Photoresponsive Chirality-Tunable Supramolecular Metallacycles

Chirality-tunable supramolecular metallacycles containing two light-responsive dithienylethene units and two chiral 1,1′-bi-2-naphthol (BINOL) units have been successfully constructed via coordination-driven self-assembly. These new metallacycles are well-characterized with 1D multinuclear NMR (¹H and ³¹P NMR), 2D ¹H-¹H COSY and DOSY, ESI-TOF-MS, and PM6 semiempirical molecular orbital methods. Interestingly, upon irradiation with ultraviolet and visible light, the conformation of these metallacycles can undergo reversible transformation between ring-open and ring-closed forms accompanied with the obvious change of CD signals. Further investigation reveals that the photoisomerization of the dithienylethene moieties induces the change in the dihedral angle of the binaphthyl rings, thus leading to the chiral modulation of supramolecular metallacycles. Thus, this study provides very few examples of the light-induced chirality-tunable metallosupramolecular assemblies, which may find potential application in mimicking the function of natural systems in the future.