Reversible O2-binding and activation with dicopper and diiron complexes stabilized by various hexapyridine ligands.: Stability, modulation, and flexibility of the dinuclear structure as key aspects for the dimetal/O2 chemistry
Reversible O2-binding and activation with dicopper and diiron complexes stabilized by various hexapyridine ligands.: Stability, modulation, and flexibility of the dinuclear structure as key aspects for the dimetal/O2 chemistry
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DOI：
10.1246/bcsj.80.662
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发表时间：
2007-04-15
影响因子：
4
通讯作者：
Kano, Koji
中科院分区：
文献类型：
--
作者：
Kodera, Masahito;Kano, Koji
以不同六氢吡啶配体的二铜和二铁配合物分别作为血蓝蛋白(HC)和可溶性甲烷单加氧酶(SMMO)的功能模型，研究了它们与O-2的可逆结合和活化。空间受阻的六氢吡啶双(L)络合物与O-2反应生成室温下稳定的Mu-β(2)：eta(2)-过氧二铜(II)络合物，释放O-2，实现可逆的O-2结合。当使用在桥头位置甲基化的空间受阻的六吡啶配体时，O-2-的释放变得更容易，可逆性大大提高。空间受阻的三吡啶配体的铜-I和铜-II配合物的详细结构研究表明，桥头烷基引起吡啶位移，导致铜配合物的结构调制。六氢吡啶配体可用于形成热稳定的过氧二铁(III)络合物，该络合物可在酸氯/DMF的作用下氧化碳氢化合物。双-TPA型六氢吡啶配体的二铁(III)配合物催化各种烯烃与H_2O_2的环氧化反应。检测到过氧二铁(III)络合物作为中间体。详细的同位素标记实验表明，过氧基中间体转化为二氧基-钼氧-二铁(IV)络合物，活性物种中的三个氧原子相互竞争。稳定的双核结构、结构调节和结构柔性可能来自于六氢吡啶配体，它们在二铜和二铁络合物可逆的O-2结合和活化中起着关键作用。
Reversible O-2-binding and activation have been studied using dicopper and diiron complexes of various hexapyridine ligands as functional models of hemocyanin (Hc) and soluble methane monooxygenase (sMMO), respectively. Dicopper(l) complexes of sterically hindered hexapyridine ligands react with O-2 to form mu-beta(2):eta(2)-peroxo-dicopper(II) complexes stable at room temperature, which release O-2 to attain reversible O-2-binding. When a sterically hindered hexapyridine ligand methylated at the bridgehead positions is used, the O-2-release becomes easier, and reversibility is greatly improved. Detailed structural studies of Cu-I and Cu-II complexes of sterically hindered tripyridine ligands showed that the bridgehead alkyl group causes a pyridine shift leading to structural modulation of the copper complexes. A hexapyridine ligand can be used to form a thermally stable peroxo-diiron(III) complex, which can oxygenate hydrocarbons upon addition of acid chloride/DMF. Diiron(III) complexes of a bis-tpa type hexapyridine ligand catalyze epoxidation of various alkenes with H2O2. A peroxo-diiron(III) complex is detected as an intermediate. Detailed isotope-labeling experiments showed that the peroxo intermediate is converted to dioxo-mu-oxo-diiron(IV) complex, and that three oxygen atoms of the active species scramble with each other. Stable dinuclear structure, structural modulation, and structural flexibility, which may be from the hexapyridine ligands, play key roles in reversible O-2-binding and activation by the dicopper and diiron complexes.