Controlled nitrene transfer from a tyrosinase-like arylnitroso-copper complex

The reaction between p-nitrosonitrobenzene and the tetramethylpropylenediamine-copper(i) complex yields a dinuclear complex that is structurally and electronically similar to side-on peroxo species known in Cu/O2 chemistry. The complex reacts with di-tert-butylphenolate via nitrene transfer, as observed through an intermediate and the aminophenol product obtained upon reductive work-up.

A nickel dimethyl glyoximato complex to form nickel based nanoparticles for electrocatalytic H2 production

We report on the electrochemical alteration of a nickel(II) bis-glyoximato complex into nickel-based nanoparticles at a glassy carbon electrode under acid reducing conditions. These particles show electrocatalytic activity towards hydrogen production at +410 mV compared to the bare glassy carbon electrode. Mechanistic insights are discussed based on DFT calculations.

Side-on cupric–superoxo triplet complexes as competent agents for H-abstraction relevant to the active site of PHM

Side-on cupric–superoxo complexes with triplet ground states mimic the active site of PHM and are capable of H-abstraction.

Lifestyle changes in the management of adulthood and childhood obesity

Adulthood and childhood obesity is rapidly becoming an epidemic problem and it has a short and long term impact on health. Short term consequences are mostly represented by psychological effects, in fact obese children have more chances to develop psychological or psychiatric problems than non--obese children. The main long term effect is represented by the fact that childhood obesity continues into adulthood obesity and this results in negative effects in young adult life, since obesity increases the risk to develop morbidity and premature mortality. The obesity--related diseases are mostly represented by hypertension, type 2 diabetes, dyslipidaemia, cardiovascular diseases. Medical treatment should be discouraged in childhood because of the side effects and it should be only reserved for obese children with related medical complications. Lifestyle changes should be encouraged in both adulthood and childhood obesity. This review focuses on the management of obesity both in adulthood and in childhood, paying particular attention to lifestyle changes that should be recommended.

Iminosemiquinone radical ligands enable access to a well-defined redox-active CuII–CF3 complex

The reaction of a copper complex bearing iminosemiquinone ligands with a CF₃⁺ source provides an unprecedented Cu^II–CF₃ complex through ligand-based oxidation.

N2O reduction at a dissymmetric {Cu2S}-containing mixed-valent center

Through a bio-inspired approach of the active site of the metalloenzyme nitrous oxide reductase, we isolated and characterized a dinuclear mixed-valent dicopper complex capable of N₂O reduction at room temperature.

Pulsed-EPR evidence of a manganese(II) hydroxycarbonyl intermediate in the electrocatalytic reduction of carbon dioxide by a manganese bipyridyl derivative

A key intermediate in the electroconversion of carbon dioxide to carbon monoxide, catalyzed by a manganese tris(carbonyl) complex, is characterized. Different catalytic pathways and their potential reaction mechanisms are investigated using a large range of experimental and computational techniques. Sophisticated spectroscopic methods including UV/Vis absorption and pulsed-EPR techniques (2P-ESEEM and HYSCORE) were combined together with DFT calculations to successfully identify a key intermediate in the catalytic cycle of CO2 reduction. The results directly show the formation of a metal-carboxylic acid-CO2 adduct after oxidative addition of CO2 and H(+) to a Mn(0) carbonyl dimer, an unexpected intermediate.

Stable anilinyl radicals coordinated to nickel: X-ray crystal structure and characterization

Two anilinosalen and a mixed phenol-anilinosalen ligands involving sterically hindered anilines moieties were synthesized. Their nickel(II) complexes 1, 2, and 3 were prepared and characterized. They could be readily one-electron oxidized (E(1/2)=-0.30, -0.26 and 0.10 V vs. Fc(+)/Fc, respectively) into anilinyl radicals species [1](+), [2](+), and [3](+), respectively. The radical complexes are extremely stable and were isolated as single crystals. X-ray crystallographic structures reveal that the changes in bond length resulting from oxidation do not exceed 0.02 Å within the ligand framework in the symmetrical [1](+) and [2](+). No quinoid bond pattern was present. In contrast, larger structural rearrangements were evidenced for the unsymmetrical [3](+), with shortening of one C(ortho)-C(meta) bond. Radical species [1](+) and [2](+) exhibit a strong absorption band at around 6000 cm(-1) (class III mixed valence compounds). This band is significantly less intense than [3](+), consistent with a rather localized anilinyl radical character, and thus a classification of this species as class II mixed-valence compound. Magnetic and electronic properties, as well as structural parameters, have been computed by DFT methods.

