Molecular and Supramolecular Systems in Photochromism: Dihydroindolizines - New Versatile Molecules

A short summary of the known photochromic molecules is given. An approach to the new class of photochromic 5-membered heterocycles, such as dihydroindolizines (DHI), is presented. The important parameters of the photochromic 1,5-electrocyclization and its reverse of DHI's are discussed. Special DHI's can undergo a photoreversible ring closure from the colored betaines to the uncolored DHI. This reaction can be employed in photoswitches. Supramolecular effects on reactivity of DHI's are studied with especially tailored DHI allowing for host-guest-chemistry. An important commercial application of spiroxazines in ophthalmic lenses is discussed.