2,5-Thienylene-Strapped [26]Hexaphyrin as Multifunctional Chemosensor for Hg, Cu, and F Ions.

The sensing behavior of 2,5-thienylene-bridged tetrakis(2,6-dichlorophenyl)-[26]hexaphyrin (2) towards various metal ions and anions were investigated by UV-vis and fluorescence spectroscopies. Using this strapped hexaphyrin (2), the molecular sensor displayed highly selective and sensitive colorimetric responses to Cu and Hg in MeOH/THF. The spectral changes are distinctive enough in the visible region of the spectrum to enable naked-eye detection.

A side-on Mn(III)-peroxo supported by a non-heme pentadentate NPy ligand: synthesis, characterization and reactivity studies.

A mononuclear manganese(iii)-peroxo complex [MnIII(N3Py2)(O2)]+ (1a) bearing a non-heme N,N'-dimethyl-N-(2-(methyl(pyridin-2-ylmethyl)amino)ethyl)-N'-(pyridin-2-ylmethyl)ethane-1,2-diamine (N3Py2) ligand was synthesized by the reaction of [Mn(N3Py2)(H2O)](ClO4)2 (1) with hydrogen peroxide and triethylamine in CH3CN at 25 °C. The reactivity of 1a in aldehyde deformylation using 2-phenyl propionaldehyde (2-PPA) was studied and the reaction kinetics was monitored by UV-visible spectroscopy. A kinetic isotope effect (KIE) = 1.

MACoBr: lead-free cobalt-based perovskite for electrochemical conversion of water to oxygen.

We have synthesized a lead-free stable organic-inorganic perovskite (MA2CoBr4) by using non-hazardous solvents such as methanol and ethanol, which are eco-friendly and safe to handle in comparison to DMF, toluene, etc. Single crystals of MA2CoBr4 were grown using a simple solution technique, and their electrochemical oxygen evolution was investigated in a wide pH range.

Autocatalytic dioxygen activation to produce an iron(v)-oxo complex without any reductants.

An iron(v)-oxo complex with a tetraamido macrocyclic ligand, [(TAML)Fe(O)], was produced by reacting [(TAML)Fe] with dioxygen without any electron source in acetone at 298 K. The autocatalytic mechanism of dioxygen activation for the formation of an iron(v)-oxo complex has been clarified based on the autocatalysis by radical chain initiators.

A Mononuclear Nonheme Iron(V)-Imido Complex.

Mononuclear nonheme iron(V)-oxo complexes have been reported previously. Herein, we report the first example of a mononuclear nonheme iron(V)-imido complex bearing a tetraamido macrocyclic ligand (TAML), [(TAML)Fe(NTs)] (1). The spectroscopic characterization of 1 revealed an S = 1/2 Fe(V) oxidation state, an Fe-N bond length of 1.

Influence of Ligand Architecture in Tuning Reaction Bifurcation Pathways for Chlorite Oxidation by Non-Heme Iron Complexes.

Reaction bifurcation processes are often encountered in the oxidation of substrates by enzymes and generally lead to a mixture of products. One particular bifurcation process that is common in biology relates to electron transfer versus oxygen atom transfer by high-valent iron(IV)-oxo complexes, which nature uses for the oxidation of metabolites and drugs. In biomimicry and bioremediation, an important reaction relates to the detoxification of ClO in water, which can lead to a mixture of products through bifurcated reactions.

A Manganese(V)-Oxo Complex: Synthesis by Dioxygen Activation and Enhancement of Its Oxidizing Power by Binding Scandium Ion.

A mononuclear non-heme manganese(V)-oxo complex, [Mn(V)(O)(TAML)](-) (1), was synthesized by activating dioxygen in the presence of olefins with weak allylic C-H bonds and characterized structurally and spectroscopically. In mechanistic studies, the formation rate of 1 was found to depend on the allylic C-H bond dissociation energies (BDEs) of olefins, and a kinetic isotope effect (KIE) value of 16 was obtained in the reactions of cyclohexene and cyclohexene-d10. These results suggest that a hydrogen atom abstraction from the allylic C-H bonds of olefins by a putative Mn(IV)-superoxo species, which is formed by binding O2 by a high-spin (S = 2) [Mn(III)(TAML)](-) complex, is the rate-determining step.

Enhanced Electron Transfer Reactivity of a Nonheme Iron(IV)-Imido Complex as Compared to the Iron(IV)-Oxo Analogue.

Reactions of N,N-dimethylaniline (DMA) with nonheme iron(IV)-oxo and iron(IV)-tosylimido complexes occur via different mechanisms, such as an N-demethylation of DMA by a nonheme iron(IV)-oxo complex or an electron transfer dimerization of DMA by a nonheme iron(IV)-tosylimido complex. The change in the reaction mechanism results from the greatly enhanced electron transfer reactivity of the iron(IV)-tosylimido complex, such as the much more positive one-electron reduction potential and the smaller reorganization energy during electron transfer, as compared to the electron transfer properties of the corresponding iron(IV)-oxo complex.

Influence of ligand architecture on oxidation reactions by high-valent nonheme manganese oxo complexes using water as a source of oxygen.

Mononuclear nonheme Mn(IV)=O complexes with two isomers of a bispidine ligand have been synthesized and characterized by various spectroscopies and density functional theory (DFT). The Mn(IV)=O complexes show reactivity in oxidation reactions (hydrogen-atom abstraction and sulfoxidation). Interestingly, one of the isomers (L(1) ) is significantly more reactive than the other (L(2) ), while in the corresponding Fe(IV)=O based oxidation reactions the L(2) -based system was previously found to be more reactive than the L(1) -based catalyst.

Long-range electron transfer triggers mechanistic differences between iron(IV)-oxo and iron(IV)-imido oxidants.

Nature often utilizes molecular oxygen for oxidation reactions through monoxygenases and dioxygenases. In many of these systems, a high-valent iron(IV)-oxo active species is found. In recent years, evidence has accumulated of possible iron(IV)-imido and iron(V)-nitrido intermediates in enzymatic catalysis, although little is known about their activity.

Comparison of the reactivity of nonheme iron(IV)-oxo versus iron(IV)-imido complexes: which is the better oxidant?

Which is better? The first detailed comparison of the reactivity of nonheme iron(IV)-imido versus nonheme iron(IV)-oxo intermediates with substrates is presented. The iron(IV)-imido variant reacts with sulfides five times faster than iron(IV)-oxo, whereas the reverse trend is observed for hydrogen atom abstraction. These observed trends are analyzed and explained.

Mechanistic insight into halide oxidation by non-heme iron complexes. Haloperoxidase versus halogenase activity.

This work presents the first detailed study on mechanistic aspects of halide oxidation by non-heme iron complexes. We show that while iron(III)-hydroperoxo complexes oxidise halides via oxygen atom transfer, the corresponding iron(IV)-oxo complex reacts via electron transfer.

Nonheme ferric hydroperoxo intermediates are efficient oxidants of bromide oxidation.

This work presents the first combined experimental and computational study that gives evidence of the electrophilic reactivity of a nonheme iron(III)-hydroperoxo species. We show that in contrast to their heme counterparts the nonheme iron(III)-hydroperoxo complexes are catalytically much more active and even more so than nonheme iron(IV)-oxo species.