A phenol-imidazole pro-ligand that can exist as a phenoxyl radical, alone and when complexed to copper(II) and zinc(II)
A phenol-imidazole pro-ligand that can exist as a phenoxyl radical, alone and when complexed to copper(II) and zinc(II)
复制标题
DOI：
10.1039/b212209j
复制
发表时间：
2003-01-01
影响因子：
4
通讯作者：
Wilson, C
中科院分区：
文献类型：
--
作者：
Benisvy, L;Blake, AJ;Wilson, C
设计、合成并表征了一种新的 N,O-二齿苯酚咪唑前配体 2'-(4',6'-二叔丁基羟基苯基)-4,5-二苯基咪唑 (LH)。 LH 不具有易氧化的位置（苯酚除外），并且在苯酚环上包含邻位和对位取代基，可防止自由基偶联反应。 LH 经历可逆的单电子氧化，生成相应的具有苯氧基自由基特征的 [LH](.+) 自由基阳离子。 [LH]/[ LH](.+) 氧化还原对的异常可逆性至少部分归因于通过分子内 O-H....N 氢键稳定 [LH](.+)。化合物 [CuL2] (1) 和 [ZnL2] (2) 已被合成并进行了结构、光谱和电化学表征。 1.4DMF、1.3MeOH 和 2.2.5MeCN.0.3CH(2)Cl(2) 的晶体结构已被确定，并且各自具有 N2O2 配位球，其几何形状随金属的性质和共结晶溶剂的性质而变化。 1和2各自经历两次可逆的、基于配体的单电子氧化，首先形成[M(L)(L-.)](+)，然后形成[M(L-.)(2)](2+)。 [M(L)(L-.)](+) (M=Cu, Zn) 阳离子是通过电化学和化学氧化产生的，其 [ML2][BF4] 盐被分离为空气稳定的深绿色结晶固体。这些化合物的 UV/vis、EPR 和磁性特征与涉及与酚盐 (L-) 和苯氧基自由基 (L-.) 结合的 M-II（M=Cu 或 Zn）中心的每种阳离子一致。通过测定[CuL2][BF4].2CH(2)Cl(2)和[ZnL2][BF4].2CH(2)Cl(2).0.75戊烷的晶体结构获得的结构信息完全支持这一解释。对于这些盐中的每一种，都有明确的迹象表明配位的苯氧基自由基参与分子内 pi-pi 堆积相互作用，与半乳糖氧化酶中的相互作用相似。
A new N,O-bidentate, phenol-imidazole pro-ligand 2'-(4',6'-di-tert-butylhydroxyphenyl)-4,5-diphenyl imidazole (LH) has been designed, synthesised, and characterised. LH possesses no readily oxidisable position (other than the phenol) and involves o- and p-substituents on the phenol ring that prevent radical coupling reactions. LH undergoes a reversible one-electron oxidation to generate the corresponding [LH](.+) radical cation that possesses phenoxyl radical character. The unusual reversibility of the [LH]/[ LH](.+) redox couple is attributed, at least in part, to a stabilisation of [LH](.+) by intramolecular O-H....N hydrogen bonding. The compounds [CuL2] (1) and [ZnL2] (2) have been synthesised and characterised structurally, spectroscopically, and electrochemically. The crystal structures of 1.4DMF, 1.3MeOH, and 2.2.5MeCN.0.3CH(2)Cl(2) have been determined and each shown to possess an N2O2-coordination sphere, the geometry of which varies with the nature of the metal and the nature of the co-crystallised solvent. 1 and 2 each undergo two, reversible, ligand-based, one-electron oxidations, to form, firstly, [M(L)(L-.)](+) and secondly [M(L-.)(2)](2+). The [M(L)(L-.)](+) (M=Cu, Zn) cations have been generated by both electrochemical and chemical oxidation and their [ML2][BF4] salts isolated as air-stable, dark green, crystalline solids. The UV/vis, EPR, and magnetic characteristics of these compounds are consistent with each cation involving an M-II (M=Cu or Zn) centre bound to a phenoxide (L-) and a phenoxyl radical (L-.). The structural information obtained by a determination of the crystal structures of [CuL2][BF4].2CH(2)Cl(2) and [ZnL2][BF4].2CH(2)Cl(2).0.75 pentane fully supports this interpretation. For each of these salts, there is a clear indication that the coordinated phenoxyl radical is involved in intramolecular pi-pi stacking interactions that parallel those in galactose oxidase.