Stares Daniel L, Szumna Agnieszka, Schalley Christoph A
Institut für Chemie und Biochemie, Freie Universität Berlin, Arnimallee 20, 14195, Berlin, Germany.
Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, Warsaw, Poland.
Chemistry. 2023 Dec 19;29(71):e202302112. doi: 10.1002/chem.202302112. Epub 2023 Oct 31.
The ability of various hydrogen-bonded resorcinarene-based capsules to bind α,ω-alkylbisDABCOnium (DnD) guests of different lengths was investigated in solution and in the gas-phase. While no host-guest interactions were detected in solution, encapsulation could be achieved in the charged droplets formed during electrospray ionisation (ESI). This included guests, which are far too long in their most stable conformation to fit inside the cavity of the capsules. A combination of three mass spectrometric techniques, namely, collision-induced dissociation, hydrogen/deuterium exchange, and ion-mobility mass spectrometry, together with computational modelling allow us to determine the binding mode of the DnD guests inside the cavity of the capsules. Significant distortions of the guest into horseshoe-like arrangements are required to optimise cation-π interactions with the host, which also adopt distorted geometries with partially open hydrogen-bonding seams when binding longer guests. Such quasi "spring-loaded" capsules can form in the charged droplets during the ESI process as there is no competition between guest encapsulation and ion pair formation with the counterions that preclude encapsulation in solution. The encapsulation complexes are sufficiently stable in the gas-phase - even when strained - because non-covalent interactions significantly strengthen in the absence of solvent.
研究了各种基于氢键的间苯二酚芳烃胶囊在溶液和气相中结合不同长度的α,ω-烷基双二氮杂二环[2.2.2]辛烷（DnD）客体的能力。虽然在溶液中未检测到主客体相互作用，但在电喷雾电离（ESI）过程中形成的带电液滴中可以实现包封。这包括一些客体，它们在最稳定构象下太长，无法装入胶囊的腔内。结合三种质谱技术，即碰撞诱导解离、氢/氘交换和离子迁移质谱，以及计算建模，使我们能够确定DnD客体在胶囊腔内的结合模式。客体需要显著扭曲成马蹄形排列，以优化与主体的阳离子-π相互作用，主体在结合较长客体时也会采用扭曲的几何结构，氢键接缝部分打开。这种准“弹簧加载”胶囊可以在ESI过程中的带电液滴中形成，因为在客体包封和与抗衡离子形成离子对之间不存在竞争，而在溶液中抗衡离子会阻止包封。即使存在应变，包封复合物在气相中也足够稳定，因为在没有溶剂的情况下非共价相互作用会显著增强。
