A STUDY OF SUPRAMOLECULAR HYDROGEN-BONDED COMPLEXES FORMED BY ALIPHATIC DICARBOXYLIC-ACIDS WITH AZAAROMATIC DONORS

Crystal structures of the hydrogen bonded, 1:1 molecular complexes of malonic, glutaric, adipic, thiodiglycolic and thiodipropionic acids wi th 4,4'-bipyridyl have been investigated in detail. All the dicarboxyl ic acids form molecular tape-like structures, but thiodiglycolic acid gives a cyclic structure, favoured by intermolecular pi-pi interaction between the heteroatom-rings. The cyclic structure is indeed unique, in the sense that it represents a noncovalent synthesis of a rectangle . Crystal structures of hydrogen bonded molecular complexes of malonic , succinic, glutaric, adipic and thiodipropionic acids with 2,4,6-tria minopyrimidine have been studied. By and large, only tape-like structu res are formed, the crossed ribbon network being favoured in the compl exes of malonic and glutaric acids with an odd number carbon atoms. In all the complexes of 2,4,6-triaminopyrimidine, proton transfer occurs from the carboxyl group to the heteroatom nitrogen, giving rise to a strong hydrogen bonded cyclic system. (C) 1998 Elsevier Science Ltd. A ll rights reserved.