Effect of ethanol on micellization and on decarboxylation of 6-nitrobenzisoxazole-3-carboxylate in aqueous cationic micelles

The effects of ethanol on the critical micellar concentration (cmc) and the rates of decarboxylation of 6-nitrobenzisoxazole-3-carboxylate (6-NBIC) have been investigated in aqueous cationic surfactants of the cetyltrialkylammonium family with bromide [CT(R)ABr], chloride [CT(R)ACl], and nitrate [CT(R)ANO3] counterions, and methyl (CTAX), n-propyl (CTPAX), and n-butyl (CTBAX) as the head group alkyl moieties. Effects upon cmc and reactivity are similar, featuring a break at the ethanol mole fraction, x(EtOH), of ca. 0.055; these effects have been related to changes in solvent structure, with formation of a clathrate at x(EtOH) = 0.055. Rate data in CTBABr were further investigated and fitting of raw kinetic data to the pseudophase model is possible up to x(EtOH) = 0.1, showing an unexpected decrease of rate constant values in the micellar pseudophase, kM', as ethanol content increases: a significant variation of micellar ionization degree could account for this kinetic effect.     

Kristallstrukturbestimmung von N-Trimethylsily-N′-methylimidazoliumbromid

Crystal Structure Determination of N-Trimethylsilyl-N′-Methylimidazolium Bromide The reaction of Trimethylbromosilane and N-Methylimidazole (NMI) led to a 1:1 compound stable at room temperature. The reaction was carried out at room temperature and colorless single crystals were obtained by sublimation. The addition compound crystallizes in the orthorhombic space group Pbnb (No. 56) with lattice constants a = 1218.3(2)pm, b = 1333.6(1)pm, c = 1360.2(2)pm, Z = 8, D_calc = 1.414 g/cm³. For 1506 independent reflections, measured at 21°C the structure could be refined to R = 0.067 and R_w = 0.062.     

Weak localization and electron-electron interactions in thin Pd and PdHx films

We investigate the temperature and magnetic field dependence of the resistance R of thin Pd and PdHx films. We show that the logarithmic behaviour R(T) ≈ A ln T is dominated in Pd by the interaction effect. Loading progressively with hydrogen shows first no change in A and then a decrease followed by a sign reversal when superconducting fluctuations prevail. The application of a magnetic field restores then a positive and large value of A. These data are analyzed within recent theories.     

Crystal structure and magnetic properties of copper formate anhydrate [α-Cu(HCOO)2]

The crystal structure of anhydrous copper formate [α-Cu(HCOO)₂] has been refined from neutron powder data by the profile analysis technique at three different temperatures. Hydrogen atoms were located and refined with anisotropic temperature factors. The copper ion has a Jahn-Teller distorted tetragonal pyramidal coordination. Magnetic measurements showed a paramagnetic behaviour in the temperature region 10–300 K. The positive Curie temperature of θ_{c = 9.8(3}) suggests, however, a ferromagnetic ordering at low temperatures.