Institut für Anorganische Chemie, Georg-August-Universität Göttingen , Tamannstrasse 4, 37077 Göttingen, Germany.
J Am Chem Soc. 2014 May 21;136(20):7428-34. doi: 10.1021/ja5025047. Epub 2014 May 9.
The ability of many copper metalloenzymes to activate O2 and transfer it to organic substrates has motivated extensive attention in the literature. Investigations focusing on synthetic analogues have provided a detailed understanding of the structures of potential intermediates, thereby helping to guide mechanistic studies. We report herein a crystallographically characterized synthetic Cu(II)2(μ-η(1):η(1)-O2) complex exhibiting cis-peroxo bonding geometry, known in iron chemistry but previously unobserved for copper. Detailed investigation by UV-vis, resonance Raman, and infrared spectroscopies provides evidence for a significantly diminished copper-oxygen interaction (ε ≈ 3000 M(-1) cm(-1), ν(Cu-O) = 437 cm(-1), ν(O-O) = 799 cm(-1)) relative to those in known 'coupled' Cu2O2 species, consistent with magnetic measurements which show that the peroxide mediates only weak antiferromagnetic coupling (-2J = 144 cm(-1)). These characteristics are comparable with those of a computationally predicted transition state for O2 binding to type 3 copper centers, providing experimental evidence for the proposed mechanism of O2 activation and supporting the biological relevance of the Cu(II)2(μ-η(1):η(1)-O2) cis-species. The peroxide bonding arrangement also allows binding of sodium cations, observed both in the solid state and in solution. Binding induces changes on an electronic level, as monitored by UV-vis spectroscopy (K(a) = 1700 M(-1)), reminiscent of redox-inactive metal binding by iron-oxygen species. The results presented highlight the analogous chemistry these reactive oxygen species undergo, with respect to both their mechanism of formation, and the molecular interactions in which they participate.
许多铜金属酶能够激活 O2 并将其转移到有机底物上，这在文献中引起了广泛的关注。针对合成类似物的研究提供了对潜在中间体结构的详细了解，从而有助于指导机理研究。我们在此报告了一种结晶学表征的合成 Cu(II)2(μ-η(1):η(1)-O2)配合物，其具有顺式过氧键合几何形状，这种几何形状在铁化学中是已知的，但以前在铜中未观察到。通过紫外-可见、共振拉曼和红外光谱的详细研究提供了证据，表明铜-氧相互作用显著减弱（ε≈3000 M(-1) cm(-1)，ν(Cu-O)=437 cm(-1)，ν(O-O)=799 cm(-1)），与已知的“偶联”Cu2O2 物种相比，这与磁测量结果一致，表明过氧化物仅介导较弱的反铁磁耦合（-2J=144 cm(-1)）。这些特性与计算预测的 3 型铜中心结合 O2 的过渡态相当，为 O2 活化的提议机制提供了实验证据，并支持 Cu(II)2(μ-η(1):η(1)-O2)顺式物种的生物学相关性。过氧化物键合排列也允许钠离子的结合，这在固态和溶液中都有观察到。电子水平的监测表明，结合会引起变化，这可以通过紫外-可见光谱来监测（K(a)=1700 M(-1)），类似于铁-氧物种的氧化还原非活性金属结合。所呈现的结果突出了这些反应性氧物种在其形成机制以及它们参与的分子相互作用方面所经历的类似化学。
