Occurrence of radical cation localization in chemically modified poly(methylphenylsilane): Poly(methylphenyl-co-4-dimethylaminophenylmethylsilane)s and poly (methylphenyl-co-4-bromophenylmethylsilane)s
Tj. Cleij et al., Occurrence of radical cation localization in chemically modified poly(methylphenylsilane): Poly(methylphenyl-co-4-dimethylaminophenylmethylsilane)s and poly (methylphenyl-co-4-bromophenylmethylsilane)s, CHEM MATER, 12(1), 2000, pp. 84-89
Chemical modification of poly(methylphenylsilane) 1 using triflate chemistr
y gave two series of random copolymers with different composition ratios, v
iz., poly(methylphenyl-co-4-dimethylaminophenylmethylsilane)s 3-7 and poly(
methylphenyl-co-4-bromophenylmethylsilane)s 8-9. The optical and electronic
properties of the copolymers have been studied and are compared with those
of the homopolymers 1 and poly(4-dimethylaminophenyl-methylsilane) 2. Elec
trochemical measurements in THF/LiClO4 give strong evidence that, in marked
contrast to the results observed for 1 and 2, the onset of oxidation (V-i)
of 3-7 and 8-9, respectively, does not represent the silicon backbone vale
nce band. Instead, in these copolymers, a mixture of decoupled electronic d
omains exists of which those possessing the lowest V-i govern the electroch
emical response. As a consequence, the radical cations become confined, i.e
. localization occurs. This interpretation is further supported by fluoresc
ence emission spectroscopy, the presence of a confined exciton is indicated
by the appearance of an additional broad band for the copolymers. Remarkab
ly, copolymers with optical and electronic properties comparable to those o
f 3-7 are also accessible by (reversible) protonation of the 4-dimethylamin
o substituents of 2.