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  • 1
    Electronic Resource
    Electronic Resource
    ESR spectroscopy of the 4,5-bis(methoxycarbonyl)-1,3,2-dithiazol-2-yl radical labelled with sulphur-33 and nitrogen-15 (1988)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 26 (1988), S. 755-759 
    Details
    ISSN: 0749-1581
    Keywords: ESR ; 1,3,2-Dithiazol-2-yl radicals ; 33S-labelled free radicals ; Energy calculations of conformers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A derivative of the 1,3,2-dithiazol-2-yl radical was labelled with 33S in order to evaluate the p spin densities on the sulphur atoms. This information is required to provide a full description of the SOMO which, in turn, aids the understanding of the structure of the radical dimers. An unexpected result is that the two sulphur atoms are non-equivalent in the solid state. Calculations suggest that this is due to out-of-plane twisting of the substituent groups. Comparison of the ESR parameters of the bis(methoxycarbonyl) derivative with other members of the 1,3,2-dithiazol-2-yl group of radicals (including the parent radical) shows that it is a good model for the whole group.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260260906
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  • 2
    Electronic Resource
    Electronic Resource
    EPR spectra in γ-irradiated PPN+HFeW(CO)9- crystalsNRCC No. 32321. (1991)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 29 (1991), S. 476-481 
    Details
    ISSN: 0749-1581
    Keywords: Electron paramagnetic resonance ; Electron spin resonance ; Metal carbonyl radical ; Iron-tungsten carbonyl ; Unpaired electron ; g Matrix ; Odd-electron carbonyl ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Single crystals of PPN+HFeW(CO)9- prepared from THF · W(CO)5 and PPN+HFe(CO)4- exhibit weak single-line EPR spectra corresponding to the presence of two paramagnetic impurities. One of the spectra increases in intensity by an order of magnitude on 60Co γ-irradiation. The g2 matrices for both species in an orthogonal crystal-axis system were assembled from measurements of g values made at 77 K on crystallographically oriented samples. The intense spectrum has principal g values of 2.0064, 2.0468 and 2.1320 and principal directions of g which lie close to bonds emanating from the Fe nucleus of the undamaged anion. Consideration of the principal g values and directions for this species leads to an assignment to a FeW(CO)9- radical in which the unpaired electron is principally located in a Fe 3dz2 orbital directed along the Fe—H bond of the host anion. The other signal has principal g values (2.0229, 2.0425, 2.0950) close to those established for the singly bridged isomer of Fe2(CO)8-, but their directions do not correlate well with bond directions within the host anion. It is concluded that small amounts of the persistent Fe2(CO)8- radical generated in the preparative procedures substitute for the host anion in the crystals of PPN+HFeW(CO)9-.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260290512
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  • 3
    Electronic Resource
    Electronic Resource
    Electron spin resonance spectroscopy of free radicals (1993)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 31 (1993), S. 1027-1030 
    Details
    ISSN: 0749-1581
    Keywords: ESR ; Isotropic spectra ; Powder spectra ; Dithiadiazolyl radicals ; Dimerization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solution and powder ESR spectra of the 4-trifluoromethyl-1,2,3,5-dithiadiazolyl and 4-pentafluorophenyl-1,2,3,5-dithiadiazolyl free radicals were analysed. Comparison of the ESR parameters with those obtained for the protonated equivalents shows that fluorination produces a drift of unpaired electron spin density away from the nitrogen 2px orbitals towards sulphur 3px orbitals (x is the direction perpendicular to the heterocyclic ring), consistent with an increase in electronegativity of the substituent. The fluorinated radicals dimerize more readily than their protonated counterparts.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260311114
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  • 4
    Electronic Resource
    Electronic Resource
    ESR spectroscopic investigation of some 4-substituted 1,3,2-dithiazolyl and 2,3,1-dithiazolyl radicals (1992)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 30 (1992), S. 666-672 
    Details
    ISSN: 0749-1581
