Department of Chemical and Biomolecular Engineering, University of California, Berkeley, Berkeley, CA, 94720, USA.
Institut für Physikalische Chemie, Westfälische Wilhelms-Universität Münster, Münster, Germany.
Angew Chem Int Ed Engl. 2021 Apr 26;60(18):10239-10246. doi: 10.1002/anie.202100166. Epub 2021 Mar 17.
We investigate the interaction between a molecule and a pore mouth-a critical step in adsorption processes-by characterizing the conformation of a macrocyclic calix[4]arene-Ti complex, which is grafted on the external surface of a zeotype (*-SVY). X-ray absorption and C{ H} CPMAS NMR spectroscopies independently detect a unique conformation of this complex when it is grafted at crystallographically equivalent locations that lie at the interface of 7 Å hemispherical microporous cavities and the external surface. Electronic structure calculations support the presence of this unique conformation, and suggest that it is brought about by a specific orientation of the macrocycle that maximizes non-covalent interactions between calix[4]arene upper-rim tert-butyl substituents and the microporous-cavity walls. Our comparative study provides a rare "snapshot" of a molecule partially confined at a pore mouth, an essential intermediate for adsorption into micropores, and demonstrates how surrounding environment controls this confinement in a sensitive fashion.
我们通过表征一种大环杯[4]芳烃-钛配合物在沸石型（*-SVY）外表面上的接枝情况，研究了分子与孔口之间的相互作用，这是吸附过程中的一个关键步骤。X 射线吸收和 C{ H} CPMAS NMR 光谱独立地检测到当该配合物在晶相等同的位置接枝时，其独特的构象，这些位置位于 7 Å 半球形微孔腔和外表面的界面处。电子结构计算支持这种独特构象的存在，并表明它是由大环的特定取向引起的，该取向最大限度地增加了杯[4]芳烃上缘叔丁基取代基与微孔腔壁之间的非共价相互作用。我们的比较研究提供了一个罕见的“快照”，即部分受限在孔口处的分子，这是微孔吸附的必要中间体，并展示了周围环境如何以敏感的方式控制这种限制。
