title: Intramolecular charge transfer photoemission of a silicon-based copolymer containing carbazole and divinylbenzene chromophores. Electron transfer across silicon bridges.
abstract: A new copolymer consisting of N-isopropylcarbazole/dimethylsilylene bridge/divinylbenzene units was synthesized and characterized. Dual fluorescence was observed in this copolymer in polar solvents. The absence of the second band at the lower transition energy of the two emission maxima in nonpolar solvents and the quantitative correlation of the lower-energy emission band maxima with solvent polarity indicate that the lower-energy emission band arises from an intramolecular charge transfer (ICT) state. A series of model compounds was synthesized to investigate the source of the charge transfer. It was found that the Si-bridged dyad with a single N-isopropylcarbazole and a single divinylbenzene was the minimum structure necessary to observe dual luminescence. The lack of dual luminescence in low-temperature glasses indicates that the ICT requires a conformation change in the copolymer. Analogous behavior in the Si-bridged dyad suggests that the ICT in the copolymer is across the silicon bridge. Results from time-resolved luminescence measurements with picosecond and subnanosecond excitation were used to support the thesis that twisted charge-transfer states are the likely source of the observed dual luminescence.
authors.affiliation: Center of Advanced Technologies, Adam Mickiewicz University , Grunwaldzka 6, 60-780 Poznan, Poland.
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Bayda
authors.forename: Monika
authors.initials: M
authors.lastname: Ludwiczak
authors.forename: Gordon L
authors.initials: GL
authors.lastname: Hug
authors.forename: Mariusz
authors.initials: M
authors.lastname: Majchrzak
authors.forename: Bogdan
authors.initials: B
authors.lastname: Marciniec
authors.forename: Bronislaw
authors.initials: B
authors.lastname: Marciniak