Multi-thiophene-substituted NIR boron-dibenzopyrromethene dyes: synthesis and their spectral properties

摘要

Thiophene-substituted boron-dibenzopyrromethene dyes has been synthesized and characterized. We found that the optical properties of dithienyl-substituted dibenzo-BODIPYs depend on the substituted pattern. Namely, thiophene substitutions at the 5,5'-positions of the isoindole rings (5-2T) led to a bathochromic shift of 37 nm and an increase in the molar extinction coefficient (epsilon), whereas the replacement of the phenyl rings with thiophene rings at the 3,3'-positions (3-2T) resulted in a significant decrease of the e value, despite a large bathochromic shift of 65 nm. The emission properties were also characterized; the replacement of phenyl units with thiophene units at the 3,3'-positions led to a larger Stokes shift than that of thiphene-free dibenzo-BODIPY 0T, which was rationalized to occur through geometry relaxation upon photoexcitation. Newly synthesized dendritic oligothiophene dibenzo-BODIPY conjugates have emitted near-infrared light at 766 nm when excited with UV light, through fluorescence resonance energy transfer (FRET) from the thiophene dendron unit to the dibenzo-BODIPY core. (C) 2015 Elsevier Ltd. All rights reserved.