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1Author    H. J. Keller, W. Moroni, D. Nöthe, M. Scherz, J. WeissRequires cookie*
 Title    und 5.10-Dihydro-5.10-diethylphenaziniumtriiodid  
 Abstract    Molecular and Crystal Structure of 5.10-Dihydro-5,10-dimethylphenaziniumtriiodide and 5,10-Dihydro-5,10-diethylphenazinium triiodide Oxidation of 5,10-dihydro-5,10-dimethylphenazine and 5,10-dihydro-5,10-diethyl-phenazine under different reaction conditions leads to several iodine containing solids. The preparation and X-ray structure of two of them, 5,10-dihydro-5,10-dimethyl-phenaziniumtriiodide (3) and 5,10-dihydro-5,10-diethylphenaziniumtriiodide (4) are reported here. Compound 3 crystallizes in space group P 2i/n with lattice parameters a = 8.552(6) A, b = 16.953(2) A, c= 12.157(9) A and ß= 103.46(2)° with four formula units in the unit cell. The structure was refined to an i?-value of 0.046 using 2387 independent reflections. The lattice constains distinct, slightly distorted triiodide ions and bent 5,10-dihydro-5,10-dimethylphenazinium radical cations. Compound 4 crystallizes in the same space group P2i/n with lattice parameters a = 8.531(6) A, b = 8.332(21) A, c = 13.320(15) A and ß— 94.44(19)° with two formula units in the unit cell. The structure was refined to an i?-value of 0.076 using 1195 independent reflections. The lattice contains strictly linear symmetrical triiodide ions and planar centrosymmetrical 5,10-dihydro-5,10-diethyl-phenazinium radical cations. 
  Reference    Z. Naturforsch. 33b, 838—842 (1978); eingegangen am 27. April 1978 
  Published    1978 
  Keywords    Radical Cations, Structure, ESR 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0838.pdf 
 Identifier    ZNB-1978-33b-0838 
 Volume    33 
2Author    Heinz-Peter Schuchmann, Rita Wagner, Clemens Von SonntagRequires cookie*
 Title    7-Radiolysis of 2'-Deoxycytidine-5'-phosphate in Deoxygenated Aqueous Solutions. OH Radical-Induced Alterations at the Sugar Moiety  
 Abstract    In order to elucidate some aspects of the mechanism of radical-induced strand break formation in DNA, the y-radiolysis of N20-saturated aqueous solutions of 2'-deoxycytidine-5'-phosphate has been studied as a model system. At pH 4 it has been observed that upon OH attack at the sugar moiety phosphate (G ^ 0.6) and cytosine (G = 1) are released and the following cytosine-free sugars are formed: 2,5-dideoxypentos-3,4-diulose, 1 (G = O.22), 2-deoxy-pentos-4-ulose, 2 (G = 0.1s), 2-deoxy-pentos-4-ulose-5-phosphate, 3 (G=0.06), 2-deoxypentonic acid-5-phosphate and its lactone, 5 (G «0.5). Some 2-deoxyribose-5-phosphate, 4 is also formed. Upon addition of H2O2 (up to 10 -2 M) prior to irradiation, G(l) is drastically reduced without giving rise to another cytosine-free product. G(3) increases at the expense of G(2). G (4 + 5) also increase upon H2O2 addition. The formation of these products and the change of their G values as a function of H2O2 concentration are discussed in the light of well-documented radical reactions of carbohydrates and related compounds. The precursor of 1 has been considered to be the radical at C-3', that of 2 and 3 the radical at C-4' and that of 5 the radical at C-l'. Product 4 is thought to arise from a radical-induced destruction of the cytosine moiety. These primary radicals which may undergo rearrangement, or eliminate phosphate, are readily oxidised by H202, a reaction which leads to the change of product distribution mentioned above. 
  Reference    Z. Naturforsch. 38b, 1213—1220 (1983); received June 27 1983 
  Published    1983 
  Keywords    Free Radicals, Radical Cations, Carbohydrates, DNA Model 
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 TEI-XML for    default:Reihe_B/38/ZNB-1983-38b-1213.pdf 
 Identifier    ZNB-1983-38b-1213 
 Volume    38 
3Author    G. Em Ot, F. Renkingb, A. Nton, R. Ieker2, Josef Salbeck0, BerndS. Peiser1Requires cookie*
 Title    2,5,8,11-Tetra-terMmtyl-pen-xanthenoxanthene and its Dication Spectroelectrochemistry and Model Calculations on a Dioxa-22-7r-system  
 Abstract    Spectroelectrochemistry of 2,5,8,1 l-tetra-rm-butyl-p^n'-xanthenoxanthene 1 yields the UV/VIS spectra of the corresponding radical cation l '+ and dication 12+. The bathochromic shift for the dication 12+ relative to 1 and to the isoelectronic hydrocarbon anthanthrene (2) can be understood by quantum mechanical calculations {ab initio, AM 1) of model structures. 
