ctronic network of bis ( a - oligothienyl ) - substituted hexaphyrins between helical versus rectangular circuit †

The switching phenomena of conformation with p-electronic network through deprotonation– protonation processes were investigated by employing a series of 5,20-bis(a-oligothienyl) substituted hexaphyrins(1.1.1.1.1.1). They showed significant changes in the absorption and emission spectra with deprotonation, and returned to the initial state with protonation. Through NMR measurements and single crystal X-ray diffraction analysis, we found that the 5,20-bis(a-oligothienyl) substituted hexaphyrins, which possess acyclic, helical electronic networks involving oligothienyl chains in dumbbell conformations (type-I) in a neutral form, underwent effective deprotonation upon treatment with tetrabutylammonium fluoride (TBAF) to generate the corresponding dianions, which display cyclic electronic networks with enhanced aromaticity in rectangular conformations (type-II). Our quantum calculation results provide an unambiguous description for the switchable conformation and pconjugation, which revealed that a deprotonation-induced enhanced aromatic conjugation pathway is involved in the switchable p-electronic network.