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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Models for biological trinuclear copper clusters.Characterization and enantioselective catalytic oxidation of catechols by the copper(II)complexes of a chiral ligand derived from(S)-(-)-l,l'-binaphthyl-2,2'-diamine
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Models for biological trinuclear copper clusters.Characterization and enantioselective catalytic oxidation of catechols by the copper(II)complexes of a chiral ligand derived from(S)-(-)-l,l'-binaphthyl-2,2'-diamine

机译：三核生物铜团簇模型。（S）-（-）-1,1'-联萘-2,2'-二胺衍生的手性配体的铜（II）配合物对儿茶酚的表征和对映选择性催化氧化

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The dinuclear and trinuclear Cu(II)complexes of an octadentate ligand derived from(S)-l,1'inaphthyl-2,2'-diamine have been prepared and characterized by UV/Vis,CD,EPR and NMR spectroscopy.The ligand contains two tridentate aminobis(benzimidazole)donor arms connected to a central bidentate diaminobinaphthyl linker,which hosts the chiral unit.In the dinuclear Cu complex the ligation occurs essentially within the tridentate amis of the ligand.The two Cu centers are EPR nonequivalent and noninteracting.The EPR data suggests that one of the Cu ions additionally interacts with one of the tertiary aminonaphthyl donors.In the trinuclear complex the two aminonaphthyl donors bind the third Cu ion.The EPR spectrum of this complex shows the signal for a mononuclear Cu(II)center bound to a tridentate arm,while the remaining two Cu(II)centers are coupled through hydroxo groups.The CD spectrum shows that in the free ligand a severe reduction of the dihedral angle between the naphthyl groups from the strain free range occurs.This conformation is stabilized by ring stacking interactions with the benzimidazole groups.On complex formation this interaction is removed because the benzimidazole groups are involved in metal binding.In the dinuclear Cu complex the conformation of the binaphthyl chromophore probably approaches the strain free range,while in the trinuclear Cu complex a marked flattening of the dihedral angle between the two naphthyl rings occurs.Both complexes are active catalysts in the oxidation of L-/D-Dopa derivatives to quinones.High enantioselectivity is observed in the oxidation of L-/D-Dopa methyl ester catalyzed by the dinuclear Cu complex,which exhibits strong preference for the D enantiomer.The enantioselectivity is largely lost for the trinuclear Cu complex.
机译：制备了由（S）-1,1'萘基-2,2'-二胺衍生的八齿配体的双核和三核Cu（II）配合物，并通过UV / Vis，CD，EPR和NMR进行了表征。包含两个三齿氨基双（苯并咪唑）供体臂，连接到一个中央手性双齿二氨基联萘基连接体，该连接体为手性单元。在双核Cu络合物中，连接基本上发生在配体的三齿氨基中。两个Cu中心是EPR不等价且不相互作用的。 EPR数据表明，其中一个Cu离子还与另一个叔氨基萘基供体相互作用。在三核配合物中，两个氨基萘供体与第三个Cu离子结合。该EPR谱图显示了单核Cu（II）的信号。中心结合到三齿臂上，而其余两个Cu（II）中心通过羟基基团偶联。CD光谱显示，在游离配体中，萘基与萘基之间的二面角严重降低。该构象通过与苯并咪唑基团的环堆积相互作用而得以稳定，在络合物形成时，由于苯并咪唑基团参与金属结合而消除了这种相互作用。在双核Cu络合物中，联萘生色团的构象可能接近该菌株。自由范围，而在三核铜络合物中，两个萘基环之间的二面角明显变平。这两种络合物都是将L- / D-Dopa衍生物氧化为醌的活性催化剂。双核铜配合物催化的L- / D-多巴甲酯，对D-对映体表现出强烈的偏爱性。三核铜配合物的对映选择性大大降低。

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