Lin Zhenda, Su Hao, Huang Wenhuan, Zhang Xuepeng, Zhang Guoqing
Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China Hefei 230026 China
RSC Adv. 2024 Jan 25;14(6):3771-3775. doi: 10.1039/d3ra07729b. eCollection 2024 Jan 23.
The molecular orbital (MO) theory is one of the most useful methods to describe the formation of a new chemical bond between two molecules. However, it is less often employed for modelling non-bonded intermolecular interactions because of the small charge-transfer contribution. Here we introduce two simple descriptors, the energy difference () of the HOMO of an electron donor and the LUMO of an acceptor against such HOMO-LUMO overlap integral (), to show that the MO theory could give a unified charge-transfer picture of both bonding and non-bonding interactions for two molecules. It is found that similar types of interactions tend to be closer to each other in this 2D graph. Notably, in a transition region from strong bonding to single-electron transfer, the interacting molecular pairs appear to present a "hybrid" between chemical bonding and a radical pair, such as anion-π* interactions. It is concluded that the number of nodes in the HOMO and LUMO play a crucial role in determining the bonding character of the molecular pair.
分子轨道（MO）理论是描述两个分子之间形成新化学键的最有用方法之一。然而，由于电荷转移贡献较小，它较少用于模拟非键合分子间相互作用。在此，我们引入两个简单的描述符，即电子供体的最高占据分子轨道（HOMO）与受体的最低未占据分子轨道（LUMO）之间的能量差（）以及这种HOMO-LUMO重叠积分（），以表明MO理论可以给出两个分子键合和非键合相互作用的统一电荷转移图景。发现在此二维图中，相似类型的相互作用往往彼此更接近。值得注意的是，在从强键合到单电子转移的过渡区域中，相互作用的分子对似乎呈现出化学键合和自由基对之间的“混合”，例如阴离子-π*相互作用。得出的结论是，HOMO和LUMO中的节点数在确定分子对的键合特性方面起着关键作用。
