Flavylium Fluorophores as Near‐Infrared Emitters

This theoretical work rationalizes the absorption and fluorescence emission properties of conjugated dyes composed of dimethylamino flavylium heterocycles linked by a polymethine chain, which were recently reported to act as efficient shortwave infrared emitters. Density functional theory is used to characterize the electronic structure of the low‐lying excited states as a function of the polymethine chain length. Decomposition of the computed excitations in terms of diabatic states is also performed to deconvolute the excited states wavefunction into charge‐transfer intramolecular excitations. Based on these results, chemical substitution patterns consisting in enhancing the electron‐withdrawing strength of the polymethine bridge and the electron‐donating ability of the lateral flavylium fragments, are proposed to further redshift the photoluminescence of the fluorophores.