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Lead-free halide perovskites have emerged as promising optoelectronic materials owing to their non-toxic composition, structural adaptability, and exceptional photophysical characteristics. In this work, novel lead-free KZnF₃: Eu³⁺, Tb³⁺/OA complexes were synthesized through introducing oleic acid (OA) during the solvothermal synthesis of the KZnF₃: Eu³⁺, Tb³⁺ perovskite. This synthetic strategy induces the formation of Tb–O coordination bonds, significantly enhancing the broadband blue emission (425–525 nm) with a dominant peak at 495 nm in the photoluminescence (PL) spectra. The synthesized KZnF₃: Eu³⁺, Tb³⁺/OA complexes exhibit characteristic blue, green, and red emission peaks of Tb³⁺ and Eu³⁺ ions upon excitation at 375 nm, thereby achieving a lead-free single-phase white light material through ultraviolet (UV) excitation. Additionally, these complexes demonstrate excellent thermal stability, retaining approximately 60% (495 nm), 70% (545 nm), and 90% (594 nm) of their relative PL intensities at 120 °C compared to those at 40 °C. The calculated lifetime of the complexes is 18.33 μs. Finally, the white-emitting KZnF₃: Eu³⁺, Tb³⁺/OA complexes are encapsulated on an ultraviolet (UV)-emitting chip to fabricate a white light-emitting diode (WLED) with the Commission International de L'Eclairage (CIE) color coordinates at (0.336, 0.333), approaching ideal white-light emission.

We propose a new subclass of non-covalent interactions, which we call refractory bonds. These bonds are characterized by the attractive interaction between a group 4 element (Ti, Zr, or Hf) and a nucleophilic site, either within the same molecule or with a neighboring entity. This interaction can be seen as a sister to the other σ-/π-hole interactions. In σ-hole (π-hole) bonding, the σ-hole (or a π-hole) is an electron-density deficient region on the surface of an atom (or an array of atoms) (R), opposite (or orthogonal) to the outermost extension of a covalent or coordinate bond formed by a substituent (S) in an S–R molecule. The σ-/π-hole acts as an electrophilic center, capable of interacting with electron-rich species. We provide both crystallographic and computational gas-phase evidence to support the existence of the refractory bond in chemical systems. We show that these σ-hole bonds, as well as refractory π-hole interactions, exhibit significant similarities with other non-covalent interactions, including triel, tetrel, pnictogen, chalcogen, halogen, aerogen, coinage, alkali, alkaline earth, as well as erythronium, wolfium, osme, spodium, and regium bonds. Our findings open new avenues for the study of non-covalent interactions and are expected to offer valuable insights to the broader non-covalent chemistry community, particularly in molecular recognition, crystallography, self-assembly, supramolecular chemisty and catalysis.

Lithium iron phosphate (LFP) and its derivatives are an extremely promising class of cathode materials for lithium-ion batteries with an ever-expanding range of applications. The development of improved, cost-effective methods to synthesize this class of materials is a challenging task, and in this work, we explored the synthesis of LiFePO₄ under hydrothermal conditions without using the traditional three-fold lithium excess. By partially replacing LiOH with NaOH, we were able to synthesize single-phase LFP demonstrating good electrochemical performance. Studying the synthesis stages, we identified an unexpected alluaudite-triphylite phase transformation. A careful examination of this intermediate phase through powder X-ray diffraction, Mössbauer spectroscopy, Fourier-transform infrared spectroscopy, and inductively coupled plasma atomic emission spectroscopy brought us to discover a new sodium iron bis(hydrogen phosphate) phosphate — Na_0.7Fe₃(HPO₄)₂(PO₄) — that forms at the first stage of the synthesis. Further hydrothermal treatment facilitates Na → Li exchange, and instability of the alluaudite-type framework with high Li content results in the formation of the triphylite LiFePO₄ phase.

In this manuscript, we report the synthesis and X-ray characterization of two new Au(III)–cytosine systems: AuCl₃(CytC₆) (1) and (HCytC₆)₂[AuCl₄]Cl (2), where CytC₆ is N1-hexylcytosine. Compound 1 is an inner sphere complex where the AuCl₃ unit is coordinated to N3, while compound 2 is an outer sphere complex (salt) where two N1-hexylcytosinium cations are charge compensated by one chloride anion and one tetrachloroaurate anion. Inner sphere complexes of Au(III) with cytosine and nucleobases, in general, are scarcely found in the CSD. In fact, compound 1 is only the third example of a cytosine derivative coordinated to Au(III). Such complexes remain elusive for other nucleobases. The formation of regium bonds in the solid state of compound 1 has been analysed using DFT calculations and characterized with several computational tools, including molecular electrostatic potential (MEP), energy decomposition analysis (EDA), quantum theory of atoms in molecules (QTAIM), and noncovalent interaction plot (NCIplot).