  Reference    Z. Naturforsch. 51b, 377—380 (1996); received October 4 1995 
  Published    1996 
  Keywords    Spectroelectrochemistry, MO-Calculations, Xanthenoxanthenes, Radical Cation, Dication 
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 TEI-XML for    default:Reihe_B/51/ZNB-1996-51b-0377.pdf 
 Identifier    ZNB-1996-51b-0377 
 Volume    51 
4Author    Requires cookie*
 Title    Radiation Chemistry of DNA-Model Compounds, VII* On the Formation of 5-Deoxy-D-erythro-pentos- 4-ulose and the Identification of Twelve Further Products from y-Irradiated Aqueous Solutions of Ribose-5-phosphate  
 Abstract    L o t h a k S t e l t e r , C l e m e n s v o n S o n n t a g , a n d D i e t r i c h S c h u l t e -F r o h l i n d e Different mechanisms are considered to explain the formation of 5-deoxy-D-erythro-pentos-4-ulose in the y-radiolysis of ribose-5-phosphate in aqueous solution. On the basis of deuterium labelling experiments one mech­ anism involving an enol as an intermediate could be excluded. The identification of twelve further radio-lysis products from ribose-5-phosphate is reported. 
  Reference    (Z. Naturforsch. 30b, 656—657 [1975]; received February 19 1975) 
  Published    1975 
  Keywords    y-Radiolysis, Ribose-5-phosphate, Carbohydrates, Radical Reactions, Radical Cations 
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 TEI-XML for    default:Reihe_B/30/ZNB-1975-30b-0656_n.pdf 
 Identifier    ZNB-1975-30b-0656_n 
 Volume    30 
5Author    Gemot Frenking, Helmut SchwarzRequires cookie*
 Title    ab i/ifüo-Rechnungen zur relativen Stabilität der Neutralmoleküle, Radikalkationen und -anionen von Allen und Propin ab initio Calculations on the Relative Stabilities of the Neutrals, Radical Cations and Anions of Allene and Propvne  
 Abstract    Ab initio calculations demonstrate that, in agreement with experimental results, the oxidation of both allene (1) and propyne (2) to their corresponding cation radicals (1+ -and 2+ -) is associated with a reversal of the stability order. Whereas for the neutral molecules 1 is thermochemically less stable than 2 (zMHf° = 1.3 kcal/mol) the opposite holds for the cation radicals (1+ -is 13.3 kcal/mol more stable than 2 +-). The radical anions of 1 and 2 do also show a reversed stability order (l +< being 5.1 kcal/mol more stable than 2 _ .); however, both radical anions are predicted to undergo spontaneous electron detachement, thus giving their neutral counterparts (negative electron affinities). The changes in geometries and charge distributions associated with the redox reactions of 1 and 2 are briefly dis-cussed. 
  Reference    Z. Naturforsch. 37b, 1602—1605 (1982); eingegangen am 5. August 1982 
  Published    1982 
  Keywords    Molecular Orbital Calculations, Unsaturated Hydrocarbons, Radical Cations, Radical Ions 
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 TEI-XML for    default:Reihe_B/37/ZNB-1982-37b-1602.pdf 
 Identifier    ZNB-1982-37b-1602 
 Volume    37 
6Author    S., C.E A —c E N G RenobleRequires cookie*
 Title    Struktur und Magnetismus stabiler Radikalkation-Salze: N,N'-Diethylchinoxalinium Tetraphenylborat im Vergleich mit Pyrazinium-und Phenazinium-Analogen  
 Abstract    tructure and M agnetism of Stable C ation R adical Salts: N ,N '-D iethylquinoxalinium T etra p h en y lb o rate as C o m p ared w ith Pyrazinium and Phenazinium A nalogues H .-D . H au sen 3, W olfgang K aim a *, A nd reas Schulz3 und E b e rh a rd R o th 3 b Crystal and m olecular structure analysis o f N ,N '-diethylquinoxalinium tetraphenylborate shows a virtually planar quinoxaline ring with 1 1 conjugated .t electrons and approxim ately antiperipla-nar ethyl groups. In comparison with the benzo-analogous phenazinium system s and the de-benzo derivative N.N'-diethylpyrazinium cation, the quinoxalinium species adopts an interm ediate posi­ tion in terms o f intra-and intermolecular structural features. In particular, increasing benzanella-tion seem s to favour a cation/anion approach for electrostatic reasons w hereas the N —C bonds to the hyperconjugatively charge delocalizing alkyl groups increase due to peri interactions. Solid state magnetic and ESR measurements are com patible with the crystallographically determined structure. 
