Bredenkötter Björn, Grzywa Maciej, Alaghemandi Mohammad, Schmid Rochus, Herrebout Wouter, Bultinck Patrick, Volkmer Dirk
Augsburg University, Institute of Physics, Chair of Solid State and Materials Chemistry, Universitätsstrasse 1, 86159 Augsburg (Germany).
Chemistry. 2014 Jul 14;20(29):9100-10. doi: 10.1002/chem.201304980. Epub 2014 Jun 25.
The synthesis of a stereochemically pure concave tribenzotriquinacene receptor (7) for C60 fullerene, possessing C3 point group symmetry, by threefold condensation of C2 -symmetric 1,2-diketone synthons (5) and a hexaaminotribenzotriquinacene core (6) is described. The chiral diketone was synthesized in a five-step reaction sequence starting from C2h -symmetric 2,6-di-tert-butylanthracene. The highly diastereo-discriminating Diels-Alder reaction of 2,6-di-tert-butylanthracene with fumaric acid di(-)menthyl ester, catalyzed by aluminium chloride, is the relevant stereochemistry introducing step. The structure of the fullerene receptor was verified by (1)H and (13)C NMR spectroscopy, mass spectrometry and single crystal X-ray diffraction. VCD and ECD spectra were recorded, which were corroborated by ab initio DFT calculations, establishing the chiral nature of 7 with about 99.7 % ee, based on the ee (99.9 %) of the chiral synthon (1). The absolute configuration of 7 could thus be established as all-S [(2S,7S,16S,21S,30S,35S)-(7)]. Spectroscopic titration experiments reveal that the host forms 1:1 complexes with either pure fullerene (C60) or fullerene derivatives, such as rotor 1'-(4-nitrophenyl)-3'-(4-N,N-dimethylaminophenyl)-pyrazolino[4',5':1,2][60]fullerene (R). The complex stability constants of the complexes dissolved in CHCl3/CS2 (1:1 vol. %) are K([C60 ⊂7]) = 319(±156) M(-1) and K([R⊂7]) = 110(±50) M(-1). With molecular dynamics simulations using a first-principles parameterized force field the asymmetry of the rotational potential for [R⊂7] was shown, demonstrating the potential suitability of receptor 7 to act as a stator in a unidirectionally operating nanoratchet.
描述了通过C2对称的1,2 - 二酮合成子（5）与六氨基三苯并三蝶烯核心（6）的三次缩合反应，合成具有C3点群对称性的用于C60富勒烯的立体化学纯的凹形三苯并三蝶烯受体（7）。手性二酮是从具有C2h对称性的2,6 - 二叔丁基蒽开始，通过五步反应序列合成的。2,6 - 二叔丁基蒽与富马酸二（-）薄荷酯在氯化铝催化下的高度非对映选择性狄尔斯 - 阿尔德反应是引入相关立体化学的步骤。通过（1）H和（13）C NMR光谱、质谱和单晶X射线衍射对富勒烯受体的结构进行了验证。记录了VCD和ECD光谱，并通过从头算DFT计算得到证实，基于手性合成子（1）的ee（99.9％）确定了7的手性性质，ee约为99.7％。因此，7的绝对构型可以确定为全S型[（2S，7S，16S，21S，30S，35S）-（7）]。光谱滴定实验表明，主体与纯富勒烯（C60）或富勒烯衍生物，如转子1'-（4 - 硝基苯基）-3'-（4 - N，N - 二甲基氨基苯基）-吡唑啉并[4'，5'：1，2][60]富勒烯（R）形成1：1配合物。溶解在CHCl3/CS2（1：1体积％）中的配合物的配合物稳定性常数为K（[C60⊂7]）= 319（±156）M（-1）和K（[R⊂7]）= 110（±50）M（-1）。使用第一性原理参数化力场进行分子动力学模拟，显示了[R⊂7]旋转势的不对称性，证明了受体7作为单向操作纳米棘轮中的定子的潜在适用性。
