Division of Functional Materials Chemistry, SSI "Institute for Single Crystals," National Academy of Science of Ukraine, 60 Lenina ave., Kharkiv 61001, Ukraine.
J Chem Phys. 2013 Sep 28;139(12):124308. doi: 10.1063/1.4821999.
Quantum-chemical calculations of the H-O-N=O molecule in the equilibrium and transition states and the complexes of the HONO with BH3, study of the intramolecular interactions using NBO theory, and investigation of the electron distribution on the basis of topological analysis of the ELF function clearly indicate the influence of the n-π* conjugation and n-σ* hyperconjugation interactions on a par with exchange repulsion of lone pairs the character of the N-O bond. It is shown that repulsion between lone pairs of oxygen and nitrogen atoms causes the elongation of the N-O bond only but character of this bond remains covalent. The interaction between lone pair of the terminal oxygen atom and antibonding orbital of the N-O bond (n-σ* hyperconjugation) coincides with influence of repulsion and reinforces it changing the character of the N-O bond from covalent to protocovalent. In contrary, the n-π* conjugation interaction between lone pairs of the bridged oxygen atom and π-orbital of the N=O double bond leads to the strengthening of the N-O bond making it more covalent.
H-O-N=O 分子在平衡态和过渡态的量子化学计算，以及 HONO 与 BH3 的配合物，使用 NBO 理论研究分子内相互作用，以及基于 ELF 函数拓扑分析研究电子分布，这些都清楚地表明了 n-π共轭和 n-σ超共轭相互作用与孤对电子的交换排斥对 N-O 键性质的影响是相当的。结果表明，氧原子和氮原子的孤对电子之间的排斥仅导致 N-O 键的伸长，但该键的性质仍然是共价的。末端氧原子的孤对电子与 N-O 键的反键轨道（n-σ超共轭）之间的相互作用与排斥作用一致，并加强了它，从而将 N-O 键的性质从共价键变为部分共价键。相反，桥接氧原子的孤对电子与 N=O 双键的π轨道之间的 n-π共轭相互作用导致 N-O 键的加强，使其更具共价性。
