Synthesis and properties of endohedral C60 encapsulating molecular hydrogen.
Synthesis and properties of endohedral C60 encapsulating molecular hydrogen.
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DOI：
10.1021/ja061857k
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发表时间：
2006-05
影响因子：
15
通讯作者：
M. Murata;Y. Murata;K. Komatsu
中科院分区：
文献类型：
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作者：
M. Murata;Y. Murata;K. Komatsu
我们报告了我们研究的细节，合成了一个新的内嵌富勒烯，H2@C60，在超过100毫克的量通过关闭13元环孔的开笼富勒烯使用四步有机反应。先前以100%产率合成的含氢开笼富勒烯的13元环孔通过挤压孔边缘的硫原子而还原为12元环，并通过孔上的两个羰基的还原偶联进一步还原为8元环。孔口的最终关闭是通过热反应完成的。利用循环高效液相色谱法对H2@C60进行纯化。基于非量规原子轨道（GIAO）和非核化学位移（NICS）计算，解释了孔尺寸减小时封装氢的核磁共振信号逐渐下移。对H2@C60性质的光谱和电化学检测表明，被封装的氢与外部C60 pi-体系之间的电子相互作用很小，但当外部pi-体系获得3个以上的额外电子时，电子相互作用变得明显。合成了四种H2@C60的外面体衍生物。发现内部氢的核磁共振信号的位移趋势与3He@C60相应衍生物的3He核磁共振信号的位移趋势非常相似。
We report the details of our study to synthesize a new endohedral fullerene, H2@C60, in more than 100 mg quantities by closure of the 13-membered ring orifice of an open-cage fullerene using four-step organic reactions. The 13-membered ring orifice in a previously synthesized open-cage fullerene incorporating hydrogen in 100% yield was reduced to a 12-membered ring by extrusion of a sulfur atom at the rim of the orifice, and the ring was further reduced into an eight-membered ring by reductive coupling of two carbonyl groups also at the orifice. Final closure of the orifice was completed by a thermal reaction. Purification of H2@C60 was accomplished by recycle HPLC. A gradual downfield shift of the NMR signal for the encapsulated hydrogen observed upon reduction of the orifice size was interpreted based on the gauge-independent atomic orbital (GIAO) and the nucleus-independent chemical shift (NICS) calculations. The spectral as well as electrochemical examination of the properties of H2@C60 has shown that the electronic interaction between the encapsulated hydrogen and outer C60 pi-system is quite small but becomes appreciable when the outer pi-system acquires more than three extra electrons. Four kinds of exohedral derivatives of H2@C60 were synthesized. The tendency in the shift of the NMR signal of the inner hydrogen was found to be quite similar to that observed for the 3He NMR signal of the corresponding derivatives of 3He@C60.