Temperature- and Pressure-Dependent Emissions and Crystal- Glass Transition of a Hybrid Manganese Bromide†

Abstract

Herein, the temperature- and pressure-stimulated responsive behavior as well as crystal-glass phase transition of a new zero-dimensional hybrid manganese bromide [4-MTPP]₂[MnBr₄] [4-MTPP⁺ = (4-methoxybenzyl)tris(phenyl)phosphonium)] were reported. Our experiment results demonstrate that [4-MTPP]₂[MnBr₄] shows typical green photoluminescence emission centered at 522.4 nm excited by UV light, with a high photoluminescence quantum yields value of 79.36% and a large lifetime of 368.6 μs, attributing to its direct bandgap electronic structure. Further, the photoluminescence emission of [4-MTPP]₂[MnBr₄] presents a monotonically blue shift with the increased temperature, originating from the decreased crystal field strength where the Mn²⁺ stays owing to lattice thermal expansion effect. On the contrary, as the pressure increases, the photoluminescence emission of [4-MTPP]₂[MnBr₄] exhibits a progressive red shift, which can be attributed to the increased crystal field strength of Mn²⁺ due to the effect of pressure-induced lattice shrinkage. Meanwhile, its quenched emission can be successfully restored when the pressure returns to the ambient pressure. In addition, [4-MTPP]₂[MnBr₄] crystals show a crystal-glass phase transition at the temperature of 74 °C. Intriguingly, the melt-quenched glass of [4-MTPP]₂[MnBr₄] exhibits green emission under UV light excitation with a large lifetime of 302.2 μs.