Dipyrrolonaphthyridinedione - (still) a mysterious cross-conjugated chromophore

Dipyrrolonaphthyridinediones (DPNDs) entered the chemical world in 2016. This cross-conjugated donor-acceptor skeleton can be prepared in two steps from commercially available reagents in overall yield approximate to 15-20% (5 mmol scale). DPNDs can be easily and regioselectively halogenated which opens an avenue to numerous derivatives as well as to pi-expansion. Although certain synthetic limitations exist, the current derivatization possibilities provided impetus for numerous explorations that use DPNDs. Structural modifications enable bathochromic shift of the emission to deep-red region and reaching the optical brightness 30 000 M-1 cm-1. Intense absorption and strong emission of greenish-yellow light attracted the interest which eventually led to the discovery of their strong two-photon absorption, singlet fission in the crystalline phase and triplet sensitization. Dipyrrolonaphthyridinedione-based twistacenes broadened our knowledge on the influence of twisting angle on the fate of the molecule in the excited state. Collectively, these findings highlight the compatibility of DPNDs with various applications within organic optoelectronics. We present and discuss the discovery, structures, photophysics, and applications of novel functional dyes - dipyrrolonaphthyridinediones.

Automated summary

Dipyrrolonaphthyridinediones (DPNDs) are a novel class of functional dyes with high potential in organic optoelectronics. They can be easily synthesized in high yield and have shown the ability for structural modifications to achieve enhanced optical brightness and tunable emission wavelength. Their unique behavior in the excited state has also been explored, making them useful for various applications.