Supported Platinum Nanoparticles Catalyzed Carbon-Carbon Bond Cleavage of Polyolefins: Role of the Oxide Support Acidity.

Supported platinum nanoparticle catalysts are known to convert polyolefins to high-quality liquid hydrocarbons using hydrogen under relatively mild conditions. To date, few studies using platinum grafted onto various metal oxide (MxOy) supports have been undertaken to understand the role of the acidity of the oxide support in the carbon-carbon bond cleavage of polyethylene under consistent catalytic conditions. Specifically, two Pt/MxOy catalysts (MxOy = SrTiO3 and SiO2-Al2O3; Al = 3.0 wt %, target Pt loading 2 wt % Pt ∼1.5 nm), under identical catalytic polyethylene hydrogenolysis conditions (T = 300 °C, P(H2) = 170 psi, t = 24 h; Mw = ∼3,800 g/mol, Mn = ∼1,100 g/mol, D = 3.45, Nbranch/100C = 1.0), yielded a narrow distribution of hydrocarbons with molecular weights in the range of lubricants (Mw = < 600 g/mol; Mn < 400 g/mol; D = 1.5). While Pt/SrTiO3 formed saturated hydrocarbons with negligible branching, Pt/SiO2-Al2O3 formed partially unsaturated hydrocarbons (<1 mol % alkenes and ∼4 mol % alkyl aromatics) with increased branch density (Nbranch/100C = 5.5). Further investigations suggest evidence for a competitive hydrocracking mechanism occurring alongside hydrogenolysis, stemming from the increased acidity of Pt/SiO2-Al2O3 compared to Pt/SrTiO3. Additionally, the products of these polymer deconstruction reactions were found to be independent of the polyethylene feedstock, allowing the potential to upcycle polyethylenes with various properties into a value-added product.

Chiral and Polar Duality Design of Heteroanionic Compounds: Sr18 Ge9 O5 S31 Based on [Sr3 OGeS3 ]2+ and [Sr3 SGeS3 ]2+ Groups.

Chirality and polarity are the two most important and representative symmetry-dependent properties. For polar structures, all the twofold axes perpendicular to the principal axis of symmetry should be removed. For chiral structures, all the mirror-related symmetries and inversion axes should be removed. Especially for duality (polarity and chirality), all of the above symmetries should be broken and that also represents the highest-level challenge. Herein, a new symmetry-breaking strategy that employs heteroanionic groups to construct hourglass-like [Sr3 OGeS3 ]2+ and [Sr3 SGeS3 ]2+ groups to design and synthesize a new oxychalcogenide Sr18 Ge9 O5 S31 with chiral-polar duality is proposed. The presence of two enantiomers of Sr18 Ge9 O5 S31 is confirmed by the single-crystal X-ray diffraction. Its optical activity and ferroelectricity are also studied by solid-state circular dichroism spectroscopy and piezoresponse force microscopy, respectively. Further property measurements show that Sr18 Ge9 O5 S31 possesses excellent nonlinear optical properties, including the strong second harmonic generation efficiency (≈2.5 × AGS), large bandgap (3.61 eV), and wide mid-infrared transparent region (≈15.3 µm). These indicate that the unique microstructure groups of heteroanionic materials are conducive to realizing symmetry-breaking and are able to provide some inspiration for exploring the chiral-polar duality materials.

Rapid and Reversible Lithium Insertion in the Wadsley-Roth-Derived Phase NaNb13O33.

