Cadmium(II) complexes with monoiodo- and dibromodipyrromethenes: synthesis,molecular structure,spectral-luminescent properties,and stability in solutions

Cadmium(II) chelates with 4-iodo-, 5,5´-, and 4,4´-dibromo-2,2´-dipyrromethenes (HL¹, HL², and HL³, respectively) with the composition of [CdL₂] were synthesized. The influence of structural features of their molecules and properties of the medium on the characteristics of absorption and fluorescence spectra, and also on the thermodynamic stability constants in solutions was evaluated. The results of quantum chemical calculations revealed that the additional coordination interactions between the bromine atoms at the α-positions of dipyrromethene ligands and the complexing atom are possible in the molecular structure of α,α´- dibromosubstituted dipyrromethenate [Cd(L²)₂] in contrast with β-halogenated analogues [Cd(L¹)₂] and [Cd(L³)₂].     

Experimental study of the potential of multichannel acoustic thermotomography

We describe the results of experimental studies of reconstruction of the temperature profiles from heated sources using the method of acoustic thermometry performed with the help of a multichannel scanning acoustic thermotomograph. The sensitivity of an actual system is estimated. The results of laboratory experiments on the localization of heated objects in the medium with absorption and the results of in vivo experiments on the recording of variation of the acoustic-brightness temperature of human extremities in response to an external thermal effect are presented. Institute of Applied Physics, Russian Academy of Sciences, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 5, pp. 479–484, May 1999.     

Tin in silicate glasses: structure, thermodynamics and kinetics

In this work Mössbauer spectroscopy is used to investigate the oxidation states and structures of tin in silicate glasses. Thermal treatment of the glasses in atmospheres with varying oxygen partial pressure leads to the simultaneous appearance of reduction and diffusion. Experiments with varying treatment time give the opportunity to study diffusion and reduction processes in detail. Comparison of the hyperfine parameters of reference materials with measured parameter provides information about the local surroundings of the tin atoms. An octahedral surrounding for Sn^4?+? is presumed, while Sn^2?+? and three oxygen atoms form a tetrahedral coordination.     

A spin transition molecular material with a wide bistability domain

[Fe(hyptrz)3](4-chloro-3-nitrophenylsulfonate)22 H2O (1; hyptrz=4-(3-hydroxypropyl)-1,2,4-triazole) has been synthesized and its physical properties have been investigated by several physical techniques including magnetic susceptibility measurements, calorimetry, and M?ssbauer, optical, and EXAFS spectroscopy. Compound 1 exhibits a spin transition below room temperature, together with a very wide thermal hysteresis of about 50 K. This represents the widest hysteresis loop ever observed for an FeII-1,2,4-triazole spin transition material. The cooperativity is discussed on the basis of temperature-dependent EXAFS studies and of the structural features of a CuII analogue. The EXAFS structural model of (1) in both spin states is compared to that obtained for a related material whose spin transition occurs above room temperature. EXAFS spectroscopy suggests that 1,2,4-triazole chain compounds retain a linear character whatever the spin state of the iron(II).     

Isomerization of cyclic hydrocarbons mediated by an AlCl3-based ionic liquid as catalyst

Cyclohexane and methylcyclopentane isomerization were carried out under mild conditions using an ionic liquid consisting of n-butylpyridinium chloride and aluminum chloride as catalyst. The ionic liquid showed reasonably high catalytic activity in both reactions with a selectivity to corresponding products of 100%. In the case of cyclohexane isomerization, the thermodynamic equilibrium methylcyclopentane ⇌cyclohexane was almost achieved. For the reaction of cyclohexane isomerization, the kinetic study was performed, and the rate constants and the activation energy of the process were determined. This revised version was published online in June 2006 with corrections to the Cover Date.     

Production of Complex Hydrosulphates in the K3H(SO4)2–Rb3H(SO4)2 Series: Part I

Crystallography Reports - The phase equilibria in the K3H(SO4)2–Rb3H(SO4)2–H2O cross section have been investigated under isothermal conditions at 25°C. The concentration limits of...