Substituted stilbenes fluorescence quantum yield

The electronic spectroscopy of trans-isomers of 3-(N-phenylamino)stilbene (mlc), 3-(N-methyl-N-phenylamino)stilbene (mid), 3-(N,N-diphenylamino)stilbene (mle), and 3-(N-(2,6-dimethylphenyl)amino)stilbene (mlf) and their double-bond constrained analogues, m2a-m2c and m2e, were studied [71]. When compared with trans-3-aminostilbene (mla), mlc-mle displayed a redshift of the So —> Si absorption and fluorescence spectra, lower oscillator strength and fluorescence rate constants, and more effldent Si —> Ti intersystem crossing. The N-Ph derivatives mlc-mle had lower fluorescence quantum yields and higher photoisomerization quantum yields. The role of Si —> Ti transition in the amino-substituted stilbenes as the predominant nonradiative decay pathway was discussed. The excited triplet (Ti) state formation of stilbene dendrimers (tetramethoxystilbene (generation G) GO, Gl,... 

The effect of temperature on the quantum yields of isomerization and fluorescence was determined for frons-stilbene and for certain halogen-substituted frans-stilbenes (Dyck and McClure, 1962 Malkin and Fischer, 1962). It was found that as the temperature is decreased (below about 200°K) the trans cis quantum yield decreases but that the fluorescence quantum yield increases. These results suggest that an activated process (i.e., internal conversion or intersystem crossing) competes with fluorescence from S - and that this process is an essential step in the mechanism for isomerization. The results for intersystem crossing into T. ... 

The fluorescence of Irons-stilbene and four methoxy-substituted stUbene derivatives has been detected in a variety of solvents [37]. Compared to other stUbene derivatives, trons-3,5-dimethoxystilbene displayed a large quantum yield of fluorescence and a low quantum yield of trans-cis isomerization in polar organic solvents. 

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