Synthesis and characterisation of luminescent fluorinated organoboron compounds

The reaction of 8-hydroxyquinoline (HQ) with B(C(6)F(5))(3) leads to the formation of the zwitterionic compound (C(6)F(5))(3)BQH (1), involving a proton migration from O to N. Compound 1 can be converted thermally to (C(6)F(5))(2)BQ (2), which can also be prepared from (C(6)F(5))(2)BCl and HQ. The reaction of HQ with (C(6)F(5))B(OC(6)F(5))(2) generates initially (C(6)F(5))(OC(6)F(5))BQ (3), which easily hydrolyses to give the diboron compound ((C(6)F(5))BQ)(2)O (4). Compounds 1, 2 and 4 have been fully characterised, including X-ray analysis. The spectroscopic properties of these compounds, including photoluminescence (PL) have been investigated and compared with the non-fluorinated luminescent boron compound (C(6)H(5))(2)BQ and also with AlQ(3). The changes in luminescent behaviour upon fluorination of these boron quinolinate compounds have been rationalised using computational studies.     

The Molybdenum(V) and Tungsten(VI) Oxoazides [MoO(N3)3], [MoO(N3)3⋅2 CH3CN], [(bipy)MoO(N3)3], [MoO(N3)5]2−, [WO(N3)4], and [WO(N3)4⋅CH3CN]

A series of novel molybdenum(V) and tungsten(VI) oxoazides was prepared starting from [MOF₄] (M=Mo, W) and Me₃SiN₃. While [WO(N₃)₄] was formed through fluoride–azide exchange in the reaction of Me₃SiN₃ with WOF₄ in SO₂ solution, the reaction with MoOF₄ resulted in a reduction of Mo^VI to Mo^V and formation of [MoO(N₃)₃]. Carried out in acetonitrile solution, these reactions resulted in the isolation of the corresponding adducts [MoO(N₃)₃?2 CH₃CN] and [WO(N₃)₄?CH₃CN]. Subsequent reactions of [MoO(N₃)₃] with 2,2′‐bipyridine and [PPh₄][N₃] resulted in the formation and isolation of [(bipy)MoO(N₃)₃] and [PPh₄]₂[MoO(N₃)₅], respectively. Most molybdenum(V) and tungsten(VI) oxoazides were fully characterized by their vibrational spectra, impact, friction and thermal sensitivity data and, in the case of [WO(N₃)₄?CH₃CN], [(bipy)MoO(N₃)₃], and [PPh₄]₂[MoO(N₃)₅], by their X‐ray crystal structures.     

Preparation of magnesium hydroxide from nitrate aqueous solution

Nucleation of Mg(OH)₂ was investigated by measuring the electrical conductivity and pH of the Mg(NO₃)₂ reaction solution to which ammonia containing different amounts of NH₄NO₃ was added. NH₄NO₃ increases solubility and slows down precipitation of Mg(OH)₂ in the system. Data are presented on the influence of NH₄NO₃ on the solubility of Mg(OH)₂ at 25°C. The phenomena observed can be explained by the solvation effect of nitrate ions brought to the system with the addition of ammonium nitrate, which was proved by NMR spectroscopy. When the mass fraction of NH₄NO₃ exceeds 15 %, homogeneous nucleation does not proceed. It was found that seeding of the system with Mg(OH)₂ crystals only influenced the rate of Mg(OH)₂ crystallisation, not the size and shape of the crystals. Primary crystals are smaller than 0.1 μm. The large difference in the surface energy of individual crystal planes leads to oriented agglomeration. This process is accelerated in a pressure reactor at 130°C. The resulting polycrystals are hexagonal plates 0.2 μm thin with a diameter of 1–2 μm. Under variable reaction conditions, agglomerates as big as 30 μm can be prepared.     

On the role of thermal activation in selective photochemistry: mechanistic insight into the oxidation of propene on the V4O11- cluster

An experimental methodology for a mechanistic analysis of gas phase chemical reactions is presented in the context of structure-reactivity relationships of metal oxide clusters relevant to photocatalysis. The spectroscopic approach is demonstrated with the investigation of the photoinduced oxygenation of propene on the V(4)O(11)(-) cluster, where the thermal activation and subsequent photoreaction are deduced with the information from (i) the temperature dependency of the aggregation kinetics in the propene-seeded helium atmosphere of an ion-trap reactor; (ii) the fluence dependency in the yield of different product channels of the photoreaction and (iii) the intensity dependency in the fragmentation of neutral reaction products that are probed via in situ multi-photon ionization. For the thermal reaction, selective hydrogen abstraction from the allylic position of propene accompanied by the linkage to the cluster at the dioxo moiety is postulated as the mechanism in the aggregation of propene on the V(4)O(11)(-) cluster. In accordance with an insightful neutralization-reionization study (Schr?der et al., J. Mass. Spectrom., 2010, 301, 84), the subsequent photoinduced reaction is defined by an allylic oxidation in the formation of acrolein from the initial allyloxy radical photoproduct. The relevance of the observed selectivity is discussed in view of the electronic structure and bond motifs offered by high valence oxide systems such as the V(4)O(11)(-) cluster.     

Risk management in power markets: The Hedging value of production flexibility

Since the 1990s power markets are being restructured worldwide and nowadays electrical power is traded as a commodity. The liberalization and with it the uncertainty in gas, fuel and electrical power prices requires an effective management of production facilities and financial contracts. Thereby derivatives build essential instruments to exchange volume as well as price risks. The challenge for participants in the newly competitive market environment is how to design, price and hedge derivative contracts in particular combination with the flexibility embedded in dispatch strategies of production assets. Accordingly, an adequate basis for management and investment decisions is needed which responds to the highly complex market situation.     

The cross sections for the binary and ternary fission of thorium induced by 14, 18, and 23 GeV protons

In this work the cross sections for the binary and ternary fission of thorium induced by 14, 18, and 23 GeV protons were determined. A polycarbonate (macrofol) was used as the detector of fission fragments.