The nature of supermolecular bonds: Investigating hydrocarbon linked beryllium solvated electron precursors
The nature of supermolecular bonds: Investigating hydrocarbon linked beryllium solvated electron precursors
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DOI：
10.1063/5.0089815
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发表时间：
2022-05-21
影响因子：
4.4
通讯作者：
Miliordos, Evangelos
中科院分区：
文献类型：
--
作者：
Jackson, Benjamin A.;Miliordos, Evangelos
铍氨络合物Be（NH3）（4）在Be（NH3）（4）（2+）骨架的外围具有两个扩散电子。用甲基取代一个氨形成具有一个外围电子的CH 3Be（NH3）（3），这表明维持了Li（NH3）（4）观察到的氢型壳层模型。两个CH_3Be（NH_3）（3）单体通过脂肪链连接在一起形成强键合的铍氨配合物（NH_3）（3）Be（CH_2）（n）Be（NH_3）（3），n = 1-6，每个铍氨中心周围有一个电子。在线性碳链的情况下，这个系统可以被看作是两个氢原子以特定距离（由n决定）彼此接近的类似物。我们发现，这两个电子占据扩散的s-型轨道，并可以完全耦合在H-2中的三重态或单重态。对于长烃链，单重态是开壳层单重态，几乎与三重态自旋态简并，当n = 1时，三重态自旋态转变为闭壳层单重态，模仿H-2的σ-共价键。分析了该体系的双自由基性质，并基于多参考计算估算了单重态-三重态分裂随n的变化。最后，我们考虑弯曲的烃链的情况下，这使得更接近的两个扩散电子的较大的链和形成的两个扩散电子之间的直接共价键，这发生在两个Li（NH3）（4）配合物转换的开壳层封闭壳层单线态。弯曲烃链的能量消耗几乎被形成弱共价键所补偿，使得弯曲和线性结构几乎等能。由AIP Publishing独家授权出版。
Beryllium ammonia complexes Be(NH3)(4) are known to bear two diffuse electrons in the periphery of a Be(NH3)(4)(2+) skeleton. The replacement of one ammonia with a methyl group forms CH3Be(NH3)(3) with one peripheral electron, which is shown to maintain the hydrogenic-type shell model observed for Li(NH3)(4). Two CH3Be(NH3)(3) monomers are together linked by aliphatic chains to form strongly bound beryllium ammonia complexes, (NH3)(3)Be(CH2)(n)Be(NH3)(3), n = 1-6, with one electron around each beryllium ammonia center. In the case of a linear carbon chain, this system can be seen as the analog of two hydrogen atoms approaching each other at specific distances (determined by n). We show that the two electrons occupy diffuse s-type orbitals and can couple exactly as in H-2 in either a triplet or singlet state. For long hydrocarbon chains, the singlet is an open-shell singlet nearly degenerate with the triplet spin state, which transforms to a closed-shell singlet for n = 1 imitating the sigma-covalent bond of H-2. The biradical character of the system is analyzed, and the singlet-triplet splitting is estimated as a function of n based on multi-reference calculations. Finally, we consider the case of bent hydrocarbon chains, which allows the closer proximity of the two diffuse electrons for larger chains and the formation of a direct covalent bond between the two diffuse electrons, which happens for two Li(NH3)(4) complexes converting the open-shell to closed-shell singlets. The energy cost for bending the hydrocarbon chain is nearly compensated by the formation of the weak covalent bond rendering bent and linear structures nearly isoenergetic. Published under an exclusive license by AIP Publishing.