Institute of Nanotechnology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz Platz 1, 76344, Eggenstein-Leopoldshafen, Germany.
Mulliken Center for Theoretical Chemistry, Institute of Physical and Theoretical Chemistry, University of Bonn, Beringstraße 4, 53115, Bonn, Germany.
Chemistry. 2022 Jul 6;28(38):e202200529. doi: 10.1002/chem.202200529. Epub 2022 May 25.
The rationalization of non-covalent binding trends is both of fundamental interest and provides new design concepts for biomimetic molecular systems. Cucurbit[n]urils (CBn) are known for a long time as the strongest synthetic binders for a wide range of (bio)organic compounds in water. However, their host-guest binding mechanism remains ambiguous despite their symmetric and simple macrocyclic structure and the wealth of literature reports. We herein report experimental thermodynamic binding parameters (ΔG, ΔH, TΔS) for CB7 and CB8 with a set of hydroxylated adamantanes, di-, and triamantanes as uncharged, rigid, and spherical/ellipsoidal guests. Binding geometries and binding energy decomposition were obtained from high-level theory computations. This study reveals that neither London dispersion interactions, nor electronic energies or entropic factors are decisive, selectivity-controlling factors for CBn complexes. In contrast, peculiar host-related solvation effects were identified as the major factor for rationalizing the unique behavior and record-affinity characteristics of cucurbit[n]urils.
非共价键相互作用趋势的合理化具有重要的理论意义，并为仿生分子体系提供了新的设计理念。葫芦[n]脲（CBn）作为一种广泛的（生物）有机化合物在水中的最强合成配体，已经被人们熟知了很长时间。然而，尽管它们具有对称且简单的大环结构和丰富的文献报道，但其主客体结合机制仍然不明确。在此，我们报告了 CB7 和 CB8 与一系列羟基化金刚烷、二金刚烷和三金刚烷作为不带电荷、刚性和球形/椭圆形客体的实验热力学结合参数（ΔG、ΔH、TΔS）。通过高精度理论计算得到了结合几何形状和结合能分解。这项研究表明，对于 CBn 配合物，伦敦色散相互作用、电子能量或熵因子都不是决定选择性的控制因素。相比之下，特殊的主体相关溶剂化效应被确定为合理化葫芦[n]脲独特行为和记录亲和力特征的主要因素。
