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[摘要]：Three new FPt1 [(2-(4', 6'-difluorophenyl) pyridinato-N, C2')(2,4-pentanedionato,O, O) Pt(II)] analogues, Ph-FPt, CzP-FPt, and mCzP-FPt, chelated with a 3-aryl-substituted acac ligand were synthesized. As shown by the results of X-ray diffraction, the nearest neighboring molecules in the FPt1, Ph-FPt, and CzP-FPt crystals have a Pt-Pt distance of similar to 4.5, 4.5, and 7.0 angstrom, respectively. In contrast, in the mCzP-FPt crystals, the nearest neighboring molecules exhibit a Pt-Pt distance of only 3.49 angstrom. All four Pt complexes show the same monomeric emission spectrum in dilute solution. However, in the crystalline state, mCzP-FPt with a clear Pt-Pt bimetallic interaction shows only the low-energy orange broadband emission; complexes FPt1, Ph-FPt, and CzP-FPt without significant Pt-Pt interaction (Pt-Pt distance >4 angstrom) give higher-energy emission closely resembling that of the monomeric species. The results provide clear evidence that the Pt-Pt bimetallic interaction is responsible for the low-energy broadband emission of these Pt complexes. Unlike in the crystalline state, all of the four platinum complexes in the thin film give only the low-energy broadband emissions with some difference in wavelength. In a similar manner, these platinum complexes-based, non-doped electroluminescence (EL) devices also emit only low-energy orange broadband light. The non-doped EL device using CzP-FPt as the emitter showed a very promising external quantum efficiency of 10%, nearly five times higher than that of the FPt1 control device. The higher EL efficiency of the CzP-FPt non-doped device is mainly ascribed to the lower concentration of Pt-Pt dimers that effectively suppresses the self-quenching between the orange emissive dimers. |
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