Near-infrared absorbing(>700 nm)aza-BODIPYs by freezing the rotation of the aryl groups

The typical aza-BODIPYs in the dye family are known for bright fluorescence,excellent stability,and tunable absorption wavelengths.Hence,these dyes are attracting the increasing attention.Aza-BODIPYs having the maxima absorption in the near-infrared(NIR)region(650-900 nm)are very favorable for bioimaging in vivo due to the less photo-damage,deeper tissue penetration,and less interference from background auto-fluorescence by biomolecules in the living systems.Many strategies have been employed to modify the structures of the aza-BODIPY core to provide the NIR absorbing dyes.Among these,the most effective method is the fusion of the aromatic rings in aza-BODIPY system.This review allsidedly summarizes the recent development of ring-fused aza-BODIPY dyes(λ_(abs)>700 nm)focusing on the design,synthesis,and potential applications in the NIR region since 2002.