Temperature/water triggered reversible emission transition in a one-dimensional Mn(ii)-based metal halide†

Abstract

While stimuli-responsive luminescence of organic–inorganic metal halides has reached maturity, the achievement of self-recovering PL (photoluminescence) switching remains a challenge. Herein, we designed and synthesized a 1D organic–inorganic Mn(II) metal halide (C₈H₉N₂)_n{(MnCl₃(H₂O)·H₂O)}_n (C₈H₉N₂ = 2-methylbenzimidazolium, named compound 1), which shows bright red emission with a quantum yield of 12.9%. The compound 1 crystals exhibit an obviously blue-shifted conversion from red emission (645 nm) to yellow emission (560 nm) as the temperature increases to 410 K. TGA and IR spectra reveal that the emission transition originates from the release of free and coordinated water molecules in the lattice. Remarkably, reversible luminescent conversion was observed after exposure to air for several hours, which contributed to the uptake of water, demonstrating the achievement of self-recovering PL modulation by the absorption of water under normal air. This work provides a novel and feasible design strategy for temperature/water stimuli-responsive sensing technology.