An epilogue on the C78-fullerene family: the discovery and characterization of an elusive isomer.
An epilogue on the C78-fullerene family: the discovery and characterization of an elusive isomer.
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C78-富勒烯家族的后记：难以捉摸的异构体的发现和表征。
DOI：
10.1002/anie.200801922
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发表时间：
2008
影响因子：
--
通讯作者：
M. Jansen
中科院分区：
文献类型：
--
作者：
K. Simeonov;K. Amsharov;E. Krokos;M. Jansen
在富勒烯含量较高的闭合碳团簇中，偶数个原子数大于70-C78的碳团簇已成为许多实验和理论研究的对象。根据孤立五角形规则(IPR)，78个碳原子组成的笼子可能有5个不同连接性的异构体。这一家族的前三个代表--C78(1)(具有D3点群对称性)、C78(2)和C78(3)(均具有C2v对称性)已在煤烟提取物中被发现，并通过高效液相技术分离，并通过结晶学或CNMR分析进行了表征。下一个已知的稳定但不溶的异构体是C78(5)(D3h)，它的连接性模式最近通过其衍生物C78(CF3)12被证实。因此，这个家族中唯一未被探索的成员C78(4)(D3h)需要完成富勒烯异构体的第一个多元基团。虽然预测C78(4)在所有IPR C78异构体中在较宽的温度区间内最不稳定，[6]这一事实证明它不存在于富勒烯提取物中，7]它的每个碳原子的能量与C70的能量相当。[7]根据密度泛函理论(DFT)水平的计算，[8]C78(4)在最高占据分子轨道(HOMO)和最低未占据分子轨道(LUMO)之间有较大的能隙(2.47 eV)，与C70(2.69 eV)和C60(2.76 eV)相当。[7]
Among the higher fullerenes—closed carbon clusters with even numbers of atoms greater than 70—C78 has been a subject of many experimental, as well as theoretical investigations. According to the isolated pentagon rule (IPR), five isomers with different connectivities are possible for a cage constituted of 78 carbon atoms. The first three representatives of this family—C78(1) (with D3 point group symmetry), C78(2) and C78(3) (both with C2v symmetry), have been found in soot extracts, isolated by means of HPLC techniques, and characterized either crystallographically, or by C NMR analyses. The next known stable, but insoluble isomer is C78(5) (D3h), the connectivity pattern of which was recently confirmed through its derivative C78(CF3)12. [5] Thus, the only unexplored member of this family, C78(4) (D3h), is needed to complete the first multi membered group of fullerene isomers. Although C78(4) is predicted to be the least stable among all IPR C78 isomers across a wide temperature interval, [6] a fact justifying its absence in fullerene extracts, 7] its energy per carbon atom is comparable to that of C70. [7] According to a calculation performed at the DFT (desity functional theory) level, [8] C78(4) possesses a large energy gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of 2.47 eV, which is comparable to those of C70 (2.69 eV) and C60 (2.76 eV). [7]