Photo/thermochromic macrocycles based on dihydroazulenes, dithienylethenes, and spiropyrans

Suitably functionalized dihydroazulenes (DHAs), dithienylethenes (DTEs), and spiropyrans (SPs) are photo-active molecules that upon irradiation undergo isomerization by ring-opening/closure reactions, which involve carbon-carbon or carbon-heteroatom bond formation/breakage. These photo-isomers may return to the original ones under light or thermal activation. Introducing molecular photoswitches into macrocyclic structures can have strong implications for the forward and backward switching properties. In this report we summarize synthetic protocols for making macrocycles based on one or more units of DHA, DTE, and SP and the resulting properties of these macrocycles.