Azulene fluorescence quenching

Fluorescence Quenching. The fluorescence intensity (/f) of trans-stil-benes is reduced in the presence of additives such as ferrocene or azulene. For stilbene and several bromostilbenes Saltiel and co-workers studied the effect of fluorescence quenching by azulene [105,295], From linear Stern-Volmer plots (Eq. 10) values of Ks = rskq between 20 and 30 M1 have been obtained (Table 13). 

In several excellent surveys, Saltiel and co-workers have presented the advances in interpretation of the azulene effect [25, 26, 105, 194, 195]. The evaluation of results from comparative quenching measurements of fluorescence and cis trans photoisomerization under direct and sensitized excitation conditions confirms a singlet pathway for stilbene. For bromo-substituted stilbenes, however, participation of the triplet state has been... 

Irradiation of l-(l-naphthyl)-l,3-butadiynes in aqueous sulfuric acid yields both type A and type B photohydration products [75]. Fluorescence of starting material is quenched by sulliiric acid, and azulene quenching experiments showed that the singlet excited state yielded type A and type B photoadducts. 

We consider the system Azulen-Biacetyl. Scheme of figure A clearly shows that the S2 fluorescence of Azulen (tq = l.A ns) can be quenched by biacetyl and, by the same mechanism, the fluorescence of biacetyl (tq = 8.5 ns) can be quenched by azulen. Experiments have been carried out for different solvents with a range of viscosities (O.A to 8 cp). 

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