Topological analysis of the electron localisation function (ELF) applied to the electronic structure of oxaziridine: the nature of N-O bond

Topological analysis of the electron localisation function (ELF), natural bond orbital and Wiberg bond index calculations have been applied to study the electronic structure of the oxaziridine molecule with a special focus on the nitrogen-oxygen bond. The calculations have been performed at the DFT(B3LYP, CAM-B3LYP, ωB97XD, M06-L, M06-2X) and post-Hartree-Fock (CCSD(T) and CASSCF) computational levels with applied aug-cc-pVTZ basis set. Nature of N-O bonding has been characterised by two resonance forms, N+<br />O− and N−O+, owing to a very small population (< 0.60e) of the bonding basin V(N,O), localised in the ELF field for the N-O region. The importance of electron correlation effects for the description of the N-O bonding has been observed in the CASSCF calculations. The orbital description (Wiberg, NBO) differs from topological characterisation, indicating a single N-O bond.