One-Step Cascade Synthesis of ortho–bay-Imidazolo-Extended Perylene Biscarboximides (OBISIM) and Their Application as Broad-Spectrum Fluorescent Dyes

A one-step synthesis of perylene dyes with lateral extension by condensed imidazoles in a cascade reaction of sodium amide and benzonitrile is described in which multiple extensions can be controlled by the reaction conditions. The extensions lead to bathochromic shifts in absorption and fluorescence while maintaining high fluorescence quantum yields. The condensed imidazole units cause additional absorption bands in the hypsochromic visible region, resulting in broad-band absorbers. Multiple extensions of the aromatic system enable the NIR spectral approach of the spectra. Energy transfer (fluorescence resonance energy transfer, FRET) of dyads with perylene biscarboximides is very efficient and achieves quantum yields close to unity regardless of the lengths and orientation of the spacer. Applications as broad-band-absorbing fluorescent dyes, such as in solar collectors, are discussed.