Host鈥揋uest Chemistry from Solution to the Gas Phase: An Essential Role of Direct Interaction with Water for High-Affinity Binding of Cucurbit[n]urils

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• 作者：Shin Jung C. Lee ; Jong Wha Lee ; Hong Hee Lee ; Jongcheol Seo ; Dong Hun Noh ; Young Ho Ko ; Kimoon Kim ; Hugh I. Kim
• 刊名：The Journal of Physical Chemistry B
• 出版年：2013
• 出版时间：July 25, 2013
• 年：2013
• 卷：117
• 期：29
• 页码：8855-8864
• 全文大小：453K
• 年卷期：v.117,no.29(July 25, 2013)
• ISSN：1520-5207

文摘

An investigation of the host鈥揼uest chemistry of cucurbit[n]uril (CB[n], n = 6 and 7) with 伪,蠅-alkyldiammonium guests (H₂N(CH₂)_xNH₂, x = 4, 6, 8, 10, and 12) both in solution and in the gas phase elucidates their intrinsic host鈥揼uest properties and the contribution of solvent water. Isothermal titration calorimetry and nuclear magnetic resonance measurements indicate that all alkyldiammonium cations have inclusion interactions with CB[n] except for the CB[7]鈥搕etramethylenediamine complex in aqueous solution. The electrospray ionization of mixtures of CB[n] and the alkyldiammonium guests reflects their solution phase binding constants. Low-energy collision-induced dissociations indicate that, after the transfer of the CB[n]鈥揳lkyldiammonium complex to the gas phase, its stability is no longer correlated with the binding properties in solution. Gas phase structures obtained from density functional theory calculations, which support the results from the ion mobility measurements, and molecular dynamics simulated structures in water provide a detailed understanding of the solvated complexes. In the gas phase, the binding properties of complexation mostly depend on the ion鈥揹ipole interactions. However, the ion鈥揹ipole integrity is strongly affected by hydrogen bonding with water molecules in the aqueous condition. Upon the inclusion of water molecules, the intrinsic characteristics of the host鈥揼uest binding are dominated by entropic-driven thermodynamics.