Iodine as a Probe for Demonstrating Solvatochromism

As a result of the interaction with solvent molecules that surround them, some substances exhibit different colors in different solvents. Such differences in colors are usually the result of changes in orbital energies caused by a solvent cage. The difference in energy levels may be larger, which results in a shift to shorter wavelength for an electronic transition, or it may be smaller, which causes a shift to longer wavelength. These shifts in band positions have been used to develop “solvent polarity” scales that are used to correlate the effects of solvents on reaction rates. Generally, the molecules utilized as probes are complex organic substances. In this report, the use of iodine as an indicator of solvatochromism and polarity is explored.