Phase behaviour,structural properties and intermolecular interactions of systems based on substituted thiacalix[4]arene and nonionic surfactants

Supramolecular organised materials were prepared from nonionic surfactants and the following macrocyclic ionic liquids: n-tert-butylthiacalix[4]arenes containing quaternary ammonium fragments with amino acid substituents. Tetraethylene glycol monododecyl ether and decadiethylene glycol monododecyl ether were used as nonionic surfactants. They form lamellar and hexagonal mesophases in aqueous media, respectively. Liquid crystal and structural properties of these systems were studied. Intermolecular interactions of system components leading to formation of lyomesophases were estimated. Molecular structure of thiacalixarene contributes to the formation of a hydrogen bonding with surfactants. This process, in turn, initiates formation of a denser packed hexagonal structure.     

Synthesis of 4-polyfluoroalkyl-1,3-dithiolanes via [3+2] cycloaddition of thiocarbonyl ylide to polyfluoroalkanethioamides

Chemistry of Heterocyclic Compounds - New 4-polyfluoroalkyl-1,3-dithiolanes were synthesized by reaction of polyfluoroalkanethioamides with thiocarbonyl ylide that was generated in situ by...     

Monodisperse magnetic poly(glycidyl methacrylate) microspheres for isolation of autoantibodies with affinity for the 46 kDa form of unconventional Myo1C present in autoimmune patients

Monodisperse nonmagnetic macroporous poly(glycidyl methacrylate) (PGMA) microspheres were synthesized by multistep swelling polymerization of glycidyl methacrylate, ethylene dimethacrylate and 2-[(methoxycarbonyl)methoxy]ethyl methacrylate (MCMEMA). This was followed (a) by ammonolysis to modify the microspheres with amino groups, and (b) by incorporation of iron oxide (γ-Fe₂O₃) into the pores to render the particles magnetic. The resulting porous and magnetic microspheres were characterized by scanning and transmission electron microscopy (SEM and TEM), atomic absorption and Fourier transform infrared spectroscopy (AAS and FTIR), elemental analysis, vibrating magnetometry, mercury porosimetry and Brunauer-Emmett-Teller adsorption/desorption isotherms. The microspheres are meso- and macroporous, typically 5 μm in diameter, contain 0.9 mM · g^?1 of amino groups and 14 wt.% of iron according to elemental analysis and AAS, respectively. The particles were conjugated to p46/Myo1C protein, a potential biomarker of autoimmune diseases, to isolate specific autoantibodies in the blood of patients suffering from multiple sclerosis (MS). The p46/Myo1C loaded microspheres are shown to enable the preconcentration of minute quantities of specific immunoglobulins prior to their quantification via SDS-PAGE. The immunoglobulin M (IgM) with affinity to Myo1C was detected in MS patients.

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Graphical abstract Monodisperse magnetic poly(glycidyl methacrylate) microspheres were synthesized, conjugated with 46 kDa form of unconventional Myo1C protein (p46/Myo1C) via carbodiimide (DIC) chemistry, and specific autoantibodies isolated from blood of multiple sclerosis (MS) patients; immunoglobulin M (IgM) level increased in MS patients.

     

Structural localization of trace amounts of impurity ions in Langmuir-Blodgett films by the X-ray standing wave method

The molecular organization of Langmuir-Blodgett films based on the liquid crystal europium complex has been studied by the X-ray standing-wave method at the synchrotron radiation source BESSY (Germany). Analysis of the experimental data obtained made it possible to determine the composition of the organic multilayer nanosystems and localize the position of metal ions incorporated in organic layers from the aqueous subphase during film deposition. It is shown that, despite the low content of metal ions in the aqueous subphase (no higher than 10^?7 mol/l), their incorporation into the Langmuir layer affects the molecular film organization significantly.     

1,3,2‐(2H)‐dioxaborine polymethine dyes on the base of dehydroacetic acid — effective fluorescent amine probes

A number of new polymethine dyes based on the boron difluoride complexes of dehydroacetic acid and 3‐acetyl‐4‐hydroxypyridone has been synthesized. Their spectral‐luminescent properties have been investigated. The reaction of obtained merocyanines with primary and secondary amines has been studied. These low fluorescent dyes gave highly fluorescent open chain products, which on further heating cyclized to weakly fluorescent pyridone dyes.     

