Tethered monolayers of poly((N-pyrrolyl)alkanethiol) on Au

The electrochemical oxidation of pyrrole-terminated, self-assembled alkanethiol monolayers on Au surfaces in dry electrolyte media (<0.005% H2O) results in tethered poly(N-alkylpyrroles) of varying monomer repeat lengths. After pristine (monomeric) monolayers of 10-(N-pyrrolyl)decane-1-thiol (1), 7-(N-pyrrolyl)heptane-l-thiol (2), and 6-(N-pyrrolyl)hexane-l-thiol (3) on Au have been oxidized in nonaqueous electrolyte media, electrochemistry characteristic of poly(N-alkylpyrroles) is observed. Reflection-absorption infrared spectra of the oxidized monolayers exhibit aromatic C-H out-of-plane deformation bands between 700 and 800 cm(-1) that can be used to determine the effective conjugation length of the poly(N-alkylpyrroles) produced. The number of monomer repeat units in the backbone ranges from 2 to similar to 20 and depends on the oxidation potential applied to the monomeric monolayers. In comparison to the monomeric monolayers, the electrochemically polymerized monolayers are demonstrated to be more stable with respect to exchange by a redox-labeled alkanethiol.