Exploring structural and conformational behaviour of cyclophanes incorporating imidazole-2-thiones

New cyclophanes containing two imidazole-2-thione moieties linked by two xylylene groups have been synthesized by the reaction of imidazolium-linked cyclophanes with sulfur in the presence of K₂CO₃. The conformational behaviour of the new cyclophanes was explored by NMR spectroscopy and X-ray diffraction studies. In cyclophanes containing o-xylylene or 2,4,6-trimethyl-m-xylylene linking groups, the imidazole-2-thione groups were mutually syn in both the solid state and in solution, the cyclophanes adopting a conformation reminiscent of the cone conformation of calix4]arenes. Cyclophanes containing p-xylylene or m-xylylene linking groups exhibited two conformations in solution, one in which the imidazole-2-thione groups are mutually syn, the other in which they are mutually anti, and these conformations did not interconvert on the NMR timescale. Both conformations co-crystallised in the m-xylylene linked cyclophane, while for the p-xylylene-linked cyclophane the anti conformation crystallised separately.