Molecular design and theoretical investigation on novel (D)2-π-a photosensitizers based on coumarin dye: Impact of boron dipyrromethene bridge on UV–vis and optoelectronic properties

In this study, eight new photosensitizers based on the (D)₂-π-A molecular architecture were theoretically designed using two, 7-diethylaminocoumarin dyes as the donor and cyanoacrylic acid or (Z)-2-Cyano-3-phenylacrylic acid as the acceptor unit. Boron dipyrromethene (BODIPY) functionalized with various heterocycles was used as an π-bridge. We aim to enhance the light-harvesting efficiency of dyes derived from the coumarin molecule in the red and near-infrared regions of the solar spectrum. Theoretically, investigation using density functional theory (DFT) and time-dependent DFT (TD-DFT) show that all the dyes designed exhibit intense and broad absorption in the visible and near-infrared range, denoting panchromatic absorption. The maximum absorption wavelength values for all designed dyes found in acetonitrile (648 to 757 nm) with maximum molar extinction coefficients between 76,815 to 106,445 M⁻¹.cm⁻¹ are remarkably higher than those obtained for other dyes based on a single coumarin donor reported in the literature.