N.V. Avramenko

The standard enthalpy of formation of 1,2,3,4-tetrachlorodibenzo-p-dioxine

The energy of combustion of crystalline 1,2,3,4-tetrachlorodibenzo-p-dioxine (-5122.9 ± 7.4 kJ/mol) was measured using an isothermic-shell calorimeter with a rotating platinum plated bomb. The result was used to calculate the enthalpy of combustion (-5120.4 ± 7.4 kJ/mol) and formation (−267.8 ± 7.6 kJ/mol) for the crystalline state. The enthalpy of sublimation was measured using a Calvet microcalorimeter at 411.5 K (116.0 ± 2.6 kJ/mol); recalculation to T = 298.15 K gave 118.7 ± 2.6 kJ/mol. The enthalpy of formation of 1,2,3,4-tetrachlorodibenzo-p-dioxine in the gas state was calculated (−149.1 ± 8.0 kJ/mol)

Improving the dispersity of detonation nanodiamond: differential scanning calorimetry as a new method of controlling the aggregation state of nanodiamond powders

Detonation nanodiamond (ND) is a suitable source material to produce unique samples consisting of almost uniform diamond nanocrystals (d = 3-5 nm). Such samples exist in the form of long stable aqueous dispersions with narrow size distribution of diamond particles. The material is finding ever increasing application in biomedicine. The major problem in producing monodispersed diamond colloids lies in the necessity of deagglomeration of detonation soot and/or removing of clusters formed by already isolated core particles in dry powders. To do this one must have an effective method to monitor the aggregation state or dispersity of powders and gels prior to the preparation of aqueous dispersions. In the absence of dispersity control at various stages of preparation the reproducibility of properties of existing ND materials is poor. In this paper we introduce differential scanning calorimetry (DSC) as a new tool capable to distinguish the state of aggregation in dry and wetted ND materials and to follow changes in this state under different types of treatment. Samples with identical X-ray diffraction patterns (XRD) and high resolution transmission electron microscopy (HRTEM) images gave visibly different DSC traces. Strong correlation was found between dynamic light scattering (DLS) data for colloids and DSC parameters for gels and powders of the same material. Based on DSC data we improved dispersity of existing ND materials and isolated samples with the best possible DSC parameters. These were true monodispersed easily dispersible fractions of ND particles with diameters of ca. 3 nm.

Thermodynamic properties of fullerene C60 solutions in a mixture of tetrachloromethane and toluene

The solubility of fullerene C60 in the tetrachloromethane-toluene system is measured over the entire range of compositions of the mixed solvent in the temperature range 298.15–338.15 K. An equation is proposed for describing the solubility of C60 as a function of the temperature and the composition of the mixed solvent. The equation is used for calculating the thermodynamic characteristics of solution of the fullerene. It is found that, in the investigated C60-CCl4/C6H5CH3 system, two types of solid solvates of the fullerene with the solvent are formed. The enthalpies and temperatures of incongruent melting of the crystalline solvates are determined by differential scanning calorimetry. The thermodynamic characteristics of solution and solvation of C60 in CCl4 and C6H5CH3 are obtained. It is shown that the entropy factor plays a decisive role in the temperature dependence of the Gibbs energy of solvation of the fullerene.

The first solid phase synthesis of pincer palladium complexes

Both dimeric μ-chlorine bridged and monomeric bidentate Pd(II) complexes with SCN hybrid pincer-type ligands, bearing thiophosphoryl group and imine moiety of the benzothiazole ring as coordination arms, formed in the reaction with (PhCN)(2)PdCl(2) under kinetic control (20 °C, dichloromethane solution) were readily converted into the corresponding SCN pincer complexes via solid phase synthesis (neat, 200 °C, 15 min). The synthesis of pincer complexes can be performed also by heating (200 °C, 5 min) of a homogeneous mixture of the initial reactants, namely, the ligand and (PhCN)(2)PdCl(2), obtained by manual grinding in a mortar. The efficacy of solid phase approaches is comparable with the analogous synthesis in solutions under severe conditions.

Binary systems of C60 with positional isomers 1,2- and 1,3-C6H4Br2

Abstract Thermodynamic properties of binary systems of C 60 with 1,2- and 1,3-dibromobenzenes have been studied by means of differential scanning calorimetry (DSC). Solid solvates with the compositions C 60 3(1,2-C 6 H 4 Br 2 ); C 60 2(1,3-C 6 H 4 Br 2 ) and C 60 0.6(1,3-C 6 H 4 Br 2 ) have been found. The solvates have been characterised by their enthalpies and temperatures of incongruent melting transition and in part by X-ray powder data. It has been shown that positional isomers 1,2- and 1,3- of the substituted benzenes formed two series of “typical” phase diagrams. Solubility behaviour of C 60 in positional isomers has been discussed.

Crystal solvate of C60 with tricloroethylene, C60 · C2HCl3

Extraction of fullerenes from carbon soot by trichloroethylene has been studied. We have found that C60 forms a solvate with trichloroethylene (C60 · C2HCl3:a=31.31(1);b= 10.156(4);c=10.146(4) Å;V=3228.6 Å3,Z=4,dcalc=1.752 g cm−3, orthorhombic symmetry). Its thermal stability has been studied using TG and DSC. A phase transition of the first order at 167 K has been detected.

Thermodynamic properties of the binary system C60-1,3,5-trimethylbenzene

Abstract Differential scanning calorimetry (DSC), Thermogravimetry (TG) and X-ray showed the formation of two solid solvates of C 60 with 1,3,5-trimethylbenzene. Temperatures and enthalpies of decomposition of both solvates were measured by DSC. TG and DSC were applied to determine the composition of solvates. The influence of solvates on solubility of C 60 in 1,3,5-trimethylbenzene was discussed.

Do Primary Particles of Detonation Nanodiamond Form a Secondary Structure

Gels and dried powders of the single-nano buckydiamond (SNBD) have been studied by means of differential scanning calorimetry (DSC) and gas adsorption methods. Nanophase of water (NPhW) (D = 8.4 ± 0.5 nm) was confirmed in SNBD hydrogel by DSC. Nitrogen adsorption isotherms of the dried powder demonstrated the presence of nano voids (D = 7 nm). The characteristic size and volume of the nano voids were almost equal to those of NPhW. Based on DSC and adsorption data, it was concluded that SNBD material though originally divided into individual diamond crystals (d = 5.2 nm) in the water dispersion forms stable networks as gel and dried powder.

Preparation and investigation of the crystals formed in the buckminsterfullerene-tetraselenotetracene-carbon disulfide system

Crystals containing up to 30 wt. % CS2, according to the data of IR and X-ray photoelectron spectroscopy, were isolated from the C60-TSeT-CS2 (TSeT is tetraselenotetracene) system. The unusually high concentration of carbon disulfide results in the complete sublimation of the crystals at a relatively high temperature (520 °C). The electron energy loss spectra of the crystals obtained were measured and analyzed.