PCM Study of Some N-Nitroso-N′,N′-dimethylphenylurea Biological Molecules: A Natural Bond Orbital Analysis

The density functional B3LYP method with the 6-31++G(d,p) basis set was used to investigate several N-nitroso-N′,N′-dimethylphenylurea biological molecules in MeCN solution. Geometries obtained from DFT calculation were used to perform natural bond orbital (NBO) analysis. The p characters of two nitrogen natural hybrid orbital (NHO), \(\sigma_{\mathrm{N}_{3}\mbox{\scriptsize{--}}\mathrm{N}_{2}}\) bond orbitals, increase with increasing σ p values of the substituents on the benzene, which results in a lengthening of the N3–N2 bond. The p character of the oxygen NHO \(\sigma_{\mathrm{O}_{1}\mbox{\scriptsize{--}}\mathrm{N}_{2}}\) bond orbital decreases with increasing σ p values of the substituents on the benzene, which results in a shortening of the N2=O1 bond. It is also noted that decreased occupancy of the localized \(\sigma_{\mathrm{N}_{3}\mbox{\scriptsize{--}}\mathrm{N}_{2}}\) orbital occurs in the idealized Lewis structure, or increased occupancy of \(\sigma_{\mathrm{N}_{3}\mbox{\scriptsize{--}}\mathrm{N}_{2}}^{*}\) of the non-Lewis orbital, and their subsequent impact on molecular stability and geometry (bond lengths) are also related to the resulting p character of the corresponding nitrogen NHO of the \(\sigma_{\mathrm{N}_{3}\mbox{\scriptsize{--}}\mathrm{N}_{2}}\) bond orbital. In addition, the partial charge distribution on the skeletal atoms shows that the electrostatic repulsion or attraction between atoms can give a significant contribution to the intra- and intermolecular interaction.