| Autor: |
Pavlović, Radoslav Z., Zhiquan, Lei, Güney, Murat, Lalisse, Remy F., Hopf, Ryan G., Gallucci, Judith, Moore, Curtis, Xie, Han, Hadad, Christopher M., Badjić, Jovica D. |
| Předmět: |
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| Zdroj: |
Chemistry - A European Journal; 10/11/2019, Vol. 25 Issue 57, p13124-13130, 7p |
| Abstrakt: |
In this work, we report a mechanism by which stereoisomeric and twisted capsules P/M‐1 direct their dynamic chirality in the presence of haloalkane guests. The capsule comprises a static, but twisted, cage that is linked to a dynamic tris(2‐pyridylmethyl)amine (TPA) lid at its top. From the results of experimental (NMR spectroscopy and X‐ray crystallography) and computational (DFT) studies, the TPA lid was shown to assume clockwise (+) and counterclockwise (−) folds with diastereomeric (but racemic) capsules M‐1(+) and M‐1(−) interconverting at a rapid rate (ΔG≠189K=9.1 kcal mol−1). The relative stability of the capsules was found to be a function of guest(s) residing in their interior (243/262 Å3) with small CH2Cl2 (61 Å3) yielding roughly equal population of diastereomeric inclusion complexes. Larger guests, such as CCl4 (89 Å3) and CBr4 (108 Å3), however, formed M‐1(−)⊂CX4 at the expense of M‐1(+)⊂CX4 in circa 3:1 ratio. To account for the observation, theory (DFT:M06‐2X/6–31+G*) and experiments (1H NMR spectroscopy) were used to deduce that CX4 guests become localized inside the twisted cage of the capsule by forming a C−X⋅⋅⋅π halogen bond [Nc=d/(rH+rX)=0.91–0.92] with the benzene "floor" while encountering electrostatic repulsions with closer naphthalimide boundaries. At last, the TPA lid used its central methylene hydrogens to establish, within the M‐1(−)⊂CX4, three stabilizing C−H⋅⋅⋅X−C interactions with the guest. The same C−H⋅⋅⋅X−C interactions, however, became weaker (or possibly vanished) after the conformational reorganization of the lid and the formation of less stable M‐1(+)⊂CX4 complex. On individual basis, C−H⋅⋅⋅X−C intermolecular contacts are weak and hardly detectable in the solution phase. In the case of capsule P/M‐1, however, these contacts were multivalent and altogether strong enough to direct the host's dynamic chirality. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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