How the Concept of Solvent Polarity Investigated with Solvatochromic Probes Helps Studying Intermolecular Interactions

Intermolecular interactions form the basis of the properties of solvents, such as their polarity, and are of central importance for chemistry; such interactions are widely discussed. Solvent effects were reported on the basis of various polarity probes with the ET(30) polarity scale of Dimroth and Reichardt being of special interest because of its sensitivity, precise measurability and other advantages, and has been used for the investigation of solvent interactions. A two-parameter equation for the concentration dependence of medium effects has been developed, providing insights into structural changes in liquid phases. Moving from condensed gases to binary solvent mixtures, where the property of one solvent can be continuously transformed to the other, it was shown how the polarity of a solvent can be composed from the effect of polar functional groups and other structural elements that form the matrix. Thermochromism was discussed as well as the effect of very long-range interactions. Practical applications were demonstrated.