AbstractThe reaction of [(L)MnII]2+ (L = neutral polypyridine ligand framework) in the presence of mCPBA (mCPBA = m‐Chloroperoxybenzoic acid) generates a putative MnV=O species at RT. The proposed MnV=O species is capable of performing the aromatic hydroxylation of Cl‐benzoic acid derived from mCPBA to give [(L)MnIII(m‐Cl‐salicylate)]+, which in the presence of excess mCPBA generates a metastable [(L)MnV(O)(m‐Cl‐salicylate)]+, characterized by UV/Vis absorption, EPR, resonance Raman spectroscopy, and ESI‐MS studies. The current study highlights the fact that [(L)MnIII(m‐Cl‐salicylate)]+ formation may not be a dead end for catalysis. Further, a plausible mechanism has been proposed for the formation of [(L)MnV(O)‐m‐Cl‐salicylate)]+ from [(L)MnIII(m‐Cl‐salicylate)]+. The characterized transient [(L)MnV(O)‐m‐Cl‐salicylate)]+ reported in the current work exhibits high reactivity for oxygen atom transfer reactions, supported by the electrophilic character depicted from Hammett studies using a series of para‐substituted thioanisoles. The unprecedented study starting from a non‐heme neutral polypyridine ligand framework paves a path for mimicking the natural active site of photosystem II under ambient conditions. Finally, evaluating the intracellular effect of Mn(II) complexes revealed an enhanced intracellular ROS and mitochondrial dysfunction to prevent the proliferation of hepatocellular carcinoma and breast cancer cells.
摘要[(L)MnII]2+(L = 中性聚吡啶配体框架)在 mCPBA(mCPBA = 间氯过氧苯甲酸)存在下的反应在 RT 时生成一种推定的 MnV=O 物种。该 MnV=O 物种能够对来自 mCPBA 的 Cl-苯甲酸进行芳香羟基化反应,生成[(L)MnIII(m-Cl-水杨酸)]+,而在过量 mCPBA 的存在下,该 MnV=O 物种又会生成一种可转移的[(L)MnV(O)(m-Cl-水杨酸)]+,并通过 UV/Vis 吸收、EPR、共振拉曼光谱和 ESI-MS 研究对其进行表征。目前的研究突出表明,[(L)MnIII(间氯水杨酸)]+ 的形成可能并不是催化的死胡同。此外,还提出了由 [(L)MnIII(m-Cl-salicylate)]+ 生成 [(L)MnV(O)-m-Cl-salicylate)]+ 的合理机制。本研究报告中表征的瞬时[(L)MnV(O)-m-Cl-水杨酸盐)]+ 在氧原子转移反应中表现出很高的反应活性,这一点得到了使用一系列对位取代的硫代苯甲醚进行的哈米特研究中描述的亲电特性的支持。这项前所未有的研究以非血红素中性多吡啶配体框架为起点,为在环境条件下模拟光系统 II 的天然活性位点铺平了道路。最后,对 Mn(II) 复合物的细胞内效应进行了评估,结果显示,Mn(II) 复合物增强了细胞内 ROS 和线粒体功能障碍,从而防止了肝癌和乳腺癌细胞的增殖。