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The syntheses and crystal structures of two bimetallic molecular compounds, namely, bis[bis(6,6′-dimethyl-2,2′-bipyridine)copper(I)] hexafluoridozirconate(IV) 1.134-hydrate, [Cu(dmbpy) 2 ] 2 [ZrF 6 ]·1.134H 2 O (dmbpy = 6,6′-dimethyl-2,2′-bipyridyl, C 12 H 12 N 2 ), (I), and bis[bis(6,6′-dimethyl-2,2′-bipyridine)copper(I)] hexafluoridohafnate(IV) 0.671-hydrate, [Cu(dmbpy) 2 ] 2 [HfF 6 ]·0.671H 2 O, (II), are reported. Apart from a slight site occupany difference for the water molecule of crystallization, compounds (I) and (II) are isostructural, featuring isolated tetrahedral cations of copper(I) ions coordinated by two dmbpy ligands and centrosymmetric, octahedral anions of fluorinated early transition metals. The tetrahedral environments of the copper complexes are distorted owing to the steric effects of the dmbpy ligands. The extended structures are built up through Coulombic interactions between cations and anions and π–π stacking interactions between heterochiral Δ- and Λ-[Cu(dmbpy) 2 ] + complexes. A comparison between the title compounds and other [Cu(dmbpy) 2 ] + compounds with monovalent and bivalent anions reveals a significant influence of the cation-to-anion ratio on the resulting crystal packing architectures, providing insights for future crystal design of distorted tetrahedral copper compounds. 

Perovskite oxides containing cations with unusually high-valent states such as Fe4+, Ni3+, and Cu3+ have attracted significant attention, often requiring a strong oxidizing atmosphere. This study addresses the challenges associated with the conventional precursor preparation for the high-pressure synthesis of BiNi1–xFexO3, a material exhibiting negative thermal expansion (NTE), specifically the need for mixed oxidants and the emission of NOx. We successfully established a modified method for preparing a highly oxidized, amorphous precursor containing Bi5+ and Ni3+ ions, ensuring high elemental dispersion by employing a reverse coprecipitation method with simultaneous oxidation using hypochlorite ions, enabling the synthesis of the target phase without the addition of external oxidizing agents. When subjected to high-pressure and high-temperature treatment, the BiNi1–xFexO3 phase crystallized directly from the amorphous precursor at a relatively low temperature (750 °C) and in a short time of less than 1 min, unlike the crystalline precursor prepared by conventional methods. Furthermore, leveraging the advantage of direct crystallization from the amorphous phase, we demonstrated that reducing the heating duration allows for the fabrication of fine particles, decreasing the size from 15 to 5 μm. These fine particles exhibited NTE over a wider temperature range without any degradation of the volume shrinkage magnitude. This synthetic method provides a safe, pollution-free, and potentially scalable route for BiNi1–xFexO3 fine particles and is expected to be applicable to the synthesis of other oxides containing anomalously high-valent ions. 

Crystalline solids are governed by universal structure-property relationships derived from their crystal symmetry, leading to paradigmatic rules on what properties they can and cannot exhibit. A long-held structure-property relationship is that centrosymmetric crystals cannot differentially absorb circularly polarized light. In this study, we demonstrate the design, synthesis, and characterization of the centrosymmetric material Li2Co3(SeO3)4, which violates this relationship not by defying symmetry-imposed selection rules but by invoking a photophysical process not previously characterized for crystalline solids. This process originates from an interference between linear dichroism and linear birefringence, referred to as LD-LB, and involves strong chiroptical signals that invert upon sample flipping. In addition to enabling a chiroptical response under centrosymmetry, this process opens up photonic engineering opportunities based on crystalline solids. 

A revised crystal structure of La(OH)2Cl is reported. This material is found to crystallize in space group P21/m and is isostructural to a series of Ln(OH)2Cl (Ln = Ce – Lu excluding Pm). The Ln(OH)2Cl series has been thoroughly studied, serving as analogues to proposed actinide structures for used nuclear fuel storage. The P21/m space group has been reported for each isostructural variant in this series. La(OH)2Cl is described in the context of the structural trends identified with this series. A lanthanum variant was previously reported, however, with symmetry corresponding to the space group P2/m. The data collected herein is compared to the previously published La(OH)2Cl in the space group P2/m. Here, we report an updated hydrothermal synthesis and revised crystallographic structure for La(OH)2Cl in P21/m. The reflection conditions of the collected X‐ray diffraction data, the bond valence sums of both structures, and density functional theory calculations are examined to justify the revised space group assignments. 

We present electronic structure calculations on layered nickelate oxyfluorides derived from the Ruddlesden- Popper aristotype structure in search of unidentified materials that may host nickelate superconductivity. By performing anion exchange of oxygen with fluorine, we create two heteroanionic La2NiO3F polymorphs and stabilize Ni1+ in four-coordinate and five-coordinate square planar and square pyramidal geometries, respectively. We further predict chemical reactions with high thermodynamic driving forces to guide their synthesis. These oxyfluorides are weakly correlated antiferromagnetic insulators, and their nonmagnetic phases exhibit quasi-two-dimensional Fermi surfaces dominated by Ni dx2−y2 states, which strikingly resemble undoped cuprate superconductors. We discuss how the oxyfluoride anion chemistry promotes Ni-O covalency and single-band character that is more similar to the cuprates than homoanionic infinite-layer nickelates. We use our understanding to propose doping strategies and layered LaSrNiO2F2 and La3Ni2O4F3 nickelate oxyfluorides with tunable electronic and magnetic structures for experimentation. 

The design of both molecular and non-molecular solid materials with specific properties fundamentally relies on the controlled synthesis of crystals with desired functional groups, bonding motifs, polarity, chirality, and more. To this end, fluoride and oxide-fluoride anions have been utilized as basic building units (BBUs) in the synthesis of noncentrosymmetric racemic materials for their ability to create polar axes that facilitate the breaking of an inversion center as demonstrated in a series of compounds with [MF6]2- anions (M = Ti, Zr, Hf). Targeting an analog with a [TaOF5]2- anion, the phase space of (CuO, Ta2O5)/bpy/HF(aq)/H2O (bpy = 2,2′- bipyridine) was investigated and three new compounds with Cu-bpy cations and Ta-fluoride or Ta-oxyfluoride anions were synthesized: [Cu(bpy)2][TaF6], [Cu (bpy)2][Ta2OF10], and [Cu(bpy)F(H2O)2]2[TaF7]•H2O with the anions [TaF6]-, [Ta2OF10]2-, and [TaF7]2-, respectively. The formation of these anions was found to be a product of both the concentration of hydrofluoric acid in solution and the ratio of metal-oxide starting materials to ligand. This work contributes to the understanding of mixed anion formation in the solid state.