Why does thionating a carbonyl molecule make it a better electron acceptor?
Why does thionating a carbonyl molecule make it a better electron acceptor?
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为什么羰基分子硫代可以使其成为更好的电子受体？
DOI：
10.1039/d2cp05186a
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Wu YL
中科院分区：
文献类型：
--
作者：
Wu YL
在过去的十年里，硫代羰基分子（R2 CS）在生物医学和材料方面的应用激增，如光动力治疗，有机场效应晶体管和可充电电池。这些应用的成功源于硫代羰基在可见光区的小光学带隙和与羰基类似物（R2 CO）相比增强的电子亲和力。虽然这些观察结果似乎与基于简单电负性考虑的暗示相反（硫为2.58，氧为3.44），但自然键轨道（NBO）分析给出了CO → CS取代的LUMO降低效应的直接解释。与CO中的价态（2 p）C/（2 p）O相互作用相比，硫的较高3 p轨道及其与碳的2 p能级的较弱重叠导致NBO中较弱的反键相互作用，这是LUMO的突出贡献者。这种分析还提供了对取代基在（硫代）羰基官能团上或与（硫代）羰基官能团π-共轭中的电子效应的半定量理解。这里揭示的直观概念提供了一个简单的规则来预测包含重杂元素的π共轭分子的电子性质，并将促进材料的开发。
The past decade has witnessed a surge of biomedical and materials applications of thiocarbonyl molecules (R2CS), such as in photodynamic therapy, organic field-effect transistors, and rechargeable batteries. The success of these applications originates from thiocarbonyl's small optical gap in the visible region and the enhanced electron affinity compared to the carbonyl analogues (R2CO). Although these observations seem to be contrary to the implication based on a simple electronegativity consideration (2.58 for sulfur and 3.44 for oxygen), a natural bond orbital (NBO) analysis gives a straightforward explanation for the LUMO-lowering effect of CO → CS substitution. In comparison to the valence (2p)C/(2p)O interactions in CO, the higher 3p orbital of sulfur and its weaker overlap with the 2p level of carbon result in a weaker antibonding interaction in NBO, a prominent contributor to the LUMO. Such an analysis also provides a semi-quantitative understanding of the electronic effect of substituents on or in π-conjugation with a (thio)carbonyl functionality. The intuitive concepts uncovered here offer a simple rule to predict the electronic properties of π-conjugated molecules that incorporate heavy heteroelements and would facilitate materials development.