MOLECULAR AND SUPRAMOLECULAR SYSTEMS IN PHOTOCHROMISM - DIHYDROINDOLIZINES - NEW VERSATILE MOLECULES

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