Chemistry Department, Loras College, 1450 Alta Vista Street, Dubuque, IA 52001, USA.
Chemistry Department, Colorado School of Mines, 1500 Illinois Street, Golden, CO 80401, USA.
Molecules. 2023 Feb 12;28(4):1746. doi: 10.3390/molecules28041746.
The nascent field of computationally aided molecular design will be built around the ability to make computation useful to synthetic chemists who draw on their empirically based chemical intuition to synthesize new and useful molecules. This fact poses a dilemma, as much of existing chemical intuition is framed in the language of chemical bonds, which are pictured as possessing physical properties. Unfortunately, it has been posited that calculating these bond properties is impossible because chemical bonds do not exist. For much of the computationalchemistry community, bonds are seen as mythical-the unicorns of the chemical world. Here, we show that this is not the case. Using the same formalism and concepts that illuminated the atoms in molecules, we shine light on the bonds that connect them. The real space analogue of the chemical bond becomes the bond bundle in an extended quantum theory of atoms in molecules (QTAIM). We show that bond bundles possess all the properties typically associated with chemical bonds, including an energy and electron count. In addition, bond bundles are characterized by a number of nontraditional attributes, including, significantly, a boundary. We show, with examples drawn from solid state and molecular chemistry, that the calculated properties of bond bundles are consistent with those that nourish chemical intuition. We go further, however, and show that bond bundles provide new and quantifiable insights into the structure and properties of molecules and materials.
新兴的计算辅助分子设计领域将围绕着使计算对合成化学家有用的能力来构建，合成化学家凭借基于经验的化学直觉来合成新的有用分子。这一事实带来了一个困境，因为现有的许多化学直觉都是用化学键的语言来表达的，这些语言被描述为具有物理性质。不幸的是，有人假设计算这些键性质是不可能的，因为化学键并不存在。对于大多数计算化学家来说，键被视为虚构的——化学世界的独角兽。在这里，我们表明事实并非如此。我们使用相同的形式主义和概念来阐明分子中的原子，从而揭示连接它们的键。化学键的实空间类似物成为扩展的原子分子量子理论（QTAIM）中的键束。我们表明，键束具有与化学键相关的所有特性，包括能量和电子计数。此外，键束的特征还包括许多非传统属性，包括显著的边界。我们通过来自固态和分子化学的例子表明，键束的计算性质与滋养化学直觉的性质一致。然而，我们更进一步，表明键束为分子和材料的结构和性质提供了新的、可量化的见解。
