Crucial role of paramagnetic ligands for magnetostructural anomalies in "breathing crystals"

Breathing crystals based on polymer-chain complexes of Cu(hfac)(2) with nitroxides exhibit thermally and light-induced magnetostructural anomalies in many aspects similar to a spin crossover. In the present work, we report the synthesis and investigation of a new family of Cu(hfac)(2) complexes with tert-butylpyrazolylnitroxides and their nonradical structural analogues. The complexes with paramagnetic ligands clearly exhibit structural rearrangements in the copper(II) coordination units and accompanying magnetic phenomena characteristic for breathing crystals. Contrary to that, their structural analogues with diamagnetic ligands do not undergo rearrangements in the copper(II) coordination environments. This confirms experimentally the crucial role of paramagnetic ligands and exchange interactions between them and copper(II) ions for the origin of magnetostructural anomalies in this family of molecular magnets.     

Numerical solution of the Dirichlet problem for nonlinear parabolic equations by a probabilistic approach

A number of new layer methods for solving the Dirichlet problemfor semilinear parabolic equations are constructed by usingprobabilistic representations of their solutions. The methodsexploit the ideas of weak sense numerical integration of stochasticdifferential equations in a bounded domain. Despite their probabilisticnature these methods are nevertheless deterministic. Some convergencetheorems are proved. Numerical tests are presented.     

Effects of Spiro-Cyclohexane Substitution of Nitroxyl Biradicals on Dynamic Nuclear Polarization

Spiro-substituted nitroxyl biradicals are widely used as reagents for dynamic nuclear polarization (DNP), which is especially important for biopolymer research. The main criterion for their applicability as polarizing agents is the value of the spin–spin exchange interaction parameter (J), which can vary considerably when different couplers are employed that link the radical moieties. This paper describes a study on biradicals, with a ferrocene-1,1′-diyl-substituted 1,3-diazetidine-2,4-diimine coupler, that have never been used before as DNP agents. We observed a substantial difference in the temperature dependence between Electron Paramagnetic Resonance (EPR) spectra of biradicals carrying either methyl or spirocyclohexane substituents and explain the difference using Density Functional Theory (DFT) calculation results. It was shown that the replacement of methyl groups by spirocycles near the N-O group leads to an increase in the contribution of conformers having J ≈ 0. The DNP gain observed for the biradicals with methyl substituents is three times higher than that for the spiro-substituted nitroxyl biradicals and is inversely proportional to the contribution of biradicals manifesting the negligible exchange interaction. The effects of nucleophiles and substituents in the nitroxide biradicals on the ring-opening reaction of 1,3-diazetidine and the influence of the ring opening on the exchange interaction were also investigated. It was found that in contrast to the methyl-substituted nitroxide biradical (where we observed the ring-opening reaction upon the addition of amines), the ring opening does not occur in the spiro-substituted biradical owing to a steric barrier created by the bulky cyclohexyl substituents.     

Opening of the Furandione Ring with o-Aminothiophenol: Synthesis of 2H-1,4-Benzothiazine-2,3(4H)-dione

Russian Journal of Organic Chemistry - 5-Aryl-4-(3-arylquinoxalin-2-yl)furan-2,3-diones react with o-aminothiophenol to form 2H-1,4-benzothiazin-2,3-(4H)-dione and...     

Synthesis of 2-[(Pyrrol-2-yl)sulfanyl]acetic Acids by Reaction of Pyrrolo[2,1-c][1,4]oxazinetriones with 2-Sulfanylacetic Acid

Russian Journal of Organic Chemistry - 8-Aroyl-3,4-dihydro-1H-pyrrolo[2,1-c][1,4]oxazine-1,6,7-triones reacted with 2-sulfanylacetic acid to give...     

Molecular-Thermodynamic Model of Solubilization in Direct Spherical Micelles of Nonionic Surfactants

Colloid Journal - A thermodynamic model has been formulated for the formation work of a molecular aggregate consisting of molecules of a nonionic surfactant and a solubilisate in a...     

Digital Colorimetry of Indicator Test-Systems Using a Smartphone and Chemometric Analysis in Determination of Quinolones in Pharmaceuticals

Journal of Applied Spectroscopy - A combined approach was developed for the identification and determination of quinolone antibiotics in pharmaceuticals using solid-state fluorescence digital...     

Reaction of Pyrrolooxazinetriones with Diphenylguanidine. Synthesis of Substituted Spiro[imidazole-4,2′-pyrroles]

Russian Journal of Organic Chemistry - 8-Aroyl-3,4-dihydropyrrolo[2,1-c][1,4]oxazine-1,6,7(1H)-triones reacted with 1,3-diphenylguani­dine to give...     

Preparation of filter catalysts with the use of alkoxides

New methods for the synthesis of poly(organyloxy)elementoxanes containing Zr, Zr−Y, Al−Ba (Ca, Sr, Ce, Zr) and La−Sr−Co have been developed. The application of these elementoxanes as oxide precursors in the preparation of catalyst supports, catalytic coatings and filter catalysts has been studied.     

Ionic-electronic conductors based on lithium-containing oxide bronzes

Lithium-containing oxide bronzes Li_xV_2?yM_yO₅-β (M=Mo or W) have been studied in wide range of temperature (25–550°C) and composition (0.22?x?0.47, 0?y?0.25) as prospective ionic-electronic conductors. By coulometric titration tecknique, $\text{Δ}\text{G}{}_{\mathrm{<mtext>Li</mtext>}}$, $\text{Δ}\text{H}{}_{\mathrm{<mtext>Li</mtext>}}$ and $\text{Δ}\text{S}{}_{\mathrm{<mtext>Li</mtext>}}$ have been found and ordering of the lithium ions within the channel structure Li_xV₂O₅-β has been discussed depending on composition and temperature. The chemical diffusion coefficient for lithium D?_Li has been measured by potentiometric technique on hot-pressed ceramic samples. The lithium self-diffusion coefficient D_Li and partial lithium-ionic conductivity have been calculated.