Near‐Infrared‐Absorbing α ‐Functionalized TCBD‐BODIPYs : Synthesis, Photophysical, and Electrochemical Properties

Boron‐dipyrromethene (BODIPY) dyes absorb in the visible region; however, expanding their optical absorption into the near‐infrared (NIR) window is beneficial for optoelectronic applications. Herein, we report a set of α ‐functionalized meso ‐anisyl BODIPYs, BDS1 – BDS4 , synthesized via Sonogashira cross‐coupling and [2 + 2] cycloaddition‐retroelectrocyclization reaction. The photophysical, electrochemical, and computational studies of the ethynyl‐bridged α ‐BODIPYs ( BDS1 and BDS3 ) and mono‐1,1,4,4‐tetracyanobutadiene (TCBD)‐incorporated α ‐BODIPYs ( BDS2 and BDS4 ) are investigated. The TCBD‐incorporated BODIPYs exhibit a broad absorption band between 620 and 1000 nm, with an absorption maximum above 700 nm. The TCBD‐BODIPYs ( BDS2 and BDS4 ) display about 40 nm red shift in absorption maxima compared to the ethynyl‐bridged BODIPYs ( BDS1 and BDS3 ). The electrochemical studies reveal that the TCBD unit in BDS2 and BDS4 significantly lowers the LUMO energy levels, leading to smaller energy gaps for BDS2 and BDS4 compared to their corresponding ethynyl‐bridged BODIPYs, BDS1 and BDS3 . The computational studies were performed to optimize the geometry and estimate the electrostatic potential of the α ‐BODIPYs. This study highlights the effect of an additional acceptor TCBD on the photophysical and electrochemical properties of α ‐functionalized BODIPYs, providing valuable insights for designing new NIR‐absorbing molecules for optoelectronic applications.