Cyclometalated Platinum(II) Metallomesogens Based on Half-Disc-Shaped β-Diketonate Ligands with Hexacatenar: Crystal Structures, Mesophase Properties, and Semiconductor Devices

A series of new half-disc-shaped platinum(II) complexes [Pt(ppy)(ALⁿ-6OC_nH_2n+1)] (Pt-An), [Pt(ppyF)(ALⁿ-6OC_nH_2n+1)] (Pt-Bn), and [Pt(ppyCF₃)(ALⁿ-6OC_nH_2n+1)] (Pt-Cn) (ALⁿ-6OC_nH_2n+1 = 1,3-bis(3,4,5-trialkoxyphenyl)propane-1,3-dionato; n = 1, 6, 12) with concise structures have been designed and synthesized, in which 2-phenylpyridine (ppy) derivatives were used as cyclometalated ligands and hexacatenar β-diketonate derivatives ALⁿ-6OC_nH_2n+1 as auxiliary ligands. The single-crystal data of the methoxy diketonate analogues Pt-A1, Pt-B1, and Pt-C1 indicate that they all display excellent square planarity. These platinum(II) complexes show a certain emission tunability (ranging from λ = 506-535 nm) by the introduction of fluorine or trifluoromethyl into ppy. Thermal studies reveal that the fluorine-substituted complexes are liquid crystals but the trifluoromethyl-substituted complexes are not. The platinum(II) complexes Pt-A12, Pt-B6, and Pt-B12 can form a hexagonal columnar mesophase via intermolecular π-π interactions. In addition, compared to the reported platinum(II) metallomesogens, Pt-A12 and Pt-B12 exhibit improved ambipolar carrier mobility behaviors in semiconductor devices at the liquid crystal states.