Center for Tsukuba Advanced Research Alliance, University of Tsukuba, Tsukuba, Ibaraki 305-8577, Japan.
Chemistry. 2009 Sep 21;15(37):9486-93. doi: 10.1002/chem.200900713.
Herein we show the synthesis and characterization of the second known Ce(2)@C(80) isomer. A (13)C NMR spectroscopic study revealed that the structure of the second isomer has D(5h) symmetry. Paramagnetic NMR spectral analysis and theoretical calculation display that the encapsulated Ce atoms circulate two-dimensionally along a band of ten contiguous hexagons inside a D(5h)-C(80) cage, which is in sharp contrast to the three-dimensional circulation of two Ce atoms in an I(h)-C(80) cage. The electronic properties were revealed by means of electrochemical measurements. The D(5h) isomer of Ce(2)@C(80) has a much smaller HOMO-LUMO gap than cluster fullerenes (M(3)N@C(80), M = Sc, Tm, and Lu) with the same D(5h)-C(80) cages. The chemical reactivity was investigated by using disilirane as a chemical probe. The high thermal reactivity toward 1,1,2,2-tetramesityl-1,2-disilirane is consistent with the trends of the redox potentials and the lower LUMO level of the D(5h) isomer of Ce(2)@C(80) compared with that of C(60).
在此，我们展示了第二种已知的 Ce(2)@C(80) 异构体的合成和表征。¹³C NMR 光谱研究表明，第二种异构体的结构具有 D(5h)对称性。顺磁共振波谱分析和理论计算表明，包封的 Ce 原子在 D(5h)-C(80)笼内沿着十个相邻六边形的带二维循环，这与 I(h)-C(80)笼内两个 Ce 原子的三维循环形成鲜明对比。通过电化学测量揭示了其电子性质。与具有相同 D(5h)-C(80)笼的团簇富勒烯 (M(3)N@C(80)，M = Sc、Tm 和 Lu) 相比，Ce(2)@C(80)的 D(5h)异构体具有更小的 HOMO-LUMO 能隙。通过使用二硅烷作为化学探针研究了其化学反应性。对 1,1,2,2-四甲基-1,2-二硅烷具有很高的热反应性，这与氧化还原电位的趋势以及 Ce(2)@C(80)的 D(5h)异构体的较低 LUMO 能级一致，与 C(60)相比。