    Keywords: Electron spin resonance spectroscopy ; Sulphur-nitrogen-containing radicals ; Dithiadiazolyl radicals ; Dithiadiazolyl radicals ; Dithiazophospholyl radicals ; Phosphaalkynes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Further information has been obtained on the electronic structure of 1,3,2-dithiazol-2-yl radicals. The structure has been well characterized previously except for positions 4 and 5 in the ring. We have obtained solution and powder ESR spectra of radicals substituted with 13C in both positions and of radicals substituted with nitrogen or phosphorus in the 4-position. It is probably the first time that a compound has been prepared containing the ring. Two especially interesting facts emerged from the ESR spectra of these 1,3,2-dithiazolyl radicals: the 13C-substituted radical has a considerable amount of p spin density in the plane of the ring and the phosphorussubstituted radical has a very low unpaired spin density at the phosphorus atom. It is known that 1,3,2,4-dithiadiazolyl radicals isomerize readily by photolysis to the symmetrical 2,3,1,4-dithiadiazolyl radicals; we attempted the same reaction with But and a new radical was produced that we have been unable to identify.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260300717
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  • 5
    Electronic Resource
    Electronic Resource
    ESR spectroscopy of some dicyano-, pyrazino- and quinoxalino-1,3,2-dithiazolyl radicals (1992)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 30 (1992), S. 774-778 
    Details
    ISSN: 0749-1581
    Keywords: ESR ; 1,3,2-Dithiazol-2-yl radicals ; Pyrazine ; Quinoxaline ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several symmetrical 1,3,2-dithiazol-2-yl radicals have been examined that have in common nitrogen-containing substituents at the 4- and 5-positions, namely 4,5-dicyano-1,3,2-dithiazol-2-yl, [15N2]-1,3,2-dithiazolo [4,5-b] pyrazin-2-yl and 1,3,2-dithiazoleo [4,5-b] quinoxalin-2-yl. The ESR spectrum of the 4,5-dicyano radical does not reveal any 14N splittings from the cyanide groups; however, the pyrazine and the quinoxaline derivatives do have multi-lined well resolved spectra arising from substantial hyperfine interactions with these nuclei. The interactions are sufficiently large to be observed in the powder spectra of the latter. The presence of proton hyperfine interactions shows that unpaired-electron spin density is delocalized over all the rings. It has been found that the radicals attached to pyrazine and quinoxaline can be incorporated into single crystals of naphthalene and phenazine, respectively.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260300814
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  • 6
    Electronic Resource
    Electronic Resource
    EPR study of iron - nitrosyl clusters in the oxidation of Fe(NO)2(CO)2Presented at the ‘L. H. Sutcliffe’ Symposium on Magnetic Resonance, University of Surrey, 24 March 1995.NRCC No. 37313. (1995)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. S14 
    Details
    ISSN: 0749-1581
    Keywords: EPR ; ESR ; iron-nitrosyl radicals ; cluster nitrosyls ; Fe(NO)2+ ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The oxidation of Fe(NO)2(CO)2 by tetracyanoethylene (TCNE), by the nitrosonium ion (NO+), or by electrolysis in polar solvents was studied by EPR spectroscopy. A number of long-lived (τ1/2 of the order of hours) free radicals were detected in the early stages of reaction, all having similar isotropic g-factors and 14,15N hyperfine interactions. These have been identified as the mononuclear cations, Fe(NO)2(CO)2-nStn+ (St = solvent molecule). They slowly disappear and are replaced by persistent radicals (τ1/2 of the order of days) that show equal isotropic hyperfine interactions with four-, six- or eight-nitrogen nuclei. Infrared and EPR spectroscopic data suggest that two of these species are trinuclear nitrosyl clusters, Fe3(NO)2n(CO)(12-3n)+ (n = 3, 4), in which the unpaired spin is localized on one iron nucleus, but which are fluxional on the EPR time-scale. The third nitrosyl radical with four equivalent NO ligands is tentatively identified as a binuclear intermediate that may be a precursor of the trinuclear clusters.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260331305
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  • 7
    Electronic Resource
    Electronic Resource
    Review of recent EPR and theoretical studies on the addition of free radicals to C60 and C70NRCC No. 39058 (1995)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. S20 
    Details
    ISSN: 0749-1581
    Keywords: ESR, EPR ; C60 ; C70 ; MNDO ; INDO. MO calculations ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: EPR spectra of free-radical adducts of C60 and C70 are described and discussed. In the case of addition to C60 the prototype radical is HC60 or perhaps MuC60. The H/Mu hyperfine anomaly in these radicals is explained. The spectra of alkyl-C60 and fluoroalkyl-C60 radicals are also described, including factors determining the equilibrium configuration over the C60 surface of radicals of the general formula XYZCC60. The structure of the higher adducts R3C60 and R5C60 is mentioned. In the case of H addition to C70, four of the five possible isomers of HC70 have been identified, but only one of the 2792 isomers of H3C70 is reported.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260331306
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