401846-08-0Relevant articles and documents
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.
Synthesis and characterization of Co(iii) amidoamine complexes: Influence of substituents of the ligand on catalytic cyclic carbonate synthesis from epoxide and carbon dioxide
Ramidi, Punnamchandar,Gerasimchuk, Nikolay,Gartia, Yashraj,Felton, Charlette M.,Ghosh, Anindya
supporting information, p. 13151 - 13160 (2013/09/12)
A series of amidoamine ligands (1) and their cobalt(iii) complexes (2) were synthesized and characterized by various spectroscopic techniques including 1H-NMR and X-ray crystallographic techniques. X-ray crystallography shows that one of the complexes, 2a, forms a chiral coordination polymer due to bridge formation with Li+ associated with the complex, although the ligand is achiral. Complex 2 was employed for catalytic synthesis of cyclic carbonates from epoxides and carbon dioxide (CO2) in a solvent free condition. A strong influence of the substituents on the ligand 1 was revealed by the varied activity of complex 2. The presence of electron withdrawing groups such as chloro (2b) and nitro (2c) increases the Lewis acidity of the catalyst, which, in turn, enhances the catalytic activity of 2. An electron withdrawing group containing complexes (2b and 2c) showed exceptionally high catalytic activity with a turnover frequency (TOF) of 662 and 602 h-1 respectively at 130°C and 300 psig CO2 pressure. On the other hand, our studies indicate that a catalyst with an electron releasing group (2d) showed relatively lower activity with a TOF of 488 h-1 under similar reaction conditions. Our results show that cobalt(iii) complexes follow the reactivity order of 2d 2a 2c 2b.
