Spectroscopy and photophysics of 4- and 7-hydroxycoumarins and their thione ana...

• Author(s): Seixas de Melo, J. ; Fernandes, P. F.
• Date: 2001
• Persistent ID: http://hdl.handle.net/10316/5212
• Origin: Estudo Geral - Universidade de Coimbra
• Subject(s): Coumarins; Photophysics; Singlet state; Triplet state; Fluorescence; Phosphorescence
• Document Type: Article
• Language: English

Description

Acid-base equilibria were studied for 4-hydroxycoumarin, 7-hydroxy-4-methylcoumarin and their thione derivatives in different media for their ground and lowest energy singlet and triplet excited states. The ethoxylated and/or methoxylated derivatives were also investigated. Characterization involves fluorescence spectra, quantum yields, lifetimes, phosphorescence spectra, lifetimes, and triplet-triplet absorption spectra. From their pKa values it was found that 4 and 7-hydroxycoumarins are more acidic in their lowest excited singlet states than in S0. The origin and character of the lowest singlet and triplet excited states is discussed. http://www.sciencedirect.com/science/article/B6TGS-433W90H-D/1/f761cc9ee9d9ef35b30fc14090ada58c