Synthesis, characterization and color-purity near-infrared (NIR; λem = 780 nm) phosphorescence of one C1-symmetric [Ir(C^N)2(N^O)]-bis-heteroleptic Ir(III)-complex

Abstract

In sharp contrast to the success of Ir(III)-complex-based visible-phosphors, the molecular design of their efficient NIR-emissive counter-parts, as constrained by the so-called “energy gap law”, is distinctively difficult. Especially, it remains a great challenge to develop new Ir(III)-complex-based phosphors with both efficient and color-purity NIR-emission. Herein, based on the molecular design of [Ir(dpbq)2(L)], the highly conjugated HC^N-main ligand Hdpbq renders the desirable color-purity NIR-phosphorescence (λPL = 780 nm), and the electron-rich while N^OH-ancillary HL is beneficial to augmented 3MLCT effect and large transition dipole moment (TDM). Accordingly, its color-purity NIR-phosphorescent efficiency (ΦPL = 3.9 %) is significantly higher than those (ΦPL = 1.9–2.5 %) of the [Ir(dpbq)2(O^O)]-analogue.