Experimental Electron Density of 1-Phenyl-4-nitroimidazole and Topological Analysis of C−H···O and C−H···N Hydrogen Bonds

The electron density of 1-phenyl-4-nitroimidazole was analyzed by X-ray diffraction at 0.55 Å resolution. The topology of the bonding scheme within the molecule as well as of the weak intermolecular C−H···O and C−H···N hydrogen bonds has been investigated. The topological analysis and the deformation density peak heights on the covalent bonds of the imidazole ring are consistent with the usual chemical knowledge. The nitro group has an electron-withdrawing effect, as it is globally negatively charged and the electrostatic potential around it is slightly negative. This potential is significantly weaker than that generated by other oxygen-containing chemical entities, which is related to the hydrophobicity of the nitro group. The nitro group forms three weak C−H···O hydrogen bonds, and the unsubstituted imidazole nitrogen is also hydrogen-bonded to a C−H group, as confirmed by the presence of critical points in the topological analysis.