Facile O-atom insertion into C-C and C-H bonds by a trinuclear copper complex designed to harness a singlet oxene

Two trinuclear copper [Cu(I)Cu(I)Cu(I)(L)](1+) complexes have been prepared with the multidentate ligands (L) 3,3'-(1,4-diazepane-1,4-diyl)bis(1-((2-(dimethylamino)ethyl)(methyl)amino)propan-2-ol) (7-Me) and (3,3'-(1,4-diazepane-1,4-diyl)bis(1-((2-(diethylamino) ethyl)(ethyl) amino)propan-2-ol) (7-Et) as models for the active site of the particulate methane monooxygenase (pMMO). The ligands were designed to form the proper spatial and electronic geometry to harness a "singlet oxene," according to the mechanism previously suggested by our laboratory. Consistent with the design strategy, both [Cu(I)Cu(I)Cu(I)(L)](1+) reacted with dioxygen to form a putative bis(mu(3)-oxo)Cu(II)Cu(II)Cu(III) species, capable of facile O-atom insertion across the central C-C bond of benzil and 2,3-butanedione at ambient temperature and pressure. These complexes also catalyze facile O-atom transfer to the C-H bond of CH(3)CN to form glycolonitrile. These results, together with our recent biochemical studies on pMMO, provide support for our hypothesis that the hydroxylation site of pMMO contains a trinuclear copper cluster that mediates C-H bond activation by a singlet oxene mechanism.

Thermodynamics of solutions IV: Solvation of ketoprofen in comparison with other NSAIDs

The present work discusses the characteristics of solvation (Gibbs energy, enthalpic and entropic terms of Gibbs energy) for ketoprofen together with other nonsteroidal antiinflammatory drugs (NSAIDs) in aliphatic alcohols. Ketoprofen was studied by classical thermoanalytical methods of sublimation calorimetry, solution calorimetry, and solubility. Temperature dependence of the saturated vapor pressure was determined, and the sublimation enthalpy, delta H(sub) (0) and sublimation entropy, delta S(sub)(0), as well as their respective relative fractions in the total process were calculated. The parameters yielded for ketoprofen were compared with the respective literature data of other benzophenone derivatives. The Gibbs energy of solvation as well as enthalpic and entropic terms thereof in aliphatic alcohols were also studied for ketoprofen and compared with the properties of model substances and other NSAIDs (benzoic acid, diflunisal, flurbiprofen, and naproxen). In all cases, the major driving force of the solvation process is enthalpy. Correlations were derived between Gibbs energy of solvation in octanol, delta G(solv)(oct), and the transfer Gibbs energy from water to octanol, delta G(tr)(0).

Photo-Fries rearrangements of phenyl phenylacylates in polyethylene films: comparison of reactivity and selectivity with 1-naphthyl phenylacylates

The fates and kinetics of recombination of singlet radical pairs generated by photolyses of three phenyl phenylacylates have been examined in unstretched and stretched polyethylene films. Comparisons with results from photolyses of analogous 1-naphthyl phenylacylates in the same media lead to the conclusions that (1) phenoxy is less reactive overall than 1-naphthoxy toward a common phenylacyl radical but (2) the constrained cages in which the radical pairs reside exert greater control over the movements of the 1-naphthoxy/phenylacyl pairs. The reasons for these observations are discussed in the context of the shapes and van der Waals volumes of the radical pairs, the void volumes of sites in native polyethylene films, and the electronic properties of the aryloxy radicals.