  Reference    Z. Naturforsch. 44b, 1233 (1989); eingegangen am 27. April 1989 
  Published    1989 
  Keywords    H eterocycles, Radical Cations, Structure, M agnetism E SR Spectra 
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 TEI-XML for    default:Reihe_B/44/ZNB-1989-44b-1233.pdf 
 Identifier    ZNB-1989-44b-1233 
 Volume    44 
7Author    Structure, M. Spectroscopy, H.-D Agnetism, WolfgangK. Hausena, Aim, Andreas Schulz3, MichaelM. Oscherosch3, Jeanne Jordanovb, C.E A, -CE N GrenobleRequires cookie*
 Title    Erstmaliger Nachweis von ;r-;r-Dimerenbildung bei stabilen 1,4-Dialkylchinoxalinium-Radikalkationen. Struktur, Spektroskopie und Magnetismus First Evidence for 7t-7r-Dimerization of the Stable 1,4-Dialkylquinoxalinium Radical Cations  
 Abstract    Crystal and molecular structure analysis o f 1,4-diethylquinoxalinium iodide shows a virtual­ ly planar quinoxaline ring with 11 conjugated 7r-electrons. In contrast to the triiodide o f the I,4,6,7-tetramethyl derivative or to the tetraphenylborate salt o f 1,4-diethylquinoxalinium cat­ ion radical the iodide exhibits 7r-7r-dimerized radical cations in the solid state with synplanar ethyl groups and a rather small intermolecular distance o f about 315 pm between the 7r-planes o f the primarily interacting 1,4-diazine rings. Solid state magnetic measurements between 2 and 300 K show considerably diminished magnetic m om ents due to partial spin-pairing, and UV/VIS spectroscopic measurements in acetonitrile reflect the 7r-7r-interaction in solution through the appearance o f a long-wavelength absorption band. 
  Reference    Z. Naturforsch. 48b, 1181—1186 (1993); eingegangen am 1. Juni 1993 
  Published    1993 
  Keywords    Heterocycles, Radical Cations, Structure, M agnetism, A ssociation Phenomena 
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 TEI-XML for    default:Reihe_B/48/ZNB-1993-48b-1181.pdf 
 Identifier    ZNB-1993-48b-1181 
 Volume    48 
8Author    Gemot Frenking, Nikolaus Heinrich, Jochen Schmidt, Helmut SchwarzRequires cookie*
 Title    Neutrale und ionische Keto/Enoltautomere: Zum Ursprung der Stabilitätsumkehr und zu ungewöhnlichen Substituenten-Effekten Neutral and Ionic Keto/Enol Tautomers: On the Origin of Stability Reversal and Unusual Substituent Effects  
 Abstract    The reversal in stability for neutral keto/enol tautomers and their cation radicals is mainly due to the removal of an electron from an ^-orbital of the enol, which has anti-bonding properties for the C-0-bond. The total electronic energy gained in the oxidation of enols is more than sufficient to compensate for the increase in nuclear/nuclear repulsion when comparing keto/enol tautomers; this, however, does not hold for the keto systems investigated. The marked methyl substituent effect found in O, C-l, and C-2 substituted enol cation radicals is not reflected in the charge distribution of the corresponding ions. Comparison of the MNDO calculated heats of formation of ions with that of their neutral counterparts indicates that the changes in bond dissociation energies account at least qualitatively for the experimentally observed effects. 
  Reference    Z. Naturforsch. 37b, 1597—1601 (1982); eingegangen am 30. Juni 1982 
  Published    1982 
  Keywords    Molecular Orbital Calculations, Methyl Substituent Effects, Gas Phase Ion Stability, Radical Cations, Radical Anions 
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 TEI-XML for    default:Reihe_B/37/ZNB-1982-37b-1597.pdf 
 Identifier    ZNB-1982-37b-1597 
 Volume    37