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[MnBr ₄] [4-MTPP ⁺ = (4-methoxybenzyl)tris(phenyl)phosphonium)] were reported. Our experiment results demonstrate that [4-MTPP] ₂[MnBr ₄] 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[MnBr ₄] presents a monotonically blue shift with the increased temperature, originating from the decreased crystal field strength where the Mn ²⁺ stays owing to lattice thermal expansion effect. On the contrary, as the pressure increases, the photoluminescence emission of [4-MTPP] ₂[MnBr ₄] exhibits a progressive red shift, which can be attributed to the increased crystal field strength of Mn ²⁺ 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[MnBr ₄] crystals show a crystal-glass phase transition at the temperature of 74 °C. Intriguingly, the melt-quenched glass of [4-MTPP] ₂[MnBr ₄] exhibits green emission under UV light excitation with a large lifetime of 302.2 µs.

Keywords

Hybrid manganese halides / Photoluminescence / Stimuli-responsive behavior / Crystal-glass phase transition

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