Pyrazolate-Bridged NHC Cyclometalated [Pt] Complexes and [PtAg(PPh)] Clusters in Electroluminescent Devices.

The ionic transition metal complexes (iTMCs) [{Pt(CC*)(μ-Rpz)}Ag(PPh)]X (HCC* = 1-(4-(ethoxycarbonyl)phenyl)-3-methyl-1-imidazole-2-ylidene, X = ClO/PF Rpz = pz , 4-Mepz , and 3,5-dppz ) were prepared from the neutral [{Pt(CC*)(μ-Rpz)}] (Rpz = pz , 4-Mepz , and 3,5-dppz ) and fully characterized. The "Ag(PPh)" fragment is in between the two square-planar platinum units in an "open book" disposition and bonded through two Pt-Ag donor-acceptor bonds, as shown by X-ray diffraction (d ∼ 2.78 Å, -). Pt{H} and P{H} NMR confirmed that these solid-state structures remain in solution. Photoluminescence studies and theoretical calculations on , were performed. The diphenylpyrazolate derivatives show the highest photoluminescence quantum yield (PLQY) in the solid state. Therefore, and its neutral precursor were selected as active materials on light-emitting devices. OLEDs fabricated with showed a turn-on voltage of 3.2 V, a luminance peak of 21,357 cd m at 13 V, and a peak current efficiency of 28.8 cd A (9.5% EQE). They showed a lifetime t of 15.7 h. OLEDs using showed a maximum luminance of 114 cd m, while LECs exhibited a maximum luminance of 20 cd m and a current efficiency of around 0.2 cd A, with a t value of 50 min.