Multi-thiophene-substituted NIR boron-dibenzopyrromethene dyes: synthesis and their spectral properties
2015
Suda, Yukie | Nishiyabu, Ryuhei | Kubo, Yuji
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 (ε), whereas the replacement of the phenyl rings with thiophene rings at the 3,3′-positions (3-2T) resulted in a significant decrease of the ε 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.
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