NIR-I Fluorescent Probes Based on Distyryl-BODIPYs with Two-Photon Excitation in NIR-II Window

Fluorescent dyes which exhibit emission/excitation in the second near-infrared (NIR-II, 1000-1350 nm) region are currently attracting significant attention in bioimaging and diagnostics applications. Furthermore, dyes with high two-photon absorption cross-section (TPA), such as BODIPY derivatives, are of a particular interest due to deeper signal penetration into biological tissues, better image contrast, reduced phototoxicity and photobleaching. Herein we report the synthesis and properties of new monomeric and dimeric di-styryl-BODIPY dyes, which have absorption maxima near 625 nm and emission in the range of 600-800 nm (NIR-I, 650-950 nm). For the first time, we used a femtosecond Cr:Forsterite laser with a wavelength of 1250 nm (NIR-II) for the excitation of NIR-I di-styryl-BODIPY dyes by TPA. A cooperative effect was observed for TPA for the dimeric di-styryl-BODIPY dyes. The results obtained may be of great interest due to their potential applications in bioimaging and photodynamic therapy.