Triarylamines are demonstrated as novel, tunable electroactivated photocatalysts that use dispersion precomplexation to harness the full potential of the visible photon (>4.0 V vs. SCE) in anti-Kasha photo(electro)chemical super-oxidations of arenes.

A detailed theoretical investigation of the charge transport mechanism in poly(4-vinyl-imidazole) (P4VI), the parent polymer of a series of N-heterocyclic-based membranes used as an electrolyte in proton exchange membrane fuel cells, is presented. In particular, Density Functional Theory (DFT) results obtained for small model systems (protonated imidazole dimers and trimers) suggest that the commonly accepted conduction mechanism, based on a sequential proton transfer between imidazole moieties, could be impeded by the geometrical constraints imposed by the polymeric backbone. Indeed only one kind of proton transfer reaction is energetically allowed between adjacent imidazoles, so that a rotation of the protonated imidazole is required for a second proton transfer. Molecular dynamics simulations on a larger model (15 oligomers with an excess proton) show that the rotation of the imidazole carrying the excess proton is a soft large amplitude motion. These results allow us to propose a new proton conduction mechanism in P4VI, where a frustrated rotation of the protonated imidazole before each proton transfer reaction represents the rate-limiting step. Furthermore, in contrast with the Grotthuss proton transport mechanism in water, our results indicate that here it is the same proton which could be successively transferred. From a chemical point of view, these new insights into the mechanism are relevant for a rational design of modified azole-based systems for Proton Exchange Membrane Fuel Cells.

Environmentally persistent free radicals (EPFRs) are toxic products deriving from incomplete combustion and are able to generate DNA damage and pulmonary dysfunction. They are formed on particulate matter through interaction with aromatic hydrocarbons, catalyzed by transition metal oxides, and produce reactive oxygen species (ROS) in aquatic media. The processes are already described for substituted aromatic molecules, for example, phenol, but not for unsubstituted aromatic systems, such as benzene. This Article reports on the reaction of benzene with molecular oxygen in the presence of CuxO/SiO2, suggesting a mechanism based on cluster and periodic computational models. The activation of O2 by interaction with silica coordinated Cu(I) centers leads to a peroxy species that yields the phenoxy radical upon reaction with benzene. Dissociation of OH• radical eventually allows for the recovery of the catalyst. The experimental characterization of the CuxO/SiO2 catalyst regarded morphology, crystal structure, copper electronic state, and crystal field around Cu(II). Electron paramagnetic resonance (EPR) spectroscopy revealed the formation of phenoxy radical entrapped in the catalyst upon reaction between benzene and CuxO/SiO2. Moreover, EPR investigation of ROS in aqueous solution evidenced the generation of OH• radicals by benzene-contacted CuxO/SiO2. All of the experimental results nicely fit the outcomes of the computational models