The electro-oxidation reactions of substituted polysilane homopolymers dissolved in methylene chloride electrolyte were studied using cyclic voltammetry and chronocoulometry. The oxidation waves appear at potentials close to those for the corresponding waves for polymer films, but the current peak height responds linearly to sweep rate, which is unexpected tbr a diffusion-controlled process. This rcsfllt suggests some accumulation of the polymer at the eiectrode surface.In contrast, the diffusion coefficients obtained from chronocoulometry are lower than those for a small molecule, e.g., ferrocene, but appropriate for an eleetroactive polymer. The o• potential is affected by the nature of the substituents on the silicon atom and the effect is reasonable in terms of the electronic characteristics of the substituents. The electrochemical stoichiometry for poly(methylphenylsilanc) varies from {}.09 to 0.7 electrons/monomer repeat unit in the chain as the applied potential is changed to more anodic values. The electrochemical stoichiometry for the initial oxidation step of poly(methylphenylsilane) has the value 0.09 electrons/monomer repeat unit in the chain, which agrees with the stoichiometry previously obtained for the polymer as a film on the electrode, 0.1 electrons/monomer repeat unit. A higher stoichiometry was obtained when applying a more anodic potential possibly reflecting the subsequent oxidation of electroactive reaction intermediates.Soluble substituted silane high polymers represent an interesting class of radiation sensitive materials for which a number of applications have recently been discovered (1). In this regard, they have been considered as (i) thermal precursors to [3-silicon carbide ceramics (2), (ii) a new class of polymeric photoconductors and charge transporting media (3), (iii) broad spectrum, oxygen insensitive photoinitiators for vinyl polymerization (4), (iv) photosensitive materials for microlithography (5), and (v) materials with interesting nonlinear optical (NLO) properties (6).Much of the recent scientific interest in the polysilanes has centered on their very unusual electronic properties (1). All substituted silane high polymers absorb strongly in the UV from 280-400 mm (1, 7). The absorption maxima for alkyl substituted materials range from 300-330 nm and are infleunced by the steric bulk of the substitutent. Polymers containing larger substituent groups tend to absorb at longer wavelengths. Aryl substituents directly attached to the polymer backbone cause red shifts of 30-40 nm which have been attributed to the electronic interaction of the substituent with the sigma delocalized backbone. For the polysilanes, both the absorption maxima and the molar extinction coefficients of the Si-Si bond depend somewhat on the molecular weight. Both increase rapidly initially with increasing catenation but approach limiting values beyond a degree of polymerization of 40-50 (7).Although the basic spectral features of oligosilane derivatives can be predicted and rationalized by simple linear ...

positiven induktiven Effektes der ,,Briicken-Alkyl-Gruppen" mit sich, was die abnehmende Stabilitat in obiger Reihe erklart.

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Die Addition des Fulvens (I) an überschüssiges Chinon (II) (Molverhältnis 1:2) liefert die Dione (IIIa) und (IIIb) im Verhältnis 65 235. Arbeitet man mit einem Molverhältnis von 1:1, so entsteht zu über 95% (IIIa), aber mit einer Gesamtausb.