Non-radiative deactivation via biradicaloid charge-transfer states in oxazine and thiazine dyes

✍ Scribed by Martin Vogel; Wolfgang Rettig; U. Fiedeldei; H. Baumgärtel

• Book ID: 103023603
• Publisher: Elsevier Science
• Year: 1988
• Tongue: English
• Weight: 446 KB
• Volume: 148
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(88)87286-5

✦ Synopsis

Oxazine and thiazine dyes with dialkylamino (NR2) substituents exhibit a temperature/viscosity-dependent intramolecular fluorescence quenching which is absent if the substituents are NH2 and is especially fast for piperidino substituent groups. These results suggest that the driving force for this process is intramolecular donor-acceptor interaction (formation of a biradicaloid charge-transfer (BCT) state) which involves amino group twisting. Low-temperature studies reveal fluorescence risetimes and suggest there is an additional much faster relaxation process preceding BCT-state formation.