Thiophene is commonly employed as a backbone group in DTEs. Our calculations predict the T-Tb-T scaffold to photocyclize, this has also been experimentally demonstrated in a variety of derivatives. Yam has shown how varying the substitution in the thiophene ring at the backbone allows blocking of the photoreactivity of the T-Tb-T unit. Such tunability was demonstrated in structures with the thiophene ring in the backbone bonded to a six-membered boron-containing ring. Phenyl substitution at the boron atom (6) results in no photoswitching, whereas fluoro substitution (7) forms of 6-8 as the HOMO-LUMO excitation, with orbital topologies in 6 and 8 that are nearly identical. Our calculations identify the FMOs potentially involved in the photoinduced cyclization of these compounds (HOMO, LUMO and LUMO+1 in Figure ), which are in good agreement with the computational results. The obtained orbital diagrams for 6-8 are nearly identical, i.e., do not rationalize the lack of photoswitching in the phenyl substituted compound (6) that is experimentally observed. Therefore, the inability of 6 to produce the closed form cannot be rationalized with our simple rules and could be related to the presence of competing deactivation channels.