The polymethine nature of Vis/NIR chromophores

Abstract

AbstractThe polymethine concept is known to rationalize a plethora of spectroscopic issues, thus finding wide applications in modern color theory. This approach was questioned by the arguments in the relevant “dye” literature. Based on the critical analysis of these arguments, the errors are clarified and the superiority of the polymethine concept above other attempts to qualitatively explain color and constitution relationships is exemplified at relevant dye molecules absorbing in the visible and near‐infrared spectral region. The classical chromophore theory, topological approaches, different‐level semiempirical techniques, and DFT/ab initio methods are comparatively analyzed to interpret the optical effects of structural modifications in conjugated compounds regarded as polymethine derivatives.