Homoleptic Alkynylphosphonium Au(I) Complexes as Push-Pull Phosphorescent Emitters.

A series of compounds P1 - P4 bearing terminal alkynyl sites connected with a phosphonium group via different π-conjugated linkers have been synthesized. The compounds themselves are efficient push-pull emitters and exhibit bright fluorescence in blue and near-UV regions. P1 - P4 were used as alkynyl ligands to obtain a series of homoleptic bis-alkynyl Au(I) complexes 1 - 4 . The complexes demonstrate bright phosphorescence and dual emission with dominating phosphorescence ( 2-4 ). Terphenyl derivative complex 3 exhibits warm white emission in DMSO solution and pure white emission in PMMA films. Time-dependent density functional theory calculations have shown that the T 1 excited state has a hybrid MLCT/ILCT nature with a dominant contribution of charge transfer across a ligand-centered "D-π-A" system. The variation of linker allows tuning the effect of intermolecular charge transfer and thus changing the electronic and photophysical properties of the organogold "D-π-A" system. The results presented unambiguously display the advances of the conception of organometallic "D-π-A" construction.