Molecular Switches for Photorelease

Significance

A novel approach to the selective and sequential photorelease of a chemical species was developed by using two different thermally bistable dithienylethene (DTE) photoswitches and low-energy visible light of two different wavelengths. Diels-Alder reaction of fulvenes (1 and 2) with fumarate (3) generated cycloadducts 4 and 5, which transformed into thermally stable compounds 6 and 7 upon irridiation of the solution with 313 nm light. Further irridiation of the solutions with light of longer wavelengths triggers the ring-opening reactions and subsequent release of dienophile 3. The release mechanism was studied by NMR spectroscopy and UV/Vis absorption spectroscopy.