ELECTROCHEMICAL POLYMERIZATION STUDIES OF AZA-15-CROWN-5 VINYL-2,2'-BIPYRIDINE RUTHENIUM(II) COMPLEXES

The electrochemical polymerisation of the mono(ligand) and tris(ligand ) ruthenium(II) complexes, [RuL(1,2)(bipy)(2)](2+) and [RuL(3)(1,2)](2 +) (bipy = 2,2'-bipyridine, L(1) = thyl-4'-(N-styryl-aza-15-crown-5)-2 ,2'-bipyridine, L(2) = 4,4'-bis(N-styryl-aza-15-crown-5)-2,2'bipyridin e), has been investigated in acetonitrile. Preparation of electroactiv e polymer films was established on reductive electropolymerisation of the tris(ligand) ruthenium(II) complexes. Electropolymerisation of [Ru L(1)(bipy)(2)](2+) did not take place, suggesting that the polymer for mation mechanism involves radical-radical hydrodimerisation for pairs of vinyl groups rather than 'polyvinyl-type' chain propagation. Lack o f electropolymerisation for [RuL(2)(bipy)(2)](2+), with two vinyl link ages on the same ligand, is explained by steric constraints preventing repeated linkages between aza-15-crown-5 vinyl-pyridine units. While polymer formation via the alternative route of oxidative coupling of t he N-styryl-aza-15-crown-5 moieties might be anticipated, electro-oxid ation for the [RuL(2)(bipy)(2)](2+) and [RuL(3)(1,2)](2+) complexes le d only to the formation of electroinactive orange films with concurren t electrode passivation.