The development of new high-performing battery materials is critical for meeting the energy storage requirements of portable electronics and electrified transportation applications. Owing to their exceptionally high rate capabilities, high volumetric capacities, and long cycle lives, Wadsley-Roth compounds are promising anode materials for fast-charging and high-power lithium-ion batteries. Here, we present a study of the Wadsley-Roth-derived NaNb13O33 phase and examine its structure and lithium insertion behavior. Structural insights from combined neutron and synchrotron diffraction as well as solid-state nuclear magnetic resonance (NMR) are presented. Solid-state NMR, in conjunction with neutron diffraction, reveals the presence of sodium ions in perovskite A-site-like block interior sites as well as square-planar block corner sites. Through combined experimental and computational studies, the high rate performance of this anode material is demonstrated and rationalized. A gravimetric capacity of 225 mA h g-1, indicating multielectron redox of Nb, is accessible at slow cycling rates. At a high rate, 100 mA h g-1 of capacity is accessible in 3 min for micrometer-scale particles. Bond-valence mapping suggests that this high-rate performance stems from fast multichannel lithium diffusion involving octahedral block interior sites. Differential capacity analysis is used to identify optimal cycling rates for long-term performance, and an 80% capacity retention is achieved over 600 cycles with 30 min charging and discharging intervals. These initial results place NaNb13O33 within the ranks of promising new high-rate lithium-ion battery anode materials that warrant further research.

Beyond π-π Stacking: Understanding Inversion Symmetry Breaking in Crystalline Racemates.

The design of noncentrosymmetric (NCS) solid state materials, specifically how to break inversion symmetry between enantiomers, has intrigued chemists, physicists, and materials scientists for many years. Because the chemical complexity of molecular racemic building units is so varied, targeting these materials is poorly understood. Previously, three isostructural racemic compounds with a formula of [Cu(H2O)(bpy)2]2[MF6]2·2H2O (bpy = 2,2'=bipyridine; M = Ti, Zr, Hf) were shown to crystallize in the NCS space group Pna21, of polar, achiral crystal class mm2. In this work, we synthesized five new racemic compounds with the formula [Cu(H2O)(dmbpy)2]2[MF6]2·xH2O (dmbpy = 4,4'/5,5'-dimethyl-2,2'-bipyridine; M = Ti, Zr, Hf). Single crystal X-ray diffraction reveals that the five newly synthesized compounds feature equimolar combinations of Δ- and Λ-Cu(dmbpy)2(H2O)2+ complexes that are assembled into packing motifs similar to those found in the reported NCS structure but all crystallize in centrosymmetric (CS) space groups. Seven structural descriptors were created to analyze the intermolecular interactions on the assembly of Cu racemates in the CS and NCS structures. The structural analysis reveals that in the CS structures, the inversion center results from parallel heterochiral π-π stacking interactions between adjacent Cu racemates regardless of cation geometries, hydrogen bonding networks, or interlayer architectures, whereas in the NCS structure, nonparallel heterochiral π-π interactions between the adjacent Cu racemates preclude an inversion center. The parallel heterochiral π-π interactions in the CS structures can be rationalized by the restrained geometries of the methyl-substituted ligands. This work demonstrates that the introduction of nonparallel stacking can suppress the formation of an inversion center for an NCS racemate. A conceptual framework and practical approach linking the absence of inversion symmetry in racemates is presented for all NCS crystal classes.

Wet to Dry Controls Lanthanide Scandate Synthesis.

The choice of temperature and gas conditions used in a water pressure-controlled reactor is guided by density functional theory (DFT) to synthesize nearly phase-pure lanthanide scandate nanoparticles (LnScO3, Ln = La, Nd, Sm, Gd). In this synthetic method, low water-vapor partial pressures, well below water's gas liquidus, inhibit particle growth, while an excess of water vapor results in undesired rare-earth hydroxide and oxyhydroxide secondary phases. The optimal humidity for high-purity LnScO3 particle synthesis is shown to vary with the lanthanide; DFT is used to calculate the thermodynamics of secondary phase formation for each lanthanide tested such that the role of water vapor may be quantified and used to maintain phase purity (greater than 96 mol %) across the series. The combination of thermodynamic calculation and experimental confirmation with this pressure-controlled reactor provides an opportunity to explore analogous syntheses of other inorganic perovskite nanoparticles.

