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A Mononuclear Non-heme Mn(III)-Hydroperoxo Complex from Direct Protonation of a Peroxo Species

A Mononuclear Non-heme Mn(III)-Hydroperoxo Complex from Direct Protonation of a Peroxo Species
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대학원 화학·나노과학과
이화여자대학교 대학원
촉매 효소의 활성 자리인 금속-산소 결합체는 산소 활성화의 촉매 순환반응에서 발견되는 핵심적인 중간체이다. 생체 모방학 분야에서는 이 촉매 효소의 반응성 및 중간체의 구조 그리고 반응 메커니즘을 규명하고자, 효소의 활성화 자리를 모방한 여러 가지 모델 화합물의 합성 및 화학 반응성에 대한 연구가 진행되어 왔다. 이 연구에서는 14-membrered marcrocyclic ligand가 배위된nonheme Manganese(III)-peroxo종과 HClO4를 반응시켜 [MnIII(OOH)(14-TMC)]2+ 을 생성시키고 다양한 분광학적 기술을 통하여 특성평가를 하였다. 그 후 생성된 hydroperoxo 종을 axial ligand 인 NCS와 반응시켰다. 생성된 [MnIII(OOH)(NCS)(14-TMC)]+ 종 역시 다양한 분광학적 기술을 통하여 특성평가를 하였다. 이 중간체 들의 반응성 연구로는 sulfoxiation반응을 연구하였고 [MnIII(OOH)(NCS)(14-TMC)]+ 와의 반응성을 비교하여 보았다. ;Manganese(III)-peroxo and -hydroperoxo species are believed to be key i-ntermediates in biological systems performing many enzymatic reactions. We report the first example of a non-heme manganese(III)-hydroperoxo complex by protonation of the manganese(III)-peroxo complex bearing an N-methylated cyclam ligand. The manganese(III)-hydroperoxo, [Mn(III)(TMC) (OOH)]2+ and its thiocyanate adduct, [Mn(III)(TMC)(NCS)(OOH)]+ have been characterized by a variety of spectroscopic methods including electronic absorption, resonance Raman, electron paramagnetic resonance and X-ray absorption spectroscopy (XAS) as well as DFT calculations. In particular, for the first time, we were able to detect a parallel mode EPR signal from [Mn(III)(TMC)(NCS)(OOH)]+ monocation showing g-value of 8.7 and the hyperfine constant of 56 G. The reactivity of the Mn(III)-hydroperoxo species have been investigated in electrophilic sulfoxidation reaction. A series of preliminary kinetic studies revealed that the [Mn(III)(TMC)(OOH) ]2+ is more powerful oxidant than the [Mn(III)(TMC)(NCS)(OOH)]+ in sulfoxidation reaction. In addition, we observed a good linear correlation when the rates were plotted against oxidation potentials of Thioanisoles.
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