Authors:P. Storoniak, K. Krzymiński, and J. Błażejowski
Enthalpies of sublimation of acridine, 9-acridinamine, N-methyl-9-acridinamine, 10-methyl-9-acridinimine, N,N-dimethyl-9-acridinamine
and N-methyl-10-methyl-9-acridinimine were determined by fitting to thermogravimetric curves with the Clausius-Clapeyron relationship.
These values compare well with crystal lattice energies predicted theoretically as the sum of electrostatic, dispersive and
repulsive interactions. Partial charges for these calculations were obtained on an ab initio level, while atomic parameters
were taken from literature.
A general approach to the theoretical evaluation of the crystal lattice energy of ionic substances, particularly those composed of monoatomic ions, is outlined in detail. Subsequently, the possibilities of theoretical prediction of the lattice energy of complex organic and inorganic ionic substances are discussed. Lastly, the importance of the lattice energy in examinations of the properties and behaviour of solid-state systems, is treated, together with the prospects of developing a model describing the kinetics of solid-state processes.
Authors:G. I. Zharkova, S. V. Sysoev, P. A. Stabnikov, V. A. Logvinenko, and I. K. Igumenov
contacts are considered based on the structural data. The van der Waals latticeenergies were calculated and compared to the experimental sublimation enthalpy values of the complexes.
Due to high volatility and thermal stability the palladium(II) β
/kJ mol−1 = −259.0 ± 1.6 (LiSC2H5), −199.9 ± 1.8 (NaSC2H5), −254.9 ± 2.4 (NaSC4H9), −240.6 ± 1.9 (KSC2H5), −235.8 ± 2.0 (CsSC2H5). These results where compared with the literature values for the corresponding alkoxides and together with values for
Authors:N. Smirnov, Yu. Shirokov, A. Artamonov, and M. Nikeshina
The analysis of structural state and energetic properties of active catalyst component in oxide copper-containing catalytic system has been performed on the basis of comparing the data of thermochemical, X-ray diffraction and catalytic activity determinations. The analysis of thermochemical data obtained makes it possible to evaluate changes in lattice energy and the nearest coordination sphere energetic parameters of copper cations during the formation of solid solutions. The high degree of correlation of catalytic properties and the formation enthalpy of solid solutions can be explained by the fact that alongside with the factors influencing the catalytic activity it is the strength of cation—cation interaction that is the most important.
Authors:P. Skurski, M. Jasionowski, and J. Błażejowski
MNDO/d and PM3 quantum chemistry methods were used to examine reaction pathways and predict thermodynamic and kinetic barriers
for the thermal dissociation of isolated conglomerates of N,N,N-trimethylmethanaminium cations (TMA+) and halide anions (X = Cl−, Br− and I−). Theoretically obtained changes in enthalpy and entropy for the above-mentioned process were subsequently supplemented with
theoretically determined crystal lattice energies, that enabled prediction of relevant characteristics for the dissociation
of crystalline phases. Data thus obtained compare only qualitatively with those available in literature and resulting predominantly
from thermoanalytical investigations, although values of theoretical characteristics generally follow the same trends as experimental
Authors:G. Patyi, A. Bódis, I. Antal, B. Vajna, Zs. Nagy, and Gy. Marosi
Solvent and melt techniques were used to obtain molecular dispersion of the poorly soluble spironolactone (SPIR) model drug
enhancing its dissolution rate. DSC study of the interaction between SPIR and hydroxypropyl-β-cyclodextrin confirmed the need
for molecular dispersion if their complexation is required. Solvent-free twin-screw extrusion was suitable for forming inclusion
complex significantly below the melting temperature of the SPIR. According to DSC, Raman and XRPD results fine dispersion
of both components was achieved in a hydrophilic polymer. The molecules of the active ingredient are separated from each other
in the polymer and the lack of the lattice energy causes faster dissolution.
The melting temperatures and absolute values of melting enthalpies of lanthanide trichlorides decrease from LaCl3to TbCl3and then increase to LuCl3. The preceding decrease cannot be explained by the lattice energies of the trichlorides, since they increase continuously
from the lanthanum to the lutetium compounds. However, it may be attributed to the structural features of the liquid state.
The liquids near the melting points consist of clusters of complex units, which become larger with decreasing radii of the
metal ions. To prove this assumption additional quantitative investigations are necessary.
The initial retentions (at ∼20°C) of (n, γ) activated rare earth bromates were studied using a252Cf fission neutron source with respect to80Br,80mBr and82Br. They lay over the ranges 19–23, 21–23 and 28–32%, respectively. On heating, retention progressively increases and closes
on ∼100% for Sm-bromate while for other systems the optimum values reach <85%. Thus, cation effect becomes more pronounced
during thermal annealing. The isothermal data show that the weight-loss is due to dehydration. The cation effect on retention
is discussed in the light of various parameters like lanthanide contraction, crystal structure, lattice energy, crystal water,
properties of anion and mode of thermal decomposition.