The fluxional nature of halogen bonds (XBs) in small molecular clusters, supramolecules, and molecular crystals has received considerable attention in recent years. In this work, based on extensive density‐functional theory calculations and detailed electrostatic potential (ESP), natural bonding orbital (NBO), non‐covalent interactions‐reduced density gradient (NCI‐RDG), and quantum theory of atoms in molecules (QTAIM) analyses, we unveil the existence of fluxional halogen bonds (FXBs) in a series of linear (IC6F4I)m(OONC6H4NOO)n (m + n = 2–5) complexes of tetrafluorodiiodobenzene with dinitrobenzene which appear to be similar to the previously reported fluxional hydrogen bonds (FHBs) in small water clusters (H2O)n (n = 2–6). The obtained fluxional mechanisms involve one FXB in the systems which fluctuates reversibly between two linear CI···O XBs in the ground states (GS and GS') via a bifurcated CI O2N van der Waals interaction in the transition state (TS). The cohesive energies (Ecoh) of these complexes with up to four XBs exhibit an almost perfect linear relationship with the numbers of XBs in the systems, with the average calculated halogen bond energy of Ecoh/XB = 3.48 kcal·mol−1 in the ground states which appears to be about 55% of the average calculated hydrogen bond energy (Ecoh/HB = 6.28 kcal·mol−1) in small water clusters.

中文翻译：

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四氟二碘苯与二硝基苯线性配合物中的卤卤键


近年来，小分子簇、超分子和分子晶体中卤素键（XB）的流动性质受到了广泛的关注。在这项工作中，基于广泛的密度泛函理论计算和详细的静电势（ESP）、自然键合轨道（NBO）、非共价相互作用-约化密度梯度（NCI-RDG）和分子中原子的量子理论（QTAIM） ）分析中，我们揭示了四氟二碘苯与二硝基苯的一系列线性 (IC6F4I)m(OONC6H4NOO)n (m + n = 2–5) 配合物中存在流卤键 (FXB)，这似乎与之前报道的类似小水簇 (H2O)n (n = 2–6) 中的流变氢键 (FHB)。所获得的通量机制涉及系统中的一个 FXB，该 FXB 通过过渡态中的分叉 CI O2N 范德华相互作用，在基态的两个线性 CI…O XB（GS 和 GS'）之间可逆波动（ TS）。这些具有多达四个 XB 的配合物的内聚能 (Ecoh) 与系统中 XB 的数量表现出几乎完美的线性关系，平均计算的地面卤素键能为 Ecoh/XB = 3.48 kcal·mol−1状态似乎约为小水簇中平均计算氢键能 (Ecoh/HB = 6.28 kcal·mol−1) 的 55%。