Sterically Hindered Luminescent Pt^II–Phosphite Complexes for Electroluminescent Devices

Abstract

Pt(II) complexes with one bulky, sterically demanding, tertiary phosphite ancillary ligand and a coordinating chromophore are herein presented. The phosphite ligand, tris(2,4-di-tert-butylphenyl) acts as a bidentate ligand coordinating the platinum ion through the central phosphorus atom and a cyclometalating carbon atom of one of the substituents. The two free phenoxy moieties lie above and below the coordination plane, leading to steric hindrance that avoids aggregation and provides solubility in organic solvents. The other two coordination sites on the central metal ion are occupied by a chromophoric ligand, which is responsible for the energy of the luminescent excited state. This separation of functions, on the two coordinated ligands, allows the use of a wider range of luminophores with good luminescent properties, maintaining the control of the intermolecular interactions with the non-chromophoric ligand. Based on this approach we were able to achieve a bright deep blue emission (λ=444 nm, Φem =0.38) from a complex with a tailored ligand, which was then used for the fabrication of an electroluminescent device. In addition commercially available luminophores were also employed to synthesize green emitters.

Fluorescent Pyrene‐Based Bis‐azole Compounds: Synthesis and Photophysical Analysis

“…To further explore the capabilities of this family of pyrene‐based bis‐imidazoliums, we used them as precursors in the preparation of cyclometalated platinum complexes. Cyclometalated platinum complexes have shown potential in highly efficient OLEDs9, 18 and, in conjunction with NHC ligands, have provided Pt II complexes with luminescent properties 5a…”

“…For current applications of OLEDs, the processability of their emitters is also of major interest. Designing high‐yield reactions and easy‐to‐purify components to avoid losses of material and issues related with the presence of impurities is highly desirable 9…”

Homoleptic platinum(ii) complexes with pyridyltriazole ligands: excimer-forming phosphorescent emitters for solution-processed OLEDs

“…12c Heteroleptic complexes, comprising one pyridyltriazole ligand and a second -different -ligand, have meanwhile been explored by others. 13,14 More recently, dianionic tridentate ligands based on -N^N^N --coordinating 2,6-bis(1,2,4-triazol-5yl)pyridine have been used to prepare an -4 -extensive range of complexes, whose photophysical properties have been put forward for various applications. 15…”

Fluorination‐controlled Aggregation and Intermolecular Interactions in Pt(II) Complexes with Tetradentate Luminophores

“…However, a deeper understanding and a defined control of intermolecular interactions are still required, as stacking most frequently causes lowered solubility, undesired triplet−triplet annihilation and lowered quantum yields ,. We have recently reported on the use of bidentate and tridentate luminophores in Pt(II) complexes that are able to emit as blue or green monomeric species, due to the presence of bulky ancillary ligands preventing intermetallic interactions. On the other hand, aggregation‐induced phosphorescence was observed for planar luminophores and ancillary ligands stacking into bright aggregates in which Pt−Pt interactions play a significant role ,,.…”