Dinuclear Cu 2 (II,II)-cores stabilized by the N 3 O donorset of HL 1 = (2-{[[di(2-pyridyl)methyl](methyl)amino]methyl}phenol), HL 2 = 2-({[di(2-pyridyl)methyl]amino}methyl)phenol), and HL 3 = 2-({[di(2-pyridyl)methyl]amino}methyl)-4-nitrophenol display a unique superoxide dismutase (SOD) combined with catalase (CAT)-like activity in water, at neutral pH. The Cu 2 L 1 2 < Cu 2 L 2 2 < Cu 2 L 3 2 structure− reactivity trend puts a spotlight on the electron-deficient core of Cu 2 L 3 2 that exhibits the highest SOD (log k cat (O 2 •− ) = 7.55) and CAT-like (k H 2 O 2 = 0.66 M −1 s −1 ) performance. Time-lapse ESI-MS and EPR experiments indicate that a dimeric core is essential for oxygenic turnover upon H 2 O 2 decomposition.

An ew FeL/Fe 2 L 2 manifold,w ith HL = 2-({[di(2-pyridyl)methyl]-(methyl)amino}methyl)phenol, was preparedi ng ram scale (> 50 %y ield) and characterized in solution and solid state. The monomer/dimer interconversion is controlled in aqueous phase, upon varying the pH conditions. The electrocatalytic hydrogen evolution reaction (HER) occurs through the FeL monomer with added trifluoroacetic acid (TFA)a nd through the Fe 2 L 2 m-oxo dimer in acetate buffer (pH 4.9), with an overpotential of about 1Vand faradaic yield up to 75 %. The resulting i cat /i p valuesi nthe range 15-28a re among the highest reported for Fe-based electrocatalysts (i cat is the catalytic current, whereas i p is the current of an Fe-based redox event).Iron is the most abundant transition metal on earth, and nature employs this element as the active co-factor of several proteins. [1] Following bioinspired guidelines, vis-à-vist heir vast redox chemistry,s ynthetic Fe complexes have been intensively investigated as catalysts in some fundamental oxidation and reduction processes, including selective oxygen transfer, [2] catechol dioxygenation, [3] water oxidation, [4] neutralization of reactive oxygen species( ROS), [5] and proton/water reduction to hydrogen,g enerally described as the hydrogen evolution reaction (HER). [6] In this latter case, recent efforts have been directed towardt he modelling of the dinucleara nd mononuclear active site of [FeFe]-, [NiFe]-,a nd [Fe]-hydrogenase enzymes (H 2 ase mimetics, see Ta ble S1 in the Supporting Information). [7, 8] Most of the resulting complexes display H 2 ase-like activity in organic solvents, with acidic additives,w hereas systems operating in aqueous media are still rare. [7, 8] Interestingly,F e II and Fe III single-site complexes with porphyrins, [9] fluorinated di-glyoxime, [10] and polypyridyl ligands were also reported as active HER catalysts. [11] In particular,a tetradendate N 3 Odonorset provided by apolypyridyl platform was recently exploited to stabilize mononuclear Fe III catalysts for HER in aqueous media. [11] Figures of merit include am oderate overpotential (h,i nt he range 0.66-0.80 V) in CH 3 CN/TFA (TFA: trifluoroacetic acid) solutions as well as in aqueous buffers (pH 3-5) and an i cat /i p (i cat is the catalytic current, whereas i p is the currento fa nF e-basedr edox event) ratio up to 13. [11b] Photo-assisted H 2 evolution has been reported in ethanols olutions with fluoresceina st he photosensitizer,r eaching up to a turnover number of 2100 for the Fe catalyst, with an overall 3% quantum yield. [11c] Therefore, this class of polydentate ligands appears as ap romising one for optimizing the HER performance in water owing to their versatile coordination chemistry and tunable stereoelectronic impact.Here, we address the HERb ym ononuclear and dinuclear Fe III electrocatatalysts, originating from pH-triggered equilibria in the presenceo fl igand HL = 2-({[di(2-pyridyl)methyl](methyl)amino}methyl)phenol (Scheme 1). Thisp olydentate ligand has shown ap rominentb...

A novel stimuli-responsive strategy against the irreversible fouling of porous materials and surfaces is presented herein. This is based on the molecular design of catalytic pore walls that foster a chemo-mechanical, self-cleaning behavior under neutral pH and mild conditions of pressure and temperature. This approach builds on bioinspired remediation mechanisms involving natural catalase enzymes for H2O2 dismutation and endogenous oxygen production. It is thus demonstrated that a very efficient antifouling activity is observed when the material pores are armed with oxygen evolving catalysts that are known to liberate nascent oxygen gas when exposed to H2O2 as chemical trigger. To this aim, the catalase-like behavior of the tetra-ruthenium substituted polyoxometalate (Ru4(SiW10)2), has been exploited for in-pore oxygen evolution so to induce an active fluid mixing and the displacement of foulant particles. The present study includes the fabrication of hybrid polymeric films with porous architecture embedding Ru4(SiW10)2 as artificial catalase to guarantee the material self-defense against pore occlusion and oxidative damage with aqueous H2O2 as mild chemical effector. The self-catalytic “in-pore” remediation is readily applied to various materials/interfaces with porous texture and high surface area with the aim to provide long-lasting functional performance

The dinuclear zinc complex Zn 2 L 2 (HL=2-{ [[di(2-pyridyl) methyl](methyl)amino]methyl}phenol) has been synthesized and isolated as colorless crystals. The interaction of the compound with superoxide in anhydrous organic solvents has been evaluated by CV, stopped-flow Uv-vis, EPR and ESI-MS suggesting the binding and the activation of the coordinated superoxide, thanks to the Lewis acidity of the Zn(II) centers. The results obtained in this study highlight the formation of a Zn 2 L 2 À O 2 * À intermediate and a metastable phenoxyl-radical driven by the coordinated superoxide.

The coupling of a polycationic Mn(III)-porphyrin, with a dinuclear Mn2(II,II)L2 core (HL = 2-{[[di(2-pyridyl)methyl](methyl)amino]methyl}phenol), results in a dual Superoxide Dismutase (SOD) and Catalase (CAT) functional analogue, Mn2L2Pn+, enabling a detoxification cascade of the superoxide anion and hydrogen peroxide into benign H2O and O2. The SOD/CAT artificial manifolds, joined in one asset, exhibit a peak catalytic performance under physiological conditions, with log kcat(O2• –) ≥ 7 and kcat(H2O2)/KM = 1890. The dual-enzyme (dizyme) concept allows for a built-in self-protection against the irreversible bleaching of the porphyrin unit (>75% protection), readily induced by H2O2 (200 μM, 20 equiv, in buffer solution, pH 7.8). We show herein that incubation of the photosynthetic green algae, Chlamydomonas reinhardtii, with the synthetic dizyme (as low as 0.1 μM), prevents H2O2 accumulation under high-light illumination conditions, thus providing antioxidant surveillance and photoprotection