A characterization study on 2,6-dimethyl-4-nitropyridine N-oxide by density functional theory calculations

This study deals with the identification of a title compound, 2,6-dimethyl-4-nitropyridine N-oxide by means of theoretical calculations. The optimized molecular structures, vibrational frequencies, corresponding vibrational assignments, thermodynamic properties and atomic charges of the title compound in the ground state were evaluated using density functional theory (DFT) with the standard B3LYP/6-311G(d,p) method and basis set combination for the first time. Theoretical vibrational spectra were interpreted with the aid of normal coordinate analysis based on scaled density functional force field. The results show that the optimized geometric parameters (bond lengths and bond angles) and vibrational frequencies were observed to be in good agreement with the available experimental results. Based on the results of comparison between experimental results and theoretical data, the chosen calculation level is powerful approach for understanding the molecular structures and vibrational spectra of the 2,6-dimethyl-4-nitropyridine N-oxide. Moreover, we not only simulated frontier molecular orbitals (FMO) and molecular electrostatic potential (MEP) but also determined the transition state and energy band gap. Based on the investigations, the title compound is found to be useful to bond metallically and interact intermolecularly. Infrared intensities and Raman activities were also reported.

(a) Highest occupied molecular orbital (HOMO) and (b) lowest unoccupied molecular orbital (LUMO) are very important parameters for quantum chemistry. HOMO, which can be thought the outermost orbital containing electrons, tends to give these electrons such as an electron donor. On the other hand; LUMO can be thought the innermost orbital containing free places to accept electrons. Owing to the interaction between HOMO and LUMO orbital of a structure, transition state transition of π–π* type is observed with regard to the molecular orbital theory. Therefore, while the energy of the HOMO is directly related to the ionization potential, LUMO energy is directly related to the electron affinity. Energy difference between HOMO and LUMO orbital is called as energy gap that is an important stability for structures. In this figure, HOMOs are localized mainly on the molecule but slightly on hydrogen atoms whereas LUMOs are localized mainly on the molecule except methyl groups.Figure optionsDownload as PowerPoint slideHighlights
► This study deals with novel theoretical aspects of the title compound for the first time.
► Theoretical vibrational spectra are interpreted with the aid of normal coordinate analysis.
► Theoretical data are found to be in good agreement with experimental results.
► FMO are also investigated to show the way to the novel applications in technology.