Abstract
We report, for the first time, the solid-phase gram-scale synthesis of two lead-free, zero-dimensional (0D) fluorescent organic-inorganic hybrid compounds, [Bu4N](2)[MnBr4] (1) and [Ph4P](2)[MnBr4] (2), achieved by grinding the organic and inorganic precursor salts. The solid-phase synthetic route has several advantages for modulating molecular dimensionalities. During grinding, organic cations and Mn2+ cations are co-crystallized together in the solid-state, forming a 0D assembly at the molecular level where each individual metal center is surrounded by organic cations. Both compounds exhibit an emission peak at 520 nm and a photoluminescence (PL) quantum yield (QY) of 47%. Here, we also report, for the first time, the upconversion phenomena which trigger different emission energies occurring in different quartet states of Mn, T-4(1)((4)G), T-4(2)((4)G), (4)A(1)((4)G), E-4((4)G), T-4(2)(D-4), E-4(D-4), and T-4(1)(P-4). These optical properties are unusual phenomena which break Kasha's rule of emission. Single particle imaging and low-temperature PL measurement are performed to obtain a deeper insight into these ground products. These results pave a new path to develop highly fluorescent non-toxic hybrid compounds with remarkable optical properties.