Zinc templated synthesis—a route to get metal ion free tripodal ligands and lariat coronands, containing Schiff bases

A new series of tripodal receptors bearing imine linkages have been prepared in high yields, by a single step condensation reaction between tripodal aromatic amines and aldehydes, using zinc perchlorate as a template. The template cation leaves the pseudo cavity after the Schiff base condensation to give metal free multidentate ligands. These products have been characterized by 1H, 13C NMR, IR, elemental analysis, UV–vis absorption spectroscopy and X-ray crystallographic studies. It has been seen that the presence of a coordinating atom such as O, S, and N at position-2 with respect to the carbonyl group, is mandatory for the reaction to proceed. The template reaction has been also successfully employed to synthesize a lariat type coronand by reacting the tripodal amine with a dialdehyde.