Charge order superstructure with integer iron valence in Fe(2)OBO(3)

Solution-grown single crystals of Fe(2)OBO(3) were characterized by specific heat, M?ssbauer spectroscopy, and x-ray diffraction. A peak in the specific heat at 340 K indicates the onset of charge order. Evidence for a doubling of the unit cell at low temperature is presented. Combining structural refinement of diffraction data and M?ssbauer spectra, domains with diagonal charge order are established. Bond-valence-sum analysis indicates integer valence states of the Fe ions in the charge ordered phase, suggesting Fe(2)OBO(3) is the clearest example of ionic charge order so far.     

Application of technetium and rhenium carbonyl chemistry to nuclear medicine. Preparation of [NEt4]2[TcCl3(CO)3] from [NBu4][TcO4] and structure of [NEt4][Tc2(μ-Cl)3(CO)6]; structures of the model complexes [NEt4][Re2(μ-OEt)2(μ-OAc)(CO)6] and [ReBr({-CH2S(CH2)2Cl}2)(CO)3]

Transition Metal Chemistry - A detailed investigation of the one-pot synthesis of [NEt4]2[MX3(CO)3] [M=Tc (1a) or Re (1b); X= Cl?, Br?] is presented. The intermediates...     

Magneto-optical study of the superconducting gap of MgB(2) single crystals

We present magneto-optical reflectivity results in the basal plane of the hexagonal MgB(2). The data were collected on a mosaic of MgB(2) single crystals with T(c)=38 K from the ultraviolet down to the far infrared as a function of temperature and magnetic field oriented along the c axis. In the far infrared, there is a clear signature of the superconducting gap with a gap ratio 2 Delta/k(B)T(c) approximately 1.2, well below the weak-coupling value. The gap is suppressed in an external magnetic field, which is a function of temperature. We extract the upper critical field H(c2) along the c axis. The temperature dependence of H(c2) is compatible with the Helfand-Werthamer behavior.     

Fe(III)-Catalyzed direct C3 chalcogenylation of indole: The effect of iodide ions

A mild and efficient iron (III)-catalyzed C3 chalcogenylation of indoles has been developed and the role of the iodide ions in this transformation was investigated. EPR experiments revealed the reduction of Fe(III) to Fe(II) under the reaction conditions, supporting the formation of molecular iodine in the system, which in effect catalyze the reaction. The scope of the chalcogenylation was broad and the synthesis of more functionalized 3-selenylindoles was explored.     

Effect of pressure on the superconducting transition temperature of doped and neutron-damaged MgB2

Measurements of the superconducting transition temperatures for Al-doped, C-doped and neutron-damaged–annealed MgB₂ samples under pressure up to 8 kbar are presented. The dT_c/dP values change systematically with the decrease of the ambient pressure T_c in a regular fashion. The evolution of the pressure derivatives can be understood assuming that the change in phonon spectrum is a dominant contribution to dT_c/dP.