[Ir(C1^N1)(C2^N2)(O^O)]-tris-heteroleptic and [Ir(C1^N1)2(O^O)]-bis-heteroleptic Ir(III)-complexes with one or two color-responsible HC1^N1 ligands towards efficient color-purity near-infrared (NIR) phosphorescence

Abstract

Despite the great success of homo-/heteroleptic Ir(III)-complexes as visible-phosphors, the development of their efficient NIR-emissive (NIR = near infrared) counterparts, especially color-purity ones with full emission beyond 700 nm, is highly challenging. In the paper, a robust [Ir(C¹^N¹)(C²^N²)(O^O)]-tris-heteroleptic molecular design strategy to [Ir(dpbq)(ppy)(acac)] (2) with single color-responsible Hdpbq ligand, is founded for desirable color-purity NIR-emission (λ_em^Max = ca. 786 nm). Importantly, owing to the augmented ³MLCT while less ³ILCT contributions to their comparable T₁ excited state, the larger quantum efficiency (Φ_PL = 4.9 %) of the [Ir(dpbq)(ppy)(acac)] (2) than that (3.9 %) of its [Ir(C¹^N¹)₂(O^O)]-bis-heteroleptic counterpart [Ir(dpbq)₂(acac)] (1) is observed. Therefore, the molecular design strategy to [Ir(C¹^N¹)(C²^N²)(O^O)]-tris-heteroleptic Ir(III)-complexes with one color-responsible HC¹^N¹ ligand, should pave one way to develop efficient and color-purity NIR-emitters.