LAUSR

Abstract A series of styryl-carbazole derivatives (with and without a silicon atom) were investigated in n-hexane and in acetonitrile in terms of their spectroscopic and photophysical properties. The major question addressed in this work is how the presence of a trimethylsilyl group modifies the absorption and emission properties of styryl-carbazoles depending whether vinyl groups are in a meta- or para- position. It was observed that only para-styryl-carbazole containing silicon undergoes a solvent-induced inversion of its lowest singlet excited states whereas meta-styryl-carbazole containing silicon retains the properties of the meta-styryl-carbazole itself. The different character of the emissive state was deduced from its 7-fold larger radiative rate constant in acetonitrile compared to results in n-hexane. DFT calculations revealed on the molecular level why inversion of the excited states occurs only for this silicon-based styryl-carbazole whose vinyl group is in the para- and not in the meta- position.