Concerted and stepwise proton-coupled electron transfers in aquo/hydroxo complex couples in water: oxidative electrochemistry of [Os(II)(bpy)(2)(py)(OH(2))](2+)

Successive oxidation of transition metal(II) aqua complexes (M(II)OH(2) to M(III)OH) is a domain in which proton-coupled electron transfer reactions are extremely common. The mechanism of these PCET reactions-concerted or stepwise-is an important issue in the understanding and design of natural or artificial systems catalyzing the formation of dioxygen by four-electron oxidation of water. Concerted proton-coupled electron transfer from an aqua metal(II) to a hydroxo metal(III) complex requires the close proximity of a proton-accepting group with a pK value between those of the aqua complexes. Otherwise, stepwise electron-proton or proton-electron pathways involving high-energy intermediates are followed. Concerted proton-electron pathways involving water as proton-acceptor or proton-donor group are inefficient. Cyclic voltammetry of the title complex in buffered aqueous solution and re-examination of previous results for the same complex attached to an electrode surface are used to establish these conclusions, which provide a starting point on the route to higher degrees of oxidation, such as those involved in the catalysis of water oxidation.     

A combined experimental and theoretical study on the effect of doping and interface formation on Ppv-ether copolymer

We present a detailed optoelectronic and vibrational study devoted to the transformation from neutral to doped PPV-ether copolymer in both powder and thin film states. The full geometries were optimized with the density functional theory (DFT) for neutral and doped states, where a comparative geometric study was established. The lowest singlet excited-state geometries have been investigated by using the configuration interaction single (CIS/3-21G(d)) method. The absorption spectra are then calculated respectively on the basis of the ground- and excited-state geometries. Our calculation results are in close agreement with those available from experiments. The charge distribution and excitation energies of singly charged PPV-ether are calculated, where two subgap absorption features are found to dominate the optical spectrum correlated with the polaron picture. These theoretical results are compared to experimental optical data illustrated by iodine-doped PPV-ether. Next, we have performed a simulation to model the conformations and the electronic structure modifications of interface formation of PPV-ether copolymer thin film with calcium (Ca), magnesium (Mg), and aluminum (Al) metal as a cathode and indium tin oxide (ITO) as anode in polymer LEDs. By providing the optical parameter obtained and the chemical reaction at the interface, we present the energetic diagram near the interface and the energy position of the lowest occupied molecular orbital with respect to the electrode Fermi level.     

Solvent‐free Synthesis,Characterization and Solvent‐Vapor Interaction of Zinc(II) and Copper(II) Coordination Polymers containing Nitrogen‐donor Ligands

Coordination polymers of [Zn(INA)₂] ( 1 ) (INA = isonicotinate), [Cu₂(mal)₂(H₂O)₂(bipy)] ( 2 ) (mal = malonate, bipy = 4,4‐bipyridine), and [Zn₂(OAC)₄(bipy)₂] ( 3 ) (OAC = acetate) were prepared using mechanochemical grinding and heating methods. The materials were characterized with elemental analysis, FT‐IR spectroscopy, TGA, SEM, EI‐MS, BET, and PXRD. Comparison of PXRD patterns of the materials with patterns simulated from single‐crystal X‐ray diffraction data allowed identification of the products. Compared to conventional synthetic techniques such as solvothermal/hydrothermal solvent‐based methods, solvent‐free method was found to be simple, highly efficient, and environmentally friendly especially for the preparation of these coordination polymers on a large scale. Solvent‐vapor interaction properties of 1 , 2 , and 3 were investigated by exposure of the compounds to water and methanol at room temperature.