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Anion Transporters Based on Noncovalent Balance including Anion−π, Hydrogen, and Halogen Bonding

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posted on 17.06.2019, 00:00 authored by Wen-Long Huang, Xu-Dong Wang, Sen Li, Rui Zhang, Yu-Fei Ao, Jun Tang, Qi-Qiang Wang, De-Xian Wang
Anion transmembrane transport mediated by novel noncovalent interactions is of central interest in supramolecular chemistry. In this work, a series of oxacalix[2]­arene[2]­triazine-derived transporters 1 and 2 bearing anion−π-, hydrogen-, and halogen-bonding sites in rational proximity were designed and synthesized by a one-pot strategy starting from gallic acid ester derivatives and mono- or di-halogen-substituted triazines. 1H NMR titrations demonstrated efficient binding of 1 and 2 toward Cl and Br in solution, giving association constants in the range of 102–104 M–1. Cooperation of anion−π, hydrogen, and halogen bonding was revealed as a driving force for anion binding by single-crystal structures of two complexes and density functional theory calculations. Fluorescence assays indicated that compounds 1 are efficient chloride transporters with effective concentrations (EC50) falling in the range of 3.1–7.4 μM and following an order of 1a > 1b > 1c > 1d. The contribution of halogen bonding and cooperative noncovalent bonds to ion transport was then discussed. Significantly, transporters 1 exhibit high anticancer activity. In the presence of 1 and KCl (60 mM), the cell survival of HCT116 reduces to 11.9–24.9% with IC50 values in the range of 52.3–66.4 μM.