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Abstract A bimetallic hydroxychalcogenide, BaZn₂Se₂(OH)₂, was synthesized through hydrothermal pouch methods. The single crystal X‐ray diffraction and electron diffraction indicates that the phase crystallizes in the orthorhombic space groupPnmaand is composed of anionic layers [ZnSe_3/3(OH)_1/1]⁻that are separated and charged balanced by Ba²⁺cations. The [ZnSe_3/3(OH)_1/1]^–layer comprises two unique Zn sites, which form interpenetrating zigzag chains with an in‐plane dipole moment and adopts a brownmillerite‐type structural motif. The adjacent layers contain tetrahedrally coordinated Zn chains of opposite handedness related by an inversion center, which cancel the microscopic dipoles to minimize the macroscopic electric polarization. The adoption of a brownmillerite structural motif in BaZn₂Se₂(OH)₂can be rationalized by the distinct charge difference between Se²⁻and OH⁻anions, which creates a sufficient dipole moment in the ZnSe₃(OH) tetrahedra to allow the occurrence of twisted chains. FTIR spectroscopy confirms the existence of OH⁻anions and DFT calculations indicate that BaZn₂Se₂(OH)₂is a semiconductor with a direct band gap. This work expands the chemistry of the brownmillerite family from traditional homoanionic oxides to multianion hydroxychalcogenides, offering a new opportunity to explore tunable structural complexity for better design of functional materials. 

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. 

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. 

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.