Crystal structure and emission study of [(PPh3)2Cu(dmp)-O-(dmp)Cu(PPh3)2]2+ (dmp = 2,9-dimethyl-1,10-phenanthroline)

The synthesis and crystal structure of a luminescent dinuclear Cu(I) complex as the BF^– ₄ salt from toluene and methanol containing triphenylphosphine and -oxo-bis(2,9-dimethyl-1,10-phenanthroline) is described. The coordination geometry about the Cu(I) center is distorted tetrahedral. An unusual feature of the structure is a pseudo-inversion center located near the oxygen atom at approximately 0.51, 0.26, 0.25, such that all of the atoms except for the oxygen are related by a pseudo-inversion center to another atom in the same molecule, as well as by crystallographic inversion to the other molecule in the unit cell. The complex displays luminescence from an MLCT band in fluid solution and emission from both a metal-centered charge-transfer and intraligand (phenanthroline) state at 77K in a chloroform snow. Crystal data: triclinic, P , a = 15.163(2), b = 16.985(2), c = 18.731(2) Å, = 106.458(9), = 91.416(8), = 102.557(9)°, V = 4496(1) ų, and Z = 2.     

Enhancing sonochemical activity in aqueous media using power-modulated pulsed ultrasound: an initial study

Relatively little is known about the effects of pulsed ultrasound on the facilitation of chemical reactivity. Previous studies have indicated that sonochemistry using pulses is generally less effective than continuous ultrasonic irradiation. However, the pulse trains employed were such that the peak power of the pulses was the same as the maximum power used in continuous irradiation. As a result, less acoustic energy was transmitted to the solutions over the same period of time. The effectiveness of ultrasound when the pulse is adjusted so that the same amount of acoustic energy is input compared to continuous irradiation over a given time has not been previously explored. In this study we have embarked on an examination of the efficacy of power-modulated pulsed (PMP) sonochemistry. Specifically, we have explored the effects of pulse type and pulse frequency on the oxidation of potassium iodide and the degradation of acid orange, a common industrial colorant. A rate increase by a factor of three was observed compared with continuous irradiation under conditions of equivalent acoustic input power.     

Effects of high intensity ultrasound on inorganic solids

Ultrasonic irradiation dramatically affects the reactivity of a variety of inorganic solids. We have found, for example, large increases in the rates of intercalation of a wide range of compounds into various layered inorganic solids (such as ZrS2, V2O5, TaS2 and MoO3. High intensity ultrasound also enhances the heterogeneous catalysis of alkene hydrogenation by Ni powders. Scanning electron microscopy reveals that ultrasound has multiple effects on the morphology and surface characteristics of inorganic solids, creating substantial surface damage, increasing surface areas significantly and causing increased particle aggregation.     

Methanol electrochemical oxidation at nanometer-scale PtRu materials

The electrochemical oxidation of CH₃OH at nanometer-scale PtRu catalyst materials is reported. Comparisons are made between the properties of a Johnson Matthey (JM) PtRu black sample (50 at.% Ru (X_Ru ≈ 0.5)) and PtRu particles (2-6 nm, nominally X_Ru ≈ 0.5) prepared by sonication under anhydrous conditions. Cyclic voltammetry and in situ infrared spectroscopy measurements show the catalysts are active for the oxidation of 0.5 M CH₃OH in 0.1 M HClO₄ at temperatures between ambient and 70 °C. The sonochemically prepared PtRu sample displayed properties characteristic of bulk PtRu alloys with X_Ru ≈ 0.5. Evidence for phase separation of Pt and Ru was observed in CO stripping voltammetry from the JM catalyst adsorbed at low metal loadings (20 μg/cm²) on bulk Au electrodes. Per gram of catalyst, the JM material was more active toward CO₂ formation and displayed greater resistance to poisoning by adsorbed CO than the sonochemically prepared material during ambient temperature oxidation of 0.5 M CH₃OH in 0.1 M HClO₄.     

Sonochemical production of intermetallic coatings in heterogeneous media

The production of 5–10 μm fused particles and agglomerates occurs when metal powders in hydrocarbon solvents are exposed to high-intensity ultrasound. The principle mechanism of particle fusion is believed to be interparticle collision caused by the rapid movement of particles propelled by shock waves generated at cavitation sites. An energy-dispersive X-ray (EDX) study of the agglomerates produced during the sonication of mixed-metal powders in decane indicates that not only are the metal particles fused by the action of ultrasound but that intermetallic coatings are also developed. By examination of mixed-metal systems (Ni/Co and Cu/Mo) with substantially different tribological characteristics, it has been determined that the coatings are generated by both adhesive wear and direct impact. The mechanisms of ultrasound-induced coatings are discussed.     

Vectorial Approach to Fast Correlation Attacks

A new, vectorial approach to fast correlation attacks on binary memoryless combiners is proposed. Instead of individual input sequences or their linear combinations, the new attack is targeting subsets of input sequences as a whole thus exploiting the full correlation between the chosen subset and the output sequence. In particular, the set of all the input sequences can be chosen as the target. The attack is based on a novel iterative probabilistic algorithm which is also applicable to general memoryless combiners over finite fields or finite rings. To illustrate the effectiveness of the introduced approach, experimental results obtained for random balanced combining functions are presentedMost of this work was done while he was with Rome CryptoDesign Center, Gemplus, Italy     

On the Motion of a Dynamic System with Minimal Dissipation

The motion of a holonomic scleronomic non-conservative mechanicalsystem with minimal dissipation is considered. As applicationsof the theory several problems are studied in detail.