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The thermal effect of a model oxo-transfer reaction with the participation of a tungsten-containing synthetic analog of the enzyme active site, [WO2(mnt)2]2− (mnt = maleonitriledithiolate), has been determined for the first time. The value of the thermal effect indicates that the driving force of the oxo-transfer is the enthalpy factor. To determine the thermal effect of oxo-transfer, the dissolution enthalpies of the reaction participants in acetonitrile were determined: Δ H sol 0 PPh 3 = 24.9 ± 0.8 kJ mol−1, Δ H sol 0 OPPh 3 = 18.9 ± 0.6 kJ mol−1, and Δ H sol 0 ([Bu4N]2[WO2(mnt)2]) = (70.8 ± 1.9) kJ mol−1. In this study, the thermal effect of the transfer process of an oxygen atom from the tungsten complex [WO2(mnt)2]2− to the PPh3 substrate was determined at different ratios of reagents: ΔrH0 = (− 109 ± 4) kJ mol−1. The catalytic cycle of PPh3 oxidation with oxygen in the presence of [WO2(mnt)2]2− in acetonitrile solution was described calorimetrically. The absence of the reduced form of tungsten in the solution after the oxo-transfer reaction was shown spectroscopically, which confirms the role of the tungsten complex in the PPh3 oxidation as the catalyst. [ABSTRACT FROM AUTHOR]

The main purpose of this study was to investigate the local structure and dynamics in 'water-in-salt' solutions, namely the ternary concentrated LiCl–CsCl–D2O electrolytes. Water based electrolyte solutions are components of natural waters, they are very widespread and possess many practical abilities. NMR was applied as the main technique to study the local structure of the solutions as well as ion and solvent dynamics. The characteristic reorientation times (τc) were calculated from spin–lattice relaxation times for 2H, 7Li, and 133Cs nuclei. The diffusion coefficients (D) for 1H, 7Li, and 133Cs nuclei were also obtained. We have confirmed that most of the molecules and ions are combined into dynamic clusters, 'cybotactic groups', with lifetimes long enough for them to diffuse as a whole unit. Thus, the results provide direct experimental confirmation of the existence of 'cybotactic groups' predicted earlier for concentrated electrolyte solutions. The precise self-diffusion coefficients show the state of ions in the system and can be used as a reference for modelling of such systems. [ABSTRACT FROM AUTHOR]

Thermodynamic data on the properties of the water-based electrolyte systems are very valuable for fundamental physical chemistry and for industrial applications. The missing data both on the dilution and dissolution enthalpies for the ternary CsCl−MgCl2−H2O mixed electrolyte system were investigated by means of the calorimetry method. The dilution calorimetry was performed at 298 K for the set of solutions from diluted to concentrated at constant ratio Cs+/Mg2+ = 1.8 . The relative partial molar enthalpies, ideal, total, and excess ones were calculated. By means of the dissolution calorimetry, the standard enthalpies of formation, the enthalpies, and entropies for the double salt formation from simple salts were evaluated. The results obtained indicate that entropy as the major factor affecting the formation of the joint compound, both in the liquid and solid phases. These data can be implemented in thermodynamic databases and allow for accurate thermodynamic calculations for the salts extraction from natural water sources and for its possible application as thermochemical energy storage. [ABSTRACT FROM AUTHOR]

The enthalpy of the oxotransfer reaction of [Bu 4 N] 2 [WO 2 (mnt) 2 ] (where mnt 2- is maleonitriledithiolate) with PPh 3 in an inert atmosphere in an acetonitrile solution was determined by calorimetry. The obtained enthalpy value (-93 ± 5) kJ mol -1 differs from the enthalpy value of the reaction carried out by us earlier under aerobic conditions by (16 ± 9) kJ mol -1 . The obtained results indicate the participation of atmospheric oxygen in the catalytic process. DFT calculations of the structures [MO x (LL) 2 ] 2- (where M = Mo or W, x = 1 or 2, and LL is dithiolene ligand) were carried out. DFT calculations of the thermodynamic potential values for the oxygen transfer reaction in the system [M IV O 2 (LL) 2 ] 2- - [M VI O(LL) 2 ] 2- were also carried out. It was shown that the determining contribution to these processes is made by the enthalpy changes. The enthalpies of these processes depend on the donor-acceptor characteristics of the dithiolene ligands. In the case of good acceptors, the oxidation process is more exothermic. The opposite picture is observed for the reduction processes of the complex. The M ═O bond length can be used as a quantitative criterion for donor-acceptor properties of the ligands. Also, for molybdenum complexes, reduction processes are more favorable, while for tungsten complexes, oxidation processes are more favorable. The calculations agree well with experimental data that prove the validity of the model used for DFT calculations.

The main purpose of this study was to investigate the local structure and dynamics in 'water-in-salt' solutions, namely the ternary concentrated LiCl-CsCl-D2O electrolytes. Water based electrolyte solutions are components of natural waters, they are very widespread and possess many practical abilities. NMR was applied as the main technique to study the local structure of the solutions as well as ion and solvent dynamics. The characteristic reorientation times (τc) were calculated from spin-lattice relaxation times for 2H, 7Li, and 133Cs nuclei. The diffusion coefficients (D) for 1H, 7Li, and 133Cs nuclei were also obtained. We have confirmed that most of the molecules and ions are combined into dynamic clusters, 'cybotactic groups', with lifetimes long enough for them to diffuse as a whole unit. Thus, the results provide direct experimental confirmation of the existence of 'cybotactic groups' predicted earlier for concentrated electrolyte solutions. The precise self-diffusion coefficients show the state of ions in the system and can be used as a reference for modelling of such systems.