Abstract:Liquid-like dynamics of a covalent 1,4-phenylene rotator have been unveiled in 1 with a brominated stator showing type-II halogen bonds. This singular rotation is favored by synergistic molecular changes in stacked molecules, according to VT solid state NMR, H T relaxometry and VT X-ray experiments of this highly crystalline compound.
“…5a ). The observations indicated the presence of dynamic motions of COR molecules, and its biased non-isotropic motion was further clarified 35 . Fig.…”
The hydrogen bond is undoubtedly one of the most important non-covalent interactions. Among the several types of the hydrogen bonds, the CH–π interaction is a relatively new notion that is being recognised in chemistry and biology. Although the CH–π hydrogen bond and conventional hydrogen bonds share common features such as directionality, this weak interaction has played a secondary role in molecular recognition. In this study, we have devised a host–guest complex that is assembled solely by the CH–π hydrogen bonds. Multivalent interactions of a bowl-shaped hydrocarbon with its peripheral hydrogen atoms are made possible via CH–π hydrogen bonds by adopting a tubular hydrocarbon as a host for their enthalpy-driven complexation. Concyclic arrays of weak hydrogen bonds further allow dynamic rotational motions of the guest in the host. Solid-state analysis with crystallographic and spectroscopic methods reveal a single-axis rotation of the bowl in the tube.
“…5a ). The observations indicated the presence of dynamic motions of COR molecules, and its biased non-isotropic motion was further clarified 35 . Fig.…”
The hydrogen bond is undoubtedly one of the most important non-covalent interactions. Among the several types of the hydrogen bonds, the CH–π interaction is a relatively new notion that is being recognised in chemistry and biology. Although the CH–π hydrogen bond and conventional hydrogen bonds share common features such as directionality, this weak interaction has played a secondary role in molecular recognition. In this study, we have devised a host–guest complex that is assembled solely by the CH–π hydrogen bonds. Multivalent interactions of a bowl-shaped hydrocarbon with its peripheral hydrogen atoms are made possible via CH–π hydrogen bonds by adopting a tubular hydrocarbon as a host for their enthalpy-driven complexation. Concyclic arrays of weak hydrogen bonds further allow dynamic rotational motions of the guest in the host. Solid-state analysis with crystallographic and spectroscopic methods reveal a single-axis rotation of the bowl in the tube.
“…The carbazole group can not only serve as active site (p‐type) for energy storage but is capable of polymerization under electrochemical oxidation conditions as well. Moreover, various carbazole‐based small molecules can be synthesized in simple one‐step synthesis via C−N coupling reactions [30–32] . Therefore, the carbazole group was selected as the functional unit to construct monomers with different molecular structures.…”
Section: Resultsmentioning
confidence: 99%
“…To compare the differences between in‐situ electro‐polymerization and ex‐situ polymerization, PDCN was synthesized as well by using a chemical oxidative polymerization procedure before the cell was fabricated (Scheme S3, Supporting Information) [31] . To further verify the successful conversion from monomer to target polymer, FTIR spectroscopy was carried out (Figure S6a, Supporting Information).…”
In‐situ electro‐polymerization of redox‐active monomers has been proved to be a novel and facile strategy to prepare polymer electrodes with superior electrochemical performance. The monomer molecular structure would have a profound impact on electro‐polymerization behavior and thus electrochemical performance. However, this impact is poorly understood and has barely been investigated yet. Herein, three carbazole‐based monomers, 9‐phenylcarbazole (CB), 1,4‐bis(carbazol‐9‐yl)benzene (DCB), and 2,6‐bis(carbazol‐9‐yl)naphthalene (DCN), were applied to study the above issue systematically and achieve excellent long cycle performance. The monomers were rationally designed with different polymerizable sites and solubilities. It was found that a monomer with increased polymerizable sites and decreased solubility brought about enhanced electrochemical performance. This is because poor solubility could enhance utilization of the monomer for polymerization and more polymerizable sites could lead to a stable crosslinked polymer network after electro‐polymerization. DCN with four polymerizable sites and the poorest solubility displayed the best electrochemical performance, which showed stable cycling up to 5000 cycles with high capacity retention of 76.2 % (among the best cycle in the literature). Our work for the first time reveals the relationship between monomer structure and in‐situ electro‐polymerization behavior. This work could shed light on the structure design/optimization of monomers for high‐performance polymer electrodes prepared through in‐situ electro‐polymerization.
“…Our purpose is to use halogenated carbazoles to produce bulky stators and facilitate attractive interactions among the halogen atoms on the periphery. [33] This approach is not trivial given that the substitutions reduce the ability of the carbazole derivatives to form the desired 2:1c ocrystals with DABCO, affording the 1:1s pecies instead (not discussed here). Letu s focus on the supramolecular nature of these rotors because the lack of ac ovalent bond may result in low electronic barriers to rotationa nd, in conjunction with the globulars hape of the DABCO, very high rotational frequencies could be obtained ( Figure 1).…”
Two new crystalline rotors 1 and 2 assembled through N−H⋅⋅⋅N hydrogen bonds by using halogenated carbazole as stators and 1,4‐diaza[2.2.2]bicyclooctane (DABCO) as the rotator, are described. The dynamic characterization through 1H T1 relaxometry experiments indicate very low rotational activation barriers (Ea) of 0.67 kcal mol−1 for 1 and 0.26 kcal mol−1 for 2, indicating that DABCO can reach a THz frequency at room temperature in the latter. These Ea values are supported by solid‐state density functional theory computations. Interestingly, both supramolecular rotors show a phase transition between 298 and 250 K, revealed by differential scanning calorimetry and single‐crystal X‐ray diffraction. The subtle changes in the crystalline environment of these rotors that can alter the motion of an almost barrierless DABCO are discussed here.
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