Molecular Snuggle and Stretch of a Tetraammonium Chain in the Construction of a Hetero-[4]pseudorotaxane with CyclopentanoQ[6] and Classical Q[7].

A hetero-[4]pseudorotaxane was designed to perform a molecular machine function of contraction and expansion utilizing the binding features of CyP6Q[6] and classical Q[7]. First, the effect on guest binding of equatorial substitution on Q[6]'s was examined by comparing Me4Q[6] and CyP6Q[6] against classical Q[6] using eight guest molecules varying in shape, size, neutrality, or cations. Second, the binding data provided optimal structural features for the design of a tetraammonium ion chain to effect the synthesis of the hetero-[4]pseudorotaxane. Finally, the hetero-[4]pseudorotaxane was constructed, and the order of component placement was examined for function and thermodynamic stability in relation to component order on the molecular axle.