title: Blue phosphorescent nitrile containing C^C* cyclometalated NHC platinum(II) complexes.
abstract: Since C^C* cyclometalated Pt(II) complexes with N-heterocyclic carbene (NHC) ligands have been identified as potential emitter materials in organic light-emitting devices (OLEDs), very promising results regarding quantum yields, colour and stability have been presented. Herein, we report on four nitrile substituted complexes with a chelating NHC ligand (1-(4-cyanophenyl)-3-isopropyl-1H-benzo[d]imidazole or 4-(tert-butyl)-1-(4-cyanophenyl)-3-methyl-1H-imidazole) and a bidentate monoanionic auxiliary ligand (acetylacetone or dimesitoylmethane). The complexes have been fully characterized including extensive 2D NMR studies (COSY, HSQC, HMBC, NOESY, (195)Pt NMR), three of them also by solid-state structures. Photophysical measurements in amorphous PMMA films and pure emitter films at room temperature reveal the impact of the mesityl groups in the auxiliary ligand, which led to a significant increase of the quantum yield, while the decay lifetimes decreased. The electron withdrawing nitrile groups shift the emission towards blue colour coordinates.
authors.affiliation: Physical Organic Chemistry, Technische Universität Dresden, Bergstrasse 66, 01069 Dresden, Germany. thomas.strassner@chemie.tu-dresden.de.
authors.forename: Alexander
authors.initials: A
authors.lastname: Tronnier
authors.forename: Stefan
authors.initials: S
authors.lastname: Metz
authors.forename: Gerhard
authors.initials: G
authors.lastname: Wagenblast
authors.forename: Ingo
authors.initials: I
authors.lastname: Muenster
authors.forename: Thomas
authors.initials: T
authors.lastname: Strassner