Three isomeric 7-(pyridyl)indoles reveal very different, solvent-dependent photophysical properties. Due to rapid excited state depopulation involving intramolecular hydrogen bonding, 7-(2'-pyridyl)indole is practically nonfluorescent at room temperature. In nonpolar and polar aprotic solvents, 7-(3-pyridyl)indole and 7-(4'-pyridyl)indole fluorescence strongly, but the emission is quenched in alcohols. Syn and anti rotameric forms of 7-(3'-pyridyl)indole are detected, each quenched to a different degree. This differential quenching is interpreted as evidence of enhanced S-1 --> S-0 internal conversion being more efficient in cyclic solvates, with alcohol molecules forming a bridge between the proton donor and acceptor groups of an excited chromophore. (C) 2004 Elsevier B.V. All rights reserved.