Multi-Stimuli Responsive Circularly Polarized Luminescence in Manganese (II) Halide Hybrids

Abstract

Ionic metal halide hybrids (MHHs) possess intrinsically soft lattices that endow them with high sensitivity to external stimuli. When coupled with chirality induction from organic cations, these systems can further exhibit efficient circularly polarized luminescence (CPL). However, most reported MHH-based CPL materials respond to only a single type of stimulus, limiting their applicability in complex or dynamic environments. Developing multi-stimuli-responsive CPL systems and clarifying how external triggers modulate the luminescence dissymmetry factor (gᵤ) is therefore of great importance. Here, we report a pair of Mn(II)-based chiral hybrids, (R/S-FMBA) 2 MnBr 4 (R/S-FMBA = (R/S)-1-(4-fluorophenyl)ethylamine, R/S-1), which display distinct and reversible CPL responses toward both solvent and temperature. Exposure to methanol induces a reversible green-to-red emission transition accompanied by a fivefold enhancement in |gᵤ|, whereas exposure to water yields a reversible green-to-weak-red shift with a twofold |gᵤ| increase. Remarkably, this weak red emission reverts to strong green emission at 80 K, with |gᵤ| suppressed by a factor of four. Comprehensive analyses attribute these CPL modulations to temperature-dependent self-trapped exciton emission and transformations in the MnBr 4 coordination geometry. This work demonstrates the first multi-stimuli-responsive CPL behavior in Mn-based MHHs, offering new opportunities for intelligent chiral photonic systems and providing key insights into stimulusdependent CPL regulation.