Phosphorescent Platinum(II) Complexes with a Spiro‐fused Xanthene Unit: Synthesis and Photophysical Properties

Abstract

Novel platinum(II) complexes, derived from the spiro[fluorene‐9,9’‐xanthene] (SFX) motif, were synthesized and combined with different auxiliary ligands such as acetylacetonate (acac), bis(2,4,6‐trimethylphenyl)propane‐1,3‐dionate (mesacac) and dihydrobis(3,5‐dimethylpyrazole‐1‐yl) borate. The final products were obtained in yields of up to 36 % and characterized by NMR, X‐ray and combustion analysis. These complexes have structured green‐blue emission spectra with Commission Internationale de l’Éclairage (CIExy) coordinates of (0.21;0.46). Excellent photoluminescence quantum yields (PLQYs) ranging from 87 %–91 % were found. The emission lifetimes vary from 33 μs to 43 μs. Calculations on the B3LYP/6‐311++G** level of theory reveal, that the nature of the emissive state is dependent on the positional regioisomerism of the SFX motif. The 2‐SFX complexes demonstrate ligand‐centered (3LC) emission, while the 2’‐SFX regioisomer with the mesacac ligand shows a strong 3MLCT character.