Steric and electronic effects in methyl-substituted 2,2 '-bipyrroles and poly(2,2 '-bipyrrole)s: Part I. Synthesis and characterization of monomers and polymers

The effects of N- and C-methyl substitution on electrical and spectral prop erties of pyrrole, 2,2'-bipyrrole, and the corresponding polymers were inve stigated. The whole series of monomethyl and N- or C-beta-dimethyl-substitu ted 2,2'-bipyrroles was synthesized, and the electrochemical and spectral p roperties of all the compounds were investigated under identical testing co nditions. The corresponding polymers were prepared by electrochemical anodi c oxidation under comparable experimental conditions and their spectroscopi c and conductivity properties evaluated for comparison. The higher degree o f efficiency in transmission of electronic effects associated with methyl s ubstitution at C-beta with respect to substitution at N was clearly demonst rated. The influence of the symmetry of the starting monomer (C-2v, or C-s) on the electrical properties of the resulting polymers is discussed.