Binding discrepancy of fluoride in quaternary ammonium and alkali salts by a tris(amide) receptor in solid and solution states
作者:Sandeep Kumar Dey、Barun Kumar Datta、Gopal Das
DOI:10.1039/c2ce25592h
日期:——
A dinitrophenyl functionalized tris(amide) receptor, L, showed distinct complexation behaviour towards the F− anion when tetrabutylammonium fluoride (TBAF) and potassium fluoride (KF) salts were individually employed for the recognition of F− with L. X-ray crystallography analyses revealed the formation of a F−–encapsulated complex (1 : 1 host–guest) stabilized by three N–H⋯F− and three C–H⋯F− hydrogen bonds when TBAF was employed as the F− source, whereas in the KF complex of L (1 : 1 host–guest), the receptor is involved in side-cleft binding of a hydrated KF contact ion-pair governed by amide N–H⋯F−, aryl C–H⋯F− and lp(F−)⋯π interactions. The binding of hydrated KF is identical to the side-cleft binding of solvents such as DMSO and DMF via N–H⋯O, aryl C–H⋯O and lp(O) ⋯π interactions, which has been exemplified by X-ray crystallography and a detailed Hirshfeld surface analyses of the crystals. The binding discrepancy of F− in the TBAF and KF complexes of L has also been manifested in the solution state by 1H NMR and 2D NOESY NMR experiments. In the 1H NMR analyses, a huge downfield shift of the coordinating –NH and ortho–CH protons was observed in the TBAF complex in comparison to the KF complex whereas, in the 2D NOESY NMR experiments, a disappearance of the signals corresponding to the through-space NOE coupling between the –NH and ortho–CH protons was observed in the former when compared to the latter and free receptor, L.
当四丁基氟化铵(TBAF)和氟化钾(KF)盐被单独用于 F- 与 L 的识别时,二硝基苯官能化三(酰胺)受体 L 对 F- 阴离子表现出独特的络合行为。X 射线晶体学分析表明,当使用四丁基氟化铵(TBAF)作为 F- 源时,通过三个 N-H⋯F- 氢键和三个 C-H⋯F- 氢键稳定地形成了 F- 包裹复合物(1 : 1 主-客),而在 L 的 KF 复合物(1 : 而在 L 的 KF 复合物(1 : 1 主-客)中,受体参与了由酰胺 N-H⋯F-、芳基 C-H⋯F- 和 lp(F-)⋯π 相互作用所支配的水合 KF 接触离子对的侧裂结合。水合 KF 的结合与 DMSO 和 DMF 等溶剂通过 N-H⋯O、芳基 C-H⋯O 和 lp(O) ⋯π 相互作用产生的侧裂结合相同,这一点已通过 X 射线晶体学和详细的晶体 Hirshfeld 表面分析得到证实。L 的 TBAF 和 KF 复合物中 F- 的结合差异在溶液状态下也通过 1H NMR 和 2D NOESY NMR 实验得到了体现。在 1H NMR 分析中,与 KF 复合物相比,在 TBAF 复合物中观察到配位 -NH 和正交-CH 质子发生了巨大的下移,而在二维 NOESY NMR 实验中,与自由受体 L 相比,在前者中观察到与 -NH 和正交-CH 质子之间的通空 NOE 耦合相应的信号消失了。