Synthesis, mesomorphism, and luminescent properties of Calamitic 2-Phenylpyridines and their complexes with Platinum(II)

The liquid crystal and luminescent properties of two related series of rod-like, ortho-platinated complexes bearing a β-diketonate co-ligand are reported. The parent ligands exhibit a rich, smectic polymorphism, but when modified with a fused cyclopentene ring, nematic phases dominate. Reaction of the ligands with tetrachloroplatinate(II) leads to poorly soluble, dimeric complexes that can be cleaved using dimethylsulfoxide; the resulting monomeric complexes are then readily converted to the β-diketonate complexes. All of the complexes are mesomorphic, and the β-diketonate complexes have excited state lifetimes of 27 μs with emission quantum efficiencies exceeding 0.5, the highest yet reported for materials of this type.