Photoluminescence of pefloxacindi-ium manganese(II) and zinc(II) tetrahalides

Fabrication Strategies of Mn2+-Based Scintillation Screens for X-Ray Detection and Imaging

Scintillators play a pivotal role in multiple fields such as medical imaging, radioactive contaminant detection, non-destructive testing, high-energy physics and homeland security. However, the traditional inorganic scintillators are faced with the shortcomings of high fabrication cost and low light yield. In recent years, organic-inorganic hybrid metal halides have become the promising alternatives for their excellent luminescence properties, favorable air and irradiation stability, and low-cost preparation. Among them, organic-inorganic hybrid Mn(II) halides (OIMnHs) have attracted wide attention due to their particular flexible molecular structure design, easy synthesis and low toxicity. This minireview summarizes the latest progress in high performance Mn2+-Based scintillation screens. Herein, the scintillation mechanism of OIMnHs scintillators is firstly discussed. Then, the different synthesis methods of OIMnHs scintillators are briefly described, including solvent diffusion, cooling crystallization, evaporative crystallization and solid-state mechanochemical synthesis. After that, the recent strategies of OIMnHs for forming scintillation screens applying to X-ray imaging are emphatically reviewed, which are growing large single crystals, fabricating to glass or ceramic and blending with polymers. The fabrication progress and applications of OIMnHs-based scintillation screens were introduced and the structure-property relationship of these screens was discussed. Finally, the challenges of this new scintillator material are summarized, and the potential research directions for future exploration are proposed.

Recent strategies for triplet-state emission regulation toward non-lead organic-inorganic metal halides

Organic-inorganic metal halides (OIMHs) have strengthened the development of triplet-state emission materials due to their excellent luminescence performance. Due to the inherent toxicity of lead (Pb) significantly limiting its further advancement, numerous studies have been conducted to regulate triplet-state emission of non-Pb OIMHs, and several feasible strategies have been proposed. However, most of the non-Pb OIMHs reported have a relatively short lifetime or a low luminescence efficiency, not in favor of their application. In this review, we provide a summary of recent reports on the regulation of triplet-state emissions in non-Pb OIMHs to provide benefits for the design of innovative luminescent materials. Our focus is primarily on exploring the internal and external factors that influence the triplet-state emission. Starting from the luminescence mechanism, the current strategies for regulating triplet-state emissions are summarized. Moreover, by manipulating these strategies, it becomes feasible to achieve triplet-state emissions that span a range of colors from blue to red, and even extend into the near-infrared spectrum with high luminescence efficiency, while also increasing their lifetimes. This review not only provides fresh insights into the advancement of triplet-state emissions in OIMHs but also integrates experimental and theoretical perspectives to illuminate the trajectory of future research endeavors.

Efficient emission of Zn(II) and Cd(II) complexes with nopinane-annelated 4,5-diazafluorene and 4,5-diazafluoren-9-one ligands: how slight structural modification alters fluorescence mechanism

Zinc(II) and cadmium(II) chlorido complexes with an N,N-chelating nopinane-annelated 4,5-diazafluoren-9-one ligand (LO) were synthesized. While the zinc(II) complex is mononuclear and adopts a tetrahedral ZnN₂Cl₂ coordination geometry, its cadmium(II) analogue features a 1D polymeric structure due to the bridging coordination of chlorido ligands with Cd²⁺ ions having an octahedral CdN₂Cl₄ coordination geometry. The photophysical properties of the oxygen-containing LO ligand and its zinc(II) and cadmium(II) complexes were studied in solution and in the solid state and matched against the properties of its oxygen-free 4,5-diazafluorene congener L and its complexes of the same metal ions. Comprehensive experimental and theoretical studies revealed the impact of the oxygen atom in the ligand core on the luminescence of the ligands and the complexes. For the oxygen-free L ligand and L-based complexes, the structural differences between the S₀ and S₁ geometries are small, which leads to fluorescence with extraordinarily small Stokes shifts. The emission of these compounds is of locally excited character for L and of mixed locally excited + ligand-to-halide charge transfer character for the L-based complexes. The introduction of the oxygen atom in the ligand core results in a drastic red-shift of the emission band due to short-range charge transfer. The differences between the S₀ and S₁ geometries are much more pronounced for LO and LO-based compounds than those of their oxygen-free analogues, leading to an order of magnitude larger Stokes shifts. On going from solution to the solid state, LO and its complexes exhibit aggregation-induced emission (AIE) behaviour with photoluminescence quantum yields (PLQYs) reaching tens of percent.