Achieving near-infrared electroluminescence around 780 nm based on butterfly-shaped dinuclear platinum(ii) complexes

Abstract

Organic near-infrared (NIR) phosphorescent materials, especially platinum complexes, still attract the attention of researchers due to their excellent performance. However, most of high-efficiency mononuclear cyclometalated platinum complexes in NIR-OLEDs were...

Pyrazolate-Bridged NHC Cyclometalated [Pt2] Complexes and [Pt2Ag(PPh3)]+ Clusters in Electroluminescent Devices

“…To a lesser extent, dinuclear Pt­(II) complexes [Pt 2 ] have also been used in the fabrication of PhOLEDs. − In these cases, the bridging ligands also play an important role in controlling the Pt···Pt interaction and the nature of the excited states. Most of these complexes comprise two “Pt­(β-diketonate)” units bridged by a tetradentate ligand, which prevents intramolecular Pt···Pt interactions. ,− Among them, those in which the tetradentate ligand is doubly C ∧ N-cyclometalated are the most prevalent, ,− reaching external quantum efficiencies (EQEs) above 20%, only in a few cases. ,, Nevertheless, dinuclear complexes with a half-lantern (double decker) structure and short Pt···Pt distances have also been incorporated in PhOLEDs, obtaining EQE from 0.14 to 26.4% in the deep-red or NIR region. − Another family comprises complexes with pyrazolate bridging ligands of general formula [{Pt­(C ∧ E)­(μ-Rpz)} 2 ] (C ∧ E = 2-(4′,6′-difluorophenyl)­pyridinato-N,C 2’ ; Rpz = pyrazolate, 3-methyl-5- tert -butylpyrazolate, and 3,5-bis­( tert -butyl)­pyrazolate; C ∧ E = 2-(pyren-1-yl) pyridine, 2-(7-( tert -butyl)­pyren-1-yl)­pyridine, Rpz = 3,5-dimethylpyrazolate, and C ∧ E = Phenyl-NHC). In the former, the smaller the bulkiness of the pyrazolate, the greater the intramolecular Pt···Pt distance and the emission energy .…”