Synthesis,Characterization, Photo-physical Evaluation and Crystal Structure of 2-Methoxy-1-Methylquinolinium Tetrafluoroborate,a Potentially Selective Agent for the Quantitative Measurement of Biologically Relevant Thiols

Abstract  

We report the quantitative and facile conversion of 2-chloro-1-methylquinolinium tetrafluoroborate to 2-methoxy-1-methylquinolinium tetrafluoroborate via stirring in methanol at room temperature. The resulting compound was evaluated for use as a selective tag for biologically relevant thiols. The results displayed a fivefold increase in fluorescent quantum yield (Ф_FLUOR = 0.20) and an increased stability in pH when compared to 2-chloro-1-methylquinolinium tetrafluoroborate (Ф_FLUOR = 0.04), however, results demonstrated that it did not offer an improvement to 2-chloro-1-methylquinolinium tetrafluoroborate as a thiol specific tag. The compound was fully characterised by ¹HNMR, ESI mass spectroscopy and by single-crystal X-ray diffraction. The title compound crystallizes in the monoclinic space group P2₁/m with a = 8.2420(3) ?, b = 6.6751(2) ?, c = 10.8415 ? and β = 105.164(2)°, Z = 2, V = 575.69(3) ?³. Work is on-going to synthesise and evaluate other such analogues for their potential use as thiol tags.     

Mapping energy bands in layer compounds from the angular dependence of ultraviolet photoemission

Photoelectron energy spectra have been measured on the layer compounds 1T?TaSe₂ and 1T?TaS₂ at various polar angles of emission. The azimuthal angle was set to select only those photoelectrons propagating in a plane containing the ГMLA points of the Brillouin zone. The results are used to map energy-vs-wave-vector curves which are found to compare favorably with the first principles calculations of Mattheiss.     

Antiferromagnetic interactions between localized states in amorphous germanium

The temperature dependence of the magnetic susceptibility (300 → 1.6°K) and ESR (300 → 6°K) of amorphous germanium have been determined. There is a temperature dependent paramagnetic term to the magnetic susceptibility due to a density of localized unpaired spins (dangling bonds) of 10¹⁹ spins/cm³. There is an antiferromagnetic interaction between at least some of these localized unpaired spins with an exchange energy estimated by various models to be on the order of a degree Kelvin.     

Charge density waves in layered compounds

The metallic layered compounds of the transition metal dichalcogenide type show unusual deviations from simple metallic behavior. These deviations are due to Charge Density Wave instabilities that are driven by the Fermi surface. The Charge Density Wave is a coupled periodic distortion of the conduction electron density and the crystal lattice. The effects of the CDW on the physical properties are qualitatively discussed. The basic driving forces of the CDW are most likely responsible for structural changes in a wide variety of materials, such as high temperature superconductors and long period superlattice alloys.     

Reactions of Singlet Oxygen with Organometallic Compounds. 4. Photooxidation of Cationic Iridium(I) and Rhodium(I) Complexes with Weakly Bonded Ligands

Cationic complexes of the type [M(CO)S(PPh(3))(2)](+) (M = Ir, Rh; S = CH(3)CN) react with singlet oxygen to form the corresponding peroxo complexes [M(CO)S(PPh(3))(2)(O(2))](+). The solvent molecule remains coordinated to the metal in the oxygen adducts. The novel cationic iridium-peroxo complex is stable at room temperature, while the rhodium-peroxo complex is only stable below 0 degrees C. Rate constants for physical and chemical interaction of the complexes with singlet oxygen are somewhat smaller than those for related neutral complexes. Upon addition of alkenes (tetramethylethylene or 1-octene) to the peroxo complexes, neither oxidation of the olefins nor substitution of the acetonitrile ligand was observed. 1-Octene was isomerized to give mostly 2- and 3-octene by the cationic rhodium(I) complex. A cationic iridium complex which already possesses a coordinated diene ligand ([Ir(COD)(PPh(3))(2)](+)) did not react with or quench singlet oxygen.     

Investigation of charging/discharging phenomena in nano-crystal memories

In this work we will give a detailed account of the charging/discharging phenomena occurring in semiconductor nano-crystal memories. Memory transfer characteristics and write/ erase transient characteristics are studied for devices with different technological parameters. Experimental results are explained by means of a semi-classical model, based on a modified current continuity approach. This model depicts the effect of the tunnel/top dielectric thickness, dot recovered area and programming voltage on the device performance.     

The graal experiment: Beam polarization asymmetries in pseudoscalar meson photoproduction

The GRAAL tagged and polarized γ beam has been operating with a maximum energy of 1100 MeV. For the first time asymmetry results in ν photoproduction were obtained and will be shown. Interesting results have also been obtained for π⁰ and π⁺ photo-production, that largely confirm the already existing ones, but also extend in not yet explored angular and energetic regions, especially for backward scattering and energies greater than 900 MeV.     

Measurement of \Sigma beam asymmetry in \pi^{0}_{} photoproduction off the neutron in the second and third resonances region⋆

The $ \Sigma$ beam asymmetry in the photoproduction of neutral pions from quasi-free nucleons in a deuteron target was measured for the first time between 0.60 and 1.50GeV, with the GRAAL polarized and tagged photon beam. The asymmetry values from the quasi-free proton were found equal to the ones extracted from a pure proton target. The asymmetries from quasi-free proton and quasi-free neutron were found equal up to 0.82GeV and substantially different at higher energies. The results are compared with recent partial-wave analyses.     

Stabilized,flat iron flames on a hot counterflow burner

Metal powder combustion has traditionally been studied to mitigate the risk of industrial accidents and to determine the contributions of metals as additives to the performance of energetic materials. Recently, there has been growing interest in exploring the potential of metal powders as recyclable, zero-carbon energy carriers as an alternative to the hydrocarbons known to contribute to climate change. The present work introduces, for the first time, a stabilized flat iron flame. The counterflow burner used in this work is comprised of an inverted ceramic nozzle which sits above, and is aligned axially with, a lower nozzle producing a laminar flow of particles suspended in an oxidizing gas. A stabilized methane flame sits inside the top nozzle and the hot combustion products impinge upon the two-phase flow from the bottom nozzle, creating a stagnation plane. Spherical iron powder, with 90% of the particles less than 2.5 µm in size, is pre-loaded into a piston and dispersed using mixtures of 30% and 40% oxygen balanced in argon. Flame speeds are measured using particle image velocimetry (PIV), while flame temperatures are determined using multicolour pyrometry. It is found that flame speeds range between 30 cm/s and 45 cm/s for both oxidizing mixtures. Despite having fuel loadings below stoichiometric concentrations, the observed particle combustion temperatures are close to the adiabatic flame temperature of the stoichiometric mixture, indicating combustion in the diffusion-controlled regime for these small particles. Finally, the independence of the flame speeds with respect to oxygen concentration suggests flame propagation in the discrete regime.