Characteristics of the molecular electron density, delocalization effect and hydrogen bonding interaction of nitroxoline

The density functional theoretical (DFT) calculations have been carried out at the B3LYP/6-311G(d,p) level of theory for nitroxoline monomer and dimer molecule. The dimer molecule formed between two nitroxoline subunits has the largest stability, and is held together by two OH⋯N hydrogen bonds. Stability of the molecule arising from hyperconjugative interaction and intra/inter molecular charge transfer has been analyzed using natural bond orbital (NBO) analysis. The topological analysis of electron localization function (ELF) provides effect of delocalization. Quantum theory of atoms in molecule (QTAIM) has been applied to gain deep understanding to the existence of intra- and inter-molecular interaction.