Near-Infrared Vapochromism in Lipid-Packaged Mixed-Valence Coordination Polymers

Reversible vapochromism in the NIR region is achieved for a mixed-valence platinum complex with lipid counterions, from which exclusion of crystallization water by organic vapor alters lipid molecular orientation that...

Impact of Cooling on Water and Salt Migration of High-Chlorine Saline Soils

Secondary salinization is a common problem in saline soil projects. In order to grasp the mechanism of water and salt migration of high-chlorine saline soil during the cooling process, the saline soils along the Qarhan-Golmud Highway in the Qinghai-Tibet Plateau were selected as test samples. Firstly, the basic physical parameter test and the soluble salt chemical experiment were carried out and obtained liquid and plastic limits, dry density, etc. Secondly, freezing temperature experiments and water-salt migration experiments under one-way cooling conditions were conducted according to the actual environmental conditions, and after the temperature gradient line of the soil sample was stable, water content and labile salt chemistry experiments were conducted to obtain the distribution of water and salt contents of soil samples. Finally, the effect of crystallization-water phase transition on water and salt migration and the effect of chloride salt on the temperature of crystallization-water phase transition were considered, and a mathematical model applicable to the water and salt migration of highly chlorinated saline soils under the effect of unidirectional cooling was established and solved with COMSOL Multiphysics software, and the correctness of the model was verified by comparing the simulation results with the experimental results. The study found that (1) during the one-way cooling process, both water and salt showed a tendency to migrate to the cold end. The MC (saline soil with medium chlorine content) with an initial water content of 16.9% and Cl− content of 3.373% was measured to reach a 17.6% water content and 3.76% Cl− content at the cold (top) end after the experiment. The HC (saline soil with high chlorine content) with an initial water content of 6.6% and Cl− content of 17.928% was measured to reach a 6.83% water content and 18.8% Cl− content after the experiment and (2) after the one-way cooling experiment of the MC, the water content at a distance of 1–2 cm from the cold end has abrupt changes, which may be caused by a small amount of crystallization—water phase transition at this location. At the same time, according to the temperature change graph during the cooling process, the phase change temperature was set to −9°C in the numerical simulation process to match the experimental results.

UNUSUAL TYPES OF LAYERED ORGANIC CRYSTAL HYDRATES

In molecular crystalline hydrates with a high content of crystallization water infinite H2O...OH2 nets or finite fragments of such nets are formed. As a rule, these nets contain 5- and 6-membered cycles (H2O)n. Brand new topological types of layered organic crystal hydrates among the structures included in the Cambridge Structural Database in 2009–2019 were found and investigated. The discovered nets were deposited to the Topological Types Database. Topological characteristics of new nets are described, in particular, the maximum possible symmetry, information indices, vertex, edge and face transitivity of the nets

Effect of Activation Pretreatment on the Pyrolysis Behavior of Sludge

In the present research, TG and FTIR were used to study the effect of chemical activation pretreatment on sludge pyrolysis. The results showed that both acidic and alkaline activation promoted sludge pyrolysis. KOH inhibited the elimination of crystallization water and promoted the release of volatiles. On the other hand, H2SO4 favored the separation of crystallization water and the release of volatiles. Low concentrations of the activator promoted the production of combustible gas and inhibited the generation of CO2. By analyzing the activation energy of the pyrolysis process using the Coats-Redfern method, it was found that both, KOH and H2SO4, were able to reduce the pyrolysis activation energy. When H2SO4 was used, the effect was more significant.

STUDY OF THERMAL CHARACTERISTICS OF THE EUROPIUM (III) COMPLEX WITH HIGH-MOLECULAR HEPARIN

Синтезировано твердое комплексное соединение высокомолекулярного гепарина с европием (III) ([EuHep]•3HO). Проведен синхронный термический анализ [EuHep]•3HO. Определены термическая устойчивость, температура дегидратации и количество кристаллизационной воды, количество металла в комплексе. Описаны наиболее значимые стадии термодеструкции и на основе данных ИК-спектроскопии предположены образующиеся продукты. A solid complex compound of high molecular weight heparin with europium (III) was synthesized. A synchronous thermal analysis of [EuHep]•3HO was performed. Thermal stability, dehydration temperature and the amount of crystallization water, the amount of metal in the complex are determined. The most significant stages of thermal degradation are described and, based on the data of IR spectroscopy, the products formed are assumed.

