Computational design of quadrupolar donor-acceptor-donor molecules with near-infrared light-harvesting capabilities

The electronic and optical properties of a large series of symmetrical D–π–A–π–D chromophores are investigated. Vertical transition energies and related wavelengths, as well as absorption strengths, are computed by means of density functional theory and analyzed in the light of structural and electronic parameters such as torsional angles, bond length alternation, ground-state charge transfer and photo-induced charge displacement. This computational design allows establishing structure-property relationships linking the chemical structure of the chromophores to their absorption capability in the near-infrared (NIR) region, providing comparative guidelines for eventual syntheses.