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 theo-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 >= 5) and fluoresces (Phi(f) >= 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 Forster Resonance Energy Transfer (FRET) particles for microscopy applications.