Occurrence of radical cation localization in chemically modified poly(methylphenylsilane): Poly(methylphenyl-co-4-dimethylaminophenylmethylsilane)s and poly (methylphenyl-co-4-bromophenylmethylsilane)s

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.