Experimental and theoretical quantum chemical investigations of 8-hydroxy-5-nitroquinoline

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The FT-IR and FT–Raman spectra of 8-hydroxy-5-nitroquinoline have been recorded in the regions 4000–400 and 4000–100cm−1, respectively. The spectra were interpreted in terms of fundamentals modes, combination and overtone bands. The normal coordinate analysis was carried out to confirm the precision of the assignments. The structure of the compound was optimised and the structural characteristics were determined by density functional theory (DFT) using B3LYP method with 6-31G∗∗, 6-311++G∗∗ and cc-pVDZ basis sets. The vibrational frequencies were calculated in all these methods and were compared with the experimental frequencies which yield good agreement between observed and calculated frequencies. The infrared and Raman spectra were also predicted from the calculated intensities. 1H and 13C NMR spectra were recorded and 1H and 13C nuclear magnetic resonance chemical shifts of the molecule were calculated using the gauge independent atomic orbital (GIAO) method. UV–Visible spectrum of the compound was recorded and the electronic properties HOMO and LUMO energies were measured by time-dependent TD–DFT approach. The influences of the nitro and hydroxy groups on the skeletal modes and on the proton chemical shifts have been investigated.