Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA, U. K.
CICECO─Aveiro Institute of Materials, Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal.
J Am Chem Soc. 2022 Aug 17;144(32):14778-14789. doi: 10.1021/jacs.2c05333. Epub 2022 Aug 5.
Chalcogen bonding (ChB) is rapidly rising to prominence in supramolecular chemistry as a powerful sigma (σ)-hole-based noncovalent interaction, especially for applications in the field of molecular recognition. Recent studies have demonstrated ChB donor strength and potency to be remarkably sensitive to local electronic environments, including redox-switchable on/off anion binding and sensing capability. Influencing the unique electronic and geometric environment sensitivity of ChB interactions through simultaneous cobound metal cation recognition, herein, we present the first potassium chloride-selective heteroditopic ion-pair receptor. The direct conjugation of benzo-15-crown-5 ether (B15C5) appendages to Te centers in a bis-tellurotriazole framework facilitates alkali metal halide (MX) ion-pair binding through the formation of a cofacial intramolecular bis-B15C5 M (M = K, Rb, Cs) sandwich complex and bidentate ChB···X formation. Extensive quantitative H NMR ion-pair affinity titration experiments, solid-liquid and liquid-liquid extraction, and U-tube transport studies all demonstrate unprecedented KCl selectivity over all other group 1 metal chlorides. It is demonstrated that the origin of the receptor's ion-pair binding cooperativity and KCl selectivity arises from an electronic polarization of the ChB donors induced by the cobound alkali metal cation. Importantly, the magnitude of this switch on Te-centered electrophilicity, and therefore anion-binding affinity, is shown to correlate with the inherent Lewis acidity of the alkali metal cation. Extensive computational DFT investigations corroborated the experimental alkali metal cation-anion ion-pair binding observations for halides and oxoanions.
硫属键合（ChB）作为一种强大的基于σ-空穴的非共价相互作用，在超分子化学中迅速崭露头角，尤其在分子识别领域具有广泛的应用。最近的研究表明，ChB 供体强度和效力对局部电子环境非常敏感，包括氧化还原开关型阴离子结合和传感能力。通过同时识别共结合的金属阳离子来影响 ChB 相互作用的独特电子和几何环境敏感性，本文首次报道了钾选择性杂双位离子对受体。苯并-15-冠-5 醚（B15C5）附加物与双碲三唑骨架中的 Te 中心直接键合，通过形成共面的内分子双 B15C5M（M=K、Rb、Cs）夹心配合物和双齿 ChB···X 形成，促进了碱金属卤化物（MX）离子对的结合。广泛的定量 1H NMR 离子对亲和滴定实验、固-液和液-液萃取以及 U 型管传输研究均表明，该受体对所有其他碱金属氯化物均表现出前所未有的 KCl 选择性。证明受体离子对结合协同性和 KCl 选择性的起源是由于共结合的碱金属阳离子诱导的 ChB 供体的电子极化。重要的是，这种 Te 中心亲电性的开关程度，即阴离子结合亲和力，与碱金属阳离子的固有路易斯酸度相关。广泛的计算 DFT 研究证实了实验中观察到的碱金属阳离子-阴离子离子对卤化物和氧阴离子的结合。
