Photostable NIR-II Pigments from Extended Rylenecarboximides

A series of near-infrared (NIR) organic absorbers, named FNs and FPs, have been obtained with absorption maxima from 870 nm to 1100 nm and thus falling into the attractive second near-infrared region (NIR-II). The synthesis of their extended aromatic cores utilized an initial aryl-amination between 4-aminonaphthalene-1,8-dicarboximide (NMI-NH2) or 9-aminoperylene-3,4-dicarboximide (PMI-NH2) with chloro-substituted 9,10-anthraquinones followed by a novel base-induced cyclodehydrogenation. A NIR-II pigment, compound FPP, was obtained through de-alkylation of a soluble precursor. The synthesis of this photostable pigment is high-yielding and avoids column chromatographic purification which is important for many applications.