Photophysical properties of fluorescent pyrido[2,1-i]purines

Abstract

7-Oxo-3-(tetrahydropyranyl-2-yl)-7H-pyrido[2,1-i]purines (1) are highly fluorescent molecules with absorption and emission in the visible region. Quantum yields range from 0.33 to 0.64, while fluorescence lifetimes are rather short (2–6 ns). An increase in solvent polarity shifts absorption to shorter and emission to longer wavelengths. From this a change in dipole moment of 5.5 D could be estimated between ground and excited states of (1b). Fluorescence is quenched by tertiary amines via electron transfer. Hydrolysis of the protecting tetrahydropyranyl function results in a pyridopurine with somewhat different properties.