Optimizing the formation of 2,6-bis(N-alkyl-benzimidazolyl)pyridine-containing catenates through component design†
The 2,6-bis(N-alkyl-benzimidazolyl)pyridine (Bip) ligand has been utilized to access mechanically interlocked catenanes via metal-templating. Components containing the Bip ligand, namely macrocycles and linear threads, were designed to self-assemble upon the addition of transition metal ions into metallopseudorotaxanes that require a single olefin metathesis reaction to yield the catenate. Utilizing two-dimensional diffusion-ordered NMR spectroscopy (DOSY) the crude reaction mixture resulting from the ring-closing reaction of this template was studied. It was shown that the yield of the catenates was dependent on the preorganization and conformational flexibility of the thread-like component and the size of the N-alkyl substituents on the Bip in the macrocyclic component. Through judicious design of both components the resulting reaction distribution can be altered to predominantly favour the formation of the catenate. Furthermore, after de-metalation and purification the resulting catenanes were fully characterized by a variety of NMR and mass spectroscopy techniques.