Spectroscopic and theoretical studies of mononuclear copper(II) alkyl- and hydroperoxo complexes: Electronic structure contributions to reactivity
Spectroscopic and theoretical studies of mononuclear copper(II) alkyl- and hydroperoxo complexes: Electronic structure contributions to reactivity
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DOI：
10.1021/ja0016755
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发表时间：
2000-10-18
影响因子：
15
通讯作者：
Solomon, EI
中科院分区：
文献类型：
--
作者：
Chen, P;Fujisawa, K;Solomon, EI
用光谱研究和计算相结合的方法描述了单核四配位端对烷基过氧和氢过氧Cu（II）配合物的电子结构和振动性质。EPR定义了Cu x(2)-y(2)基态，具有类似于62% Cu的特征。从吸收光谱、MCD光谱和共振拉曼光谱中发现，烷基（氢）过氧化物与Cu（LI）之间的主要键合相互作用涉及烷基（氢）过氧化物pi*(v)在Cu x(2)-y(2)轨道上的pi -给能，这在观察到的光谱特征中占主导地位，产生了一个类似于16 600 cm(-1)（类似于600 nm）的强烈吸收带。根据振动频率、同位素位移和正坐标分析，确定了烷基（氢）过氧配合物的主导振动，并确定了Cu-O和O-O力常数。观察到的强Cu- o键和烷基（氢）过氧化物对Cu（II）的大电荷给予归因于Cu的低配位数和扭曲的T-d配体场。观察到的强O-O键主要来自于烷基碳/质子的极化。未占据的过氧化物sigma*轨道在能量上也非常稳定，并且配合物被激活以进行亲电攻击。通过实验校准的密度泛函计算，结合前沿分子轨道理论，对这些模型配合物的反应性进行了深入研究。评估了亲电攻击、O-O键切割和H原子抽象的机制，并考虑了它们与多巴胺β -单加氧酶和肽基甘氨酸α -羟化单加氧酶反应的相关性。
Spectroscopic studies combined with calculations are used to describe the electronic structure and vibrational properties of mononuclear four-coordinate end-on alkylperoxo and hydroperoxo Cu(II) complexes. EPR defines a Cu x(2)-y(2) ground state with similar to 62% Cu character. From absorption, MCD, and resonance Raman spectroscopies, the main bonding interaction between the alkyl(hydro)peroxide and Cu(LI) is found to involve the pi -donation of the alkyl(hydro)peroxide pi*(v) into the Cu x(2)-y(2) orbital, which dominates the observed spectroscopic features, producing an intense absorption band at similar to 16 600 cm(-1) (similar to 600 nm). On the basis of the vibrational frequencies, isotope shifts, and normal coordinate analyses, the dominant vibrations of the alkyl(hydro)peroxo complexes are assigned and the Cu-O and O-O force constants are determined. The observed strong Cu-O bond and the large alkyl(hydro)peroxide-to-Cu(II) charge donation are ascribed to the low coordination number of Cu and the distorted T-d ligand field. The observed strong O-O bond mainly derives from polarization by the alkylcarbon/proton. The unoccupied peroxide sigma* orbital is also greatly stabilized in energy, and the complexes are activated for electrophilic attack. Experimentally calibrated density functional calculations, coupled with frontier molecular orbital theory, are employed to obtain insight into the reactivity of these model complexes. Mechanisms of electrophilic attack, O-O bond cleavage, and H atom abstraction are evaluated, and their relevance to dopamine beta -monooxygenase and peptidylglycine alpha -hydroxylating monooxygenase reactivities is considered.