Switchable circularly polarized luminescent Mn-based hybrid metal halides†

Abstract

Hybrid metal halides with stimuli-responsive circularly polarized luminescence (CPL) have risen to prominence benefiting from their facile preparation and versatile chiral applications. Despite recent rapid developments, the ability to craft hybrid metal halides with strong and switchable CPL remains a challenging issue. This report presents the synthesis of chiral zero-dimensional (0D) hybrid metal halides demonstrating robust and switchable CPL activity. Specifically, a pair of 0D chiral hybrid metal halides (R-/S-MPZ)MnBr₄ and the corresponding racemic counterparts (rac-MPZ)MnBr₄ were synthesized by introducing R-/S-/rac-MPZ units (R-/S-/rac-MPZ = R-/S-/rac-2-methylpiperazine) as organic cations. The synthesized compounds achieved stable and efficient CPL emission with a notable luminescent anisotropy factor (g_lum) of up to 1.12 × 10⁻². Remarkably, reversible CPL can be manipulated to achieve dependence on the variation of environmental humidity and temperature. The findings open up a promising pathway to controllably tune chiroptical behavior of metal halides with large and switchable CPL to develop new security optical coding and hidden communication.