Estimation of the number of polar molecules in a solvate shell of a fluorescent probe 4-dimethylaminochalcone

The fluorescence decay kinetics has been studied in different parts of the emission spectrum of diluted solutions of a membrane fluorescent probe, 4-dimethylaminochalcone, in a binary n-heptane + acetone solvent with the volume fractions of polar and nonpolar components of the latter varying in a wide range. It has been shown that the fluorescence of these solutions has a significantly heterogeneous character, which is indicative of the presence of several types of solvate complexes with controllable ratios of components (1: 1, 1: 2, 1: 3, etc.) in the studied systems. Based on a quantitative analysis of the mentioned kinetic dependences, a model has been proposed in which these data can serve as a source of information about statistical features of the structure of solvate shells of polar dye molecules in an excited electronic state. This information can in turn be used to obtain new biophysical data.