Electron spin resonance single crystal

Structural studies, particularly those that elucidate the three-dimensional relationships of the amino acid residues in the enzyme, permit judgments about whether the involvement of one or the other side chain is physically and sterically possible. Such techniques include nuclear magnetic resonance, electron spin resonance, single-crystal x-ray diffraction, and cross-linking studies. The important question to be answered by mechanistic studies is how an enzyme catalyzes a particular reaction so rapidly. Two general factors seem to be involved. 

The title Spectroscopy in Catalysis is attractively compact but not quite precise. The book also introduces microscopy, diffraction and temperature programmed reaction methods, as these are important tools in the characterization of catalysts. As to applications, I have limited myself to supported metals, oxides, sulfides and metal single crystals. Zeolites, as well as techniques such as nuclear magnetic resonance and electron spin resonance have been left out, mainly because the author has little personal experience with these subjects. Catalysis in the year 2000 would not be what it is without surface science. Hence, techniques that are applicable to study the surfaces of single crystals or metal foils used to model catalytic surfaces, have been included. 

Huttermann J, Muller A (1969a) Free radicals in gamma-irradiated 2-deoxy-D-ribose. Electron spin resonance of single crystals and polycrystalline material. Radiat Res 38 248-259 Huttermann J, Muller A (1969b) Electron-Spin-Resonanzany-bestrahlten Einkristallen von 2-Deso-xy-D-ribose. Z Naturforsch 24b 463-464... 

Huttermann J (1970) Electron-spin-resonance spectroscopy of radiation-induced free radicals in irradiated single crystals of thymine monohydrate. Int J Radiat Biol 17 249-259 Huttermann J (1982) Solid-state radiation chemistry of DNA and its constituents. Ultramicroscopy 10 25-40... 

Huttermann J, Ward JF, Myers LS Jr (1971) Electron spin resonance studies of free radicals in irradiated single crystals of 5-methylcytosine. Int J Radiat PhysChem 3 117-129 Huttermann J, Ohlmann J, Schaefer A, Gatzweiler W (1991) The polymorphism of a cytosine anion studied by electron paramagnetic resonance spectroscopy. Int J Radiat Biol 59 1297-1311 Hwang CT, Stumpf CL, Yu Y-Q, Kentamaa HI (1999) Intrinsic acidity and redox properties of the adenine radical cation. Int J Mass Spectrom 182/183 253-259 Ide H, Otsuki N, Nishimoto S, Kagiya T (1985) Photoreduction of thymine glycol sensitized by aromatic amines in aqueous solution. J Chem Soc Perkin Trans 2 1387-1392 Idris Ali KM, Scholes G (1980) Analysis of radiolysis products of aqueous uracil + N20 solutions. J Chem Soc Faraday Trans 176 449-456... 

Zehner H, Flossmann W, Westhof E, Muller A (1976) Electron spin resonance of irradiated single crystals of uracil. Mol Phys 32 869-878... 

It has been stressed that most studies of organic radicals in single crystals have been made on radicals formed by exposure of parent crystals to high-energy radiation. For such radicals it is often found that the anisotropy in the electron spin resonance spectra shows the same point group symmetry as that of the undamaged crystal, and thus that the sets of radicals which differ only in their orientation with respect to the crystal axes are interrelated by the space group symmetry operations of the parent crystal. 

A very interesting paper by Chesnut and Phillips (1961) represents almost a cross between the topics discussed in A and C above. They have studied the electron spin resonance spectra of single crystals containing the paramagnetic (doublet) radical anion of tetracyano-quinodimethane,... 

We report an electron spin resonance (ESR) study on a C60 anion and a metal (M) encapsulated in fullerene (C ) (a metallofullerene M C ). The anisotropy components of the g-factor of Cg0 were determined accurately from the analysis of angular-dependent ESR spectra of single crystal Cg0 salt. The evaluation of the g-factor was performed according to the classification of symmetry of the C60 geometry. It was found out from the evaluation that the molecular structure of Cg0 should he distorted to lower symmetry, C2h or C,. The variety of ESR spectra of metallofullerenes of La C s was obtained in terms of a g-factor, a hyperfine coupling constant, and a line width. In the case of the isomer I of La C80 and the isomer II of La C84, an abnormally large line width was measured. The molecular structure with high symmetry would reflect on the specific spin dynamics. 

The complex morphology of most conjugated polymers prevents direct measurement, and hinders understanding, of their intrinsic properties. Such problems do not occur for the polydiacetylenes, which can be prepared as macroscopic single crystals. Since polydiacetylenes can also be obtained in less perfect forms the effects of disorder can be studied. Spectroscopic techniques have been widely used to study the intrinsic properties of polydiacetylenes and their modification by disorder. The results obtained by optical and electron spin resonance spectroscopy are discussed. 

Electron spin resonance studies of irradiated single crystals of methacryl-... 

The present work deals with soUd CT complexes of phenazines which, in the most favorable cases, include the crystal structure, single-crystal electron spin resonance (epr) data, the temperature dependence of the magnetic susceptibility or of the powder conductivity, and a CT absorption spectrum. We have not pursued complexes that could not be crystallized, nor have we investigated completely similar materials. 

Leibl, W., W. Nitschke, and J. Huttermann (1986). Spin-density distribution in the [Fe02]-complex. Electron spin resonance of myoglobin single crystals. Biochim. Biophys. Acta 870, 20-30. 

The preparation and the crystal structures of single crystals of alkali aromatic ion pairs are discussed. A close relationship was found between the ion-pair structures in solution and in the solid state. The physical properties of the pseudo-two-dimensional magnetic alkali biphenyl crystals are reviewed. The effect of spin diffusion manifests itself clearly in the line width and line shape of the exchange-narrowed electron spin resonance (ESR) line. The monoanions of cycloocta-tetraene, produced by X-ray irradiation, rotate rapidly about their eightfold axes. At 20 K this rotation is frozen, and an alternating spin density distribution is found around the ring. The equilibrium position of the monoanion is rotated by 22.5 compared with the equilibrium position of the dianion. 

Various techniques have been utilized to determine the existence of a metal-metal bond in the solid state. Single crystal x-ray analysis and neutron diffraction (17) are the most accurate methods available and are often facilitated by the strong scattering of the metal atoms. Polarized electronic spectroscopy (430), electron spin resonance, magnetic susceptibility, and dc conductivity have been used to indicate some solid state interaction. These techniques are, however, not definitive (144). Recent work indicates that resonance enhancement in Raman spectroscopy may provide a useful tool (101, 382) in elucidating metal-metal interactions. 

Electron Spin Resonance. Esr measurements on orientated single crystals of K2Pt(CN)4Bro.3o(H20)3 between 60° and 300°K give the temperature-independent values for gn and gj of 1.946 (5) and 2.336 (5), respectively. These values are characteristic of tis-like hole states (298). The decrease in the signal intensity with temperature below 150°K is consistent with a transition from... 

The esr spectrum of the paramagnetic component coincident to the metal-metal axis was observed at 4 K through the coupling of a single-crystal dielectric resonator of K2Pt(CN)4Bro.3o(H20)3 with an electron spin resonance spectrometer. Preliminary results include a line at g w 2 with a complex hyperfine structure (208). An impurity center associated with the presence of a copper(II) complex of Z>4a symmetry has recently been detected by esr (466). 

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