Solution phase, solid state and computational structural studies of the 2-aryl-3-bromoquinolin-4(1H)-one derivatives1

The structures of the potentially tautomeric 2-aryl-3-bromoquinolin-4(1H)-ones were studied using spectroscopic (NMR, IR and mass), X-ray crystallographic and computational techniques. These systems are found to exist in solution (1H NMR and 13C NMR) and solid state (IR and X-ray) as the NH-4-oxo derivatives, and their carbonyl nature is also corroborated by comparison of their spectroscopic data with those of the corresponding N-methylated and O-methylated derivatives. The presence of the quinolinol (hydroxyquinoline) isomer in the gas phase is confirmed by low and high resolution mass spectrometry.