14463-79-7Relevant articles and documents
Unifying Evaluation of the Technical Performances of Iron-Tetra-amido Macrocyclic Ligand Oxidation Catalysts
Denardo, Matthew A.,Mills, Matthew R.,Ryabov, Alexander D.,Collins, Terrence J.
, p. 2933 - 2936 (2016)
The main features of iron-tetra-amido macrocyclic ligand complex (a sub-branch of TAML) catalysis of peroxide oxidations are rationalized by a two-step mechanism: FeIII + H2O2 → Active catalyst (Ac) (kI), and Ac + Substrate (S) → FeIII + Product (kII). TAML activators also undergo inactivation under catalytic conditions: Ac → Inactive catalyst (ki). The recently developed relationship, ln(S0/S∞) = (kII/ki)[FeIII]tot, where S0 and S∞ are [S] at time t = 0 and ∞, respectively, gives access to ki under any conditions. Analysis of the rate constants kI, kII, and ki at the environmentally significant pH of 7 for a broad series of TAML activators has revealed a 6 orders of magnitude reactivity differential in both kII and ki and 3 orders differential in kI. Linear free energy relationships linking kII with ki and kI reveal that the reactivity toward substrates is related to the instability of the active TAML intermediates and suggest that the reactivity in all three processes derives from a common electronic origin. The reactivities of TAML activators and the horseradish peroxidase enzyme are critically compared.
Enantioselective Hydroxylation of Benzylic C(sp3)-H Bonds by an Artificial Iron Hydroxylase Based on the Biotin-Streptavidin Technology
Barnet, Maxime,Peterson, Ryan L.,Rebelein, Johannes G.,Rumo, Corentin,Serrano-Plana, Joan,Ward, Thomas R.
supporting information, p. 10617 - 10623 (2020/07/04)
The selective hydroxylation of C-H bonds is of great interest to the synthetic community. Both homogeneous catalysts and enzymes offer complementary means to tackle this challenge. Herein, we show that biotinylated Fe(TAML)-complexes (TAML = Tetra Amido Macrocyclic Ligand) can be used as cofactors for incorporation into streptavidin to assemble artificial hydroxylases. Chemo-genetic optimization of both cofactor and streptavidin allowed optimizing the performance of the hydroxylase. Using H2O2 as oxidant, up to ～300 turnovers for the oxidation of benzylic C-H bonds were obtained. Upgrading the ee was achieved by kinetic resolution of the resulting benzylic alcohol to afford up to >98% ee for (R)-tetralol. X-ray analysis of artificial hydroxylases highlights critical details of the second coordination sphere around the Fe(TAML) cofactor.
Redox-Active Ligand Assisted Multielectron Catalysis: A Case of CoIII Complex as Water Oxidation Catalyst
Du, Hao-Yi,Chen, Si-Cong,Su, Xiao-Jun,Jiao, Lei,Zhang, Ming-Tian
supporting information, p. 1557 - 1565 (2018/02/09)
Water oxidation is the key step in both natural and artificial photosynthesis to capture solar energy for fuel production. The design of highly efficient and stable molecular catalysts for water oxidation based on nonprecious metals is still a great challenge. In this article, the electrocatalytic oxidation of water by Na[(L4-)CoIII], where L is a substituted tetraamido macrocyclic ligand, was investigated in aqueous solution (pH 7.0). We found that Na[(L4-)CoIII] is a stable and efficient homogeneous catalyst for electrocatalytic water oxidation with 380 mV onset overpotential in 0.1 M phosphate buffer (pH 7.0). Both ligand- and metal-centered redox features are involved in the catalytic cycle. In this cycle, Na[(L4-)CoIII] was first oxidized to [(L2-)CoIIIOH] via a ligand-centered proton-coupled electron transfer process in the presence of water. After further losing an electron and a proton, the resting state, [(L2-)CoIIIOH], was converted to [(L2-)CoIV=O]. Density functional theory (DFT) calculations at the B3LYP-D3(BJ)/6-311++G(2df,2p)//B3LYP/6-31+G(d,p) level of theory confirmed the proposed catalytic cycle. According to both experimental and DFT results, phosphate-assisted water nucleophilic attack to [(L2-)CoIV=O] played a key role in O-O bond formation.
