Crystal structure and reversible O2-binding of a room temperature stable μ-η2:η2-peroxodicopper(II) complex of a sterically hindered hexapyridine dinucleating ligand
Crystal structure and reversible O2-binding of a room temperature stable μ-η2:η2-peroxodicopper(II) complex of a sterically hindered hexapyridine dinucleating ligand
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DOI：
10.1021/ja992295q
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发表时间：
1999-12-01
影响因子：
15
通讯作者：
Suzuki, M
中科院分区：
文献类型：
--
作者：
Kodera, M;Katayama, K;Suzuki, M
氧合血蓝蛋白（oxyHc）1和氧合酪氨酸酶（oxyTy）2在活性位点具有相似的µ-η2：η2-过氧二铜（II）（Cu 2 O2）结构2，但显示出不同的功能，分别是可逆的O2-结合3和O2-活化4（见方案1）。根据deoxyHc和oxyHc的Cu-Cu距离分别为4.6和3.6 μ m的巨大差异，推测当Cu-Cu距离延长时，O2从oxyHc释放。2 μ-η2：η2-Cu 2 O2配合物的反应可能受各种因素的影响，如Cu-Cu距离，Cu配位几何形状和氮供体配体的电子效应。然而，尽管对µ-η2：η2-Cu 2 O2络合物的反应进行了出色的机理研究，5但决定方向的是可逆的O2结合还是O2活化，尚未明确显示。2，6热稳定的μ-η2：η2-Cu 2 O2络合物[Cu（HB（3，5-Me 2 pz）3）] 2（O2）（1）7a，B和[Cu（HB（3，5-iPr 2 pz）3）] 2（O2）（2）7 c由Kitajima等人报道为oxyHc和oxyTy的结构模型，但它们的O2-结合是不可逆的。因此，为了阐明μ-η2：η2-Cu 2 O2络合物的结构与O2-结合的可逆性之间的关系，需要实现可逆O2-结合的热稳定的μ-η2：η2-Cu 2 O2络合物。8首先，我们制备了空间位阻的三吡啶基甲烷配体，三（6-甲基-2-吡啶基）甲烷（tripy）。9其µ-η2：η2-Cu 2 O2配合物[Cu（tripy）] 2 O2·（PF 6）2（3）是通过将O2添加到tripy的Cu（I）配合物中制备的，但在室温下不稳定。然后，将三吡啶转化为1，2-双[2-（双（6-甲基-2-吡啶基）甲基）-6-吡啶基]乙烷（L），其具有通过乙烯间隔基连接的两个空间位阻的三吡啶基甲烷单元（参见方案2）。L形成μ-η2：η2-Cu 2 O2络合物[Cu 2 O2（L）]（PF 6）2（4）。10在25 ℃下，4在CH 2Cl 2中的半衰期为25.5 h。据我们所知，4是迄今为止报道的所有µ-η2：η2-Cu 2 O2配合物中最稳定的。虽然已经合成了许多双核配体11，期望那些在Hc的活性位点具有与咪唑基团类似的六个供体组的配体将稳定μ-η2：η2-Cu 2 O2结构，但从未达到4这样高的稳定性。4是室温稳定的具有双核配体的μ-η2：η2-Cu 2 O2络合物的第一个实例。在这里，我们描述了合成，晶体结构，和可逆的O2-结合
Oxyhemocyanin (oxyHc) 1 and oxytyrosinase (oxyTy) 2 have a similar µ-η2: η2-peroxodicopper (II)(Cu2O2) structure2 in the active sites but show different functions, reversible O2-binding3 and O2-activation, 4 respectively (see Scheme 1). On the basis of the large difference of the Cu-Cu distances, 4.6 and 3.6 Å, for deoxyand oxyHc, respectively, it is supposed that O2 is released from oxyHc when the Cu-Cu distance is elongated. 2 The reaction of the µ-η2: η2-Cu2O2 complex may be directed by various factors, such as the Cu-Cu distance, the Cu coordination geometry, and the electronic effect of the nitrogen donor ligand. However, despite excellent mechanistic studies on the reaction of the µ-η2: η2-Cu2O2 complex, 5 what determines the direction, reversible O2-binding or O2-activation, has not been clearly shown. 2, 6 Thermally stable µ-η2: η2-Cu2O2 complexes [Cu (HB (3, 5-Me2pz) 3)] 2 (O2)(1) 7a, b and [Cu (HB (3, 5-iPr2pz) 3)] 2 (O2)(2) 7c were reported by Kitajima et al. as structural models of oxyHc and oxyTy but their O2-binding is irreversible. Therefore, to clarify the relationship between the structure of the µ-η2: η2-Cu2O2 complex and the reversibility in the O2-binding a thermally stable µ-η2: η2-Cu2O2 complex which realizes the reversible O2-binding is necessary. 8 First, we prepared a sterically hindered tripyridylmethane ligand, tris (6-methyl-2-pyridyl) methane (tripy). 9 Its µ-η2: η2-Cu2O2 complex [Cu (tripy)] 2O2 ‚(PF6) 2 (3) is prepared by O2 addtion to a Cu (I) complex of tripy, but not stable at room temperature. Then, tripy is converted to 1, 2-bis [2-(bis (6-methyl-2-pyridyl) methyl)-6-pyridyl] ethane (L), which has two sterically hindered tripyridylmethane units connected by an ethylene spacer (see Scheme 2). L forms the µ-η2: η2-Cu2O2 complex [Cu2O2 (L)](PF6) 2 (4). 10The half-life time of 4 in CH2Cl2 at 25 C is 25.5 h. To our knowledge, 4 is the most stable in all µ-η2: η2-Cu2O2 complexes reported so far. Although many dinucleating ligands11 have been synthesized with the expectation that those having six donor sets similar to imidazole groups in the active site of Hc would stabilize the µ-η2: η2-Cu2O2 structure, such a high stability as 4 has never been attained. 4 is the first example of the room-temperature stable µ-η2: η2-Cu2O2 complex with a dinucleating ligand. Here, we describe the synthesis, crystal structure, and reversible O2-binding