Cycloplatinated(II) metallomesogens and their binary-mediated chirality transfer and amplificated deep-red circularly polarized luminescence with ultrahigh dissymmetry factor over 0.13

Abstract

Incorporating supramolecular chirality and high emission into metallomesogens has great significance in the field of flexible electronic devices because of their emergent capacities for enlarged chiroptical activities and either thermotropic or solution-processability. In this work, an enantiomeric pair of chiral Pt(II) metallomesogens (S)/(R)-Pt1 were prepared through laboratory-synthesized chiral picolinic acid ligands and phenylpyridine derivatives to study their mesophase behaviors, chiroptical properties, and chirality transfer and amplification. The solutions of (S)/(R)-Pt1 emitted green phosphorescence at 508 nm, but the amorphous form displayed orange-red phosphorescence at 616 nm. Upon gentle grinding or heating, the emission color of Pt1 was dramatically changed with a bathochromic shift of 47 and 51 nm, respectively, because of emerged intermolecular π···π and Pt⋯Pt interactions in all aggregation states. Furthermore, the chiroptical properties and LC self-assembly model were proposed by Density Functional Theory (DFT) calculations and chiroptical spectrum measurements. The enantiotopic (S)/(R)-Pt1 complexes exhibited electronic circular dichroism (CD) and circularly polarized luminescence (CPL) activities in solution with a smaller asymmetry factor (±5 × 10−4) by chiral disturbance. This pair of exclusively enantiomeric complexes exhibited smectic mesophase behavior in the range of 31.4–76.5 °C but induced unsuccessfulness of helical packing in LC states due to weak induction ability. Contrastively, binary-component mediated supramolecular helical formation and amplificated deep-red CPL switch with ultrahigh dissymmetry factor over ±0.13 in helical twist grain boundary phases (TGBA*) mesophase has been realized.