Optimizing the formation of 2,6-bis(N-alkyl-benzimidazolyl)pyridine- containing [3]catenates through component design

The 2,6-bis(N-alkyl-benzimidazolyl)pyridine (Bip) ligand has been utilized to access mechanically interlocked [3]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 [3]metallopseudorotaxanes that require a single olefin metathesis reaction to yield the [3]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 [3]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 [3]catenate. Furthermore, after de-metalation and purification the resulting [3]catenanes were fully characterized by a variety of NMR and mass spectroscopy techniques.