Ionic liquids are intriguing media in which to study the function and dynamics of switches, sensors, and other molecular devices.  Spiropyrans are particularly interesting, as the dynamics of their photochromism have shown to be affected by the viscosity of the solvent as well as the electrostatic interactions present between the spiropyran and the ionic medium. In this work, emission spectroscopy was used to study spiropyran photochromism in imidazolium ionic liquids. In addition to the expected fluorescence from the merocyanine (open) form, phosphorescence from the spiro (closed) form was observed in all ILs studied. This is the first known example of spiropyran phosphorescence in ionic liquids, and suggests that the ring-opening reaction is slowed in the ionic liquid compared to traditional solvents, such that phosphorescence becomes competitive with the ring-opening process. This type of two-color emission could find applications in molecular switches or devices where two measurable outputs are desired.

Emission spectroscopy as a tool to study the dynamics of spiropyran photochromism in imidazolium ionic liquids

245th National Meeting (2013)

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