Hydrogen-Bond-Driven Molecular Recognition: A UV-Spectroscopic Strategy for Positional Isomer Discrimination Using...

A simple method, UV-Visible spectroscopy, was used to detect the positional isomers of imidazole derivatives. We synthesized 4,5-diphenyl-1H-imidazol-2-yl-aniline molecules, where -NH2 is present at different positions (ortho, meta, and para) and detected the para isomer using picric acid (PA). PA forms a binary self-assembled complex with the para derivatives due to an acid-base reaction and causes a detectable shifting (33 nm) in the absorption band. The binary self-assembled complex, between PA and para isomer, was characterized by UV, FT-IR, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), 1H-NMR, and mass spectrometry. We also discussed the probable mechanism of interaction involved in the self-assembly process and why the other isomers do not interact with the PA. This manuscript reveals a way of detecting positional isomers using the stereochemical aspects of acid-base reaction.