Dd. Graf et Kr. Mann, ELECTROCHEMICAL INVESTIGATION OF RUTHENIUM AND OSMIUM OLIGOTHIOPHENE COMPLEXES - HOW DOES METAL-BINDING AFFECT OLIGOTHIOPHENE PI-SYSTEM, Inorganic chemistry, 36(2), 1997, pp. 150-157
We have studied the electrochemistry of a series of oligothiophene com
plexes with one or more ''CpRu+'' ''CpRu(+)'', or ''CpOs(+)'' fragmen
ts (Cp=cyclopentadienyl; Cp=pentamethylcyclopentadienyl) attached to
the oligothiophene pi-system. This series varies the metal (Ru or Os),
ancillary ligand (Cp or Cp), ring substituents (phenyl or methyl gro
ups), and length of the oligothiophene (1-4 rings). The peak potential
s for the oxidation of the free oligothiophenes and their complexes in
dicate that the electron hole produced upon oxidation of tile complexe
s is delocalized on the uncomplexed rings of the oligothiophene. Oxida
tion of the complexes results in conductive films-on the electrode but
the composition of the electrodeposited films is unclear. The electro
n added upon reduction of the complexes is localized on the [Cp/CpM(t
hiophene)](+) unit formed by complexation of the oligothiophene. We pr
opose that complexation of a thiophene ring converts it into a [Cp/Cp
M(thiophene)](+) unit and removes it from conjugation with the remaini
ng, uncomplexed rings. The unbound rings function as a shortened, meta
l-substituted oligothiophene unit. Complexation of oligothiophenes by
''CpRu+'', ''CpRu(+)'', and ''CpOs(+)'' fragments is a rational metho
d for controlling the properties of oligothiophenes.