Fluorescence of harmol, harmalol and 2-hydroxycarbazole in concentrated hydroxide solutions.

Room temperature electronic absorption and fluorescence spectra of harmol, harmalol and 2-hydroxycarbazole have been obtained in concentrated aqueous potassium hydroxide solutions. The appearance of a new fluorescence band for all these compounds in media of H- greater than 16, has been ascribed to the emission of excited dianions formed by deprotonation. Acidity constants have been estimated from the Föster-Weller method.