Blue phosphorescent platinum(IV) complex bearing bipyridine ligand for potential application in organic light-emitting diodes (OLEDs)

Abstract

A cyclometalated Pt(IV) compound, Pt(dfpypy)2(Me)Cl (1), with blue phosphorescence was prepared using 2′,6′-difluoro-2,3′-bipyridine (dfpypy) as a C^N chelate ligand. Compound 1 exhibits distorted octahedral geometries around the platinum ion and has strong intermolecular interactions via interatomic contacts (H···N/F/Cl) involving hydrogen bond interactions based on Hirshfeld surface analysis. This compound shows bright blue phosphorescence emissions with λmax = 427 and 455 nm and a high photoluminescence quantum efficiency (ΦPL = 0.60). Furthermore, a good blue colour purity with Commission Internationale de L'Eclairage (1931) coordinates ( x, y) of (0.14, 0.17) was observed in the thin film, which was close to pure blue. TD-DFT calculations revealed that the electronic transition can be attributed to a combination of intraligand charge transfer (πbpy–π*bpy) and ligand-to-ligand charge transfer [pz(Cl)–π*(dfpypy)] with a small contribution from metal-to-ligand charge transfer (Ptd−π*bpy). Owing to the introduction of the electronegative C^N chelate dfpypy, the emission of compound 1 was blueshifted by 20 nm compared with its analog [Pt(ppy)2(Me)Cl] ( λmax = 447), where ppy is 2-phenylpyridine.