NaRb6(B4O5(OH)4)3(BO2) Featuring Noncentrosymmetry, Chirality, and the Linear Anionic Group BO2.

Noncentrosymmetric (NCS) structures are of particular interest owing to their symmetry-dependent physical properties, e.g., pyroelectricity, ferroelectricity, piezoelectricity, and nonlinear optical (NLO) behavior. Among them, chiral materials exhibit polarization rotation and host topological properties. Borates often contribute to NCS and chiral structures via their triangular [BO3] and tetrahedral [BO4] units and their numerous superstructure motifs. However, no chiral compound with the linear [BO2] unit has been reported to date. Herein, an NCS and chiral mixed-alkali-metal borate, NaRb6(B4O5(OH)4)3(BO2), with a linear BO2- unit in the structure was synthesized and characterized. The structure features a combination of three types of basic building units (BBUs), [BO2], [BO3], and [BO4] with sp-, sp2-, and sp3-hybridization of boron atoms, respectively. It crystallizes in the trigonal space group R32 (No. 155), one of the 65 Sohncke space groups. Two enantiomers of NaRb6(B4O5(OH)4)3(BO2) were found, and their crystallographic relationships are discussed. These results not only expand the small family of NCS structures with the rare linear BO2- unit but also prompt recognition to the fact that NLO materials have generally overlooked the existence of two enantiomers in achiral Sohncke space groups.

Two Distinct Cu(II)-V(IV) Superexchange Interactions with Similar Bond Angles in a Triangular "CuV2" Fragment.

The strength and sign of superexchange interactions are often predicted on the basis of the bond angles between magnetic ions, but complications may arise in situations with a nontrivial arrangement of the magnetic orbitals. We report on a novel molecular tetramer compound [Cu(H2O)dmbpy]2[V2O2F8] (dmbpy = 4,4'-dimethyl-2,2'-bipyridyl) that is composed of triangular "CuV2" fragments and displays a spin gap behavior. By combining first-principles calculations and electronic models, we reveal that superexchange Cu-V interactions carry drastically different coupling strengths along two Cu-F-V pathways with comparable bond angles in the triangular "CuV2" fragment. Counterintuitively, their strong disparity is found to originate from the restricted symmetry of the half-filled Cu dx2-y2 orbital stabilized by the crystal field, leading to one dominating antiferromagnetic Cu-V coupling in each fragment. We revisit the magnetic properties of the reported spin-gapped chain compound [enH2]Cu(H2O)2[V2O2F8] (enH2 = ethylene diammonium) containing similar triangular "CuV2" fragments, and the magnetic behavior of the molecular tetramer and the chain compounds is rationalized as that of weakly coupled spin dimers and spin trimers, respectively. This work demonstrates that fundamentally different magnetic couplings can be observed between magnetic ions with similar bond angles in a single spin motif, thus providing a strategy to introduce various exchange interactions combined with low dimensionality in heterometallic Cu(II)-V(IV) compounds.

Triple-Wavelength Lasing with a Stabilized ß-LaBSiO5:Nd3+ Crystal.

Multi-wavelength lasers, especially the triple-wavelength laser around 1060 nm, could be produced by the 4F3/2 → 4I11/2 transition of Nd3+ and present numerous challenges and opportunities in the field of optoelectronics. The Nd3+-doped high-temperature phase of LaBSiO5 (ß-LBSO) is an ideal crystal to produce triple-wavelength lasers; however, the crystal growth is challenging because of the phase transition from ß-LBSO to low-temperature phase (α-LBSO) at 162 °C. This phase transition is successfully suppressed when the doping content of Nd3+ is larger than 6.3 at. %, and the Nd3+-doped ß-LBSO is stable at room temperature. The local disorder of BO4 tetrahedra due to Nd3+ doping is essential to the stabilization of ß-LBSO. For the first time, the ß-LBSO:8%Nd3+ crystal with a dimension of 1.8 × 1.8 × 1.8 cm3 is obtained through the top-seeded solution method. The crystal shows strong optical absorption in the range of 785-815 nm, matching well with the commercial laser diode pumping source. The optical emission of 4F3/2 → 4I11/2 splits into four peaks with the highest optical emission cross section of 2.14 × 10-20 cm2 at 1068 nm. The continuous-wave triple-wavelength generation of coherent light at 1047, 1071, and 1092 nm is achieved with the highest output power of 235 mW and efficiency of 12.1%.

