β-β-alkynyl-bridged BODIPY dimers: synthesis, one- and two-photon photophysical properties

Six β-β-linked BODIPY dimers with different EDG-EDG and EDG-EWG were synthesized by changing the nature of the EDG and EWG at the meso position. The fluorescence lifetimes and quantum yield of z4 and z5 with the same substituent groups at the two meso positions are much higher than those of the BODIPY dimers with two different substituents. Compound z4 exhibits the highest fluorescence quantum yield (11.24%) and fluorescence lifetime (1.32 ns). Both compounds z4 and z5 show important two-photon induced fluorescence in the 800-1000 nm region with a clear quadratic dependency of the emission intensity vs the laser excitation power.