Directed H-bonding inhibition in molecular recognition: an NMR case study of the H-bonding of a dicarboxylic acid with a new mixed diamide receptor having one adjacent pyridine-N-oxide

The inhibition of hydrogen bond formation in the recognition of adipic acid by a new diamide receptor 1 having a pyridine-N-oxide and a simple pyridine ring adjacent to the amide moieties is observed. NMR studies show binding by the pyridine amide group in 1, which demonstrates the discrimination in hydrogen bonding between the carboxyls and an amide adjacent to pyridine versus another adjacent to the pyridine N-oxide. This specific inhibition of hydrogen bonding to a carboxyl group by the two different amides in 1 is corroborated by the NMR binding studies of 1 with propionic acid.