Acid–base and spectral properties of β-carbolines. Part 2. Dehydro and fully aromatic β-carbolines
Authors:
- Manuel BalónMBManuel Balón
- José HidalgoJHJosé Hidalgo
- Pilar GuardadoPGPilar Guardado
- María A. MuñozMMMaría A. Muñoz
- Carmen CarmonaCCCarmen Carmona
- 1 January 1993
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 1,p. 99-104
Abstract
The absorption and fluorescence spectra of a set of dehydro and fully aromatic β-carboline (9H-pyrido[3,4-b]indole) derivatives have been investigated in aqueous solutions of varying acidity. Within the pH-range, cationic (nitrogen protonation) and neutral species are evidenced from both absorption and fluorescence spectra. Additional zwitterionic species can also be detected from the fluorescence spectra. In highly basic media, outside the pH-range, anionic species (pyrrolic nitrogen deprotonation) are formed. Ground state ionization constants for the different acid–base equilibria involving these species have been determined spectrophotometrically at 25 °C. Lowest excited singlet state pKas have been estimated from the Förster–Weller cycle. The influence of structural variations on the spectra and on the acid–base properties of these compounds is discussed.Keywords
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