Ligand Effects in the Models and Mimics of Oxyhemocyanin and Oxytyrosinase. A Density Functional Study of Reversible Dioxygen Binding and Reversible O-O Bond Cleavage.
Ligand Effects in the Models and Mimics of Oxyhemocyanin and Oxytyrosinase. A Density Functional Study of Reversible Dioxygen Binding and Reversible O-O Bond Cleavage.
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氧血蓝蛋白和氧酪氨酸酶模型和模拟物中的配体效应。
DOI：
10.1021/ic970396o
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发表时间：
1997
影响因子：
4.6
通讯作者：
A. Bérces
中科院分区：
文献类型：
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作者：
A. Bérces
采用梯度修正密度泛函方法，研究了{[LCu]（2）O（2）}（2+），L = 1，4，7-三氮杂环壬烷（1）和L =氢化三吡唑硼酸酯（2）的Cu（2）（-eta（2）：eta（2）-O（2））和Cu（2）（-O）（2）核结构之间的分子氧键合和核异构化反应. 1和2的N-取代衍生物是氧合血蓝蛋白的合成无机模拟物，具有相似的物理和光谱性质，但不同的化学行为。计算的1和2的分子氧结合能分别为-60和-184 kJ/mol，与1可逆结合氧和2不可逆结合氧的观察结果一致。键能分解表明轨道相互作用对1和2的结合能的贡献相等，这解释了它们光谱性质的相似性。由于带负电荷的配体的静电相互作用是负责2中更强的结合。从Cu（2）（-eta（2）：eta（2）-O（2））异构化为1和2的Cu（2）（-O）（2）异构体的核心异构化能分别为+1和+12 kJ/mol。1和2的核心异构化相对于Cu（2）（-eta（2）：eta（2）-O（2））异构体的势垒高度分别为33和37 kJ/mol。1的结果与实验观察到的两种异构体之间快速且可逆的相互转化一致，而2的这些数据表明，（-O）（2）异构体中2的观察仅因其热不稳定性而被阻止。我们还考虑了纯理论模型化合物{[（NH（3））（3）Cu]（2）O（2）}（2+）（3）。3的计算表明，该模型是明显不足的，即使是定性的能量建模的双氧结合，而它是成功的描述光谱，结构和磁性。计算表明，3的异构化是吸热的49 kJ/mol，并且相对于较高能量的（-O）（2）异构体基本上没有能垒。3的分子氧结合能是吸热的160 kJ/mol，而不是在1和2中的放能结合。
We studied the energetics of dioxygen binding and the core isomerization between the Cu(2)(&mgr;-eta(2):eta(2)-O(2)) and Cu(2)(&mgr;-O)(2) core structures of {[LCu](2)O(2)}(2+), L = 1,4,7-triazacyclononane (1) and L = hydrotris(pyrazolyl)borate (2), by gradient-corrected density functional methods. N-Substituted derivatives of 1 and 2 are synthetic inorganic mimics of oxyhemocyanin with similar physical and spectroscopic properties but different chemical behavior. The calculated dioxygen binding energies of 1 and 2 are -60 and -184 kJ/mol, respectively, in line with the observation that 1 binds oxygen reversibly and 2 does so irreversibly. Bond energy decomposition showed that orbital interactions contribute equally to the binding energy of 1 and 2, which explains the similarities in their spectral properties. Electrostatic interactions due to the negatively charged ligand are responsible for stronger binding in 2. The core isomerization energies for isomerization from the Cu(2)(&mgr;-eta(2):eta(2)-O(2)) to the Cu(2)(&mgr;-O)(2) isomers of 1 and 2 are +1 and +12 kJ/mol, respectively. The barrier heights of the core isomerizations of 1 and 2 relative to the Cu(2)(&mgr;-eta(2):eta(2)-O(2)) isomer are 33 and 37 kJ/mol, respectively. The results on 1 are in line with the experimentally observed fast and reversible interconversion between the two isomers while these data on 2 suggest that the observation of 2 in the (&mgr;-O)(2) isomer was only prevented by its thermal instability. We also considered a purely theoretical model compound, {[(NH(3))(3)Cu](2)O(2)}(2+) (3). Calculations on 3 show that this model is clearly inadequate even for qualitative energetic modeling of dioxygen binding while it is successful in describing spectral, structural, and magnetic properties. Calculations show that the isomerization of 3 is endoergic by 49 kJ/mol, and there is essentially no energy barrier relative to the higher energy (&mgr;-O)(2) isomer. The dioxygen binding energy of 3 is endoergic by 160 kJ/mol as opposed to the exoergic binding in both 1 and 2.