Electron transfer from carbanionic salts to linear sequences of conjugated double bonds, 1. Mechanism of n doping of polyacetylene

Abstract

AbstractIt is shown that the mechanism of polyacetylene (PA) reduction (or n “doping”) by alkaline carbanionic salts and butyllithium is a simple electron transfer without addition. In this reduction reaction the dicarbanionic dimer of 1,1‐diphenylethylene (DD2– Na2+) is quantitatively converted to 1,1‐diphenylethylene. The reduction by 3‐methyl‐1,1‐diphenylpentyllithium produces free radicals which deactivate in solution by coupling and disproportionation. But the strong dependence of the ratio of disproportionation to coupling of these radicals on solvent polarity is unusual: no coupling is observed in diethyl ether or pentane, while it is the most important reaction in THF. sec‐Butyllithium in pentane also reduces PA by a simple electron transfer process. The “doping” levels can be deduced accurately from the quantitive analysis of the by‐products by gas chromatography.