Hierarchical nanoporous Sn/SnOxSn/SnO_x systems obtained by anodic oxidation of electrochemically deposited Sn Nanofoams

A simple two-step electrochemical method for the fabrication of a new type of hierarchical Sn/SnOx micro/nanostructures is proposed for the very first time. Firstly, porous metallic Sn foams are grown on Sn foil via hydrogen bubble-assisted electrodeposition from an acidulated tin chloride electrolyte. As-obtained metallic foams consist of randomly distributed dendrites grown uniformly on the entire metal surface. The estimated value of pore diameter near the surface is ~35 µm, while voids with a diameter of ~15 µm appear in a deeper part of the deposit. Secondly, a layer of amorphous nanoporous tin oxide (with a pore diameter of ~60 nm) is generated on the metal surface by its anodic oxidation in an alkaline electrolyte (1 M NaOH) at the potential of 4 V for various durations. It is confirmed that if only optimal conditions are applied, the dendritic morphology of the metal foam does not change significantly, and an open-porous structure is still preserved after anodization. Such kinds of hierarchical nanoporous Sn/SnOx systems are superhydrophilic, contrary to those obtained by thermal oxidation of metal foams which are hydrophobic. Finally, the photoelectrochemical activity of the nanostructured metal/metal oxide electrodes is also presented

Antiferromagnetic ordering in cobalt(II) and nickel(II) 1D coordination polymers with the dithioamide of 1,3-benzenedicarboxylic acid

International audienceA series of 1D coordination polymers [Co(m-dtab)Cl2]n (1), [Co(m-dtab)Br2]n (2) and [Ni(m-dtab)2(Br)2]n (3), where m-dtab = the dithioamide of 1,3-benzenedicarboxylic acid, were prepared. The structures of all complexes were determined by X-ray diffraction . Magnetic properties of the compounds were characterized by molecular susceptibility vs. T dependence in the temperature range from 2 to 300 K. All compounds possess antiferromagnetic exchange interactions, and antiferromagnetic ordering was found in [Co(m-dtab)Br2]n and [Ni(m-dtab)2Br2]n at TN = 2.9 K and 2.6 K, respectively. DFT calculations showed that exchange interactions in [Co(m-dtab)(Hal)2]n could be transferred through two pathways: m-dtab between metal ions or interchain π-π stacking of aromatic rings, so the systems are not 1D from the viewpoint of magnetochemistry. The results of DFT calculations are consistent with the existence of magnetic ordering

Catalytic Oxidation of Benzoins by Hydrogen Peroxide on Nanosized HKUST-1: Influence of Substituents on the Reaction Rates and DFT Modeling of the Reaction Path

In this research, the oxidation of a series of benzoins, R-C(=O)-CH(OH)-R, where R = phenyl, 4-methoxyphenyl, 4-bromophenyl, and 2-naphthyl, by hydrogen peroxide in the presence of nanostructured HKUST-1 (suspension in acetonitrile/water mixture) was studied. The respective benzoic acids were the only products of the reactions. The initial average reaction rates were experimentally determined at different concentrations of benzoin, H2O2 and an effective concentration of HKUST-1. The sorption of the isotherms of benzoin, dimethoxybenzoin and benzoic acid on HKUST-1, as well as their sorption kinetic curves, were measured. The increase in H2O2 concentration expectedly led to an acceleration of the reaction. The dependencies of the benzoin oxidation rates on the concentrations of both benzoin and HKUST-1 passed through the maxima. This finding could be explained by a counterplay between the increasing reaction rate and increasing benzoin sorption on the catalyst with the increase in the concentration. The electronic effect of the substituent in benzoin had a significant influence on the reaction rate, while no relation between the size of the substrate molecule and the rate of its oxidation was found. It was confirmed by DFT modeling that the reaction could pass through the Baeyer–Villiger mechanism, involving an attack by the HOO− anion on the C atom of the activated C=O group

Versatile Reactivity of Mn-II Complexes in Reactions with N-Donor Heterocycles: Metamorphosis of Labile Homometallic Pivalates vs. Assembling of Endurable Heterometallic Acetates

International audienceReaction of 2,2'-bipyridine (2,2'-bipy) or 1,10-phenantroline (phen) with [Mn(Piv)(EtOH)] led to the formation of binuclear complexes [Mn(Piv)L] (L = 2,2'-bipy (), phen (); Piv is the anion of pivalic acid). Oxidation of or by air oxygen resulted in the formation of tetranuclear Mn complexes [MnO(Piv)L] (L = 2,2'-bipy (), phen ()). The hexanuclear complex [Mn(OH)(Piv)(pym)] () was formed in the reaction of [Mn(Piv)(EtOH)] with pyrimidine (pym), while oxidation of produced the coordination polymer [MnO(Piv)(pym)] (). Use of pyrazine (pz) instead of pyrimidine led to the 2D-coordination polymer [Mn(OH)(Piv)(µ-pz)] (). Interaction of [Mn(Piv)(EtOH)] with FeCl resulted in the formation of the hexanuclear complex [MnFeO(Piv)(MeCN)(HPiv)] (). The reactions of [MnFeO(OAc)(HO)] with 4,4'-bipyridine (4,4'-bipy) or -1,2-(4-pyridyl)ethylene (bpe) led to the formation of 1D-polymers [MnFeO(OAc)L]·2DMF, where L = 4,4'-bipy (·2DMF), bpe (·2DMF) and [MnFeO(OAc)(bpe)(DMF)]·3.5DMF (·3.5DMF). All complexes were characterized by single-crystal X-ray diffraction. Desolvation of ·3.5DMF led to a collapse of the porous crystal lattice that was confirmed by PXRD and N sorption measurements, while alcohol adsorption led to porous structure restoration. Weak antiferromagnetic exchange was found in the case of binuclear Mn complexes ( = -1.03 cm for and ). According to magnetic data analysis ( = -(2.69 ÷ 0.42) cm) and DFT calculations ( = -(6.9 ÷ 0.9) cm) weak antiferromagnetic coupling between Mn ions also occurred in the tetranuclear {Mn(OH)(Piv)} unit of the 2D polymer . In contrast, strong antiferromagnetic coupling was found in oxo-bridged trinuclear fragment {MnFeO(OAc)} in ·3.5DMF ( = -57.8 cm, = -20.12 cm)