Strong Nonlinearity Induced by Coaxial Alignment of Polar Chain and Dense [BO3 ] Units in CaZn2 (BO3 )2.

Discovery of new efficient nonlinear optical (NLO) materials with large second-order nonlinearity for the short-wave ultraviolet spectral region (λPM ≤266 nm, PM=phase-matching) is still very challenging. Herein, a new beryllium-free borate CaZn2 (BO3 )2 with Sr2 Be2 B2 O7 (SBBO) double-layered like configuration was rationally designed, which not only preserves the structural merits but also eliminates the limitations of the SBBO crystal. CaZn2 (BO3 )2 shows a large PM second harmonic generation (SHG) reponse of 3.8×KDP, which is 38 times higher than that of its barium analogue. This enhancement mainly originates from the 1 [Zn2 O6 ]∞ polar chains with a large net dipole moment and [BO3 ] units with a high NLO active density. Our findings show the great significance of the [ZnO4 ] tetrahedra introduced strategy to design beryllium-free SBBO-type NLO crystals and also verify the feasibility of using simple non-isomorphic substitution to induce giant second-order nonlinearity enhancement.

Low Thermal Conductivity in Heteroanionic Materials with Layers of Homoleptic Polyhedra.

Although BiAgOSe, an analogue of a well-studied thermoelectric material BiCuOSe, is thermodynamically stable, its synthesis is complicated by the low driving force of formation from the stable binary and ternary intermediates. Here we have developed a "subtraction strategy" to suppress byproducts and produce pure phase BiAgOSe using hydrothermal methods. Electronic structure calculations and optical characterization show that BiAgOSe is an indirect bandgap semiconductor with a bandgap of 0.95 eV. The prepared sample exhibits lower lattice thermal conductivities (0.61 W·m-1·K-1 at room temperature and 0.35 W·m-1·K-1 at 650 K) than BiCuOSe. Lattice dynamical simulations and variable temperature diffraction measurements demonstrate that the low lattice thermal conductivity arises from both the low sound velocity and high phonon-phonon scattering rates in BiAgOSe. These in turn result primarily from the soft Ag-Se bonds in the edge-sharing AgSe4 tetrahedra and large sublattice mismatch between the quasi-two-dimensional [Bi2O2]2+ and [Ag2Se2]2- layers. These results highlight the advantages of manipulating the chemistry of homoleptic polyhedra in heteroanionic compounds for electronic structure and phonon transport control.

Expanding the Ambient-Pressure Phase Space of CaFe2O4-Type Sodium Postspinel Host-Guest Compounds.

CaFe2O4-type sodium postspinels (Na-CFs), with Na+ occupying tunnel sites, are of interest as prospective battery electrodes. While many compounds of this structure type require high-pressure synthesis, several compounds are known to form at ambient pressure. Here we report a large expansion of the known Na-CF phase space at ambient pressure, having successfully synthesized NaCrTiO4, NaRhTiO4, NaCrSnO4, NaInSnO4, NaMg0.5Ti1.5O4, NaFe0.5Ti1.5O4, NaMg0.5Sn1.5O4, NaMn0.5Sn1.5O4, NaFe0.5Sn1.5O4, NaCo0.5Sn1.5O4, NaNi0.5Sn1.5O4, NaCu0.5Sn1.5O4, NaZn0.5Sn1.5O4, NaCd0.5Sn1.5O4, NaSc1.5Sb0.5O4, Na1.16In1.18Sb0.66O4, and several solid solutions. In contrast to earlier reports, even cations that are strongly Jahn-Teller active (e.g., Mn3+ and Cu2+) can form Na-CFs at ambient pressure when combined with Sn4+ rather than with the smaller Ti4+. Order and disorder are probed at the average and local length-scales with synchrotron powder X-ray diffraction and solid-state NMR spectroscopy. Strong ordering of framework cations between the two framework sites is not observed, except in the case of Na1.16In1.18Sb0.66O4. This compound is the first example of an Na-CF that contains Na+ in both the tunnel and framework sites, reminiscent of Li-rich spinels. Trends in the thermodynamic stability of the new compounds are explained on the basis of crystal-chemistry and density functional theory (DFT). Further DFT calculations examine the relative stability of the CF versus spinel structures at various degrees of sodium extraction in the context of electrochemical battery reactions.

