Kempʹs triacid attached to octa-O-methyl resorc[4]arenes: conformations in solution and comparative binding studies with various 2-amino pyridines

We synthesized the new supramolecular host molecules 7 and 13 based on functionalized resorcarenes bearing Kempʹs triacid. Conformations in solution have been investigated and the influence of intra- and intermolecular hydrogen bonds from the triacid was shown by low temperature and DOSY NMR experiments. The results of host 7 are supported by DFT calculations. The binding behaviour of 7 towards different 2-amino pyridines in chloroform has been investigated by NMR titrations. The association constants reach from K=207 M−1 for 2-amino-5-cyano pyridine to K=1551 M−1 for 2-amino-4-methyl pyridine. The association constants of the formed complexes of 7 with 2-amino pyridines were compared with those of the simple host systems 14 and 15 in order to evaluate the influence of the attached resorcarene host.