Halogen bond interactions are investigated in four halopyridine iodine monochloride complexes nXPy(N)–ICl in the solid state, solution and in silico, where nXPy = n-halopyridine, X = I or Br and n = 2 or 3. Two types of halogen bonding interactions were observed: stronger three-center Py(N)–ICl halogen bonds and weaker two-center Py(C)–X···Cl halogen bonds. Theoretical calculations (thermodynamic data and optimized bond distances) and solution NMR studies indicated that Py(N)–ICl halogen bonding interactions are stronger in 3XPy(N)–ICl complexes than in 2XPy(N)–ICl complexes. In the solid state, relying on bond distances, nBrPy(N)–ICl complexes show the same behavior to that in solution and in silico. In contrast, nIPy(N)–ICl halogen bonding interactions are stronger in 2IPy(N)–ICl than in 3IPy(N)–ICl. The ionic and covalent characters of I–Cl and N–I bonds were studied by the analysis of electron density topology using Quantum Theory of Atoms in Molecules (QTAIM), and Natural Population Analysis (NPA)/Natural Bond Orbital (NBO) analysis. According to the NBO analysis of the solid state structure, the ionic character of the I–Cl bond is higher in 2IPy(N)–ICl than in 3IPy(N)–ICl.

中文翻译：

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卤代吡啶-碘一氯化物络合物中的卤素键相互作用。

研究了四种固态，溶液和计算机状态下的四卤代吡啶碘一氯化物n XPy（N）-ICl中的卤素键相互作用，其中n XPy = n-卤代吡啶，X = I或Br，n = 2或3。两种类型观察到卤素键相互作用：较强的三中心Py（N）-ICl卤素键和较弱的两个中心Py（C）-X···Cl卤素键。理论计算（热力学数据和优化的键距）和溶液NMR研究表明，在3XPy（N）-IC1配合物中，Py（N）-IC1卤素键相互作用比在2XPy（N）-IC1配合物中更强。在固态下，依赖于键距nBrPy（N）-ICl配合物在溶液和计算机模拟中显示出相同的行为。相反，n IPy（N）–ICl的卤素键相互作用在2IPy（N）–ICl中比在3IPy（N）–ICl中更强。通过使用分子中的原子量子理论（QTAIM）和自然种群分析（NPA）/自然键轨道（NBO）分析电子密度拓扑分析，研究了I–Cl和N–I键的离子和共价特性。根据对固态结构的NBO分析，2IPy（N）-ICl中I-Cl键的离子特征高于3IPy（N）-ICl中的I-Cl键的离子特征。