Electropolymerization bipyridine ligands

Bipyridine ligands 42a have also been prepared [84] and the resulting electropolymerized films are more conductive when Ru is complexed to the bipyridine [85]. 

To solve these problems, we developed the synthesis of symmetrically disubstituted bipyridine ligands 150, which possess two electropolymerizable bithiophenic groups fixed at an internal (3-position of thiophene by an alkylsuUknyl or an alkoxy spacer [161]. The analysis of the electropolymerization of these compounds shows that the association of low oxidation potential polymerizable groups and two-site precursors allows us to synthesize stable functional polymers. 

Useful reviews of work done at The University of North Carolina present the evolution from covalent attachment of pyridine and bipyridine ligands to surfaces of electrodes, through physical adsorption, of poly(vinylpyridine) and related polymers, to electropolymerization of metal complexes containing vinylpyridine and vinylbipyridine ligands (33,3 ). 

Vinyl substituted bipyridine complexes of ruthenium 9 and osmium 10 can be electropolymerized directly onto electrode surfaces The polymerization is initiated and controlled by stepping or cycling the electrode potential between positive and negative values and it is more successful when the number of vinyl groups in the complexes is increased, as in 77 A series of new vinyl substituted terpyridinyl ligands have recently been synthesized whose iron, cobalt and ruthenium complexes 72 are also susceptible to electropolymerization... 

Electropolymerization of 4-Vinylpyridine Complexes. Investigations of Structural and Electronic Influences on Thin Film Formation. The recent discovery of the reductive polymerization of complexes containing vinylpyridyl ligands (lg), such as Ru -(bpy)2(vpy)22+ has led to the preparation of homogeneous thin layers of very stable electroactive polymers. This method has been extended to 4-vinyl-4 -methyl-2,2 -bipyridine (lg, 21a) and 4-vinyl-l,10-phenanthroline (21b) on both ruthenium and iron. In the following section we discuss our results on thin films derived from the polymerizable ligands BPE and the trans-4 -X-stilbazoles, (4 -X-stilb X - Cl, OMe, CN and H). 

Electropolymerization represents a useful method to control precisely the deposition of thin films of conducting polymers. These thin films have a wide variety of applications in optical devices [29]. Walder and coworkers showed that photocurrents could be generated using a trilayer thin film. The three different electropolymerized polymers were cleverly prepared from a common precursor, 4-methyl-4 -(2-pyrrolyl-1 -ethyl)-2,2 -bipyridine 7 two were alkylated, diquat derivatives and one was the Ru metal complex of this ligand, which acted as a sensitizer. The appropriate ordering of the triad in terms of their redox potentials led to the maximizing of the photocurrent (Scheme 7.2) [30],... 

The electropolymerization method of functional monomers has proved successful in many cases, in particular to incorporate various ligands and their metallic complexes, like salen [66,245], porphyrin [246], diphosphine [247], pyridine [71,80,248,249], crown ether [250,251], metallofullerene [252], tetraazacyclotetradecane [253], or Prussian blue type [254] in a conjugated organic material like PPy, PTh, or PANE Thick films are likely to be obtained provided that the polymer is redox active at the deposition potential due to this, Zotti et al. demonstrated that 5,5 -bis(3,4-(ethylenedioxy)thien-2-yl)-2,2 -bipyridine could be electropolymerized when complexed by iron and ruthenium, but not in the case of complexation by nickel or copper [71]. 

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