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Bright Blue and White Electrophosphorescent Triarylboryl-Functionalized C^N-Chelate Pt(II) Compounds: Impact of Intramolecular Hydrogen Bonds and Ancillary Ligands



New blue and blue-green phosphorescent C^N chelate Pt(II) compounds that contain a dimesitylboryl-functionalized phenyl-1,2,3-triazole ligand (Bptrz) are synthesized. The influence of three different ancillary ligands, namely acetylacetonato (acac), picolinate (pic) and pyridyl-1,2,4-triazolyl (pytrz), on phosphorescence quantum efficiency and excimer emission is examined. Pt(II) compounds with a p-Bptrz ligand consistently emit a blue-green color with an emission wavelength = 490–500 nm while those with a m-Bptrz ligand emit a blue color with λem = 450–460 nm and a quantum efficiency as high as 0.97. In addition to the blue monomer emission peak, Pt(m-Bptrz)(pytrz) compounds display an excimer emission peak at ∼550 nm in a solid matrix whose intensity is dependent on the substituent group on pytrz and the doping concentration. As a result of the monomer and excimer emission, bright white phosphorescence is observed for several members of Pt(m-Bptrz)(pytrz) compounds. Intramolecular CH···N hydrogen bonds are found to play an important role in the high stability and high phosphorescent quantum efficiency of Pt(m-Bptrz)(pytrz) compounds. Single-dopant blue and white electrophosphorescent devices using Pt(m-Bptrz)(CF3-pytrz-Me) or Pt(m-Bptrz)(t-Bu-pytrz-Me) as the emitter are successfully fabricated. White electroluminesence devices with external quantum efficiency of 15.6% and CIE (xy) of 0.31, 0.44 are achieved.