Conjugation with phosphorus atom participation

Conclusions The UV and Raman spectra of phenyl and-styryl derivatives of phosphorus were investigated. The results agree with concepts regarding the insulating effect of tetracoordinated phosphorus atoms and participation in electron effects of the unshared pair of electrons of trivalent phosphorus in the excited state.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 722–724, March, 1972.The authors thank V. S. Galeev and S. S. Krokhina for supplying us with compounds synthesized by them.     

Diffusion-limited aggregation: A relationship between surface thermodynamics and crystal morphology

We have combined the original diffusion-limited aggregation model introduced by Witten and Sander with the surface thermodynamics of the growing solid aggregate. The theory is based on the consideration of the surface chemical potential as a thermodynamic function of the temperature and nearest-neighbor configuration. The Monte Carlo simulations on a two-dimensional square lattice produce the broad range of shapes such as fractal dendritic structures, densely branching patterns, and compact aggregates. The morphology diagram illustrating the relationship between the model parameters and cluster geometry is presented and discussed.     

Determination of Inorganic Fluorine in High-Purity Silane

A method was proposed for determining inorganic fluorine in high-purity silane. The method is based on the hydrolytic extraction of fluorine as fluorides to the aqueous phase, followed by the analysis of the extract by ion chromatography with a conductometric detector. The detection limit for inorganic fluorine was 1 × 10^–5mass %.     

Linking local environments and hyperfine shifts: a combined experimental and theoretical (31)P and (7)Li solid-state NMR study of paramagnetic Fe(III) phosphates

Iron phosphates (FePO(4)) are among the most promising candidate materials for advanced Li-ion battery cathodes. This work reports upon a combined nuclear magnetic resonance (NMR) experimental and periodic density functional theory (DFT) computational study of the environments and electronic structures occurring in a range of paramagnetic Fe(III) phosphates comprising FePO(4) (heterosite), monoclinic Li(3)Fe(2)(PO(4))(3) (anti-NASICON A type), rhombohedral Li(3)Fe(2)(PO(4))(3) (NASICON B type), LiFeP(2)O(7), orthorhombic FePO(4)·2H(2)O (strengite), monoclinic FePO(4)·2H(2)O (phosphosiderite), and the dehydrated forms of the latter two phases. Many of these materials serve as model compounds relevant to battery chemistry. The (31)P spin-echo mapping and (7)Li magic angle spinning NMR techniques yield the hyperfine shifts of the species of interest, complemented by periodic hybrid functional DFT calculations of the respective hyperfine and quadrupolar tensors. A Curie-Weiss-based magnetic model scaling the DFT-calculated hyperfine parameters from the ferromagnetic into the experimentally relevant paramagnetic state is derived and applied, providing quantitative finite temperature values for each phase. The sensitivity of the hyperfine parameters to the composition of the DFT exchange functional is characterized by the application of hybrid Hamiltonians containing admixtures 0%, 20%, and 35% of Fock exchange. Good agreement between experimental and calculated values is obtained, provided that the residual magnetic couplings persisting in the paramagnetic state are included. The potential applications of a similar combined experimental and theoretical NMR approach to a wider range of cathode materials are discussed.     

Ionic and micellar effects in supramolecular self-organizing surfactant media on an example of analytical systems amines-carbonyl compounds

The influence of supramolecular self-organizing surfactant-based media on the condensation reactions of some carbonyl compounds with arylamines (formation of Schiff bases, hydrazones and naphthoquinones) was studied by conductometry, light-scattering spectroscopy, molecular spectroscopy, and tensiometry. The function of surfactants was proved to differ, depending on its concentration: below the critical micelle concentration (CMC) they acted as a reagent, while at higher concentrations, they demonstrated properties of reaction media. The effects observed were analyzed, regarding their potency to govern indicatory reactions in the systems specified, reduce limits of detection for the determination of carbonyl and amino-compounds, refine analytical parameters of the condensation reactions, and broaden the area of their application.     

IR and NMR spectra,intramolecular hydrogen bonding and conformations of para-tert-butyl-aminothiacalix[4]arene in solid state and chloroform solution

It is demonstrated that dissolution of aminothiacalix[4]arene in chloroform results in transformation of 1,3-alternate conformation, adopted in single-crystal and bulk polycrystalline solids, to the pinched-cone form. This conformer is stabilised by the intramolecular hydrogen bonds of two distal amino-groups acting as H-donors with another two amino moieties that appear as H-acceptors. The H-bonds cause quite small (ca. 10–20 cm^?1) red shift of the IR bands of the NH₂ stretching vibrations, which suggests rather weak NH?N hydrogen bonding. This latter is sufficient to stabilize the pinched-cone conformation in the chloroform solution, but the energy gap between the pinched-cone and other conformations is small, and solid-state intermolecular forces easily overcome it, leading to realisation of the 1,3-alternate conformer. The comparison of the DFT computed and experimental vibrational and NMR spectra demonstrates good quality of present quantum-chemical computations, allows complete interpretation of the spectra and reveals simple IR and NMR spectroscopic markers of the conformers of aminothiacalix[4]arenes.     

Varying surface morfology of oxide-carbonate ores in the synthesis of an adsorbent catalyst

Investigation of the surface morphology of oxide-carbonate manganese ore and dolomite and also adsorbent catalyst samples synthesized on their basis showed that heat treatment of ores resulted in variation of their qualitative composition, surface state, and hardening their structure.