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.

Efficiently luminescent heteroleptic neutral platinum(II) complexes based on N^O and N^P benzimidazole ligands

A series of new luminescent cycloplatinated(II) complexes (5a-8a and 5b-8b) with formulas Pt(bt)(N^O) and Pt(bt)(N^P) have been synthesized [bt = phenylbenzothiazole, N^O = (2-(1H-benzimidazole)-phenyl)diphenylphosphine oxide derivatives for 1a-4a and N^P = (2-(1H-benzimidazole)-phenyl)diphenylphosphine derivatives for 1b-4b]. The crystal structures of the complexes show distorted square planar geometries around the platinum centers. There are no obvious π-π and Pt-Pt intermolecular interactions in the crystal lattice due to the presence of sterically bulky ancillary ligands. Consequently, these complexes exhibit structured monomeric emissions in the range of 527-540 nm in CH₂Cl₂ solution. The photoluminescent quantum yields of Pt(bt)(N^O) (5a-8a) in CH₂Cl₂ solution at room temperature are higher than those of Pt(bt)(N^P) (5b-8b). The above result is well consistent with the crystal structural characteristics of the complexes. The structured emission with microsecond radiative lifetimes and the result of TD-DFT calculations indicate that the emissions of these complexes are mainly attributed to a mixed ³LC-MLCT state.

Novel tetranuclear PdII and PtII anticancer complexes derived from pyrene thiosemicarbazones

Cyclometallated palladium(ii) and platinum(ii) pyrenyl-derived thiosemicarbazone (H₂PrR) complexes of the type [M₄(μ-S-PrR-κ³-C,N,S)₄] (M = Pd^II, Pt^II; R = ethyl, cyclohexyl) have been synthesised in good yields and fully characterised.

X-ray Generated Recombination Exciplexes of Substituted Diphenylacetylenes with Tertiary Amines: A Versatile Experimental Vehicle for Targeted Creation of Deep-Blue Electroluminescent Systems

Customizable and technology-friendly functional materials are one of the mainstays of emerging organic electronics and optoelectronics. We show that recombination exciplexes of simple substituted diphenylacetylenes with tertiary amines can be a convenient source of tunable deep-blue emission with possible applications in organic electroluminescent systems. The optically inaccessible exciplexes were produced via recombination of radiation-generated radical ion pairs in alkane solution, which mimics charge transport and recombination in the active layer of practical organic light-emitting diodes in a simple solution-based experiment. Despite varying and rather poor intrinsic emission properties, diphenylacetylene and its prototypical methoxy (donor) or trifluoromethyl (acceptor) monosubstituted derivatives readily form recombination exciplexes with N,N-dimethylaniline and other tertiary amines that produce emission with maxima ranging from 385 to 435 nm. The position of emission band maximum linearly correlates with readily calculated gas-phase electron affinity of the corresponding diphenylacetylene, which can be used for fast computational prescreening of the candidate molecules, and various substituted diphenylacetylenes can be synthesized via relatively simple and universal cross-coupling reactions of Sonogashira and Castro. Together, the simple solution-based experiment, computationally cheap prescreening method, and universal synthetic strategy may open a very broad and chemically convenient class of compounds to obtain OLEDs and OLED-based multifunctional devices with tunable emission spectrum and high conversion efficiency that has yet not been seriously considered for these purposes.