“…Photochromism in molecular systems refers to a photoinduced reversible transformation between two isomers having distinct absorption spectra. In addition to the color change, such a reaction is often accompanied with changes in some other physical/chemical properties such as fluorescence emission, geometry structure as well as chemical reactivity, et cetera, which gives it various applications in the fields of optical materials, memories, photoswitches and biological systems [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ]. Motivated by their wide applications, several photochromic families such as azobenzenes, furylfulgides, spiropyrans, diarylethenes, et cetera, have been developed, in which the azobenzenes and furylfulgides change structures via Z / E isomerization while spiropyrans and diarylethenes transform between their open and closed forms via ring closing and opening reactions [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ].…”