Experimental and theoretical study on free 5-nitroquinoline, 5-nitroisoquinoline, and their zinc(II) halide complexes

In this study where the interpretations of the experimental IR and Raman spectra recorded at room temperature for the ligands 5-nitroquinoline (5NQ) and 5-nitroisoquinoline (5NIQ) and also for their Zn(II) halide (halogen: chlorine, bromine, iodine) complexes were first reported, the assignments of the observed fundamental bands were achieved in the light of the vibrational spectral data and total energy distribution (TED) values calculated at B3LYP/6-311++G(d,p) and B3LYP/LANL2DZ levels of theory. The equilibrium geometrical parameters, Natural Bond Orbital (NBO) charges and frontier orbital (HOMO, LUMO) energies of these molecular structures were also calculated at the same level of theory. Comparisons over the corresponding experimental and theoretical data obtained for the title ligands and their complexes revealed that in complex form both ligands bond to Zn(II) ion through their ring nitrogen atoms and NO2 groups at the same time.