Maji Subir, Gope Biplab, Sharma Madhur, Das Arpan, Jose Anex, Biswas Amit, Bhattacharyya Kalishankar, Mandal Swadhin K
Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, 741246, India.
Chemistry Department, Indian Institute of Technology Guwahati, Assam, 781039, India.
Angew Chem Int Ed Engl. 2025 Jan 27;64(5):e202418673. doi: 10.1002/anie.202418673. Epub 2024 Nov 12.
Mesoionic compounds, with positive and negative charges, are expected to have dual-site highest occupied molecular orbital (HOMO, donor) and lowest unoccupied molecular orbital (LUMO, acceptor) reactivity. Herein, we report a novel class of air-stable mesoionic N-heterocyclic thiones (mNHTs) synthesized from abnormal N-heterocyclic carbenes (aNHCs). DFT studies revealed a highly polarized exocyclic thione moiety and computed Fukui function analysis suggests the dual-site HOMO/LUMO reactivity of mNHTs predicting donor property at the negatively charged 'S' center while acceptor property at the cationic imidazole ring. The independent LUMO reactivity of the mNHT was realized by its chemical reduction to an elusive radical anion, which was characterized by a single crystal X-raydiffraction study. Further, we explore the reactivity of radical anion for the activation of SO gas, C-Br bonds of aryl bromide and photocatalytic functionalization of C-X (X = F, Br) bonds. This work unlocks the independent LUMO reactivity of a mesoionic compound.
具有正负电荷的中离子化合物有望具有双位点最高占据分子轨道（HOMO，给体）和最低未占据分子轨道（LUMO，受体）反应性。在此，我们报道了一类由异常N-杂环卡宾（aNHCs）合成的新型空气稳定的中离子N-杂环硫酮（mNHTs）。密度泛函理论（DFT）研究揭示了一个高度极化的环外硫酮部分，计算的福井函数分析表明mNHTs具有双位点HOMO/LUMO反应性，预测在带负电荷的“S”中心具有给体性质，而在阳离子咪唑环上具有受体性质。mNHT的独立LUMO反应性是通过将其化学还原为难以捉摸的自由基阴离子来实现的，该自由基阴离子通过单晶X射线衍射研究进行了表征。此外，我们探索了自由基阴离子对SO气体的活化、芳基溴的C-Br键以及C-X（X = F，Br）键的光催化官能化的反应性。这项工作揭示了中离子化合物的独立LUMO反应性。
