The development of accurate chemical kinetic models capable of predicting the combustion of methane and dimethyl ether in common combustion environments such as compression ignition engines and gas turbines is important as it provides valuable data and understanding of these fuels under conditions that are difficult and expensive to study in the real combustors. In this work, both experimental and chemical kinetic model-predicted ignition delay time data are provided covering a range of conditions relevant to gas turbine environments (T = 600 − 1600 K, p = 7 − 41 atm, φ = 0.3, 0.5, 1.0, and 2.0 in 'air' mixtures). The detailed chemical kinetic model (Mech 56.54) is capable of accurately predicting this wide range of data, and it is the first mechanism to incorporate high-level rate constant measurements and calculations where available for the reactions of DME. This mechanism is also the first to apply a pressure-dependent treatment to the low-temperature reactions of DME. It has been validated using available literature data including flow reactor, jet-stirred reactor, shock-tube ignition delay times, shock-tube speciation, flame speed, and flame speciation data. New ignition delay time measurements are presented for methane, dimethyl ether, and their mixtures; these data were obtained using three different shock tubes and a rapid compression machine. In addition to the DME/CH 4 blends, high-pressure data for pure DME and pure methane were also obtained. Where possible, the new * address:

The synthesis of novel, monocationic iridium(III) photosensitisers (Ir-PSs) with the general formula [Ir(III)(C^N)(2)(N^N)](+) (C^N: cyclometallating phenylpyridine ligand, N^N: neutral bidentate ligand) is described. The structures obtained were examined by cyclic voltammetry, UV/Vis and photoluminescence spectroscopy and X-ray analysis. All iridium complexes were tested for their ability as photosensitisers to promote homogeneously catalysed hydrogen generation from water. In the presence of [HNEt(3)][HFe(3)(CO)(11)] as a water-reduction catalyst (WRC) and triethylamine as a sacrificial reductant (SR), seven of the new iridium complexes showed activity. [Ir(6-iPr-bpy)(ppy)(2)]PF(6) (bpy: 2,2'-bipyridine, ppy: 2-phenylpyridine) turned out to be the most efficient photosensitiser. This complex was also tested in combination with other WRCs based on rhodium, platinum, cobalt and manganese. In all cases, significant hydrogen evolution took place. Maximum turnover numbers of 4550 for this Ir-PS and 2770 for the Fe WRC generated in situ from [HNEt(3)][HFe(3)(CO)(11)] and tris[3,5-bis(trifluoromethyl)phenyl]phosphine was obtained. These are the highest overall efficiencies for any Ir/Fe water-reduction system reported to date. The incident photon to hydrogen yield reaches 16.4% with the best system.

Molecularly defined Ir complexes and different samples of supported IrO(2) nanoparticles have been tested and compared in the catalytic water oxidation with cerium ammonium nitrate (CAN) as the oxidant. By comparing the activity of nano-scaled supported IrO(2) particles to the one of organometallic complexes it is shown that the overall activity of the homogeneous Ir precursors is defined by both the formation of the homogeneous active species and its conversion to Ir(IV)-oxo nanoparticles. In the first phase of the reaction the activity is dominated by the homogeneous active species. With increasing reaction time, the influence of nano-sized Ir-oxo particles becomes more evident. Notably, the different conversion rates of the homogeneous precursor into the active species as well as the conversion into Ir-oxo nanoparticles and the different particle sizes have a significant influence on the overall activity. In addition to the homogeneous systems, IrO(2)@MCM-41 has also been synthesized, which contains stabilized nanoparticles of between 1 and 3 nm in size. This latter system shows a similar activity to IrCl(3)⋅xH(2)O and complexes 4 and 5. Mechanistic insights were obtained by in situ X-ray absorption spectroscopy and scanning transmission electron microscopy.

The coordination chemistry of new fluorinated dialkoxy-diimino ligands onto Al(III) centers has been studied. Diimino-diols) react selectively with AlMe 3 , AlMe 2 Cl, and Al(OiPr) 3 to give the corresponding complexes {ON Et NO}AlX (X ) Me, 1; Cl, 2; OiPr, 3), {ON Cy NO}AlX (X ) Me, 5; Cl, 6; OiPr, 7), and { Me ON Et NO}AlX (X ) Me, 8; Cl, 9) with concomitant alkane or alcohol elimination, respectively. Single-crystal X-ray diffraction studies revealed that complexes 2, 5, 7, 8, and 9 are mononuclear in the solid state with distorted trigonal-bipyramidal to square-pyramidal geometries. Complexes 1-9 were also characterized in CD 2 Cl 2 solution by 1 H, 13 C, and 19 F NMR spectroscopy. Only one symmetric isomer was observed for complexes 1-7, but mixtures of two isomers (one symmetric, one dissymmetric on the NMR time scale) were observed for complexes 8 and 9. The Al-OiPr complexes 3 and 7 are effective initiators for the ring-opening polymerization of ε-caprolactone and racemic lactide, giving polymers with high molecular weights (M n up to 37 500 g mol -1 ) and relatively narrow polydispersities (M w /M n ) 1.08-1.91). The PLAs produced, both under slurry or melt conditions, with either achiral complex 3 or chiral complex 7, have a highly isotactic-enriched stereoblock microstructure (P meso ) 0.87).