Stability of the adsorption properties of the metal-organic framework HKUST-1

Russian Chemical Bulletin - Adsorption isotherms of methane for two samples of the metal-organic framework HKUST-1 with copper ions were measured on a precise vacuum high-pressure...     

Synthesis and properties of novel 4-(diarylmethyl)pyridines based on pyridoxal 5′-phosphate

Russian Chemical Bulletin - The reaction pyridoxal 5′-phosphate with resorcinols in EtOH in the presence of concentrated HCl gives hydrochlorides of the corresponding...     

On the Thermodynamics of Hydrogen Adsorption at Pt Electrodes

Russian Journal of Electrochemistry - In the mid 1960th–early 1970th, A. Frumkin and O. Petrii investigated the adsorption of hydrogen at a platinized platinum electrode surface performing...     

Synthesis,Structure, and Biological Activity of N-p-(Dimethylamino)-N′-(p-dimethylaminobenzylidene)-N,N′′-diphenylbenzohydrazonohydrazide

Russian Journal of General Chemistry - A three-component reaction of 3,5-diacetyl-2,6-dimethylpyridine, p-N-dimethylaminobenzaldehyde and phenylhydrazine in the presence of KOH in ethanol gave the...     

Reaction of alkyl 3-bromo-3-nitroacrylates with substituted hydrazines. Synthesis of N′-substituted alkyl 3-nitropyruvate hydrazones

Russian Chemical Bulletin - The reaction of alkyl 3-bromo-3-nitroacrylates with substituted phenylhydrazines and hydrazides of aromatic acids proceeds through the formation of aza-Michael adducts....     

Synthesis of tetraarm stars with polyetherimide-polyether block copolymer arms

Russian Chemical Bulletin - The method of one-stage catalytic polycyclocondensation according to the B4 + AB scheme was used to synthesize new tetraarm star-shaped oligoimides (SOIs) with terminal...     

Operando XAFS on Hydrated Calcium Vanadium Bronze Cathode for Aqueous Zn-ion Storage

Multivalent ion storage and aqueous electrochemical systems continue to build interest for energy application. The Zn-ion system with 2 electron transfer and an ideal metal anode is a strong candidate but is still at the early stage of development. Using both in situ near-edge (XANES) and X-ray absorption fine structure spectroscopy, EXAFS, a nanostructured cathode material, Ca_xV₂O₅-H₂O (CVO), was probed at the V-K absorption edge. This operando study reveals the local electronic and geometric structure changes for CVO during galvanostatic cycling as the active material in an aqueous Zn-ion cell. The XANES data provides a fine resolution to track the evolution of the vanadium oxidative state and near-neighbor coordination sphere showing subtle shifts and delocalized charge. The Zn-ion influence on the V-K absorption edge is visualized using a difference technique called Δμ. Coupled with theoretical calculations and modelling, the extended region extracted local bonding information further confirms excellent electronic and structural reversibility of this vanadium oxide bronze in an aqueous Zn-ion electrochemical cell.     

Modeling of the Simultaneous Hydrogen Evolution and Cobalt Electrodeposition

A mathematical model of simultaneous cobalt deposition and hydrogen evolution was developed and applied to the electroreduction process of 5 mM Co²⁺ ions investigated by cyclic voltammetry (CV) technique at different hydrogen ion concentrations (pH=2, 3, 4). The kinetic parameters of such a complex process were determined, and the validity of the model and its sensitivity to changes in individual parameters were verified. The relative value of the approximate standard deviation (ASD_%) was used to determine the degree of fit of the model to the experimental data. The catalytic effect of cobalt on the hydrogen evolution process was comprehensively confirmed.     

Local Structure Analysis and Modelling of Lignin-Based Carbon Composites through the Hierarchical Decomposition of the Radial Distribution Function

Carbonized lignin has been proposed as a sustainable and domestic source of activated, amorphous, graphitic, and nanostructured carbon for many industrial applications as the structure can be tuned through processing conditions. However, the inherent variability of lignin and its complex physicochemical structure resulting from feedstock and pulping selection make the Process-Structure-Property-Performance (PSPP) relationships hard to define. In this work, radial distribution functions (RDFs) from synchrotron X-ray and neutron scattering of lignin-based carbon composites (LBCCs) are investigated using the Hierarchical Decomposition of the Radial Distribution Function (HDRDF) modelling method to characterize the local atomic environment and develop quantitative PSPP relationships. PSPP relationships for LBCCs defined by this work include crystallite size dependence on lignin feedstock as well as increasing crystalline volume fraction, nanoscale composite density, and crystallite size with increasing reduction temperature.     

The Chemical Bond: When Atom Size Instead of Electronegativity Difference Determines Trend in Bond Strength

We have quantum chemically analyzed element−element bonds of archetypal H_nX−YH_n molecules (X, Y=C, N, O, F, Si, P, S, Cl, Br, I), using density functional theory. One purpose is to obtain a set of consistent homolytic bond dissociation energies (BDE) for establishing accurate trends across the periodic table. The main objective is to elucidate the underlying physical factors behind these chemical bonding trends. On one hand, we confirm that, along a period (e. g., from C−C to C−F), bonds strengthen because the electronegativity difference across the bond increases. But, down a period, our findings constitute a paradigm shift. From C−F to C−I, for example, bonds do become weaker, however, not because of the decreasing electronegativity difference. Instead, we show that the effective atom size (via steric Pauli repulsion) is the causal factor behind bond weakening in this series, and behind the weakening in orbital interactions at the equilibrium distance. We discuss the actual bonding mechanism and the importance of analyzing this mechanism as a function of the bond distance.