Why ionic liquids can possess extra solvent power

We use the Flory-Huggins theory to demonstrate conditions of extra solvent power of ionic liquids. The short-range interactions between anions, cations, and molecules of the solute are taken into account. We find that solvent power of the ionic liquids is enhanced if non-Coulomb interactions between the anions and cations are repulsive. The mechanism responsible for the extra solvent power is related to the "shielding" of the anion-cation interactions by the molecules of the solute.     

Furan ring opening — isocoumarine ring closure: A recyclization reaction of 2‐carboxyaryldifurylmethanes

A general method for the synthesis of isocoumarine derivatives has been developed. Bis(5‐R‐2‐furyl)methylbenzoic acids (R = methyl, ethyl) underwent recyclization and subsequent cyclization into tetracyclic isochromene‐1‐one derivatives under treatment with hydrogen chloride in methanol. It has been shown that intermediate 4‐(5‐R‐furan‐2‐yl)‐3‐(3‐oxo‐3‐R‐propyl)‐isochromene‐1‐ones can be obtained selectively by varying a concentration of the hydrogen chloride and reaction times. In the case of R = tert‐butyl only corresponding 4‐[5‐(tert‐butyl)‐2‐furyl]‐3‐(4,4‐dimethyl‐3‐oxopentyl)‐1‐isochromenones were isolated regardless of the reaction conditions.     

Role of surface hydroxyl groups in promoting room temperature CO sensing by Pd-modified nanocrystalline SnO2

SnO₂/Pd nanocomposites were synthesized via sol-gel method followed by variable processing procedures. The materials are sensitive to CO gas in the concentration range 2-100 ppm at room operating temperature. It was shown that modification of nanocrystalline tin dioxide by Pd changes the temperature dependence of sensor response, decreasing the temperature of maximal signal. To understand the mechanism of room temperature CO sensitivity, a number of SnO₂/Pd materials were characterized by XRD, TEM, BET, XPS and TPR techniques. From the results of FTIR, impedance and sensing measurements under variable ambient conditions it was concluded that improvement in CO sensitivity for Pd-modified SnO₂ is due to alteration of CO oxidation pathway. The reaction of CO with surface OH-groups at room temperature was proposed, the latter being more reactive than oxygen species due to the possible chain character of the reactions. It was proposed that Pd additive may initiate chain processes at room temperature.     

Influence of the nature of organic components in dinuclear copper(II) pivalates on the composition of thermal decomposition products

Tetrabridged dinuclear complexes ((2-NH₂)C₅H₄N)₂Cu₂(μ₂-OOCCMe₃)₄ (2·С₆Н₆) and ((3-NH₂)C₅H₄N)₂Cu₂(μ₂-OOCCMe₃)₄ (3) and the cocrystallization product ((4-NMe₂)C₅H₄N)₂Cu(η²–OOCCMe₃)₂·2((4-NMe₂)C₅H₄N)₂Cu₂(μ₂-OOCCMe₃)₄ (4) were synthesized by the reaction of the polymer [Cu(OOCCMe₃)₂]_n (1) with aminopyridine ligands (L) of different nature (Cu: L = 1:1) in С₆Н₆. The solid-state thermal decomposition of these compounds was studied by differential scanning calorimetry and thermogravimetry, and their electrochemical behavior was investigated by cyclic voltammetry. All newly synthesized complexes were studied by X-ray diffraction, the magnetic properties of the complexes were investigated, and ESR measurements were performed.     

A Novel Tantalum Cluster Chalcohalide Ta4S1.5Se7.5I8

Single crystals of Ta₄S_1.5Se_7.5I₈ are obtained by heating Ta, S, Se and I₂ at 300 °C in 4.0:1.0:8.0:4.4 molar ratio. The structure was determined by X-ray analysis and consists of molecular clusters [Ta₄(μ₄-S)(μ₂-Q_axSe_eq)₄I₈] (Q ≈ Se_0.87S_0.13). The tantalum atoms form a square with long Ta…Ta distances (3.26–3.32 Å), with four dichalcogenide ligands bridging the Ta–Ta edges and a sulfur atom capping the square. Each Ta atom has two terminal iodine atoms. Raman spectroscopy study shows the presence of the characteristic absorption band at 396 cm^?1 which is due to the Ta₄–μ₄-S vibrations. Cyclic voltammetry shows that Ta₄S_1.5Se_7.5I₈ in solid state undergoes quasi-reversible one-electron oxidation which is metal-centered.     

An approach to measure electromechanical properties of atomic and molecular junctions

We describe a new setup for simultaneous measurements of force and current in conductive nanocontacts in a liquid environment with a high sampling rate and resolution. A lab-built current-to-voltage converter allows measurements of the current over seven orders of magnitude. As examples, we studied conductances and mechanical forces upon formation and breaking of gold atomic contacts and of two molecular junctions containing 1,2-di(4-pyridyl)ethyne (M1) and 1,4-di(4-pyridyl)buta-1,3-diyne (M2). We found that the forces required to deform or break gold atomic contacts depend critically on the surrounding medium. Further, they show non-linear behaviour in dependence of the number N of gold atoms detached. The electromechanical properties of the two types of molecular junctions upon stretching were analysed by correlating breaking forces with simultaneously measured junction conductances. A rather complex behaviour in a wide range of forces was discovered. Comparison of the current-probe atomic force microscopy experiments on the rupture of molecular junctions with STM-based break junction experiments enables the assignment of breaking forces of molecular junctions to the corresponding junction conductances.     

Regularized differential extragradient method for searching for an equilibrium point in two-person saddle-point games with approximate input data

A two-person saddle-point game with approximately given input data is examined. In general, the search for an equilibrium point in games of this type is unstable with respect to perturbations in the input data, and special regularization methods are required for their solution. To this end, two variants of the regularized differential extragradient method are proposed. Their convergence is analyzed, and a regularizing operator is constructed.     

Regularized extragradient method for searching for an equilibrium point in two-person saddle-point games

A two-person saddle-point game with approximately given input data is examined. Since, in games of this type, the search for an equilibrium point is unstable with respect to perturbations in the input data, two variants of the regularized extragradient method are proposed. Their convergence is analyzed, and a regularizing operator is constructed.     

ChemInform Abstract: Solving the Structure of Li Ion Battery Materials with Precession Electron Diffraction: Application to Li2CoPO4F.

The crystal structure of Li₂CoPO₄F is completely solved from precession electron diffraction data, including the location of the Li atoms.