Lead-Free Hybrid Metal Halides with a Green-Emissive [MnBr] Unit as a Selective Turn-On Fluorescent Sensor for Acetone.

Organic-inorganic hybrid metal halides with zero-dimensional (0D) structure has emerged as a new class of light-emitting materials. Herein, a new lead-free compound (CNH)MnBr has been discovered and a temperature-dependent phase transition has been identified for two phases (space group 2/ and 2/) in which individual [MnBr] anions connect with organic cations, (CNH) (1-buty-1-methylpyrrolidinium), forming periodic structure with 0D blocks. A green emission band, peaking at 528 nm with a high photoluminescence quantum efficiency (PLQE) of 81.08%, has been observed at room temperature, which is originated from the T(G) to A transition of tetrahedrally coordinated Mn ions, as also elaborated by density functional theory calculation. Accordingly, a fast, switchable, and highly selective fluorescent sensor platform for different organic solvents based on the luminescence of (CNH)MnBr has been developed. We believe that the hybrid metal halides with high PLQE and the exploration of these as a fluorescence sensor will expand the applications scope of bulk 0D materials for future development.