Redox-switchable tetra-copper assembly of N,N-, N,O-phenolate-phenanthroimidazolate bridging ligands

A redox-active dianionic N,O-phenolate-imidazolate/N,N-phenanthroline bridging ligand is used to form unique square-like neutral tetra-Cu(II) assemblies, the structural, magnetic, electronic and redox properties of which are herein described.

Ligand contributions to the electronic structures of the oxidized cobalt(II) salen complexes

Square planar cobalt(II) complexes of salen ligands N,N'-bis(3-tert-butyl-5R-salicylidene)-1,2-cyclohexanediamine), where R = OMe (1) and tert-butyl (2), were prepared. 1 and 2 were electrochemically reversibly oxidized into cations [1-H(2)O](+) and [2-H(2)O](+) in CH(2)Cl(2). The chemically generated [1-H(2)O](SbF(6))·0.68 H(2)O·0.82CH(2)Cl(2) and [2-H(2)O](SbF(6))·0.3H(2)O·0.85CH(2)Cl(2) were characterized by X-ray diffraction and NIR spectroscopy. Both complexes are paramagnetic species containing a square pyramidal cobalt ion coordinated at the apical position by an exogenous water molecule. They exhibit remarkable NIR bands at 1220 (7370 M(-1) cm(-1)) and 1060 nm (5560 M(-1) cm(-1)), respectively, assigned to a CT transition. DFT calculations and magnetic measurements confirm the paramagnetic (S = 1) ground spin state of the cations. They show that more than 70% of the total spin density in [1-H(2)O](+) and [2-H(2)O](+) is localized on the metal, the remaining spin density being distributed over the aromatic rings (30% phenoxyl character). In the presence of N-methylimidazole 1 and 2 are irreversibly oxidized by air into the genuine octahedral cobalt(III) bis(phenolate) complexes [1-im(2)](+) and [2-im(2)](+), the former being structurally characterized. Neither [1-im(2)](+) nor [2-im(2)](+) exhibits a NIR feature in its electronic spectrum. 1 and 2 were electrochemically two-electron oxidized into [1](2+) and [2](2+). The cations were identified as Co(III)-phenoxyl species by their characteristic absorption band at ca. 400 nm in the UV-vis spectrum. Coordination of the phenoxyl radical to the cobalt(III) metal ion is evidenced by the EPR signal centered at g = 2.00.

Versatile effects of aurone structure on mushroom tyrosinase activity

Elucidation of the binding modes of Ty inhibitors is an important step for in-depth studies on how to regulate tyrosinase activity. In this paper we highlight the extraordinarily versatile effects of the aurone structure on mushroom Ty activity. Depending on the position of the OH group on the B-ring, aurones can behave either as substrates or as hyperbolic activators. The synthesis of a hybrid aurone through combination of an aurone moiety with HOPNO (2-hydroxypyridine N-oxide), a good metal chelate, led us to a new, efficient, mixed inhibitor for mushroom tyrosinase. Another important feature pointed out by our study is the presence of more than one site for aurone compounds on mushroom tyrosinase. Because study of the binding of the hybrid aurone was difficult to perform with the enzyme, we undertook binding studies with tyrosinase functional models in order to elucidate the binding mode (chelating vs. bridging) on a dicopper(II) center. Use of EPR combined with theoretical DFT calculations allowed us to propose a preferred chelating mode for the interaction of the hybrid aurone with a dicopper(II) center.