This investigation explored the selectivity behaviour of 9,9′-bifluorenyl-9,9′-diol (H) as a host compound for the separation, through supramolecular chemistry strategies, of mixed pyridines (pyridine (PYR) and its methylated derivatives, 2-, 3- and 4-methylpyridine (2MP, 3MP and 4MP)). Initial single-solvent crystallization experiments demonstrated that H formed 1 : 1 host–guest inclusion complexes with each of PYR, 3MP and 4MP while, in 2MP, no crystallization occurred, and a gel remained in the glass vessel. Equimolar guest competition experiments revealed a clear host preference for 3MP and 4MP, while selectivity profiles employing binary mixed guest solutions indicated that H possessed remarkable separation potential for PYR/4MP, 2MP/3MP and 3MP/4MP mixtures, amongst numerous others. Single crystal X-ray diffraction (SCXRD) analyses corroborated these findings, revealing that 3MP and 4MP engaged in more linear hydrogen bonding interactions with H, which likely contributed to their preferential inclusion. Furthermore, these two guests also formed complexes with greater crystal density compared to H·PYR. Hirshfeld surface analyses substantiated these observations, denoting a greater percentage of hydrogen atom interactions in the H complexes with 3MP and 4MP. Further support was provided by thermal analyses, where the H·4MP complex possessed the highest thermal stability, followed by H·3MP, while H·PYR was the least stable one. These results underscore 9,9′-bifluorenyl-9,9′-diol to be a highly effective host compound for the selective separation of various PYR/MP mixtures, offering an alternative separatory strategy that is efficient and, moreover, environmentally friendly, compared with more conventional approaches.

Copper halide scintillation materials with self-trapped exciton (STE) photoluminescence have attracted great interest in the field of optoelectronics. However, it is challenging for Cs₃Cu₂Br₅ materials to achieve wider spectral emission and high spatial resolution X-ray imaging in applications. Herein, combining XRD and energy dispersive spectroscopy results, it is proved that Ag⁺ is doped into the Cs₃Cu₂Br₅ lattice through an ion doping process, and PL is regulated from 460 nm to 543 nm. By density functional theory calculation, the band gap is reduced from 2.25 eV of Cs₃Cu₂Br₅ to 1.99 eV of Cs₃Cu₂Br₅:Ag, which is also consistent with the spectral redshift. The gradient study of the silver ion concentration from 5% to 35% shows that the best silver ion concentration is 25%. The experimental results show that the doped silver ions can improve the PL, PLE, PLQY, XEL and other properties of the material, such as the PLQY which increased from 27.38% to 90.62%. At the same time, Cs₃Cu₂Br₅:Ag also has good stability, it can be stored in air for 30 days, and its PL intensity remains at 90.73%. The X-ray space of the Cs₃Cu₂Br₅:Ag-UV scintillation film measured in a laboratory imaging system can reach 18.3 lp mm⁻¹.

Magnetic iron oxide is a typical narrow-band gap semiconductor photocatalyst, but its inherent magnetic aggregation effect and high electron–hole recombination rate seriously affect its photocatalytic performance. Here, α-Fe₂O₃/SiO₂ composite aerogels were prepared by combustion technology for the first time. The unique structure of α-Fe₂O₃/SiO₂ composite aerogels with amorphous silica coated with nanocrystalline iron oxide was confirmed. The composite aerogels exhibited a high specific surface area (479 m² g⁻¹ when calcined at 500 °C), so that they have excellent adsorption properties for organic pollutants (MB, RhB and TC) and Cr(VI). The composite aerogels with a Fe : Si molar ratio of 1 : 2 showed the best visible light photocatalytic properties for MB, RhB and TC. Based on the study of the band gap width, photocurrent density, transient photocurrent response, impedance of photocatalysts, and the unique structure of the composite aerogels, the mechanism of photocatalytic enhancement of composite aerogels was proposed. Finally, the mechanism of the preparation of α-Fe₂O₃/SiO₂ composite aerogels by combustion synthesis was analyzed. It is a potential technology for preparing high performance composite aerogel photocatalysts by high efficiency combustion technology.