Weakly Coupled Biologically Relevant Cu-2(II)(mu-eta(1):eta(1)-O-2) cis-Peroxo Adduct that Binds Side-On to Additional Metal Ions

作者：Dalle Kristian E; Gruene Tim; Dechert Sebastian; Demeshko Serhiy; Meyer Franc^*

来源：Journal of the American Chemical Society, 2014, 136(20): 7428-7434.

DOI：10.1021/ja5025047

The ability of many copper metalloenzymes to activate 02 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-2(II)(mu-eta(1):eta(1)-O-2) 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 (epsilon approximate to 3000 M-1 cm(-1), nu(Cu-O) = 437 cm(-1), nu(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 02 binding to type 3 copper centers, providing experimental evidence for the proposed mechanism of O-2 activation and supporting the biological relevance of the Cu-2(II)(mu-eta(1):eta(1)-O-2) 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.

• 出版日期2014-5-21