Scalable Synthesis of Pt/SrTiO3 Hydrogenolysis Catalysts in Pursuit of Manufacturing-Relevant Waste Plastic Solutions.

An improved hydrothermal synthesis of shape-controlled, size-controlled 60 nm SrTiO3 nanocuboid (STO NC) supports, which facilitates the scalable creation of platinum nanoparticle catalysts supported on STO (Pt/STO) for the chemical conversion of waste polyolefins, is reported herein. This synthetic method (1) establishes that STO nucleation prior to the hydrothermal treatment favors nanocuboid formation, (2) produces STO NC supports with average sizes ranging from 25 to 80 nm with narrow size distributions, and (3) demonstrates how SrCO3 formation and variation in solution pH prevent the formation of STO NCs. The STO synthesis was scaled-up and conducted in a 4 L batch reactor, resulting in STO NCs of comparable size and morphology (m = 22.5 g, davg = 58.6 ± 16.2 nm) to those synthesized under standard hydrothermal conditions in a lab-scale 125 mL autoclave reactor. Size-controlled STO NCs, ranging in roughly 10 nm increments from 25 to 80 nm, were used to support Pt deposited through strong electrostatic adsorption (SEA), a practical and scalable solution-based method. Using SEA techniques and an STO support with an average size of 39.3 ± 6.3 nm, a Pt/STO catalyst with 3.6 wt % Pt was produced and used for high-density polyethylene hydrogenolysis under previously reported conditions (170 psi H2, 300 °C, 96 h; final product: Mw = 2400, D = 1.03). As a well-established model system for studying the behavior of heterogeneous catalysts and their supports, the Pt/STO system detailed in this work presents a unique opportunity to simultaneously convert waste plastic into commercially viable products while gaining insight into how scalable inorganic synthesis can support transformative manufacturing.

Perovskite-like K3TiOF5 Exhibits (3 + 1)-Dimensional Commensurate Structure Induced by Octahedrally Coordinated Potassium Ions.

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) Å and c = 8.628(2) Å. 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 Å, and those for the Ti4+ cations are approximately ±0.13 Å. 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.

Crystal structures of two copper(I)-6,6'-dimethyl-2,2'-bipyridyl (dmbpy) compounds, [Cu(dmbpy)2]2[MF6]·xH2O (M = Zr, Hf; x = 1.134, 0.671).

The syntheses and crystal structures of two bimetallic mol-ecular compounds, namely, bis[bis-(6,6'-dimethyl-2,2'-bi-pyridine)-copper(I)] hexa-fluorido-zir-con-ate(IV) 1.134-hydrate, [Cu(dmbpy)2]2[ZrF6]·1.134H2O (dmbpy = 6,6'-di-methyl-2,2'-bipyri-dyl, C12H12N2), (I), and bis[bis-(6,6'-dimethyl-2,2'-bi-pyr-idine)-copper(I)] hexa-fluorido-hafnate(IV) 0.671-hydrate, [Cu(dmbpy)2]2[HfF6]·0.671H2O, (II), are reported. Apart from a slight site occupany difference for the water mol-ecule of crystallization, compounds (I) and (II) are isostructural, featuring isolated tetra-hedral cations of copper(I) ions coordinated by two dmbpy ligands and centrosymmetric, octa-hedral anions of fluorinated early transition metals. The tetra-hedral environments of the copper complexes are distorted owing to the steric effects of the dmbpy ligands. The extended structures are built up through Coulombic inter-actions between cations and anions and π-π stacking inter-actions 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 tetra-hedral copper compounds.

