An anomalous effect of the excitation energy on the fluorescence of azastilbenes

✍ Scribed by G. Bartocci; U. Mazzucato

• Publisher: Elsevier Science
• Year: 1977
• Tongue: English
• Weight: 412 KB
• Volume: 47
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(77)85036-7

✦ Synopsis

The fluorescence excitation spectra and fluorescence quantum yieIds of some azastifbenes as a function of the excitation wavelength hex are reported and compared to the behaviour of the corresponding hydrocarbon_ The compounds with the heteroatom in the meta position with respect to the ethylenic bridge display an anomalous behaviour in that their fhrorescence yield has a minimum value when hex is near 290 run. The anomaly, which disappears on protonation, is attributed to an hidden absorption to an upper exited singlet state whose decay path by-passes the fluorescent St state. A recent potential-energy model proposed for stilbene is modified to explain the wavelen$h dependence of the fluorescence yield as welI as some prehmmary results on tram + cis photoisomerization