Asymmetric anthracene-fused BODIPY dye with large Stokes shift: Synthesis, photophysical properties and bioimaging

• Asymmetric anthracene-fused BODIPY exhibits significant bathochromic shifts.
• The BODIPY dye exhibits an enlarged Stokes shift of 1425 cm−1 in CHCl3.
• The BODIPY dye can be used to image living cells.

A new asymmetric fluorescent dye of the 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) class was prepared by fusing an anthracene unit to the “zig-zag” edge of the BODIPY core by an FeCl3-mediated oxidative cyclodehydrogenation reaction and the photophysical properties of the new BODIPY analogue were investigated. The anthracene-fused BODIPY exhibits significant bathochromic shifts in both absorption and fluorescence maxima compared with a related non-fused BODIPY. In addition, the anthracene-fused BODIPY exhibited a small energy gap (1.81 eV), large Stokes shift and high photostability. Especially, the emission of the dye extended into the deep red (∼640 nm) region. The extensive π conjugation is responsible for the red-shifted emission. Moreover, the dye emits strong saturated, red fluorescence with a quantum yield of 40% and an enlarged Stokes shift of 1425 cm−1 (53 nm) in CHCl3, which can be used to image living cells by fluorescence microscopy. Cell imaging experiments demonstrated its potential application as a probe in bioorganisms due to its excellent imaging contrast.