Enthalpies and heat capacities of transfer of sodium carboxylates and sodium dodecylsulfate from water to aqueoustert-butyl alcohol solutions

Integral enthalpies of solution at very low concentrations of sodium carboxylates and sodium dodecylsulfate in aqueous tert-butyl alcohol solutions at 25°C and 35°C were measured with an isoperibol submarine calorimeter. The enthalpies and heat capacities of transfer of these surfactants from water to aqueous tertbutyl alcohol solutions were derived from integral enthalpies of solution. The results are explained in terms of the structural alteration effect of the constituent hydrophobic and hydrophilic groups of the solute.     

The study of new zinc(II) aliphatic carboxylate complex compounds by methods of thermal analysis

Four new complex compounds were prepared by the reaction of zinc bromobutyrate and organic ligands. The general formula of the synthetized complex compounds are (2-Brbut)₂ZnL and (4-Brbut)₂ZnL₂nH₂O (but=butyrate, L=theobromine (tbr), theophylline (tph), methyl-3-pyridyl carbamate (mpc), n=0-1). The compounds were characterized by chemical analysis and IR spectroscopy. The thermal behaviour of the zinc(II) complexes was studied by thermal analysis. Thermal decomposition in the case of hydrated compounds starts with the release of water molecules. Then molecules of organic ligands and the bromobutyrate anion are released and decomposed. CH₃CH₂CH=O, CO, CH₂=CHCH=O, CH₂O and ZnBr₂ were found as gaseous products of thermal decomposition during heating up to 700°C. IR, mass spectroscopy, X-ray powder diffraction and chemical analysis were used for the determination of solid and gaseous intermediates and products of the thermal decomposition.This revised version was published online in November 2005 with corrections to the Cover Date.     

“From Heteronuclear Complex to Composite Oxide” Approach in the Synthesis of Nanosized Ferrites MIIFeIII 2O4 (M = Mn,Co, Ni) with Spinel Structure and Their Catalytic Properties

A study was carried out on the preparation of ferrites M^IIFe₂O₄ (M^II = Mn, Co, Ni) by the thermal decomposition of the corresponding ₃-oxoacetates [Fe₂M^IIO(CH₃COO)₆(H₂O)₃]·2H₂O. Nanocrystallites of M^IIFe₂O₄ were formed under mild conditions at 300-400 °C in this reaction. An increase in the temperature leads to an increase in particle size. Nickel ferrite showed high catalytic activity in the reduction of nitrogen oxides (NO _x ) by hydrocarbons.     

Pt-Catalyzed sp C-H bond activation of o-alkyl substituted aromatic carboxylic acid derivatives for the formation of aryl lactones

Synthesis of aryl lactones from ortho-alkyl substituted aromatic carboxylic acids is described on the basis of sp³ C-H bond activation using either palladium or platinum catalysts. Kinetic isotope studies reveal that the reaction takes place presumably by the chelation assistance of metal catalyst to the carboxylic group followed by the C-H bond activation.     

Luminescence efficiency of aromatic carboxylates of europium and terbium when methylene bridges and nitro groups are present in the ligands

We discuss the possibility of optimizing the brightness of luminescence for phenylcarboxylates, naphthylcarboxylates, and indolylcarboxylates of europium and terbium and their adducts with 1,10-phenanthroline and 2,2′-bipyridine by modifying the ligands. We have studied the efficiency of luminescence and luminescence excitation. We consider the effect of blocking energy transfer from the ligands to the Eu³⁺ and Tb³⁺ ions by methylene (-CH₂-) bridges dividing the π-electron system of the ligands into two parts and by the electronacceptor nitro group (-NO₂). We have analyzed the pathways for transfer and degradation of the excitation energy at 77 K and 300 K. From the phosphorescence spectra of gadolinium salts, we have determined the energies of the lowest excited triplet states of the ligands. We consider the effect of the relative positions of the triplet levels of the ligands and the excited levels of the Eu³⁺ and Tb³⁺ ions on the luminescence efficiency. We found channels for dissipation of the excitation energy via the ππ* and nπ* states of the aromatic system of the carboxylate and the NO₂ group. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 48–54, January–February, 2007.     

Solution behaviour of lead(II) carboxylates in organic solvents

The solution behaviour has been studied of a series of even chain length lead(II) carboxylates (octanoate to octadecanoate) and the odd chain length lead(II) heptadecanoate in a variety of non-complexing organic solvents and in alcohols. In agreement with previous studies, solubility increases dramatically above a certain temperature, which depends on solute concentration, chain length and solvent. This solution temperature is also affected by traces of water. These results are complemented by studies using vapour pressure osmometry, dynamic light scattering, ¹H and ¹³NMR spectroscopy. The results in water-free systems are consistent with the formation of rather ill-defined, polydisperse aggregates, which increase in size with concentration and decrease with temperature. These show similar local structure to lamellar mesophases in the pure lead(II) carboxylates, and are suggested to be formed by solvent induced swelling and break-up of these mesophases. In the presence of water, a more ordered structure is formed, in which a few water molecules are suggested to be bound to the lead(II) carboxylate headgroup.     

Framework materials based on azamacrocyclic complexes of transition metals and carboxylates

Published data on the molecular and crystal structure and characteristics of coordination polymers and metal-organic frameworks based on the macrocyclic complexes of transition metals and aromatic carboxylates are analyzed. The prospects for the use of such materials as selective sorbents for gases and organic molecules are demonstrated.Translated from Teoreticheskaya i Éksperimentalnaya Khimiya, Vol. 40, No. 6, pp. 331–356, November–December, 2004.     

Jahn-Teller effect in trigonal μ-oxoclusters

A theory of the Jahn-Teller effect in trinuclear Cr^III and Fe^III -oxocomplexes based on the generalized angular overlap model is developed. The central bridging O atom is not localized at the center of the triangle formed by the metal atoms. Rather, it executes a free or hindered motion along a circular groove of radius 0.05–0.1 . The theory provides a qualitative explanation for apparent discrepancy between the X-ray structural data and the results of the heat capacity, magnetic susceptibility, and inelastic neutron scattering measurements. Namely, X-ray structural data correspond to a regular triangle symmetry while other data correspond to an equilateral or even irregular triangle symmetry.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2375–2380, November, 2004.     

Stereodivergent synthesis of chiral low-molecular bioregulators using readily available lipases

Kinetic resolution of racemic alcohols and esters or asymmetrization of prochiral meso-polyols and their esters mediated by the most readily available lipases (PPL, CCL) is a convenient method for stereodivergent synthesis of chiral biologically active molecules, particularly when the task is to determine which of the enantiomers is responsible for the biological activity. Examples of application of these enzymatic processes as key steps in the synthesis of all the possible stereoisomers of a given biomolecule and for the solution of related synthetic problems are considered.