Search results for "molecule"
showing 10 items of 5162 documents
<title>High-excitation-density luminescence as probe of mixed silver halides</title>
1992
Two kinds of intrinsic luminescence in mixed AgBr1-xClx (1 io. Dependence of the parameters of this process on crystal composition has been investigated in terms of spatially well correlated Frenkel defect recombinations. The main effect found was the linear increase of the Agio migration energy with the crystal composition x. The second kind of luminescence arising due to exciton molecules has been shown to be sensitive to the solid solution composition and the quality of a crystal. It is shown that this luminescence correlates with the optical losses of the fibers studied.
Microscopic origin of the nonexponential dynamics in a glassy crystal
2003
The origin of the slow relaxation and of the dynamic heterogeneity is studied for an orientation-ally disordered crystal, orthocarborane, composed of quasi-icosahedrally shaped molecules. Multidimensional deuteron magnetic resonance reveals that large jump angles dominate their complex, anisotropic reorientational motion. It involves a sequence of small-angle tilts about locally preferred axes as well as symmetry adapted threefold jumps. The intrinsic dynamics of this glassy crystal is nonexponential and can be fully accounted for in terms of the tilt and jump motion.
Coupled rotational and translational modes in the mixed molecular crystal KBr1?x (CN) x
1980
TheE g andT 2g acoustic phonon modes of the molecular crystals KBr0.96(CN)0.04 and KBr0.86(CN)0.14 have been investigated by inelastic neutron scattering at 6, 90 and 300 K. Clear resonances due to mode-mode coupling to molecular excitations were observed. In complementary ultrasonic experiments the elastic constants were found to pass through minima as a function of temperature. The results were quantitavely explained by a model which assumes simple forms of the molecular excitation spectrum. An alternative interpretation, though being only qualitative, postulates a freezing of the CN molecules into a glass-like phase.
Adsorption of Alcohols Onto Zinc Selenide (ZnSe) Crystal Surface
2014
Adsorption behaviour of ZnSe, a popular material used in the manufacture of crystals for total internal reflectance techniques was studied for the adsorption of alcohols from dichloromethane solutions using infrared spectrometry. A series of n-alcohols were used in this study. The results show that the integrated area for the hydrogen bonded OH stretchings decrease and suggests that there is a continuous adsorption of alcohol molecules onto the ZnSe crystal by breaking the hydrogen bonds between alcohol molecules in solution.
1,1′-[2,3,5,6-Tetramethyl-p-phenylenebis(methyleneoxy)]di-1H-benzotriazole
2009
The complete molecule of the title compound, C(24)H(24)N(6)O(2), is generated by a crystallographic inversion centre. The benzotriazole rings form dihedral angles of 2.10 (7)° with the central aromatic ring. The crystal packing is consolidated by π-π inter-actions, with centroid-centroid distances of 3.6234 (10) Å, together with weak C-H⋯π inter-actions.
Synthesis and Electrochemistry of Aluminum Porphycenes. Crystal and Molecular Structure of Methyl-σ-Bonded Aluminum Etioporphycene
1997
The synthesis and characterization of three monomeric aluminum porphycenes with anionic or σ-bonded axial ligands is reported. The investigated compounds are represented as ( EtioPc ) Al ( CH 3) and ( EtioPc ) AlX where EtioPc represents the dianion of etioporphycene and X = Cl − or OH −. Each synthesized complex was characterized by mass spectrometry. 1 H NMR, IR and UV-visible spectroscopies as well as by electrochemistry. Comparisons are made between the properties of complexes in the aluminum etioporphycene series and related chloro- or methyl σ-bonded Al ( III ) porphyrins containing octaethylporphyrin ( OEP ) or tetraphenylporphyrin ( TPP ) macrocycles. Comparisons are also made betw…
1,2-Bis(methylsulfanyl)-1,2-dicarba-closo-dodecaborane(12)
2004
3 pages, 1 figure, 2 tables
Bis[3-methyl-5-(pyridin-2-yl)-1H-pyrazol-4-yl] selenide methanol hemisolvate
2014
The asymmetric unit of the title compound, C18H16N6Se·0.5CH3OH, contains two independent molecules of bis[3-methyl-5-(pyridin-2-yl)-1H-pyrazol-4-yl] selenide with similar C—Se—C bond angles [99.30 (14) and 98.26 (13)°], and a methanol molecule of solvation. In one molecule, the dihedral angles between pyrazole and neighbouring pyridine rings are 18.3 (2) and 15.8 (2)°, and the corresponding angles in the other molecule are 13.5 (2) and 8.3 (2)°. In the crystal, the selenide and solvent molecules are linked by classical O—H...N and N—H...N hydrogen bonds, as well as by weak C—H...O and C—H...π interactions, forming a three-dimensional supramolecular architecture.
FTIR Microscopy with Polarized Radiation for the Analysis of Adsorption Processes in Molecular Sieves
1994
FTIR Microscopy with polarized light was used to study the orientation of different molecules in Silicalite I, SAPO-5 and AlPO 4 -5 molecular sieves during the adsorption process and in their equilibrium positions. While the uptake and the equilibrium positions of p-xylene are essentially not influenced by the the framework charge, large differences between AlPO 4 -5 and SAPO-5 are observed with the strongly basic p-nitroaniline molecule.
Self-assembled hydrogen-bonded coordination networks in two copper(II) carboxylates with 4-pyridylmethanol
2011
AbstractThe crystal and molecular structure of [Cu(nif)2(4-PM)2]·CH3OH (1) and [Cu(2-Clbz)2(4-PM)2(H2O)] (2), (where nif = niflumate anion, 2-Clbz = 2-chlorobenzoate anion and 4-PM is the 4-pyridylmethanol), have been determinated by X-ray crystallography. The Cu2+ cation in (1), is coordinated by two pairs of oxygen atoms from asymmetric bidentate niflumate anions and by a pair of pyridine nitrogen atoms from monodentate 4-pyridylmethanol ligands in trans position forming an extremely elongated bipyramid. The Cu2+ cation in (2), is coordinated by a pair of oxygen atoms from monodentate 2-chlorobenzoate anions, further by a pair of pyridine nitrogen atoms from monodentate 4-pyridylmethanol …