The Role of Packing,Dispersion, Electrostatics,and Solvation in High-Affinity Complexes of Cucurbit[n]urils with Uncharged Polar Guests |
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| Authors: | Dr. Laura M. Grimm Dr. Sebastian Spicher Dr. Boryslav Tkachenko Prof. Dr. Peter R. Schreiner Prof. Dr. Stefan Grimme Dr. Frank Biedermann |
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| Affiliation: | 1. Institute of Nanotechnology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz Platz 1, 76344 Eggenstein-Leopoldshafen, Germany;2. Mulliken Center for Theoretical Chemistry, Institute of Physical and Theoretical Chemistry, University of Bonn, Beringstraße 4, 53115 Bonn, Germany;3. Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392 Giessen, Germany |
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| Abstract: | 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. |
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| Keywords: | cucurbiturils density functional calculations diamondoids host-guest systems isothermal titration calorimetry thermodynamics |
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