The nature of C–I···^–O–N⁺ interactions, the first of its kind, between nonfluorinated tetraiodoethylene halogen bond (XB) donor and pyridine N-oxides (PyNO) are studied by single-crystal X-ray diffraction and density functional theory (DFT) calculations. Despite the nonfluorinated nature of the C₂I₄, the I···O halogen bond distances are similar to well-known perfluorohaloalkane/-arene donor-PyNO analogues. With C₂I₄, oxygens of the N-oxides adopt exclusively μ₂-XB coordination in contrast to the versatile bonding modes observed with perfluorinated XB donors. The C₂I₄ as the XB donor forms with PyNO’s one-dimensional chain polymer structures in which the C₂I₄···(μ-PyNO)₂···C₂I₄ segments manifest two bonding motifs, namely, side-by-side (vicinal di-iodo) and head-to-head (geminal di-iodo), due to the nearly symmetric square-planar structure of the C₂I₄. While the attractive nature between I and O atoms is mainly electrostatic, the narrow range of C···O bond parameters demonstrates that the π-bond between four iodine atoms also plays an important role in enhancing the σ-hole strength. DFT-Based monodentate XB interaction energies, ΔE_int, in 13 1:1 XB complexes vary between 31.9 and 46.5 kJ mol^–1, the strongest remarkably exceeding the value reported for I–I···^–O–N⁺ = 42.0 kJ mol^–1. In the case of C₂I₄·(pyridine N-oxide) [31.9 kJ mol^–1], the monodentate XB energy is on a par with perfluorinated donor complexes, namely, CF₃I·(pyridine N-oxide) [31.1 kJ mol^–1] and C₆F₅I·(pyridine N-oxide) [32.3 kJ mol^–1].

中文翻译：

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C–I··· ^– O–N ⁺与四碘乙烯和芳香族N-氧化物的卤素键

的性质C-1 ... ^- O-N ⁺相互作用，首先它的种，非氟化四碘卤键（XB）供体和吡啶N-氧化物（PyNO）之间通过单晶X射线衍射进行研究，并密度泛函理论（DFT）计算。尽管C ₂ I ₄具有非氟化性质，但I··O卤素键的距离与众所周知的全氟卤代烷/芳烃供体-PyNO类似物相似。用C ₂我₄，N-氧化物的氧采用专门μ ₂与用全氟化XB供体中观察到的多功能键方式-XB协调。C ₂我₄因为XB供体具有PyNO的一维链状聚合物结构，其中C ₂ I ₄ ···（μ- PyNO）₂ ···C ₂ I ₄片段表现出两个键合基序，即并排（由于C ₂ I ₄几乎是对称的正方形平面结构，因此，“邻二碘”和“头对头”（二碘）。虽然I和O原子之间的吸引性质主要是静电，但C···O键参数的范围狭窄，这表明四个碘原子之间的π键在增强σ空穴强度方面也起着重要作用。基于DFT的单齿XB相互作用能ΔE _int在13个1：1 XB络合物中的变化范围为31.9至46.5 kJ mol ^–1，最强的超过了I–I·· ^– O–N ⁺ = 42.0 kJ mol ^{–1的报告值}。在C ₂ I ₄ ·（吡啶N-氧化物）[31.9 kJ mol ^–1 ]的情况下，单齿XB能量与全氟化供体配合物CF ₃ I·（吡啶N-氧化物）[31.1 ]相当。kJ mol ^–1 ]和C ₆ F ₅ I·（吡啶N-氧化物）[32.3 kJ mol ^–1 ]。