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Abstract：
A supramolecular complex, formed by encapsulation of C60 fullerene in a molecular container built from two resorcin[4]arene rims zipped together by peptidic arms hydrogen bonded into a cylindrical β-sheet, was studied by X-ray crystallography, solid-state and solution NMR, EPR spectroscopy and differential scanning calorimetry (DSC). The crystal structure, determined at 100 K, reveals that the complex occupies 422 site symmetry, which is compatible with the molecular symmetry of the container but not of the fullerene molecule, which has only 222 symmetry. The additional crystallographic symmetry leads to a complicated but discrete disorder, which could be resolved and modelled using advanced features of the existing refinement software. Solid-state NMR measurements at 184-333 K indicate that the thermal motion of C60 in this temperature range is fast but has different activation energies at different temperatures, which was attributed to a phase transition, which was confirmed by DSC. Intriguingly, the activation energy for reorientations of C60 in the solid state is very similar for the free and encaged molecules. Also, the rotational diffusion coefficients seem to be very similar or even slightly higher for the encaged fullerene compared to the free molecule. We also found that chemical shift anisotropy (CSA) is not the main relaxation mechanism for the 13C spins of C60 in the studied complex.
摘要：
超分子复合物,通过将C60富勒烯封装在分子容器中形成，该容器由两个间苯二酚[4]芳烃边缘通过氢键键合成圆柱形β-折叠的肽臂拉链连接在一起，通过X射线晶体学研究，固态和溶液NMR，EPR光谱和差示扫描量热法(DSC)。晶体结构，在100K测定，揭示了复合物占据422位点对称性，这与容器的分子对称性相容，但与富勒烯分子不相容，只有222对称。额外的晶体学对称性导致复杂但离散的无序，可以使用现有细化软件的高级功能来解决和建模。在184-333K的固态NMR测量表明，C60在此温度范围内的热运动很快，但在不同温度下具有不同的活化能，这归因于相变，DSC证实了这一点。有趣的是，对于自由分子和被包裹分子，固态下C60重新定向的活化能非常相似。此外，与游离分子相比，包裹的富勒烯的旋转扩散系数似乎非常相似或甚至略高。我们还发现化学位移各向异性（CSA）不是所研究复合物中C60的13C自旋的主要弛豫机制。
