Bis(benzimidazolium) axles and crown ether wheels: a versatile templating pair for the formation of [2]rotaxane molecular shuttles

Condensation of an aldehyde appended benzimidazolium cation with a 1,2-benzenediamine in the presence of a crown ether allows formation of a second benzimidazole group and the facile synthesis of a [2]rotaxane molecular shuttle. The ease of this reaction and the versatility of the initial templating interaction between the benzimidazolium cation and crown ether allows for the preparation of [2]rotaxane molecular shuttles with crown ether macrocycles of various shapes and sizes. The synthesis and dynamic properties of a set of five [2]rotaxane molecular shuttles are described including the first examples of rotaxanes containing the larger macrocycles dibenzo[30]crown-10 (DB30C10) and bis-meta-phenylene-[26]crown-8 (BMP26C8).