Efficient Syntheses and Complexation Studies of Diacetylene-Containing Macrocyclic Polyethers

A series of novel macrocyclic polyethers, phenylene-diacetylene-containing macrocycles was synthesized in high yields by employing copper(II)-mediated Eglinton coupling as the key macrocyclization (80-92%). As an analogue of the bisphenylene crown ether hosts, the binding behavior of these new macrocycles was investigated by H-1 NMR spectroscopy, mass spectrometry (ESI), and X-ray crystallography. The results obtained indicate that macrocycles with tetraethylene glycol chains (3c-e) bind a paraquat guest to form [2] pseudorotaxane-like complexes in solution and in the solid state, whereas macrocycles with triethylene glycol chains (i.e., 3f-h) bind a paraquat guest to form [3] pseudorotaxane-like complexes, which implies that macrocycles 3f-h may be able to complex to (mono) pyridinium cations in a [2] pseudorotaxane-like fashion in solution.