2D NMR characterization of the La@C82 anion
2D NMR characterization of the La@C82 anion
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DOI：
10.1002/anie.200500039
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发表时间：
2005-01-01
影响因子：
16.6
通讯作者：
Nagase, S
中科院分区：
文献类型：
--
作者：
Tsuchiya, T;Wakahara, T;Nagase, S
垂直维度上的量子频率，每个峰值出现在水平维度上的两个相应的化学位移处。为了在早期确定[La@C82-A][La@C82-A]的2D谱，在B3LYP-GIAO/6-31G(D)//B3LYP/6-311+G(D)水平上计算了[La@C82-A]的~(13)C核磁共振化学位移。结果表明，表1中编号为8的C原子具有最强的13C核磁共振信号。因此，我们从图1中最上场的信号a，即从8号碳开始，开始了13CNMR指认和键连接。如表1所示，[La@C82-A]？中的所有C原子都被完全指认，这是除了C60，C70及其衍生物之外的富勒烯的第一个例子。在2D不足的核磁共振谱中，每个峰被相应的碳-碳耦合常数1JCC分裂成双峰。众所周知，1JCC随着键长的缩短和π键序的增加而增加。[12]空富勒烯的5，6和6，6环融合键，如C60和C70，分别被认为具有单键和双键特征。[13]图2a绘制了在B3LYP/6-311+G(D)水平上计算的[La@C82-A]±C键长与观察到的1JCC值的关系。为了比较[La@C82-A]与空富勒烯，C60[10b，c]和原始C70[11b]的反式-3和反式-4 Bingel双加合物的曲线图也如图2b-d所示。对于空富勒烯，具有较大1JCC值和较短计算键的C±C键对应于6，6环融合键，这些图与5，6环融合键的曲线不重叠。然而，[La@C82-A]的6，6和5，6环融合键的曲线图相互重叠。由此可以得出结论：[La@C82-A]？中的5，6和6，6环熔键分别被缩短和拉长，[La@C82-A]？的单键和双键性质的分类不如空富勒烯的分类清楚。还计算了C82(C2v)的5，6环融合键的缩短和6，6环融合键的伸长(图3)。然而，[La@C82-A]？的缩短和伸长程度远远大于
quantum frequency in the vertical dimension, and each peak appears at the two respective chemical shifts in the horizontal dimension. To assign the 2D INADEQUATE NMR spectrum at an early stage, the 13C NMR chemical shifts of [La@ C82-A] À were calculated at the B3LYP-GIAO/6-31G (d)//B3LYP/6-311+ G (d) level. It was shown that the C atom designated no. 8 in Table1 has the most upfield 13C NMR signal. Therefore, we started the 13C NMR assignment and bond connectivity from the most upfield signal a in Figure 1, that is, from carbon no. 8. As shown in Table1, all C atoms in [La@ C82-A] À are completely assigned, as the first example for fullerenes apart from C60, C70, and their derivatives. In the 2D INADEQUATE NMR spectrum, each peak is split into a doublet by the relevant carbon–carbon coupling constant 1JCC. It is well known that 1JCC increases with shortening bond length and increasing π-bond order.[12] The 5, 6 and 6, 6 ring-fusion bonds of empty fullerenes such as C60 and C70 are considered to have single-and double-bond character, respectively.[13] Figure2a plots the CÀC bond lengths calculated for [La@ C82-A] À at the B3LYP/6-311+ G (d) level against the observed 1JCC values. To compare [La@ C82-A] À with empty fullerenes, the plots for trans-3 and trans-4 Bingel bis-adducts of C60[10b, c] and pristine C70 [11b] are also shown in Figure 2 b–d. For the empty fullerenes, the CÀC bonds with larger 1JCC values and shorter calculated bonds correspond to the 6, 6 ring-fusion bonds, and these plots do not overlap with those for the 5, 6 ring-fusion bonds. However, the plots of 6, 6 and 5, 6 ring-fusion bonds for [La@ C82-A] À overlap with each other. In this context, it may be concluded that the 5, 6 and 6, 6 ring-fusion bonds in [La@ C82-A] À are shortened and elongated, respectively, and the classification of singleand double-bond character of [La@ C82-A] À is less clear than that of empty fullerenes. Shortening of the 5, 6 ring-fusion bonds and the elongation of the 6, 6 ring-fusion bonds were also calculated for C82 (C2v)(Figure 3). However, the extent of shortening and elongation in [La@ C82-A] À is much larger than