Ulrike Lechner-Knoblauch

Radikalionen: LXVIII. Cyclovoltammetrische messungen an organosilizium-substituierten π-systemen: Abschätzung des oxidationspotentials für das einelektronentransfer-system AlCl2/H2CCl2☆

Abstract The oxidation potentials of 13 organosilicon derivatives of the π systems ethene, acetylene, cyclohexadiene-1,4, benzene and biphenyl have been determined by cyclic voltammetry in H 2 CCl 2 /R 4 N + ClO 4 − solution. Correlation with the corresponding first vertical ionization potentials yields the linear regression, E ox (V) = −4.59 + 0.78 IE 1 v (eV). For the selective one-electron transfer system AlCl 3 /H 2 CCl 2 from this relationship (based on ESR evidence of radical cations, which can be generated) an oxidation potential E ox ∼ + 1.6 V is estimated.

The stable radical cation of tetrakis(dimethylamino)-p-benzoquinone

Abstract The electron-rich tetrakis(dimethylamino)-p-benzoquinone exhibits a low first ionization energy of only 7.1 eV and can be oxidized electrochemically at +0.25 V vs. SCE to its purple radical cation, whose spin population differs considerably from that of the corresponding semiquinone radical anion.

Radikalionen, 69 [1, 2] Die elektrochemische Reduktion aromatischer Nitro-Verbindungen in aprotischer Lösung / Radical Ions, 69 [1, 2] The Electrochemical Reduction of Aromatic Nitro Compounds in Aprotic Solution

The reduction potentials of 40 aromatic nitro compounds Rπ(NO2)n with Rπ = benzene, naphthalene, anthracene, fluorene and carbazole and n = 1 to 4 nitro groups are determined by cyclic voltammetry in DMF under aprotic conditions. The perturbation by the strongly electron accepting substituents can be rationalized via correlation with HMO eigenvalues. Based on reversibility criteria, the electrochemical behaviour is discussed and the compounds are classified with respect to reversible or irreversible one-electron transfer as well as up to 4 (quasi)-reversible reduction steps. The CV data measured can be used to predict redox reactions of aromatic nitro compounds in inert solvents.

Bonding in Phosphorus Compounds1: Reduction Potentials of R2(Y)P-substituted Aromatic π Systems2 and Gasphase Syntheses of 18 Valence Electron Molecules X-P=Y3,4

Abstract An up to date concept of bonding in phosphorus compounds, which has to consider the individual molecular states, their dynamics and reaction channels, is illustrated by representative examples. The reduction potentials of R2(Y)P-substituted π systems to their radical anions, measured under aprotic conditions and discussed by first order perturbation, yields a sequence of increasing acceptor effects ranging from R2P to R3P®. The gasphase syntheses of novel molecules like H3C-P=CH2, Cl-P=O or Cl-P=S, partly by surface reactions, has been optimized by photoelectron spectroscopic real-time analysis. Their radical cation state ionization patterns are assigned by quantum chemical calculations, which allow to rationalize the bonding to the only doubly coordinated P center.