Novel N^C^N-cyclometallated platinum complexes with acetylide co-ligands as efficient phosphors for OLEDs

Abstract

Two new cyclometallated platinum(II) complexes have been prepared that incorporate a terdentate N^C^N-coordinating ligand and a monodentate acetylide co-ligand. The complexes, namely [PtL 3 -C^C-C 6 H 3 F 2 ] and [PtL 6 -C^C-C 6 H 3 F 2 ] (where HL 3 ¼ 5-methyl-1,3-di(2-pyridyl)benzene; HL 6 ¼ 5-mesityl-1,3-di(2-pyridyl)benzene; H-C^C-C 6 H 3 F 2 ¼ 3,5-difluorophenylacetylene), were prepared by ligand metathesis from the corresponding chloro complex PtL n Cl. Both of the new complexes are intensely luminescent in solution, displaying quantum yields superior to PtL n Cl. OLEDs have been prepared using the new compounds as phosphorescent emitters. Although both lead to efficient devices, the best electroluminescence quantum efficiencies are obtained with the derivative of HL 6 , having the mesityl group on the cyclometallated phenyl ring. The superior performance with this complex can be rationalised in terms of the greater steric hindrance that serves to reduce aggregate-induced quenching.

Luminescent Pincer Platinum(II) Complexes with Emission Quantum Yields up to Almost Unity: Photophysics, Photoreductive CC Bond Formation, and Materials Applications

“…Luminescent Pt II complexes bearing tridentate pincer‐type ligands display rich photophysical and photochemical properties. For example, [Pt(N^C^N)(X)] (N^CH^N = 1,3‐di(2‐pyridinyl)benzene; X=Cl, σ‐alkynyl)6a,c and [Pt(C^N^C)(CN t Bu)] (HC^N^CH=3,6‐bis( p ‐anizolyl)‐2carboranyl‐pyridine)6e display high Φ em (up to 0.82) in solutions at room temperature and their emission energy could be tuned from λ em =471 to 610 nm 6a,c. Herein, we describe a series of highly emissive Pt II complexes supported by C‐deprotonated RC^N^NR′ ligands with extended π‐conjugation (Scheme ).…”

Porphyrin/Platinum(II) C^N^N Acetylide Complexes: Synthesis, Photophysical Properties, and Singlet Oxygen Generation

“…The Zn II complexes of each isolated porphyrin, that is, n PZn ( n =1–3), were obtained by reaction with anhydrous Zn(OAc) 2 in CHCl 3 /MeOH (10:1) under reflux. The porphyrin–platinum linked products, P⋅Pt n , (where n =1–3) were synthesized by removal of the TMS protecting groups of n P ( n =1–3) with K 2 CO 3 to generate the terminal alkynes; this was followed by coupling with previously‐prepared organoplatinum complex, Pt II C^N^NCl in the presence of NaOMe, as reported by Williams and co‐workers . The final products were all purified by using a Sephadex column to remove excess Pt II C^N^NCl and obtain the materials in pure form.…”

Phosphorescent Pt(II) Emitters for OLEDs: From Triarylboron‐Functionalized Bidentate Complexes to Compounds with Macrocyclic Chelating Ligands

“…[38] 2.6. N^C^N Chelate Ligands (Type III) Pt(II) complexes incorporating 1,3-dipyridylbenzene (dpb) and its derivatives as N^C^N type cyclometallating ligands have been thoroughly studied by Williams et al [39] Most of this type of tridentate complexes are bright phosphors because of their rigid structures, which also improves color purity by suppressing the low energy vibrational bands. [40] One drawback of these compounds is that they are often highly susceptible to excimer formation due to their flat structures and extended p-conjugation.…”