Pizzi Andrea, Dhaka Arun, Beccaria Roberta, Resnati Giuseppe
NFMLab, Department of Chemistry, Materials, Chemical Engineering "Giulio Natta", Politecnico di Milano, via Mancinelli 7, I-20131 Milano, Italy.
Chem Soc Rev. 2024 Jul 1;53(13):6654-6674. doi: 10.1039/d3cs00479a.
The electrostatic attraction between charges of opposite signs and the repulsion between charges of the same sign are ubiquitous and influential phenomena in recognition and self-assembly processes. However, it has been recently revealed that specific attractive forces between ions with the same sign are relatively common. These forces can be strong enough to overcome the Coulomb repulsion between ions with the same sign, leading to the formation of stable anion⋯anion and cation⋯cation adducts. Hydroden bonds (HBs) are probably the best-known interaction that can effectively direct these counterintuitive assembly processes. In this review we discuss how σ-hole and π-hole bonds can break the paradigm of electrostatic repulsion between like-charges and effectively drive the self-assembly of anions into discrete as well as one-, two-, or three-dimensional adducts. σ-Hole and π-hole bonds are the attractive forces between regions of excess electron density in molecular entities (, lone pairs or π bond orbitals) and regions of depleted electron density that are localized at the outer surface of bonded atoms opposite to the σ covalent bonds formed by atoms (σ-holes) and above and below the planar portions of molecular entities (π-holes). σ- and π-holes can be present on many different elements of the p and d block of the periodic table and the self-assembly processes driven by their presence can thus involve a wide diversity of mono- and di-anions. The formed homomeric and heteromeric adducts are typically stable in the solid phase and in polar solvents but metastable or unstable in the gas phase. The pivotal role of σ- and π-hole bonds in controlling anion⋯anion self-assembly is described in key biopharmacological systems and in molecular materials endowed with useful functional properties.
相反电荷之间的静电吸引以及相同电荷之间的排斥是识别和自组装过程中普遍存在且具有影响力的现象。然而，最近有研究表明，相同电荷离子之间的特定吸引力相对常见。这些力足够强大，能够克服相同电荷离子之间的库仑排斥力，从而导致稳定的阴离子⋯阴离子和阳离子⋯阳离子加合物的形成。氢键（HBs）可能是最著名的能够有效引导这些违反直觉的组装过程的相互作用。在这篇综述中，我们讨论了σ-空穴键和π-空穴键如何打破相同电荷之间静电排斥的范式，并有效地驱动阴离子自组装成离散的以及一维、二维或三维加合物。σ-空穴键和π-空穴键是分子实体中电子密度过剩区域（如孤对电子或π键轨道）与电子密度耗尽区域之间的吸引力，电子密度耗尽区域位于与原子形成的σ共价键相对的键合原子外表面（σ-空穴）以及分子实体平面部分的上方和下方（π-空穴）。σ-空穴和π-空穴可以存在于元素周期表p区和d区的许多不同元素上，因此由它们的存在驱动的自组装过程可以涉及各种各样的单阴离子和双阴离子。形成的同聚和异聚加合物通常在固相和极性溶剂中稳定，但在气相中是亚稳的或不稳定的。σ-空穴键和π-空穴键在控制阴离子⋯阴离子自组装中的关键作用在关键的生物药理学系统和具有有用功能特性的分子材料中得到了描述。
