Abstract
Metal coordination to a series of bis (imidazolium)…pillar[5]arene [2]rotaxanes through the formation of metal-carbene bonds facilitates a new strategy to restrict the shuttling motion in [2]rotaxanes. Whereas the pillar[5]arene macrocycle rapidly shuttles along the full length of the bis (imidazolium) rod for the parent [2]rotaxane, Ag(i) coordination to the imidazolium groups through the formation of N-heterocyclic carbenes leads to restricted motion, effectively confining the shuttling motion of the [2]rotaxane. The Ag(i) coordinated [2]rotaxanes can be reacted further, either removing the Ag-carbene species to recreate the parent [2]rotaxane, or reaction with more bulky Pd(ii) species to further restrict the shuttling motion through steric inhibition.
Highlights
The importance of molecular machines has been well established
With molecular machines and switches, a conformational or configurational change occurs as a consequence of applying an external stimulus
The coordination of metals has a rich history in catenane and rotaxane synthesis due to their role in early template-based synthetic routes
Summary
The importance of molecular machines has been well established. Over the past two decades the synthesis of mechanically-interlocked molecules (MIMs) has exceeded mere curiosity and has become a field of increasing significance in both understanding and mimicking key biological processes. Macrocycles have been shown to shuttle from one ligand/binding site to another along a rotaxane rod upon metal exchange,[14] redox processes[15] or protonation[16]. We report a series of [2]rotaxanes composed of a decamethylpillar[5]arene (heretofore termed pillar[5]arene) and bis-imidazolium rods of varying lengths prepared in high yields.
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