Phenanthrene-fused boron-dipyrromethenes as bright long-wavelength fluorophores.

A new class of boron-dipyrromethene (BDP or BODIPY) dyes was obtained by phenanthrene fusion to the beta-pyrrole positions, absorbing in the wavelength range of important laser sources. Despite a 'propeller-like' distorted structure in the crystalline state, the chromophore absorbs (log epsilon > or = 5) and fluoresces (Phif > or = 0.8) strongly and can be easily turned into a fluorescence light-up probe. Incorporation into latex beads produces bright and photostable single-dye and Förster Resonance Energy Transfer (FRET) particles for microscopy applications.