent of temperature.