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Elpasolite- and cryolite-type oxyfluorides can be regarded as superstructures of perovskite and exhibit structural diversity. While maintaining a similar structural topology with the prototype structures, changes in the size, electronegativity, and charge of cation and/or anion inevitably lead to structural evolution. Therefore, the nominal one-to-one relation suggested by a doubled formula of perovskite does not guarantee a simple 2-fold superstructure for many cases. Herein, the commensurately modulated perovskite-like K3TiOF5 was refined at 100 K from single-crystal X-ray diffraction data by using a pseudotetragonal subcell with lattice parameters of a = b = 6.066(2) A and c = 8.628(2) A. The length of the modulation vector was refined to 0.3a* + 0.1b* + 0.25c*. In the commensurate supercell of K3TiOF5, the B-site Ti4+ and K+ cations in [TiOF5]3- and [KOF5]6- octahedral units were found to be significantly displaced from the average atomic positions refined in the subcell. The displacements of the K+ cations are ±0.76 A, and those for the Ti4+ cations are approximately ±0.13 A. One- and two-dimensional solid-state 19F NMR measurements revealed two tightly clustered groups of resonances in a ratio of ca. 4:1, assigned to equatorial and axial fluorine, respectively, consistent with local [TiOF5]3- units. S/TEM results confirmed the average structure. Electronic structure calculations of the idealized I4mm subcell indicate the instability to a modulated structure arises from soft optical modes that is controlled by the octahedrally coordinated B-site potassium ions in the cryolite-type structure.

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[ZrF6]·1.134H2O (dmbpy = 6,6′-dimethyl-2,2′-bipyridyl, C12H12N2), (I), and bis[bis(6,6′-dimethyl-2,2′-bipyridine)copper(I)] hexafluoridohafnate(IV) 0.671-hydrate, [Cu(dmbpy)2]2[HfF6]·0.671H2O, (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.

We examine the role of molecular symmetry and hydrogen bonding in determining heterochiral intermolecular π–π stacking motifs in four racemic compounds with the formula [Cu(phen)2(H2O)][MF6]·xH2O (...

Complex crystal structures with subtle atomic-scale details are now routinely solved using complementary tools such as X-ray and/or neutron scattering combined with electron diffraction and imaging...

Single crystals of LiIn2SbO6 have been synthesized using a Li2MoO4 flux and characterized with X-ray diffraction. The compound crystallizes in a new structure-type with a rutile-related framework. ...

Racemates have recently received attention as nonlinear optical and piezoelectric materials. Here, a machine-learning-assisted composition space approach was applied to synthesize the missing M = Ti, Zr members of the Δ,Λ-[Cu(bpy)2(H2O)]2[MF6]2·3H2O (M = Ti, Zr, Hf; bpy = 2,2'-bipyridine) family (space group: Pna21). In each (CuO, MO2)/bpy/HF(aq) (M = Ti, Zr, Hf) system, the polar noncentrosymmetric racemate (M-NCS) forms in competition with a centrosymmetric one-dimensional chain compound (M-CS) based on alternating Cu(bpy)(H2O)22+ and MF62- basic building units (space groups: Ti-CS (Pnma), Zr-CS (P1), Hf-CS (P2/n)). Machine learning models were trained on reaction parameters to gain unbiased insight into the underlying statistical trends in each composition space. A human-interpretable decision tree shows that phase selection is driven primarily by the bpy:CuO molar ratio for reactions containing Zr or Hf, and predicts that formation of the Ti-NCS compound requires that the amount of HF present be decreased to raise the pH, which we verified experimentally. Predictive leave-one-metal-out (LOO) models further confirm that behavior in the Ti system is distinct from that of the Zr and Hf systems. The chemical origin of this distinction was probed via fluorine K-edge X-ray absorption spectroscopy. Pre-edge features in the F1s X-ray absorption spectra reveal the strong ligand-to-metal π bonding between Ti(3d - t2g) and F(2p) states that distinguishes the TiF62- anion from the ZrF62- and HfF62- anions.

Although compounds of the formula AMoO2F3 (A = K, Rb, Cs, NH4, Tl) have been known for decades, crystal structures have only been reported for CsMoO2F3 and NH4MoO2F3. The three compounds (Rb/NH4/Tl...

Ceftibuten, C15H14N4O6S2, with the systematic name (6R,7R)-7-{[(Z)-2-(2-amino-1,3-thiazol-4-yl)-4-carboxybut-2-enoyl]amino}-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid, is a third generation, orally administered cephalosporin antibiotic with broad antimicrobial activity and stability against extended spectrum β-lactamases. Ceftibuten can exist in various hydration states and to better understand the location of the water molecules of crystallization and their effect on the structure, the crystal structures of anhydrous (I) and hydrated (II) ceftibuten were determined and both occur as zwitterions with proton transfer from the carboxylate group adjacent to the β-lactam ring to the N atom of the thiazole ring. The β-lactam ring in (I) is almost planar but the equivalent grouping in (II) is slightly buckled. In the extended structure of (I), O—H...O and N—H...O hydrogen bonds link the molecules into a three-dimensional network. In (II), O—H...Oc, N—H...Oc, O—H...Ow, N—H...Ow and Ow—H...Ow (c = ceftibuten, w = water) hydrogen bonds link the components into a three-dimensional network. A large void space is present within the anhydrous crystal structure that can accommodate between two and three molecules of water.

