the engulfment of a positively charged pyridinium-based guest inside the π-rich cavity of a tris-(N-phenylureido)calix[6]arene host affects its reactivity towards a SN2 reaction. We found that the alkylation of the complexed substrates leads to the formation of pseudorotaxanes and rotaxanes with faster kinetics and higher yields with respect to the standard procedures exploited so far. More importantly
We describe the active template effect of a calix[6]arene host towards the alkylation of a complexed pyridylpyridinium guest. The acceleration of the reaction within the cavity is significant and rim-selective, enabling the efficient preparation of rotaxanes with full control of the mutual orientation of their nonsymmetric components.
We have synthesized a series of three rotaxanes constituted of a calix[6]arene wheel and a 4,4′-bipyridinium unit on the axle, which differ in the length of the two aliphatic chains that connect the central bipyridinium unit with the two terminal stoppers. We have investigated the photophysical and electrochemical properties of these systems and of suitable model compounds in two prototypical solvents
the macrocycle upper rim (active template synthesis). Here we exploit such properties to prepare two series of [3]rotaxanes, each consisting of three sequence isomers that arise from the threading of two identical but nonsymmetric wheels on a symmetric thread differing only for the reciprocal orientation of the macrocycles. The features of the calix[6]arene and the active template synthetic approach
Ethynylhelicene oligomers with TEG terminal groups showed a unique thermoresponse in aqueous solvents: double-helix formation upon heating and disaggregation upon cooling.