Expanding the chemistry of borates with functional [BO2]- anions.

More than 3900 crystalline borates, including borate minerals and synthetic inorganic borates, in addition to a wealth of industrially-important boron-containing glasses, have been discovered and characterized. Of these compounds, 99.9 % contain only the traditional triangular BO3 and tetrahedral BO4 units, which polymerize into superstructural motifs. Herein, a mixed metal K5Ba2(B10O17)2(BO2) with linear BO2 structural units was obtained, pushing the boundaries of structural diversity and providing a direct strategy toward the maximum thresholds of birefringence for optical materials design. 11B solid-state nuclear magnetic resonance (NMR) is a ubiquitous tool in the study of glasses and optical materials; here, density functional theory-based NMR crystallography guided the direct characterization of BO2 structural units. The full anisotropic shift and quadrupolar tensors of linear BO2 were extracted from K5Ba2(B10O17)2(BO2) containing BO2, BO3, and BO4 and serve as guides to the identification of this powerful moiety in future and, potentially, previously-characterized borate minerals, ceramics, and glasses.

Synthetic Lubricants Derived from Plastic Waste and their Tribological Performance.

The energy efficiency, mechanical durability, and environmental compatibility of all moving machine components rely heavily on advanced lubricants for smooth and safe operation. Herein an alternative family of high-quality liquid (HQL) lubricants was derived by the catalytic conversion of pre- and post-consumer polyolefin waste. The plastic-derived lubricants performed comparably to synthetic base oils such as polyalphaolefins (PAOs), both with a wear scar volume (WSV) of 7.5×10-5  mm-3 . HQLs also performed superior to petroleum-based lubricants such as Group III mineral oil with a WSV of 1.7×10-4  mm-3 , showcasing a 44 % reduction in wear. Furthermore, a synergistic reduction in friction and wear was observed when combining the upcycled plastic lubricant with synthetic oils. Life cycle and techno-economic analyses also showed this process to be energetically efficient and economically feasible. This novel technology offers a cost-effective opportunity to reduce the harmful environmental impact of plastic waste on our planet and to save energy through reduction of friction and wear-related degradations in transportation applications akin to synthetic oils.

Fluoridation of HfO2.

Fluoridation of HfO2 was carried out with three commonly used solid-state fluoridation agents: PVDF, PTFE, and NH4HF2. Clear and reproducible differences are observed in the reaction products of the fluoropolymer reagents and NH4HF2 with the latter more readily reacting in air. Strong evidence of distinct, previously unreported hafnium oxyfluoride phases is produced by both reactions, and efforts to isolate them were successful for the air-NH4HF2 reaction. Synchrotron XRD, 19F NMR, and elemental analysis were employed to characterize the phase-pure material which appears to be analogous to known Zr-O-F phases with anion-deficient α-UO3 structures such as Zr7O9F10. Comparison with the hydrolysis of ß-HfF4 under identical conditions depicts that the NH4HF2 route produces the oxyfluoride with greater selectivity and at lower temperatures. Thermodynamic calculations were employed to explain this result. Potential reaction pathways for the NH4HF2 fluoridation of HfO2 are discussed.

Crystal structures of three copper(II)-2,2'-bi-pyridine (bpy) compounds, [Cu(bpy)2(H2O)][SiF6]·4H2O, [Cu(bpy)2(TaF6)2] and [Cu(bpy)3][TaF6]2 and a related coordination polymer, [Cu(bpy)(H2O)2SnF6] n.

