The electronic configuration of the molecule is the foundation of its structure and reactivity. The spin state is one of the key characteristics arising from the ordering of electrons within the molecule's set of orbitals. Organic molecules that have open-shell ground states and interesting physicochemical properties, particularly those influencing their spin alignment, are of immense interest within the up-and-coming field of molecular electronics. In this advanced review, we scrutinize various qualitative rules of orbital occupation and spin alignment, viz., the aufbau principle, Hund's multiplicity rule, and dynamic spin polarization concept, through the prism of quantum mechanics. While such rules hold in selected simple cases, in general the spin state of a system depends on a combination of electronic factors that include Coulomb and Pauli repulsion, nuclear attraction, kinetic energy, orbital relaxation, and static correlation. A number of fascinating chemical systems with spin states that fluctuate between triplet and open-shell singlet, and are responsive to irradiation, pH, and other external stimuli, are highlighted. In addition, we outline a range of organic molecules with intriguing non-aufbau orbital configurations. In such quasi-closed-shell systems, the singly occupied molecular orbital (SOMO) is energetically lower than one or more doubly occupied orbitals. As a result, the SOMO is not affected by electron attachment to or removal from the molecule, and the products of such redox processes are polyradicals. These peculiar species possess attractive conductive and magnetic properties, and a number of them that have already been developed into molecular electronics applications are highlighted in this review. WIREs Comput Mol Sci 2015, 5:440-459. doi: 10.1002/wcms.1233 For further resources related to this article, please visit the WIREs website.

中文翻译：

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不常见的分子电子构型的理论和实践。

分子的电子构型是其结构和反应性的基础。自旋态是由分子轨道组中的电子有序产生的关键特征之一。在分子电子学的新兴领域中，具有开壳基态和有趣的理化性质的有机分子，特别是那些影响其自旋排列的有机分子，引起了人们的极大兴趣。在这篇高级综述中，我们将通过量子力学的角度来研究各种定性的轨道占据和自旋对准定性规则，即aufbau原理，洪德的多重性规则和动态自旋极化概念。虽然这些规则在某些简单情况下适用，通常，系统的自旋状态取决于电子因素的组合，包括库仑和保利排斥力，核引力，动能，轨道弛豫和静态相关性。强调了许多具有自旋态的迷人化学系统，它们在三重态和开壳单重态之间波动，并对辐射，pH和其他外部刺激作出响应。此外，我们概述了一系列具有有趣的非aufbau轨道构型的有机分子。在这样的准封闭壳系统中，单占据分子轨道（SOMO）在能量上低于一个或多个双占据轨道。结果，SOMO不受电子附着到分子上或从分子上去除的影响，并且这种氧化还原过程的产物是多自由基的。这些奇特的物质具有吸引人的导电和磁性，因此，本文中重点介绍了许多已开发为分子电子应用的物质。WIRES Comput Mol Sci 2015，5：440-459。doi：10.1002 / wcms.1233有关本文的更多资源，请访问WIREs网站。