Synthesis of Near-Infrared Fluorescent Two-Photon-Absorbing Fluorenyl Benzothiadiazole and Benzoselenadiazole Derivatives.

A series of dyes - based on 5-thienyl-2,1,3-benzothiadiazole and 5-thienyl-2,1,3-benzoselenadiazole cores were synthesized as near-infrared-emitting two-photon-absorbing fluorophores. Fluorescence maxima wavelengths as long as 714 nm and quantum yields as high as 0.67 were realized.