Tuning the circularly polarized phosphorescence of platinum(II) complexes through a chiral cation strategy

Circularly polarized phosphorescent (CPP) materials, especially chiral platinum(II) complexes, which combine the advantages of both circularly polarized luminescence (CPL) and phosphorescence, show broad potential applications in chiral optoelectronic devices. Developing CPP emitters with both excellent chiroptical properties and high yield is urgently needed. Here, a chiral cation strategy is employed to construct the CPP Pt(II) complexes R/S-ABA·[Pt(ppy)Cl₂] and R/S-MBA·[Pt(ppy)Cl₂] through a simple one-step reaction with almost 100% yield. The circular dichroism and CPL spectra confirm that the chirality was successfully transferred to the [Pt(ppy)Cl₂]^- anion. The luminescence asymmetry factors (g_lum) are +1.4/-1.8 × 10^-3 for R/S-ABA·[Pt(ppy)Cl₂] and +4.4/-2.8 × 10^-3 for R/S-MBA·[Pt(ppy)Cl₂]. The stronger chiroptical property of R/S-MBA·[Pt(ppy)Cl₂] is attributed to the enhanced chiral structural deformation and better matched electric and magnetic transition dipole moments. This chiral cation strategy is confirmed to efficiently construct CPP Pt(II) complexes, which will accelerate the development of CPP emitters towards commercialization.