A magnetic self-contained thermochromic system with convenient temperature range

A new ionic liquid with sugar-based ligand has been prepared and used to coordinate cobalt(ii), at low loading, in an ionic liquid solution. The system obtained reveals magnetic switching and marked thermochromism in solution/polymer films over a convenient temperature range (20-60 degrees C). This system is self-contained, devoid of any volatile substances, and reproducible over multiple thermal cycles. The colour change can be attributed to a change in the coordination geometry from octahedral (pink) at room temperature to tetrahedral (blue) on warming, monitored by Co-59 NMR spectroscopy, which was used for the first time to study the change. This material may find applications in stimuli-responsive smart systems aimed at energy storage applications.