We report the hydro-thermal syntheses and crystal structures of aqua-bis-(2,2'-bi-pyridine-κ2 N,N')copper(II) hexa-fluorido-silicate tetra-hydrate, [Cu(bpy)2(H2O)][SiF6]·4H2O (bpy is 2,2'-bi-pyridine, C10H8N2), (I), bis-(2,2'-bi-pyridine-3κ2 N,N')-di-µ-fluorido-1:3κ2 F:F;2:3κ2 F:F-deca-fluorido-1κ5 F,2κ5 F-ditantalum(V)copper(II), [Cu(bpy)2(TaF6)2], (II), tris-(2,2'-bi-pyridine-κ2 N,N')copper(II) bis[hexa-fluorido-tantalate(V)], [Cu(bpy)3][TaF6]2, (III), and catena-poly[[di-aqua-(2,2'-bi-pyridine-κ2 N,N')copper(II)]-µ-fluorido-tetra-fluorido-tin-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.

Crystal structures of [Cu(phen)(H2O)3(MF6)]·H2O (M = Ti, Zr, Hf) and [Cu(phen)(H2O)2F]2[HfF6]·H2O.

The crystal structures of three bridged bimetallic mol-ecular compounds, namely, tri-aqua-2κ3 O-µ-fluorido-penta-fluorido-1κ5 F-(1,10-phenanthroline-2κ2 N,N')copper(II)titanium(IV) monohydrate, [Cu(TiF6)(phen)(H2O)3]·H2O (phen is 1,10-phenanthroline, C12H8N2), (I), tri-aqua-2κ3 O-µ-fluorido-penta-fluorido-1κ5 F-(1,10-phenanthroline-2κ2 N,N')copper(II)zirconium(IV) monohydrate, [Cu(ZrF6)(phen)(H2O)3]·H2O, (II), and tri-aqua-2κ3 O-µ-fluorido-penta-fluorido-1κ5 F-(1,10-phenanthroline-2κ2 N,N')copper(II)hafnium(IV) monohydrate, [Cu(HfF6)(phen)(H2O)3]·H2O, (III), and one mol-ecular salt, bis-[diaqua-fluorido-(1,10-phenanthroline-κ2 N,N')copper(II)] hexa-fluorido-hafnate(IV) dihydrate, [CuF(phen)(H2O)2]2[HfF6]·2H2O, (IV), are reported. The bridged bimetallic compounds adopt Λ-shaped configurations, with the octa-hedrally coordinated copper(II) center linked to the fluorinated early transition metal via a fluoride linkage. The extended structures of these Λ-shaped compounds are organized through both intra- and inter-molecular hydrogen bonds and inter-molecular π-π stacking. The salt compound [Cu(phen)(H2O)2F]2[HfF6]·H2O displays an isolated square-pyramidal Cu(phen)(H2O)2F+ complex linked to other cationic complexes and isolated HfF6 2- anions through inter-molecular hydrogen-bonding inter-actions.

Borates: A Rich Source for Optical Materials.

The primary goal of this review is to present a clear chemical perspective of borates in order to stimulate and facilitate the discovery of new borate-based optical materials. These materials, which exhibit structures as varied as they are complex, are needed to meet the urgent technological milestones. In the current period of rapid sociotechnological breakthroughs, the need for the rational design and discovery of novel borates with superior performance is greater than ever before. Through the sustained efforts of chemists and material scientists, more than 3900 boron-containing compounds, including borate minerals and synthetic borates, have been documented in the scientific literature. This review provides a survey of all the reported anhydrous borates and an analysis of their complex structural chemistry. State-of-the-art progress related to technological advances in borate-based nonlinear optical, birefringent, and self-frequency-doubling materials is surveyed, with special emphasis on the relationships between structural architectures and optical properties. More importantly, this review serves both as a scientific introduction for graduates and post-doctoral researchers to the chemical richness of solid-state borates and as a comprehensive reference for researchers interested in borate-based optical materials.