Aurated Blue-Phosphorescent Platinum(II) Acetylide Complexes via Gold-Carbon σ Bond Formation

In this work, we present synthetic approaches to introduce two gold-containing functionalities onto blue-phosphorescent trans-bis(acyclic diaminocarbene) platinum(II) acetylide complexes via carbon-gold σ-bond formation. The first strategy described involves transmetalation between a protected boronic ester and a gold(I)-phosphine or gold(I)-NHC source to form a Au-Caryl bond on the periphery of each phenylacetylide ligand. The second strategy employs diynyl acetylide ligands as bridging ligands, which forms new Au-Calkynyl bonds upon reaction with gold(I)-phosphine precursors in the presence of base. In total, seven gold-containing platinum acetylide complexes were accessed by these routes. Structural characterization by NMR in solution and X-ray crystallography in the solid state confirms successful incorporation of two gold-containing functionalities while preserving the Pt-C bonds of the acetylide ligands. Photophysical studies reveal that blue phosphorescence is preserved in these trimetallic Au-Pt-Au complexes, with photoluminescence spectra in 2 wt % PMMA bearing strong similarity to those of their corresponding gold-free complexes. Photoluminescence quantum yields of 0.13-0.29 are observed in blue-phosphorescent analogues with Au-Caryl linkages, dropping to 0.079 and 0.091 in the green-phosphorescent diynyl versions with Au-Calkynyl linkages.