Dicyclohexyl(phenyl)phosphine Oxide-Based Neutral Manganese(II) Bromide Scintillator for X-ray Imaging

Luminescent manganese(II) halide-based materials have drawn increasing research interest because of their rich photophysical properties. The good understanding of the relationships between the photophysical property and the molecular structure of the manganese(II) complex could give deep insights to further guide the structural design of the manganese(II) emitters. Currently, neutral manganese(II) halides based on the monodentate ligand mainly rely on triarylphosphine oxide. To extend this family of luminescent manganese(II) halides, herein, by introducing two bulky cyclohexyl moieties bonded to the phosphorus atom, we employ a dicyclohexyl(phenyl)phosphine oxide (DCPPO) to synthesize manganese(II) bromide (DCPPOMnBr). The prepared manganese(II) complex not only exhibits green room-temperature photoluminescence peaking at 508 nm with narrowband emission and a photoluminescence lifetime of 0.112 ms but also shows zero-thermal-quenching luminescence below 260 K in the solid state under ultraviolet light. The complex further serves as the scintillator for high spatial resolution X-ray imaging (10.52 lp mm^-1). These results clearly demonstrate that the proposed ligand design strategy can be an effective way to extend such a family of manganese(II) emitters and will provide further insights into their relationships between the molecular structure and photophysical properties.