Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Kolkata 700 032, India.
J Org Chem. 2013 Sep 6;78(17):8759-65. doi: 10.1021/jo401504f. Epub 2013 Aug 21.
A new C3v symmetric amido-amine hybrid macrobicycle, L is synthesized toward anion recognition in its protonated states. L contains tri-amide and tetra-amine clefts separated by p-phenylene spacers. The solid-state structure of methanol-encapsulated L exhibits an overall cavity length of ~12.0 Å where the amide and amine -NH protons are converged toward the center of the respective cavities. Conformational analysis of L in solution is established by NOESY NMR. Anion binding of H3L with spherical (Cl(-), Br(-), I(-)) and tetrahedral (ClO4(-), SO4(2-)) anions are carried out by isothermal titration calorimeter in dimethylsulfoxide. The association of halides with H3L is endothermic and entropy driven. However, association of tetrahedral anions is exothermic in nature and both entropy- and enthalpy-driven. The overall association constants show the following order: HSO4(-) > Br(-)> Cl(-) ≈ ClO4(-). Single crystal X-ray structures of ClO4(-) and Br(-) complexes of protonated L show encapsulation of ClO4(-) in the amide cleft of H2L (complex 1) and encapsulation of Br(-) in the ammonium cleft of H3L (complex 2). Further, preorganization of L toward encapsulation of spherical and tetrahedral anions is established by comparing its amide, amine, and overall cavity dimensions with 1 and 2.
一种新的 C3v 对称的酰胺-胺混合大环化合物 L 被合成出来，用于在质子化状态下识别阴离子。L 包含三酰胺和四胺裂谷，由对苯撑间隔基隔开。甲醇包合物 L 的固态结构显示出总腔长度约为 12.0 Å，其中酰胺和胺 -NH 质子聚集在各自腔的中心。通过 NOESY NMR 确定了 L 在溶液中的构象分析。通过等温滴定量热法在二甲亚砜中进行了 H3L 与球形（Cl(-)、Br(-)、I(-)）和四面体（ClO4(-)、SO4(2-)）阴离子的阴离子结合。卤化物与 H3L 的结合是吸热和熵驱动的。然而，四面体阴离子的结合本质上是放热的，并且是熵和焓驱动的。总的结合常数显示出以下顺序：HSO4(-) > Br(-)> Cl(-) ≈ ClO4(-)。质子化 L 的 ClO4(-)和 Br(-)配合物的单晶 X 射线结构显示 ClO4(-)包封在 H2L（配合物 1）的酰胺裂谷中，Br(-)包封在 H3L的铵裂谷中（配合物 2）。此外，通过比较 L 的酰胺、胺和总腔尺寸与 1 和 2，确定了 L 对球形和四面体阴离子的预组织。