Effect of non-covalent interactions in 2,5-di-Me-pyrazine-di-N-oxide - methanol – Carbon nanotube electrocatalytic system

Catalytic oxidation of methanol (MeOH) in the absence of noble metals and noble metal oxides as catalysts, and the use of metal-free materials are inexpensive and attractive process for practical use in electrocatalysis, sensors, and in direct methanol fuel cells. In previous works, it was found that the use of single-walled (SWCNT) or multi-walled (MWCNT) carbon nanotube paper electrodes instead of GC increases the catalytic efficiency of organic compounds oxidation in the presence of aromatic di-N-oxides by several times. In this work, the effect of non-covalent interactions on the catalytic efficiency of MeOH oxidation in the presence of 2,5-di-Me-pyrazine-di-N-oxide (Pyr₁) in 0.1 M Bu₄NClO₄ solution in acetonitrile at SWCNT and MWСNT paper electrodes was studied by the methods of quantum chemical modeling, Raman spectroscopy, and using electrochemical data. New factors determined the features of mechanism of MeOH oxidation on CNT electrodes and lead to an increase in the catalytic efficiency of the electrode process in comparison with the GC electrode were established.     

On hyperbolicity cones associated with elementary symmetric polynomials

Elementary symmetric polynomials can be thought of as derivative polynomials of . Their associated hyperbolicity cones give a natural sequence of relaxations for . We establish a recursive structure for these cones, namely, that the coordinate projections of these cones are themselves hyperbolicity cones associated with elementary symmetric polynomials. As a consequence of this recursion, we give an alternative characterization of these cones, and give an algebraic characterization for one particular dual cone associated with together with its self-concordant barrier functional.     

Does the solid-liquid crystal phase transition provoke the spin-state change in spin-crossover metallomesogens?

