Reverse Catalase Reaction: Dioxygen Activation via Two-Electron Transfer from Hydroxide to Dioxygen Mediated By a Manganese(III) Salen Complex

‘Oxygen-Consuming Complexes’–Catalytic Effects of Iron–Salen Complexes with Dioxygen

[(salen)FeIII]+MeCN complex is a useful catalyst for cyclohexene oxidation with dioxygen. As the main products, ketone and alcohol are formed. In acetonitrile, [(salen)FeII]MeCN is rapidly oxidized by dioxygen, forming iron(III) species. Voltammetric electroreduction of the [(salen)FeIII]+MeCN complex in the presence of dioxygen causes the increase in current observed, which indicates the existence of a catalytic effect. Further transformations of the oxygen-activated iron(III) salen complex generate an effective catalyst. Based on the catalytic and electrochemical results, as well as DFT calculations, possible forms of active species in c-C6H10 oxidation have been proposed.

The effect of the orientation of the Jahn–Teller distortion on the magnetic interactions of trinuclear mixed-valence Mn(ii)/Mn(iii) complexes

The effect of the orientation of the Jahn–Teller distortion on the magnetic interactions in two new mixed-valence trinuclear Mn(iii)–Mn(ii)–Mn(iii) complexes has been investigated.

A mononuclear manganese(iii)–hydroperoxo complex: synthesis by activating dioxygen and reactivity in electrophilic and nucleophilic reactions

A manganese(iii)–peroxo complex was synthesized by activating dioxygen (O₂) and the amphoteric reactivity of a manganese(iii)–hydroperoxo complex was demonstrated in electrophilic and nucleophilic reactions.

Catalytic fixation of atmospheric carbon dioxide by copper(ii) complexes of bidentate ligands

The copper(ii) complexes of simple bidentate ligands have shown selective fixation and sequestration of atmospheric CO₂. The fixation of CO₂ proceeds via copper(i) species and geometrical interconversions and afforded CO₃²⁻ bound complexes.

Dimerization, redox properties and antioxidant activity of two manganese(III) complexes of difluoro- and dichloro-substituted Schiff-base ligands

Two mononuclear Mn^III complexes [Mn(3,5-F₂salpn)(H₂O)₂][B(C₆H₅)₄]·2H₂O (1·2H₂O) and [Mn(3,5-Cl₂salpn)(OAc)(H₂O)]·H₂O (2·H₂O), where H₂salpn=1,3-bis(salicylidenamino)propane, have been prepared and characterized. The crystal structure of 1·H₂O shows that this complex forms μ-aqua dimers with a short Mn⋯Mn distance of 4.93Å. Under anaerobic conditions, the two complexes are stable in solution and possess trans-diaxial symmetry with the tetradentate Schiff base ligand symmetrically arranged in the equatorial plane. When left in air, these complexes slowly dimerize to yield high-valent [Mn^IV₂(3,5-X₂-salpn)₂(μ-O)₂] in which each X₂-salpn ligand wraps the two Mn ions. This process is favored in basic medium where the deprotonation of the bound water molecule is concomitant with air oxidation. The two complexes catalyze the dismutation of superoxide (superoxide dismutase (SOD) activity) and peroxide (catalase (CAT) activity) in basic medium. The phenyl-ring substituents play an important role on the CAT reaction but have little effect on SOD activity. Kinetics and spectroscopic results indicate that 1 and 2 catalyze H₂O₂ disproportionation through a cycle involving Mn^III₂ and Mn^IV₂ dimers, unlike related complexes with a more rigid and smaller chelate ring, which employ Mn^III/Mn^VO monomers.

Water exchange reaction of a manganese catalase mimic: oxygen-17 NMR relaxometry study on (aqua)manganese(iii) in a salen scaffold and its reactions in a mildly basic medium

Water exchange of trans-[Mn^III(salen)(OH₂)₂]⁺ studied by line broadening ¹⁷OH₂ NMR discloses its mechanism as associative interchange (I_a).