An orifice-size index for open-cage fullerenes.
An orifice-size index for open-cage fullerenes.
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DOI：
10.1021/jo070790w
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发表时间：
2007-07
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影响因子：
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通讯作者：
Shih‐Ching Chuang;Y. Murata;M. Murata;K. Komatsu
中科院分区：
文献类型：
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作者：
Shih‐Ching Chuang;Y. Murata;M. Murata;K. Komatsu
在开笼富勒烯领域，缺乏一个通用的标准，可以关联和量化开笼富勒烯的孔径。人们不能通过简单地比较构成小孔的原子数来比较小孔的相对大小。我们提出了一个通用的术语，通过定义一个指数开笼富勒烯的相对孔尺寸容易估计。我们通过匹配计算的从开笼富勒烯释放氢的活化能Ea（计算值）（B3 LYP/6- 31 G **//B3 LYP/3- 21 G）与计算的氢分子通过环[n]碳环所需的能量来估计开笼富勒烯孔的相应有效面积A（面积）。然后，我们基于实验氢释放速率定义指数K（孔），其中K（孔）= ln k/k度（k是在160 ℃下用于比较的任何开笼富勒烯的氢释放速率的速率常数; k度是从作为标准化合物的H2@4a的氢释放速率）。我们合成了几种开笼富勒烯，并研究了一组氢包封开笼富勒烯的动力学，以评估其K值。折射率K（孔）与有效面积A（面积）的相关性显示出良好的线性拟合（r2 = 0.972），表明实验与理论之间存在良好的相互作用。这使得人们可以通过计算设计的开笼富勒烯的活化能Ea（计算值）来估计K（孔）指数和/或氢释放的相对速率k。
In the field of open-cage fullerenes, there was a lack of a universal standard that could correlate and quantify the orifice size of open-cage fullerenes. One cannot compare the relative orifice size by simple comparison of the number of atoms that composes the orifice. We present a general term for easy estimation of relative orifice size by defining an index for open-cage fullerenes. We estimated the corresponding effective areas A(area) for orifices of open-cage fullerenes by matching calculated activation energies Ea(calcd) for hydrogen release from open-cage fullerenes (B3LYP/6-31G**//B3LYP/3-21G) to the computed energies required for a hydrogen molecule passing through a cyclo[n]carbon ring. Then we define an index K(orifice) based on experimental hydrogen release rate, where K(orifice) = ln k/k degrees (k is rate constant of hydrogen-release rate of any open-cage fullerenes taken for comparison at 160 degrees C; k degrees is the hydrogen release rate from H2@4a taken as the standard compound). We synthesized several open-cage fullerenes and studied kinetics of a set of H2-encapsulated open-cage fullerenes to evaluate their K values. A correlation of the index K(orifice) with the effective areas A(area) showed a good linear fit (r2 = 0.972) that demonstrated a good interplay between experiment and theory. This allows one to estimate K(orifice) index and/or relative rate k of hydrogen release through computing activation energy Ea(calcd) for a designed open-cage fullerene.