Photochromic Dithenylethenes: From Sunglasses to the Controlled Release of Drugs

Abstract

There are several classes of molecules in organic chemistry that exhibit photochromism, one of which is dithienylenthenes (DTEs). Photochromism is defined as a light-induced reversible transformation between two isomeric compounds. Upon irradiation with ultraviolet light, DTEs undergo a change in colour from colourless open-ring isomers to blue colored closed-ring isomers. This colour change is due to the extensive change in molecular geometry between their isomeric forms. The new DTE compounds that I have synthesized will be used to develop drug delivery vehicles that will release their drug cargo upon irradiation with light. Our DTEs will act as the ON/OFF switch for this delivery. These vehicles are prepared by incorporating our DTEs into the membrane of biocompatible lipid vesicles or liposomes, which are spherical, self-closed structures, composed of curved lipid bilayers which entrap part of the solvent, in which they freely float, into their interior. I have developed a new approach for the synthesis of symmetrical and asymmetrical DTE compounds. I will discuss these results and the recent synthesis of dimeric DTE molecules that will also be used in light-activated drug delivery therapies.