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)x 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.