Three types of interplay/synergy between spin-crossover (SCO) and liquid crystalline (LC) phase transitions can be predicted: (i) systems with coupled phase transitions, where the structural changes associated to the Cr<-->LC phase transition drives the spin-state transition, (ii) systems where both transitions coexist in the same temperature region but are not coupled, and (iii) systems with uncoupled phase transitions. Here we present a new family of Fe(II) metallomesogens based on the ligand tris[3-aza-4-((5-C(n))(6-R)(2-pyridyl))but-3-enyl]amine, with C(n) = hexyloxy, dodecyloxy, hexadecyloxy, octadecyloxy, eicosyloxy, R = hydrogen or methyl (C(n)-trenH or C(n)-trenMe), which affords examples of systems of types i, ii, and iii. Self-assembly of the ligands C(n)-trenH and C(n)-trenMe with Fe(A)2 x xH2O salts have afforded a family of complexes with general formula [Fe(C(n)-trenR)](A)2 x sH2O (s > or = 0), with A = ClO4(-), F-, Cl-, Br- and I-. Single-crystal X-ray diffraction measurements have been performed on two derivatives of this family, named as [Fe(C6-trenH)](ClO4)2 (C(6)-1) and [Fe(C6-trenMe)](ClO4)2 (C(6)-2), at 150 K for C(6)-1 and at 90 and 298 K for C(6)-2. At 150 K, C(6)-1 displays the triclinic space group P, whereas at 90 and at 298 K C(6)-2 adopts the monoclinic P2(1)/c space group. In both compounds the iron atoms adopt a pseudo-octahedral symmetry and are surrounded by six nitrogen atoms belonging to imino groups and pyridines of the ligands C(n)-trenH and C(n)-trenMe. The average Fe(II)-N bonds (1.963(2) A) at 150 K denote that C(6)-1 is in the low-spin (LS) state. For C(6)-2 the average Fe(II)-N bonds (2.007(1) A) at 90 K are characteristic of the LS state, while at 298 K they are typical for the high-spin (HS) state (2.234(3) A). Compound C(6)-1 and [Fe(C18-trenH)](ClO4)2 (C(18)-1) adopts the LS state in the temperature region between 10 and 400 K, while compound C(6)-2 and [Fe(Cn-trenMe)](ClO4)2 (n = 12 (C(12)-2), 18 (C(18)-2)) exhibit spin crossover behavior at T(1/2) centered around 140 K. The thermal spin transition is accompanied by a pronounced change of color from dark red (LS) to orange (HS). The light-induced excited spin state trapping (LIESST) effect has been investigated in compounds C(6)-2, C(12)-2 and C(18)-2. The T(1/2)LIESST is 56 K (C(6)-2), 48 K (C(16)-2), and 56 K (C(18)-2). On the basis of differential scanning calorimetry, optical polarizing microscopy, and X-ray diffraction findings for C(18)-1, C(12)-2, and C(18)-2 at high temperature a smectic mesophase SX has been identified with layered structures similar to C(6)-1 and C(6)-2. The compounds [Fe(C(n)-trenH)](Cl)2 x sH2O (n = 16 (C(16)-3, s = 3.5, C(16)-4, s = 0.5, C(16)-5, s = 0), 18 (C(18)-3, s = 3.5, C(18)-4, s = 0.5, C(18)-5, s = 0), 20 (C(20)-3, s = 3.5, C(20)-4, s = 0.5, C(20)-5, s = 0)) and [Fe(C18-tren)](F)2 x sH2O (C(18)-6, s = 3.5, C(18)-7, s = 0) show a very particular spin-state change, while [Fe(C18-tren)](Br)2 x 3H2O (C(18)-8) together with [Fe(C18-tren)](I)2 (C(18)-9) are in the LS state (10-400 K) and present mesomorphic behavior like that observed for the complexes C(18)-1, C(12)-2, and C(18)-2. In compounds C(n)-3 50% of the Fe(II) ions undergo spin-state change at T(1/2) = 375 K induced by releasing water, and in partially dehydrated compounds (s = 0.5) the Cr-->SA phase transition occurs at 287 K (C(16)-4), 301 K (C(18)-4) and 330 K (C(20)-4). For the fully dehydrated materials C(n)-5 50% of the Fe(II) ions are in the HS state and show paramagnetic behavior between 10 and 400 K. In the partially dehydrated C(n)-4 the spin transition is induced by the change of the aggregate state of matter (solid<-->liquid crystal). For compound C(18)-6 the full dehydration to C(18)-7 provokes the spin-state change of nearly 50% of the Fe(II) ions. The compounds C(n)-3 and C(18)-6 are dark purple in the LS state and become light purple-brown when 50% of the Fe(II) atoms are in the HS state.     

Continuous‐scan capability at SSRL and applications to X‐ray diffraction

Typical X‐ray diffraction measurements are made by moving a detector to discrete positions in space and then measuring the signal at each stationary position. This step‐scanning method can be time‐consuming, and may induce vibrations in the measurement system when the motors are accelerated and decelerated at each position. Furthermore, diffraction information between the data points may be missed unless a fine step‐scanning is used, which further increases the total measurement time. To utilize beam time efficiently, the motor acceleration and deceleration time should be minimized, and the signal‐to‐noise ratio should be maximized. To accomplish this, an integrated continuous‐scan system was developed at the Stanford Synchrotron Radiation Lightsource (SSRL). The continuous‐scan system uses an in‐house integrated motor controller system and counter/timer electronics. SPEC software is used to control both the hardware and data acquisition systems. The time efficiency and repeatability of the continuous‐scan system were tested using X‐ray diffraction from a ZnO powder and compared with the step‐scan technique. Advantages and limitations of the continuous‐scan system and a demonstration of variable‐velocity continuous scan are discussed.     

Luminescence and energy transfer in poly(N-vinylcarbazole) blends doped by a highly anisometric Eu(III) complex

Highly fluorescent blends based on PVK (poly(N-vinylcarbazole)) doped by a new greatly anisometric Eu(III) mesogenic complex were described. The structure of the ligands in the complex was selected in such a way that its absorption maximum was close to the emission maximum of the polymer. The full-energy transfer conditions in the conjugated polymer–lanthanide complex blends were revealed. Improving luminescence efficiency of the blend occurs due to an increase in the threshold concentration of the emitting ions to prevent self-quenching phenomena. The resulting relative luminescence quantum yield of the blend increases more than twice in comparison with the individual complex. The optimized blends may be promising for application as red emitters for OLED, etc.