Thin
fil
ms o
f tetrahexylsexithiophenes,
fluorenonyl- and
fluorenyl-protected at the ter
minal
mages/gi
fchars/alpha.gi
f" BORDER=0>,
mages/gi
fchars/o
mega.gi
f" BORDER=0 >-positions, were investigated by cyclic volta
mmetry, electroche
mical quartz crystal
microbalance analysis,in situ ESR, and in situ conductivity. Reversible oxidation is co
mposed o
f three separate steps, twoone-electron processes and a
further
multielectron process. ESR indicates strong
magnetic di
merization
for the one-electron-oxidized species. Conductivity is redox type at the cation-dication (polaron-bipolaron) state and
metal-like at doping levels higher than the bipolaron with a 20-
fold increase at
fulloxidation. Hexyl-substituted
mages/gi
fchars/alpha.gi
f" BORDER=0>,
mages/gi
fchars/o
mega.gi
f" BORDER=0 >-capped octathiophene, decathiophene, and dodecathiophene
fil
ms havebeen si
milarly investigated to co
mpare the e
ffects o
f fluorenonyl and
fluorenyl extension o
f sexithiophenewith those given by additional thiophene rings. The conductivity, which increases progressively (by 3orders o
f magnitude) with the oligothiophene chain length, is
metal-like. In dodecathiophene the dopingcharge increases
markedly, approaching
four electrons per
molecule, and the conductivity,
maxi
mized atthe two-electron level, decreases linearly, approaching zero at the
four-electron level. A bipolaron
modelo
f conductivity accounts
for conductivity in oligothiophenes.