N-14 NUCLEAR-QUADRUPOLE RESONANCE-SPECTRA OF COORDINATED IMIDAZOLE
N-14 NUCLEAR-QUADRUPOLE RESONANCE-SPECTRA OF COORDINATED IMIDAZOLE
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DOI：
10.1021/ja00487a014
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发表时间：
1978-01-01
影响因子：
15
通讯作者：
BROWN, TL
中科院分区：
文献类型：
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作者：
ASHBY, CIH;CHENG, CP;BROWN, TL
测量了 N-苯甲基咪唑、碘化咪唑鎓、硝酸咪唑鎓以及咪唑 11 Zn 和 Ca 络合物在 77 K 下的 14N NQR（核四极共振）光谱。 [这些化合物可能代表蛋白质中组氨酸咪唑侧链的模型。]使用改进的汤斯-戴利模型，配位时亚氨基N处场梯度张量的变化与向路易斯酸中心提供电子的程度相关。正如预期的那样，氨基 N 处的场梯度张量变化很小。 NQR 结果强烈表明，中性配体（例如咪唑）比大多数阴离子配体（例如阴离子配体）有效地将更少的电子电荷转移到金属。例如，比卤化物。然而，阴离子（例如硝酸根）的电荷基本上是离域的，其电子供给较少。
The 14N NQR (nuclear quadrupole resonance) spectra at 77 K were measured for N-benzylimidazole, imidazolium iodide, imidazolium nitrate, and 11 Zn and Ca complexes of imidazole. [These compounds may represent models for imidazole side chain of histidine in proteins.] The changes in field gradient tensor at the imino N upon coordination were related to the extent of electron donation to the Lewis acid center, using a modified Townes-Dailey model. Changes in field gradient tensor at the amino N are small, as expected. The NQR results sugest strongly that neutral ligands such as imidazole effectively transfer less electronic charge to the metal than most anionic ligands, e. g., than halides. However, anions such as nitrate, in which the charge is substantially delocalized, are less electron donating.