Department of Chemical System Engineering, School of Engineering, The University of Tokyo, 7-3-1, Tokyo 113-8656, Japan.
Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg 2050, South Africa.
Int J Mol Sci. 2022 Aug 8;23(15):8816. doi: 10.3390/ijms23158816.
The pnictogen bond, a somewhat overlooked supramolecular chemical synthon known since the middle of the last century, is one of the promising types of non-covalent interactions yet to be fully understood by recognizing and exploiting its properties for the rational design of novel functional materials. Its bonding modes, energy profiles, vibrational structures and charge density topologies, among others, have yet to be comprehensively delineated, both theoretically and experimentally. In this overview, attention is largely centered on the nature of nitrogen-centered pnictogen bonds found in organic-inorganic hybrid metal halide perovskites and closely related structures deposited in the Cambridge Structural Database (CSD) and the Inorganic Chemistry Structural Database (ICSD). Focusing on well-characterized structures, it is shown that it is not merely charge-assisted hydrogen bonds that stabilize the inorganic frameworks, as widely assumed and well-documented, but simultaneously nitrogen-centered pnictogen bonding, and, depending on the atomic constituents of the organic cation, other non-covalent interactions such as halogen bonding and/or tetrel bonding, are also contributors to the stabilizing of a variety of materials in the solid state. We have shown that competition between pnictogen bonding and other interactions plays an important role in determining the tilting of the MX (X = a halogen) octahedra of metal halide perovskites in one, two and three-dimensions. The pnictogen interactions are identified to be directional even in zero-dimensional crystals, a structural feature in many engineered ordered materials; hence an interplay between them and other non-covalent interactions drives the structure and the functional properties of perovskite materials and enabling their application in, for example, photovoltaics and optoelectronics. We have demonstrated that nitrogen in ammonium and its derivatives in many chemical systems acts as a pnictogen bond donor and contributes to conferring stability, and hence functionality, to crystalline perovskite systems. The significance of these non-covalent interactions should not be overlooked, especially when the focus is centered on the rationale design and discovery of such highly-valued materials.
本征键，一种有些被忽视的超分子化学连接基，自上个世纪中叶以来就已为人所知，是一种有前途的非共价相互作用类型，尚未被充分理解，通过识别和利用其性质，可以为新型功能材料的合理设计提供帮助。其键合模式、能量分布、振动结构和电荷密度拓扑结构等，无论是在理论上还是实验上，都需要进行全面的描绘。在这篇综述中，主要关注的是在有机-无机杂化金属卤化物钙钛矿及其在剑桥结构数据库（CSD）和无机化学结构数据库（ICSD）中密切相关的结构中发现的以氮为中心的本征键的性质。本文重点介绍了结构特征明确的化合物，结果表明，稳定无机骨架的不仅仅是广泛假设和充分记录的电荷辅助氢键，同时还有以氮为中心的本征键合，并且根据有机阳离子的原子成分，其他非共价相互作用，如卤键和/或四键合，也是稳定各种固态材料的贡献者。我们已经表明，本征键合与其他相互作用之间的竞争在决定金属卤化物钙钛矿的 MX（X = 卤素）八面体在一维、二维和三维中的倾斜方面起着重要作用。即使在零维晶体中，本征相互作用也被确定为具有方向性，这是许多工程有序材料的结构特征；因此，它们之间的相互作用以及与其他非共价相互作用的相互作用，推动了钙钛矿材料的结构和功能特性，并使它们在光电和光电子学等领域的应用成为可能。我们已经证明，在许多化学系统中，铵及其衍生物中的氮作为本征键供体，有助于赋予钙钛矿晶体系统稳定性，从而赋予其功能性。这些非共价相互作用的重要性不应被忽视，特别是当重点集中在这种高价值材料的合理设计和发现上时。
