Ghiladi Reza A, Chufan Eduardo E, del Río Diego, Solomon Edward I, Krebs Carsten, Huynh Boi Hanh, Huang Hong-Wei, Moënne-Loccoz Pierre, Kaderli Susan, Honecker Marcus, Zuberbühler Andreas D, Marzilli Lisa, Cotter Robert J, Karlin Kenneth D
Department of Chemistry, The Johns Hopkins University, Charles and 34th Streets, Baltimore, Maryland 21218, USA.
Inorg Chem. 2007 May 14;46(10):3889-902. doi: 10.1021/ic061726k. Epub 2007 Apr 20.
In the further development and understanding of heme-copper O2-reduction chemistry inspired by the active-site chemistry in cytochrome c oxidase, we describe a dioxygen adduct, (F8TPP)FeIII-(O22-)-CuII(TMPA) (3), formed by addition of O2 to a 1:1 mixture of the porphyrinate-iron(II) complex (F8TPP)FeII (1a) {F8TPP = tetrakis(2,6-difluorophenyl)porphyrinate dianion} and the copper(I) complex (TMPA)CuI(MeCN) (1b) {TMPA = tris(2-pyridylmethyl)amine}. Complex 3 forms in preference to heme-only or copper-only binuclear products, is remarkably stable {t1/2 (RT; MeCN) approximately 20 min; lambda max = 412 (Soret), 558 nm; EPR silent}, and is formulated as a peroxo complex on the basis of manometry {1a/1b/O2 = 1:1:1}, MALDI-TOF mass spectrometry {16O2, m/z 1239 [(3 + MeCN)+]; 18O2, m/z 1243}, and resonance Raman spectroscopy {nu(O-O) = 808 cm-1; Delta16O2/18O2 = 46 cm-1; Delta16O2/16/18O2 = 23 cm-1}. Consistent with a mu-eta2:eta1 bridging peroxide ligand, two metal-O stretching frequencies are observed {nu(Fe-O) = 533 cm-1, nu(Fe-O-Cu) = 511 cm-1}, and supporting normal coordinate analysis is presented. 2H and 19F NMR spectroscopies reveal that 3 is high-spin {also muB = 5.1 +/- 0.2, Evans method} with downfield-shifted pyrrole and upfield-shifted TMPA resonances, similar to the pattern observed for the structurally characterized mu-oxo complex [(F8TPP)FeIII-O-CuII(TMPA)]+ (4) (known S = 2 system, antiferromagnetically coupled high-spin FeIII and CuII). Mössbauer spectroscopy exhibits a sharp quadrupole doublet (zero field; delta = 0.57 mm/s, |DeltaEQ| = 1.14 mm/s) for 3, with isomer shift and magnetic field dependence data indicative of a peroxide ligand and S = 2 formulation. Both UV-visible-monitored stopped-flow kinetics and Mössbauer spectroscopic studies reveal the formation of heme-only superoxide complex (S)(F8TPP)FeIII-(O2-) (2a) (S = solvent molecule) prior to 3. Thermal decomposition of mu-peroxo complex 3 yields mu-oxo complex 4 with concomitant release of approximately 0.5 mol O2 per mol 3. Characterization of the reaction 1a/1b + O2 --> 2 --> 3 --> 4, presented here, advances our understanding and provides new insights to heme/Cu dioxygen-binding and reduction.
在细胞色素c氧化酶活性位点化学启发下对血红素-铜O₂还原化学的进一步发展和理解过程中，我们描述了一种双氧加合物(F8TPP)FeIII-(O₂²⁻)-CuII(TMPA) (3)，它是通过将O₂添加到卟啉铁(II)配合物(F8TPP)FeII (1a) {F8TPP = 四(2,6-二氟苯基)卟啉二价阴离子}和铜(I)配合物(TMPA)CuI(MeCN) (1b) {TMPA = 三(2-吡啶甲基)胺}的1:1混合物中形成的。配合物3优先于仅含血红素或仅含铜的双核产物形成，非常稳定{t1/2 (室温；乙腈)约20分钟；λmax = 412 (Soret)，558 nm；EPR无信号}，并根据压力测定{1a/1b/O₂ = 1:1:1}、基质辅助激光解吸电离飞行时间质谱{¹⁶O₂，m/z 1239 [(3 + MeCN)+]；¹⁸O₂，m/z 1243}和共振拉曼光谱{ν(O - O) = 808 cm⁻¹；Δ¹⁶O₂/¹⁸O₂ = 46 cm⁻¹；Δ¹⁶O₂/¹⁶/¹⁸O₂ = 23 cm⁻¹}被确定为过氧配合物。与μ-η²:η¹桥连过氧化物配体一致，观察到两个金属 - O伸缩频率{ν(Fe - O) = 533 cm⁻¹，ν(Fe - O - Cu) = 511 cm⁻¹}，并给出了支持性的正规坐标分析。²H和¹⁹F NMR光谱表明3是高自旋的{同样μB = 5.1 ± 0.2，埃文斯方法}，吡咯共振向低场移动，TMPA共振向高场移动，类似于在结构表征的μ-氧代配合物[(F8TPP)FeIII - O - CuII(TMPA)]⁺ (4)（已知S = 2体系，反铁磁耦合的高自旋FeIII和CuII）中观察到的模式。穆斯堡尔光谱显示3有一个尖锐的四极双峰（零场；δ = 0.57 mm/s，|ΔEQ| = 1.14 mm/s），其同质异能位移和磁场依赖性数据表明存在过氧化物配体且S = 2的结构。紫外 - 可见监测的停流动力学和穆斯堡尔光谱研究都表明在3形成之前会形成仅含血红素的超氧配合物(S)(F8TPP)FeIII-(O₂⁻) (2a)（S = 溶剂分子）。μ-过氧配合物3的热分解产生μ-氧代配合物4，同时每摩尔3伴随释放约0.5摩尔O₂。此处对反应1a/1b + O₂ --> 2 --> 3 --> 4的表征推进了我们的理解，并为血红素/铜双氧结合和还原提供了新的见解。
