Novel 1,5-naphthyridine-chromophores with D-A-D architecture: Synthesis, synthesis, luminescence and electrochemical properties

A series of symmetrical 1,5-naphthyridine compounds with donor-acceptor-donor (D-A-D) architecture and different chromophores were synthesized and characterized. Their thermal, optical and electrochemical properties were investigated systematically. These compounds show robust thermal property with high phase transition temperatures (above 247 °C). In addition, all these compounds exhibit intense absorption bands in UV and visible region, which arise from the intramolecular charge transfer (ICT) transition between the donor and acceptor segments. The electron-donating chromophores on the central naphthyridine cause significant bathochromic shifts of the low energy ICT absorption bands. Meanwhile, all compounds are emissive in solution at room temperature (λ_em = 450–520 nm). When the electron-donating ability of the attached chromophores increases, the fluorescent quantum yields of these compounds increase. The calculated ground-state geometries further demonstrate the ICT transition for these molecules from HOMO to LUMO. Their luminescent and electrochemical properties could be used for understanding the structure-property relationship of naphthyridine compounds and developing optical functional materials.