A new 3-hydroxychromone derivative, 2-(6-diethylaminobenzo[b]furan-2-yl)-3-hydroxychromone. has been synthesized by a concise route. Possessing dual emission common for 3-hydroxyflavones, it exhibits strong red shifts of both absorption and fluorescence spectra, which makes it the longest wavelength fluorescent dye among all known chromones. It also demonstrates a significant increase in fluorescence quantum yield in aprotic solvents and shift in solvent-polarity-dependent switch between normal and tautomer emissive forms. This derivative offers new possibilities in designing novel molecular sensors. (C) 2001 Elsevier Science Ltd. All rights reserved.