Modulation of Supramolecular Interaction of Pt(II) Complexes Bearing Carbene Cyclometalate for Color-Tunable Luminescence

Pt(II) complexes are known for their versatility in showing aggregation-induced emission. Herein, we report four Pt(II) complexes <b>Pt-1</b>, <b>Pt-2</b>, and <b>Pt-3a/b</b> featuring both the carbene cyclometalate (C^C) and chelating pyrazolate (N^N). We evaluated two synthetic methods: the first employed the carbene intermediate <b>Pt-DMSO</b>, followed by N^N coordination to give <b>Pt-1-Cl</b> and aryl cyclometalation, while the second involved sequential addition of C^C and N^N chelates to Pt(COD)Cl₂. These Pt(II) complexes exhibited efficient sky-blue emission in a PMMA matrix at high dilution. Upon increasing the doping ratio, emission of <b>Pt-1</b> and <b>Pt-3a</b> remained essentially unchanged, but <b>Pt-2</b> and <b>Pt-3b</b> exhibited gradual emergence of a low-energy band at ∼575 nm, which was attributed to the metal-metal-to-ligand charge transfer emission band. These aggregation propensities aligned well with the time-dependent density functional theory calculations based on the dimers and trimers. For applications, the organic light-emitting diode devices based on <b>Pt-1</b> exhibited blue emission with a max. external quantum efficiency (EQE) of 11.7% at 50 wt %, while <b>Pt-2</b>-based devices gave concentration-dependent emission with max. EQEs of 9.4, 11.3, and 7.1% and CIE_<i>xy</i> coordinates of (0.26, 0.45), (0.33, 0.47), and (0.45, 0.49) at 10, 50, and 100 wt %, respectively.