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首页> 外文期刊>Physical chemistry chemical physics: PCCP >X-Ray absorption spectroscopy quantitative analysis of biomimetic copper(Ⅱ) complexes with tridentate nitrogen ligands mimicking the tris(imidazole) array of protein centres
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X-Ray absorption spectroscopy quantitative analysis of biomimetic copper(Ⅱ) complexes with tridentate nitrogen ligands mimicking the tris(imidazole) array of protein centres

机译：X射线吸收光谱法定量模拟具有三齿氮配体的仿生铜（Ⅱ）配合物，模拟蛋白质中心的三（咪唑）阵列

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In this study copper(Ⅱ) complexes with the tridentate nitrogen ligand bis[2-(1-methylbenzimidazol-2-yl)ethyl]amine (2-BB) are considered as model compounds for the Cu-tris(imidazole) array found in several copper proteins. 2-BB chelates copper(Ⅱ) forming two six-membered rings and the complexes contain methanol, nitrite, azide and water as ancillary ligands; both the coordination numbers and stereochemistries differ in these complexes. Their key structural features were investigated by using full multiple-scattering theoretical analysis of the copper K-edge X-ray absorption spectrum with the MXAN code. We showed that using cluster sizes large enough to include all atoms of the ligand, the analysis of the XANES region can give both a structural model of the metal centre and map the structure of the 2-BB complexes. Complex [Cu(2-BB)(N_3)]~+ provided a critical test through the comparison of the XANES simulation results with crystallographic data, thus permitting the extension of the method to the complex [Cu(2-BB)(H_2O)_n]~+ (n = 1 or 2), for which crystallographic data are not available but is expected to bear a five-coordinated Cu(3N)(20) core (n = 2). The structural data of [Cu(2-BB)(MeOH)(ClO_4)]~+ and [Cu(2-BB)(NO_2)]~+, both with a Cu(3N)(2O) core but with a different stereochemistry, were used as the starting parameters for two independent simulations of the XANES region of the [Cu(2-BB)(H_2O)_2]~+ cation. The two structural models generated by simulation converge towards a structure for the aqua-cation with a lower coordination number. New calculations, where four-coordinated Cu(3N)(O) cores were considered as the starting structures, validated that the structure of the aqua-complex in the powder state has a copper(Ⅱ) centre with a four-coordinated Cu(3N)(O) core and a molecular formula [Cu(2-BB)(H_2O)](ClO_4)-(H_2O). A water solvation molecule, presumed to be disordered from the simulations with the two Cu(3N)(2O) cores, is present. The successful treatment of this Cu-2-BB complex system allows the extension of the method to other biomimetic compounds when a structural characterization is lacking.
机译：在这项研究中，铜（Ⅱ）与三齿氮配体双[2-（1-甲基苯并咪唑-2-基）乙基]胺（2-BB）的配合物被认为是发现于铜-三（咪唑）阵列的模型化合物。几种铜蛋白。 2-BB螯合形成两个六元环的铜（Ⅱ），配合物含有甲醇，亚硝酸盐，叠氮化物和水作为辅助配体。这些配合物中的配位数和立体化学都不同。通过使用MXAN代码对铜K边缘X射线吸收光谱进行全面的多次散射理论分析，研究了它们的关键结构特征。我们表明，使用足够大的簇尺寸来包含配体的所有原子，对XANES区域的分析既可以给出金属中心的结构模型，又可以绘制2-BB配合物的结构图。通过将XANES模拟结果与晶体学数据进行比较，复合物[Cu（2-BB）（N_3）]〜+提供了关键测试，从而使该方法可扩展为复合物[Cu（2-BB）（H_2O） _n]〜+（n = 1或2），尚无晶体学数据，但预计将带有五配位的Cu（3N）（20）核（n = 2）。 [Cu（2-BB）（MeOH）（ClO_4）]〜+和[Cu（2-BB）（NO_2）]〜+的结构数据，均具有Cu（3N）（2O）核，但具有不同的结构立体化学被用作[Cu（2-BB）（H_2O）_2]〜+阳离子的XANES区域的两个独立模拟的起始参数。通过仿真生成的两个结构模型会收敛到具有较低配位数的水生结构。新的计算以四配位的Cu（3N）（O）核为起始结构，验证了粉状水络合物的结构具有一个铜（Ⅱ）中心和四配位的Cu（3N）中心（O）核和分子式[Cu（2-BB）（H_2O）]（ClO_4）-（H_2O）。存在一个水溶剂化分子，推测是从两个Cu（3N）（2O）核的模拟中无序的。当缺乏结构表征时，此Cu-2-BB复合系统的成功治疗使该方法可扩展至其他仿生化合物。

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