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The structure of betaxolol from single crystal X-ray diffraction and natural bo...
Canotilho, João; Castro, Ricardo A. E.; Rosado, Mário T. S.; Silva, M. Ramos; Beja, A. Matos; Paixão, J. A.; Redinha, J. SimõesThe structure of betaxolol obtained from ethanol:water solution was studied by X-ray diffraction. The geometrical parameters needed to define the structure are tabulated. The X-ray data show the existence of two conformers in the unit cell differing only in the conformation of the cyclopropylmethoxy fragment. Differences in the bond lengths angles and dihedral between both conformations are observed. The cyclop...
Optimization of filtered neutron beams for the calibration of superheated dropl...
Nascimento, F.; Ramos, A. R.; Fernandes, A. C.; Felizardo, M.; Morlat, T.; Marques, J. G.; Giuliani, F.; Girard, T. A.; Paixão, J. A.Superheated droplet detectors (SDDs) have been investigated for applications in neutron dosimetry and spectrometry. Varying the detector temperature, it is possible to change the neutron energy detection threshold of SDDs, thus allowing the use of a single detector to measure neutrons of different energy, without any change of the experimental setup. However, the neutron threshold energy versus temperature curv...
The microscopic magnetisation of the superconductor PuCoGa5
Hiess, A.; Stunault, A.; Colineau, E.; Rebizant, J.; Wastin, F.; Kernavanois, N.; McIntyre, G. J.; Fernandez-Diaz, M. T.; Lelièvre-Berna, E.The intermetallic compound PuCoGa5 is a superconductor with a surprisingly high critical temperature of in which the superconductivity has been suggested to arise from magnetic fluctuations. We investigated the microscopic magnetic properties by polarised neutron diffraction on a single crystal of 242PuCoGa5. An induced moment is observed on both the Pu and the Co sites. The total magnetisation is significantly...
Conformational Isomorphism of Organic Crystals: Racemic and Homochiral Atenolol
Castro, R. A. Esteves de; Canotilho, João; Barbosa, Rui M.; Silva, M. Ramos; Beja, A. Matos; Paixão, J. A.; Redinha, J. SimõesX-ray diffraction analysis of (R,S)- and S-atenolol crystalline forms was performed. The crystals studied were grown from evaporation of an ethanol/water solution. (R,S)-Atenolol crystallizes in the centrosymmetric space group C2/c, and S-atenolol crystallizes in a noncentrosymmetric space group C2. There is one symmetry independent molecule in (R,S)-atenolol crystals and two symmetry independent molecules in S...
Structural and magnetic properties of UFe6Ga6
Gonçalves, A. P.; Waerenborgh, J. C.; Sério, S.; Paixão, J. A.; Godinho, M.; Almeida, M.UFe6Ga6 polycrystalline samples were prepared by arc-melting, and single crystals were grown by the Czochralski method. This compound crystallizes in the orthorhombic ScFe6Ga6-type structure (space group Immm, a=5.0560(4), b=8.5484(7) and c=8.6914(7) A), an ordered variant of the ThMn12-type structure. A ferromagnetic-type transition at TC=530(5) K is seen in the magnetization and A.C.-susceptibility measuremen...
One-step synthesis of dipyrromethanes in water
Sobral, Abílio J. F. N.; Rebanda, Nuno G. C. L; Silva, Melo da; Lampreia, Sandra H.; Silva, M. Ramos; Beja, A. Matos; Paixão, J. A.In this communication we describe the first results of an efficient synthesis of [beta]-free-dipyrromethanes in water. This new method affords very pure products in moderate to high yields, using a cheap, non-toxic, environment friendly solvent, in a one-step procedure from pyrrole and carbonyl compounds, needing little or no work up procedures. ; http://www.sciencedirect.com/science/article/B6THS-48FBYP9-W/...
Low temperature polymorphism in 3-amino-1-propanol
Cacela, C.; Baudot, A.; Duarte, M. L.; Matos-Beja, A. M.; Silva, M. Ramos; Paixão, J. A.; Fausto, R.3-Amino-1-propanol (3AP) was investigated by differential scanning calorimetry, and low temperature powder X-ray diffraction and Raman spectroscopy. Within the range of temperatures studied (-150-25 °C), 3AP was found to be able to crystallize in two monotropic polymorphs. Fast cooling rates produce an amorphous state that, on heating, crystallizes into the metastable polymorph. At higher temperatures, this met...
Pyrrolidine-based amino alcohols: novel ligands for the enantioselective alkyla...
Gonsalves, António M. d'. A. Rocha; Serra, M. Elisa S.; Murtinho, Dina; Silva, Vitor F.; Beja, A. Matos; Paixão, J. A.; Silva, M. RamosA series of easily obtained pyrrolidine-based [beta]-amino alcohols derived from tartaric acid and primary amines was synthesized and used as chiral ligands in the enantioselective alkylation of benzaldehyde. Using diethylzinc, 1-phenyl-1-propanol was obtained with enantiomeric excesses of up to 80% when (3S,4S)-N-(1-naphthylmethyl)-3,4-dihydroxypyrrolidine was used. The nature of the N-substituent on the ligan...
Crystal structure of tetrakis (µ-betaine-O,O') dichloro-dicopper(II) dichloride...
Silva, M. Ramos; Paixão, J. A.; Beja, A. Matos; Veiga, L. Alte da; Martín-Gil, J.[Cu2(bet)4Cl2]Cl2·4H2O (bet = betaine: IUPAC name: trimethylammonioacetate) is monoclinic, space group P21/c, a = 11.0510(10) Å, b = 14.7140(4) Å, c = 11.1620(15) Å, ß = 107.40(2)°. The dinuclear copper(II) cation [Cu2(bet)4Cl2]2+ is counterbalanced by two naked Cl- ions. The copper(II) ions have a square bipyramidal environment with oxygen atoms from the acetato groups in the basal planes and a chlorine and a ...
Crystal structure of the nonlinear optical compound L-arginine fluoride
Silva, M. Ramos; Paixão, J. A.; Beja, A. Matos; Veiga, L. Alte daL-arginine fluoride is a promising compound that exhibits nonlinear optical properties. It efficiently converts two single photons of the same polarization and frequency ? to one photon of frequency 2? (type I phase matching). C6H15N4O2+F- is monoclinic, space group P21, a = 5.4475(4) Å, b = 8.5133(6) Å, c = 10.2195(7) Å, ß = 93.475(6)°. The cation has a zwitterionic form, protonated at both the guanidyl and am...
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