Volatility and thermal stability of vanadyl β-diketonate complexes

Thermal behavior and thermodynamic characteristics of vanadyl β-diketonates—acetylacetonate VO(acac)₂, dipivaloylmethanate VO(thd)₂, and tris-hexafluoroacetylacetonate VO(hfa)₂ (Hacac, 2,4-pentanedione; Hthd, 2,2,6,6-tetramethyl-3,5-heptanedione; Hhfa, 1,1,1,5,5,5-hexafluoro-2,4-pentanedione)—have been studied by thermal analysis and the Knudsen effusion mass spectrometry study of gas phase composition. The compounds have been shown to undergo congruent sublimation. Saturated vapor over the complexes has been shown to comprise monomeric VOL₂ molecules. Absolute values of partial pressures and sublimation enthalpies of these compounds have been determined.     

Saturation vapor pressure of the mixed-ligand calcium bis(hexafluoroacetylacetonate) complex with dyglime and water

The vapor composition and thermodynamic characteristics of vaporization of the mixed-ligand complex Ca(hfa)₂(diglyme)(H₂O) (I) (hfa^? is the hexafluoroacetylacetonate anion, diglyme is 1-methoxy-2-(2-methoxyethoxy)ethane) in the temperature range of 298–350 K were studied by the Knudsen effusion method with mass-spectrometric analysis of the gas phase. The mass spectrometry data were juxtaposed with the results of thermal analysis. It was shown that dehydration of I, resulting in a change of the intermolecular bonding system, affects the thermodynamic parameters of sublimation under conditions where dehydration and sublimation occur in parallel.     

Mixed-ligand complexes of alkaline-earth metal trifluoroacetates with monoethanolamine

The mixed-ligand complexes of the formula [M(CF₃COO)₂(MEA) _n ] (MEA is monoethanolamine; M = Ca (I) and Sr (II), n = 1.5; M = Ba (III), (n = 1) were obtained from appropriate salts M(CF₃COO)₂ · nH₂O and MEA in ethanol. Complexes I–III were characterized by elemental analysis data and IR spectra. Slow crystallization of a solution of complex III in air gave a single crystal of the formula [Ba(CF₃COO)₂(MEA)(H₂O)], which is a coordination polymer with C.N.(Ba) 9 (X-ray diffraction data). Thermal analysis showed that complexes I–III decompose under argon and in air to the corresponding fluorides at T < 400°C.     

Interaction of carboxylated polyacrylamide with chromium(III) acetate: 13C NMR study of mechanism

The interaction of chromium(III) acetate with poly(acrylamide-co-acrylic acid) in aqueous medium leads to formation of three-dimensional network of crosslinked macromolecules. Formation of the complex between chromium(III) cation and carboxylate groups is a driving force of the interaction. Depending on the reagents ratio, the complex contains two or three carboxylate groups. The amide units are not involved in any specific interaction with the cation.     

Aldimines of Cardenolides and Cardenolide-Glycosides

New aldimines were synthesized from the cardenolide strophantidin and cardenolide-glycosides erysimin and cymarin and included morpholine, nitrile, pyridine, furan, hydroxy- and methoxyphenyl, piperidine, and other derivatives. An effective modified method for synthesizing aldimines was proposed. 52 new compounds were synthesized. Their structures were confirmed by IR and PMR spectra and elemental analysis.__________Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 268–271, May–June, 2005.     

Rheological properties of cellulose-chitosan-phosphoric acid systems in different phase states

Rheological properties of 7.0–9.1% cellulose-chitosan suspensions, solutions, and gels in aqueous phosphoric acid were examined in various modes of shear flow in the range 0.15–100 s^?1 at 268–323 K. During steady state flow, the appearance of a quasi-Newtonian region was detected at shear rates between 20 and 40 s^?1 owing to orientational ordering of macromolecules in the stream. Under the conditions of transient shear flow at a constant shear rate, rheopexy was observed in both cellulose solutions and cellulose-chitosan solutions. The thixotropic behavior of cellulose-chitosan suspensions, spinning solutions, and gels was characterized during a sharp drop of shear rate from 0.15 to 10 s^?1, that is, under conditions modeling the processes of transport and extrusion of spinning solutions.