Li Wan-Lu, Zhang Qingnan, Chen Mohua, Hu Han-Shi, Li Jun, Zhou Mingfei
Department of Chemistry & Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Tsinghua University, Beijing, 100084, China.
Department of Chemistry, Collaborative Innovation Center of Chemistry for Energy Materials, Shanghai Key Laboratory of Molecular Catalysts and Innovative Materials, Fudan University, Shanghai, 200433, China.
Angew Chem Int Ed Engl. 2020 Apr 20;59(17):6923-6928. doi: 10.1002/anie.202000910. Epub 2020 Mar 3.
Through reaction of beryllium dimers with carbon monoxide, a carbonyl complex BeBeCO is formed in solid neon. Upon visible light excitation, the BeBeCO complex rearranges to a BeCOBe isomer, which further isomerizes to a low-energy BeOBeC species under UV-visible light excitation. These species are identified on the basis of infrared absorption spectroscopy with isotopic substitutions and quantum chemical studies. The BeOBeC molecule is characterized to be a multiple radical species having an electronic quintet ground state featuring an unusual quartet carbyne unit with three unpaired electrons on the carbon center. Bonding analysis indicates that the strong Pauli repulsion between carbon 2s lone pair electrons and the σ electrons of the BeOBe fragment significantly weakens the Be-C bonding and destabilizes the triplet state of the BeOBeC radical with a doublet carbyne unit. The three-center π-bonding of BeOBe is also found to play a role in stabilizing the quartet carbyne.
通过铍二聚体与一氧化碳的反应，在固态氖中形成了羰基配合物BeBeCO。在可见光激发下，BeBeCO配合物重排为BeCOBe异构体，该异构体在紫外-可见光激发下进一步异构化为低能量的BeOBeC物种。这些物种是通过同位素取代的红外吸收光谱和量子化学研究来鉴定的。BeOBeC分子的特征是具有电子五重态基态的多自由基物种，其具有不寻常的四重态卡宾单元，在碳中心有三个未成对电子。键合分析表明，碳2s孤对电子与BeOBe片段的σ电子之间强烈的泡利排斥显著削弱了Be-C键，并使具有二重态卡宾单元的BeOBeC自由基的三重态不稳定。还发现BeOBe的三中心π键在稳定四重态卡宾方面发挥了作用。
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