Einfluß von Substituenten und polaren Lösungsmitteln auf die Deaktivierung des S1Zustandes bei Donator-Akzeptor-substituierten trans-Stilbenen/Influence of Substituents and Polar Solvents on the Deactivation of the First Excited Singlet of Donor-acceptor Substituted Trans-stilbenes

Abstract

Abstract The effect of substituents on the fluorescence quantum yield φf of trans-stilbenes (1) in dimethylformamide, acetonitrile, and n-propanol, as well as in n-heptane, is mainly due to radiationless deactivation. Contrary to n-heptane, the rate kd of radiationless deactivation in the above mentioned polar solvents for compounds 1 of similar structure is not a monotoneous function of the polarity of the first excited singlet state. The maximum of kd corresponds to compounds with medium polarity (1h, 1i). The effect of substituents on the fluorescence rate kf n in polar and nonpolar solvents is small compared to that on kd. In all solvents kf n drops with increasing polarity of the first excited singlet state.