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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Metal-organic charge transfer can produce biradical states and is mediated by conical intersections
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Metal-organic charge transfer can produce biradical states and is mediated by conical intersections

机译：金属有机电荷转移可产生双自由基态，并由圆锥形相交介导

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摘要

The present paper illustrates key features of charge transfer between calcium atoms and prototype conjugated hydrocarbons (ethylene, benzene, and coronene) as elucidated by electronic structure calculations. One- and two-electron charge transfer is controlled by two sequential conical intersections. The two lowest electronic states that undergo a conical intersection have closed-shell and open-shell dominant configurations correlating with the 4s and 4s 3d states of Ca, respectively. Unlike the neutral-ionic state crossing in, for example, hydrogen halides or alkali halides, the path from separated reactants to the conical intersection region is uphill and the charge-transferred state is a biradical. The lowest-energy adiabatic singlet state shows at least two minima along a single approach path of Ca to the π system: (i) a van der Waals complex with a doubly occupied highest molecular orbital, denoted Φ_1~2, and a small negative charge on Ca and (ii) an open-shell singlet (biradical) at intermediate approach (Ca···C distance ≈ 2.5-2.7 A) with molecular orbital structure Φ_1Φ_2- where Φ_2 is an orbital showing significant charge transfer form Ca to the it-system, leading to a one-electron multicentered bond. A third minimum (iii) at shorter distances along the same path corresponding to a closed-shell state with molecular orbital structure Φ_2~2 has also been found; however, it does not necessarily represent the ground state at a given Ca···C distance in all three systems. The topography of the lowest adiabatic singlet potential energy . surface is due to the one- and two-electron bonding patterns in Ca-π complexes.
机译：本文通过电子结构计算阐明了钙原子与原型共轭碳氢化合物（乙烯，苯和二甲苯）之间的电荷转移的关键特征。一电子和二电子的电荷转移由两个连续的圆锥形交点控制。经历圆锥形相交的两个最低电子态具有分别与Ca的4s和4s 3d状态相关的闭壳和开壳主导结构。与例如在卤化氢或卤化碱中的中性离子态穿越不同，从分离的反应物到圆锥形交叉区域的路径是上坡的，而电荷转移态是双自由基的。最低能量的绝热单重态沿Ca到达π系统的单个进场路径显示出至少两个极小值：（i）Van der Waals络合物，具有双占据的最高分子轨道，表示为Φ_1〜2，并且带少量负电荷在Ca上；（ii）处于中间进场（Ca···C距离≈2.5-2.7 A）的开壳单线态（双自由基），分子轨道结构为Φ_1Φ_2-，其中Φ_2是一个轨道，显示出显着的电荷从Ca向其转移-系统，导致单电子多中心键。还发现了沿着与具有分子轨道结构Φ_2〜2的闭壳态相对应的相同路径在较短距离处的第三极小值；但是，它不一定代表所有三个系统在给定的Ca··C距离下的基态。最低绝热单线态势能的形貌。表面是由于Ca-π络合物中的单电子键和双电子键。

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