Vibrational spectroscopic study of some quinoline derivatives

This work deals with the successful synthesis, spectroscopic properties (Raman and infrared) and theoretical calculations of some quinoline derivatives, namely 4-azido-7-chloroquinoline and the commercially available 4,7-dichloroquinoline, quinolin-8-ol. The analysis of the Raman and infrared spectra of the quinoline derivatives, supported by DFT calculations, for the first time has afforded the opportunity to characterize unambiguously the main vibrational bands for these important molecules, which are mainly used as anti-malaria compounds. Despite the very similar structures of these quinolines the Raman and infrared spectra exhibit significant wavenumber shifts for several key bands. A characteristic band at ca. 1580 cm −1 can be assigned involving a δ(OH) mode for quinolin-8-ol (QNO) as well as the band at ca. 1090 cm −1 attributed to δ(CCl) for 4,7-dichloroquinoline (DCQN). The compound 4-azido-7-chloroquinoline (ACQN) shows a very characteristic marker band at ca. 1300 cm −1 , which has been assigned to the ν(NN) mode of the azide group.