The Crystal Structure of Defect KBB’O6 Pyrochlores (B,B’: Nb,W,Sb,Te) Revisited from Neutron Diffraction Data

Three defect pyrochlores KNbWO6·xH2O, KNbTeO6 and KSbWO6 were synthesized by solid state reaction at 750 °C, from stoichiometric mixtures of K2C2O4, Sb2O3, Nb2O5, WO3 and 20% excess TeO2. A neutron powder diffraction (NPD) data analysis allowed unveiling some structural features. They are all defined in the cubic F d 3 ¯ m space group symmetry, with α = 10.5068(1) Å, 10.2466(1) Å and 10.2377(1) Å, respectively. Difference Fourier synthesis for KNbWO6·xH2O clearly showed the presence of crystallization water, with extra O’ oxygen and H+ atoms that were located from NPD data. These O’ oxygen atoms are placed at 32e Wyckoff sites, conforming a K2O’ sublattice interpenetrated with the covalent framework constituted by (Nb,W)O6 octahedra. The H+ ions coordinate the O’ atoms at partially occupied 96g Wyckoff sites while K+ ions shift also along 32e sites, but closer to the 16c special site (0,0,0). By contrast, extra H2O molecules are absent in the other two pyrochlores: in KNbTeO6 and KSbWO6 K+ ions are shifted along 32e (x,x,x) sites further away from the origin than for the previous material, and the higher covalency of the octahedral network determines more compact structures, with shorter B–O distances and narrower B–O–B angles in the proposed AB2O6 defect pyrochlore structure.

How to Make a Better Magnet? Insertion of Additional Bridging Ligands into a Magnetic Coordination Polymer

A three-dimensional cyanide-bridged coordination polymer based on FeII (S = 2) and NbIV (S = 1/2) {[FeII(H2O)2]2[NbIV(CN)8]·4H2O}n (Fe2Nb) was modified at the self-assembly stage by inserting an additional formate HCOO− bridge into its cyanide framework. The resulting mixed-bridged {(NH4)[(H2O)FeII-(μ-HCOO)-FeII(H2O)][NbIV(CN)8]·3H2O}n (Fe2NbHCOO) exhibited additional FeII-HCOO-FeII structural motifs connecting each of the two FeII centers. The insertion of HCOO− was possible due to the substitution of some of the aqua ligands and crystallization water molecules in the parent framework by formate anions and ammonium cations. The formate molecular bridge not only shortened the distance between FeII ions in Fe2NbHCOO from 6.609 Å to 6.141 Å, but also created additional magnetic interaction pathways between the magnetic centers, resulting in an increase in the long range magnetic ordering temperature from 43 K for Fe2Nb to 58 K. The mixed-bridged Fe2NbHCOO also showed a much broader magnetic hysteresis loop of 0.102 T, compared to 0.013 T for Fe2Nb.

Role of crystallization water molecules on hydrogen-bonded structures and dielectric phase transitions in amino trimethylene phosphonic acid-based crystals

Amino trimethylene phosphonic acid-based organic salts show crystallization water molecule-triggered dielectric transitions and relaxations.

INFLUENCE OF SOLUBILITY OF SALTS IN THE WATER ON THEIR TENDENCY TO DEHYDRATION OF CRYSTAL HYDRATES

The process of regeneration of salts without the use of vacuum as an example of crystal hydrates with different solubility of the constituent salts in water are considered in the article. Middle orthophosphates of five alkali metal elements (lithium, sodium, potassium, rubidium and cesium) were investigated as an adsorbent. It is shown dependence of the dehydration temperature of crystal hydrates from the nature of metal elements that constitute them. It was identified a number of key factors that influence the crystalline regeneration process, namely a value factor of their solubility in water and base avidity, which is formed by hydrolysis of salts. It was proved that the optimal adsorbent that absorb water and binds it to the crystal hydrates, including one acid salts are salts of the least strong base. It is shown that the salts of sodium, potassium, rubidium and cesium in this process cause an undesirable phenomenon - melting of crystallization water. Melting temperatures of orthophosphates of sodium, potassium, rubidium and cesium in crystallization water were defined. It was proved that the most effective adsorbent is lithium orthophosphate.