Electropolymerization of Ruthenium Bis(1,10-phenanthroline)(4-methyl-4'-vinyl-2,2'-bipyridine) Complexes through Direct Attack on the Ligand Ring System

Article abstract of DOI:10.1021/j100299a022

Mixed ligand complexes of the general type RuP2(4-methyl-4'-vinyl-2,2'-bipyridine)²⁺ (where P represents phenanthroline or a substituted phenanthroline) undergo rapid electropolymerization following initial two-electron reduction.The polymerization yields redox-conductive electrode coatings and appears to proceed via radical-radical coupling between the vinyl moiety and a phenanthroline carbon, with the 4- and 7-positions of the phenanthroline being the most reactive.When the phenanthroline ligands possess substituents in the 4- and 7-positions, polymerization still proceeds, but an unexpected reversible electrochemical response near -0.2 V vs.SSCE is generated.The response is attributed to an intermediate which can exist in a stable ligand-centered free-radical form.This radical species has been observed by EPR spectroscopy and is stabilized by 4,7-disubstitution and/or the presence of proton donors.The mechanistic pathways involved in the electropolymerization are complex and lead to multiple products.Polymerized films display unusual electrochemistry, including prominent "charge-trapping" peaks for which a mechanistic system is proposed.