Molecular recognition: connection and disconnection of hydrogen bonds, a case study with dimeric and highly associated monocarboxylic acids with simple receptors

Abstract

The new receptor (5) having mixed diamide moieties is a simple synthetic model which binds carboxylic acids by three point hydrogen bonds involving pyridine nitrogen, pyridine amide as well as the flexible aliphatic amide moieties. This is in contrast to the receptor (6) which makes only two point hydrogen bonds. Binding studies of the simple pyridine amide (3) making two hydrogen bonds with a number of dimeric and highly associated monocarboxylic acids are also reported. Receptor (9) shows higher binding constant with ibuprofen compared to (3). The mixed amide receptor 5 for monocarboxylic acid elegantly shows the noncovalent complexation by making all the three possible hydrogen bonds leading to heterodimerisation over selfdimerisation. Binding study of ibuprofen with p - nitrobenzamide 9 shows higher binding constant than simple amide 3.