Organic molecules able to act as photoswitches are very attractive in the field of photoresponsive materials, with particular importance in optoelectronics and photobiological applications. Photoswitching in these molecules arises from the existence of two or more structural isomers that can interconvert upon light absorption. Several classes of photoswitchable molecules are known, including azobenzenes, spiropyrans, norbornadienes, and diarylethenes (DAEs). In general, DAEs are photoactive under UV irradiation, triggering bonding between carbon atoms at the two aryl units and resulting in the formation of a six-membered ring, which can often be reversibly converted back to the ring-open form with visible light. Molecular scaffolds based on DAEs, in particular with the dithienylethene (DTE) scaffold, have been exploited as photoswitches, as many of them exhibit thermal irreversibility, high fatigue resistance (both thermally and photochemically) and fast response times. Many of these studies explore the impact of chemical substitution in the side groups and at the backbone, resulting in improved properties in some cases and the suppression of the photocyclization reaction in others. To understand the capability of DAEs to photocyclize, chemists rely on the celebrated Woodward-Hoffmann (WH) rules. The application of the general WH rules to 4n+2 pelectron systems, e.g., 1,3,5-hexatriene and its derivatives, dictates that photo-induced electrocyclic ring-closure reactions proceed through a conrotatory mechanism (Scheme 1). Scheme 1. Photo-induced electrocyclic ring closure of 1,5-dimethyl-1,3,5-hexatriene to form 5,6dimethyl-1,3-cyclohexadiene.