Hybrid Manganese(II) Halides with Water-/Temperature-Triggered Reversible Structure Transition and Color-Tunable Emissions for Sensitive Water Sensors

Convenience, sensitivity, and selectivity are of great significance for water detection in environmental monitoring and industrial processes. We have synthesized two 0D hybrid manganese halides [C 9 H 19 N 2 ] 2 MnBr 4 and [C 9 H 19 N 2 ] 2 MnBr 4 ·H 2 O, which undergo sensitive reversible transition between green and red emission driven by reversible uptake/removal of coordination water molecules stimulated by being exposed to a high-humidity atmosphere/mildly heated at 60 °C. The former structure has a high photoluminescence quantum yield (PLQY) of 81%. On-site monitoring of visual emission color changes and photoluminescent (PL) spectral variations of two compounds revealed an ultrafast stimulus response time as short as 30 s, demonstrating their great potential as high-performance PL water sensors for real-time on-site humidity monitoring and trace water in organic solvents’ detection.