Elpasolite- and cryolite-type oxyfluorides can be regarded as superstructures of perovskite and exhibit structural diversity. While maintaining a similar structural topology with the prototype structures, changes in the size, electronegativity, and charge of cation and/or anion inevitably lead to structural evolution. Therefore, the nominal one-to-one relation suggested by a doubled formula of perovskite does not guarantee a simple 2-fold superstructure for many cases. Herein, the commensurately modulated perovskite-like K

A noncentrosymmetric mixed alkali metal borate–bicarbonate, NaRb3B6O9(OH)3(HCO3), was synthesized and characterized. The compound crystallizes in the monoclinic space group P21 (No. 4) with a = 8.9...

The crystal structures of three copper(II)-bi­pyridine–MF6 (M = Si, Ta, Sn) compounds and a related coordination polymer are reported., We report the hydro­thermal syntheses and crystal structures of aqua­bis­(2,2′-bi­pyridine-κ2 N,N′)copper(II) hexa­fluorido­silicate tetra­hydrate, [Cu(bpy)2(H2O)][SiF6]·4H2O (bpy is 2,2′-bi­pyridine, C10H8N2), (I), bis­(2,2′-bi­pyridine-3κ2 N,N′)-di-μ-fluorido-1:3κ2 F:F;2:3κ2 F:F-deca­fluorido-1κ5 F,2κ5 F-ditantalum(V)copper(II), [Cu(bpy)2(TaF6)2], (II), tris­(2,2′-bi­pyridine-κ2 N,N′)copper(II) bis[hexa­fluorido­tantalate(V)], [Cu(bpy)3][TaF6]2, (III), and catena-poly[[di­aqua­(2,2′-bi­pyridine-κ2 N,N′)copper(II)]-μ-fluorido-tetra­fluorido­tin-μ-fluorido], [Cu(bpy)(H2O)2SnF6]n, (IV). Compounds (I), (II) and (III) contain locally chiral copper coordination complexes with C 2, D 2, and D 3 symmetry, respectively. The extended structures of (I) and (IV) are consolidated by O—H⋯F and O—H⋯O hydrogen bonds. The structure of (III) was found to be a merohedral (racemic) twin.

Complex crystal structures with subtle atomic-scale details are now routinely solved using complementary tools such as X-ray and/or neutron scattering combined with electron diffraction and imaging. Identifying unambiguous atomic models for oxyfluorides, needed for materials design and structure-property control, is often still a considerable challenge despite their advantageous optical responses and applications in energy storage systems. In this work, NMR crystallography and single-crystal X-ray diffraction are combined for the complete structure solution of three new compounds featuring a rare triangular early transition metal oxyfluoride cluster, [Mo

Although compounds of the formula AMoO

Synthesis of deep-ultraviolet (DUV) transparent materials, especially those with noncentrosymmetric structures, remains a great challenge in the solid-state chemistry community. A new DUV transparent borate, K3B5O8(OH)2, was discovered with a short absorption edge below 200 nm. The title compound crystallizes in a noncentrosymmetric, polar space group, Fdd2 (point group mm2), with the following cell parameters: a = 13.736(9) A, b = 19.317(12) A, c = 7.606(5) A. The structure of K3B5O8(OH)2 features a 3D framework composed of [B5O8(OH)2]3– basic building units that are linked by contacts with K+ cations and O–H···O hydrogen bonds. Second harmonic generation (SHG) measurements were performed, and an SHG efficiency of 0.5 × SiO2 was observed. Symmetry dictates that the χ14 component of the macroscopic NLO susceptibility is equal to zero in mm2, which prevents the maximal component of the microscopic NLO susceptibility for [B5O8(OH)2]3– units (χ14) from contributing to the macroscopic NLO susceptibility of th...

A noncentrosymmetric mixed alkali metal borate-bicarbonate, NaRb

Synthesis of deep-ultraviolet (DUV) transparent materials, especially those with noncentrosymmetric structures, remains a great challenge in the solid-state chemistry community. A new DUV transparent borate, K

Single crystals of two new metal tellurates Bi MTeO

Polar materials are of great technical interest but challenging to effectively synthesize. That is especially true for iodates, an important class of visible and mid-IR transparent nonlinear optical (NLO) materials. Aiming at developing a new design strategy for polar iodates, we successfully synthesized two sets of polymorphic early transition-metal (ETM) oxide-fluoride iodates, α- and β-Ba[VFO2(IO3)2] and α- and β-Ba2[VO2F2(IO3)2]IO3, based on the distinct structure-directing properties of oxide-fluoride anions. α- and β-Ba[VFO2(IO3)2] contain the trans-[VFO2(IO3)2]2– polyanion and crystallize in the nonpolar space groups Pbcn and P212121. In contrast, α- and β-Ba2[VO2F2(IO3)2]IO3 contain the cis-[VO2F2(IO3)2]3– Λ-shaped polyanion and crystallize in the polar space groups Pna21 and P21, respectively. Detailed structural analyses show that the variable polar orientation of trans-[VFO2(IO3)2]2– polyanions is the main cause of the nonpolar structures in α- and β-Ba[VFO2(IO3)2]. However, the Λ-shaped config...