Highly Phosphorescent Planar Chirality by Bridging Two Square-Planar Platinum(II) Complexes: Chirality Induction and Circularly Polarized Luminescence

Abstract

Chiral organometallic complexes have demonstrated many potential and practical applications. However, building metal-induced chirality for square-planar complexes still remains a big challenge, because their 2D planar molecular structures are usually superimposable on their mirror images. Herein, we report a straightforward and efficient way to achieve a novel kind of planar chirality by constructing 3D double-layer molecular structures. When the achiral ligand 1,3,4-oxadiazole-2-thiol (OXT) was used to bridge two square-planar complexes, a pair of racemic R/S planar-chiral binuclear Pt­(II) complexes was obtained, which could be separated by chiral high-performance liquid chromatography (HPLC). Moreover, enantiopure R,R,R or S,S,S complexes could be prepared by the use of chiral (R)-/(S)-binaphthalene-derived OXT ligands in 99% diastereoselectivity without the use of chiral HPLC. The binaphthalene groups help to ensure good solubility and a smooth amorphous thin film morphology but have little effect on the photophysical properties. The resultant complexes display strong orange-red and near-infrared phosphorescence with quantum yields of up to 83.4% and can be applied as emitters in highly efficient solution-processed organic light-emitting diodes to achieve luminance, luminance efficiency, external quantum efficiency, and an asymmetry factor of up to 3.22 × 104 cd m–2, 28.7 cd A–1, 14.3%, and 2.0 × 10–3, respectively. With a comprehensive consideration of EL efficiency and the asymmetry factor, this is the best performance among Pt­(II) complex based circularly polarized OLEDs. Therefore, this work provides a new and simple strategy to build planar chirality for chiroptical and circularly polarized luminescence applications.

A Chiral Dual‐Core Organoboron Structure Realizes Dual‐Channel Enhanced Ultrapure Blue Emission and Highly Efficient Circularly Polarized Electroluminescence

“…[1][2][3] The current research has revealed the importance of developing efficient chiral luminescent materials that enable circularly polarized luminescence (CPL) to produce high-performance CP-OLEDs. [4][5][6][7] Generally, the performance standard of the circularly polarized photoluminescence (CPPL) or circularly polarized electroluminescence (CPEL) is characterized by the dissymmetry factor (g PL or g EL ) defined as g = 2 × ΔI/I = 2 × (I L − I R )/(I L + I R ). For example, Meijer et al first obtained CPEL with g EL factor around 10 −3 by using a chiral-substituted poly(p-phenylenevinylene) derivative as emitter.…”

Helical Induction, Chiroptical Properties, and Quantitative Prediction of the Dissymmetry Factor on the Circularly Polarized Phosphorescence of Iminopyrrolyl Platinum(II) Complexes

“…This strategy has been commonly utilized in supramolecular, polymer, 43−51 and coordination chemistry, including platinum complexes. 52,53 Recently, planar chirality and helicity inductions of Pt(II) complexes for CPP emitters have been using axial 26 and point chirality. 23 In this study, we demonstrated the helical induction of d-π-conjugated iminopyrrolyl 54−57 Pt(II) complex 1 by the point chirality of 1,2-diaminocyclohexane (Figure 1).…”

BODIPY-conjugated bis-terpyridine Ru(ii) complexes showing ultra-long luminescence lifetimes and applications to triplet–triplet annihilation upconversion

“…35 However, such systems will inevitably suffer from severe inner-filter effects. We have been focusing on manipulating the excited state properties of organic chromophores by supramolecular complexation or chemical tuning of sensitizer structures, 27,31,[36][37][38][39][40][41] and achieved efficient TTA-UC in dilute solutions. 27 On the other hand, boron-dipyrromethene (bodipy), a versatile chromophore with strong visible light absorption, high fluorescence quantum yields and photostability, has been widely used to manipulate the excited states of different metal complexes.…”

“…35 However, such systems will inevitably suffer from severe inner-filter effects. We have been focusing on manipulating the excited state properties of organic chromophores by supramolecular complexation or chemical tuning of sensitizer structures, 27,31,36–41 and achieved efficient TTA-UC in dilute solutions. 27…”