Study of preferential solvation in binary solvent mixtures by the fluorescence-detected magnetic field effect

It has been found that the magnetic field effect detected by fluorescence of the pyrene–N,N-dimethylaniline exciplex in binary liquid mixtures containing components of significantly different relative permittivities depends on VmP(δP–δN)2 values which appear in Hildebrand's theory. Here VmP is the molar volume of a polar component and δP and δN are the solubility parameters of polar and non-polar components, respectively. The results suggest that the preferential solvation of radical-ion pairs in mixtures may be affected by their concentration fluctuations. The characteristic dimension of polar microdomains produced around radical ions was determined by the magnetic-field-effect technique to be ca. 50 A.