A Phosphorescent CΛC* Cyclometalated Platinum(II) Dibenzothiophene NHC Complex

Cyclometalated platinum(II) complexes with beta-diketone ligands have recently attracted increasing interest as phosphorescent emitters for organic light-emitting devices (OLEDs). We present the synthesis of the new cyclometalated Pt(II) N-heterocyclic carbene complex [(NHC)Pt-II(acac)] (acac = acetylacetonate, NHC = 1-(dibenzo[b,d]thiophen-4-yl)-3-methyl-1H-imidazoyl). The complex was fully characterized by advanced spectroscopic methods (2D NMR, Pt NMR), elemental analysis, and solid-state structure determination, which revealed a square planar coordination of the platinum atom. The photoluminescence properties were investigated in amorphous poly (methyl methacrylate) (PMMA) thin films. Quantum chemical density functional theory (DFT) computations on the singlet and triplet ground states have shown admixing of the Pt 5d orbitals with the frontier molecular orbitals (FMOs), explaining the good quantum yield.