Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States.
J Am Chem Soc. 2017 Mar 29;139(12):4477-4485. doi: 10.1021/jacs.7b00210. Epub 2017 Mar 20.
The stretching frequency, ν(Cu-O), of the [CuOH] core in the complexes LCuOH (L = N,N'-bis(2,6-diisopropyl-4-R-phenyl)pyridine-2,6-dicarboxamide, R = H or NO, or N,N'-bis(2,6-diisopropylphenyl)-1-methylpiperidine-2,6-dicarboxamide) was determined to be ∼630 cm by resonance Raman spectroscopy and verified by isotopic labeling. In efforts to use Badger's rule to estimate the bond distance corresponding to ν(Cu-O), a modified version of the rule was developed through use of stretching frequencies normalized by dividing by the appropriate reduced masses. The modified version was found to yield excellent fits of normalized frequencies to bond distances for >250 data points from theory and experiment for a variety of M-X and X-X bond distances in the range ∼1.1-2.2 Å (root mean squared errors for the predicted bond distances of 0.03 Å). Using the resulting general equation, the Cu-O bond distance was predicted to be ∼1.80 Å for the reactive [CuOH] core. Limitations of the equation and its use in predictions of distances in a variety of moieties for which structural information is not available were explored.
通过共振拉曼光谱确定配合物 LCuOH（L = N，N'-双（2,6-二异丙基-4-R-苯基）吡啶-2,6-二羧酸酰胺，R = H 或 NO，或 N，N'-双（2,6-二异丙基苯基）-1-甲基哌啶-2,6-二羧酸酰胺）中[CuOH]核心的拉伸频率 ν(Cu-O)约为 630 cm，并通过同位素标记进行了验证。为了使用 Badger 规则估计对应于 ν(Cu-O)的键距，通过使用通过除以适当的约化质量归一化的拉伸频率，开发了规则的修改版本。该修改版本发现，对于来自理论和实验的>250 个数据点，对于各种 M-X 和 X-X 键距在约 1.1-2.2 Å 的范围内，归一化频率与键距的拟合非常好（预测键距的均方根误差为 0.03 Å）。使用所得的一般方程，预测反应性[CuOH]核心的 Cu-O 键距约为 1.80 Å。探讨了该方程的局限性及其在预测各种结构信息不可用的部分的距离中的应用。
