Tunable Emission Properties of Manganese Chloride Small Single Crystals by Pyridine Incorporation

Pure transition-metal compounds seldom produce luminescence because of electron correlation and spin-spin coupling. The Pb-free perovskite materials, C₁₀H₁₂N₂MnCl₄ and C₅H₆NMnCl₃·H₂O, were obtained by using pyridine-implanted manganese chloride lattices. The single-crystal X-ray diffraction indicates their different crystal structures. In C₁₀H₁₂N₂MnCl₄, MnCl₄ cocoordinated with two pyridine molecules forms a lattice composed of independent mononuclear structures with paramagnetic behavior, which shows a clear emission band at 518 nm from the lowest d-d transition of a single Mn(II) ion in the octahedral crystal field. In C₅H₆NMnCl₅·H₂O crystal, MnCl₅·(H₂O) octahedron-cocoordinated with less pyridine molecules than 2 lead to formation arris-share linear chains of Mn-ion octahedra, which give emission band at 620 nm due to the ferromagnetic Mn pair, and ferromagnetism. Pyridine incorporations in the transition-metal halide lattice provide a new channel to modulate the electron correlation and obtain materials with both luminescence and ferromagnetic properties.