Publication

Abstract : Statistical analysis and DFT calculations have been performed on NO2···NO2 interactions between nitrobenzene moieties to understand the preferred geometry and energy of this interaction. The favorable interplanar angle, N···O distance, ∠C–N···O, and ∠N–O···N have been determined from these two analyses which agree with each other on all the parameters. While cam-B3LYP reproduces the geometrical parameters well, energetic trends are better reflected at M06-2x level of theory. The most favorable angle is obtained when the two NO2 groups are parallel to each other and are located around an inversion center. The inversion center ensures that there would be two equivalent N···O interactions. The parallel form is computed to be more stable than the perpendicular one by 0.93 kcal/mol at M06-2x/Aug-cc-pvTZ. However, the N···O distance is interestingly slightly shorter in perpendicular geometry compared to the parallel geometry. The interacting O atom sits on the interacting N atom which makes the ∠C–N···O to be around 90°, indicating involvement of the N atom in this interaction. In the perpendicular geometry, the preferred ∠N–O···N is found to be around 155° in the statistical analysis and 148° in the DFT calculation. This indicates the involvement of the lone pair of the O atom in the interaction. Comparison of C–N and N–O bond lengths between the monomer and dimers point to the involvement of the π* LUMO, though NBO analysis shows these interactions to be minimal.