Synthesis of fully-fused bisboron azomethine complexes and their conjugated polymers with solid-state near-infrared emission.

We describe herein a robust π-conjugated molecules with solid-state emission in the near-infrared (NIR) region (ΦF = 0.03-0.06). Initially, the diastereomers of bisboron azomethine complexes having phenyl groups in the same and opposite directions to the π-plane were synthesized. These diastereomers showed emission properties with larger red-shifts (>200 nm) and 10 times larger emission efficiencies than those of the mononuclear complex. Theoretical calculation data indicate that superior optical properties of the bisboron complexes should be attributable to efficient expansion of the π-conjugated system. In addition, the bisboron compounds and their conjugated polymers exhibited intense NIR emissions even in the solid state.