A new class of hybrid materials via salt inclusion: novel copper(II) arsenates Na(5)ACu(4)(AsO(4))(4)Cl(2) (A = Rb, Cs) composed of alternating covalent and ionic lattices

Influence of Cation-Size Effects of Alkaline Earth (Ae) Metals on Dimensionality and Optical Anisotropy Regulation in K4AeP2S8 Thiophosphates

Cationic substitution demonstrates significant potential for regulating structural dimensionality and physicochemical performance owing to the cation-size effect. Leveraging this characteristic, this study synthesized a new family of K4AeP2S8 (Ae = alkaline earth elements: Mg, Ca, Sr, and Ba) thiophosphates, involving the substitution of Ae2+ cations. The synthesized compounds crystallized in distinct space groups, monoclinic P2/c (Ae = Mg) versus orthorhombic Ibam (Ae = Ca, Sr, and Ba), exhibiting intriguing dimensionality transformations from zero-dimensional (0D) [Mg2P4S16]8- clusters in K4MgP2S8 to 1D ∞[AeP2S8]4- chains in other K4AeP2S8 thiophosphates owing to the varying ionic radii of Ae2+ cations, Ae-S bond lengths, and coordination numbers of AeSn (Mg: n = 6 versus other: n = 8). Experimental investigations revealed that K4AeP2S8 thiophosphates featured wide optical bandgaps (3.37-3.64 eV), and their optical absorptions were predominantly influenced by the S 3p and P 3s orbitals, with negligible contributions from the K and Ae cations. Notably, within the K4AeP2S8 series, birefringence (Δn) increased from K4MgP2S8 (Δn = 0.034) to other K4AeP2S8 (Δn = 0.050-0.079) compounds, suggesting that infinite 1D chains more significantly influence Δn origins than 0D clusters, thus offering a feasible approach for enhancing optical anisotropy and exploring potential new birefringent materials.

(Na,Li)3(Cl,OH)[Cu3OAl(PO4)3]: a first salt-inclusion aluminophosphate oxocuprate with a new type of crystal structure

The synthesis and characterization of a first salt-inclusion aluminophosphate oxocuprate, (Na,Li)₃(Cl,OH)[Cu₃OAl(PO₄)₃], obtained as single crystals, is reported. A novel phase, with a strongly pseudo-orthorhombic structure, is described as a monoclinic crystal structure established by the study of a pseudomerohedric microtwin. It was investigated using scanning electron microscopy, microprobe analysis and low-temperature X-ray diffraction. The composite crystal structure represents an original framework assembled from Cu-centered polyhedra, AlO₆ octahedra and PO₄ tetrahedra with channels, which incorporate the Na/Li salt component [(Na,Li)₃(Cl,OH)]²⁺ that ensures electroneutrality of the compound. Layers of strongly corrugated chains of Cu-centered octahedra with shared edges and linked by PO₄ tetrahedra are shown to be topologically identical with the layers also built from Cu-centered polyhedra and AsO₄/VO₄ tetrahedra forming the crystal structure of a fumarolic mineral aleutite, (M_0.5Cl)[Cu₅O₂(AsO₄)(VO₄)] [Siidra et al. (2019). MinMag, 83, 847-853]. `Sawtooth chains' and pairs of Cu-centered octahedra inherent in the title structure may be of interest in solid-state physics, engaging studies in the field of low-dimensional and frustrated magnetism.

Hydrothermal Synthesis and a Composite Crystal Structure of Na6Cu7BiO4(PO4)4[Cl,(OH)]3 as a Candidate for Quantum Spin Liquid

A novel sodium bismuth oxo-cuprate phosphate chloride, Na₆Cu₇BiO₄(PO₄)₄[Cl_2.23(OH)_0.77], containing square-kagomé layers of Cu²⁺ has been synthesized by hydrothermal techniques. The compound crystallizes in the tetragonal space group P4/nmm, a = 10.0176(4), c = 10.8545(6), Z = 2, V = 1089.3(1) ų, R₁ = 0.021, wR = 0.053, S = 1.32. Its composite crystal structure includes [O₄Cu₆Bi]⁷⁺ layers, which are formed by the clusters of oxygen-centered tetrahedra [OCu₃Bi]. These positively charged two periodic fragments are intercalated in a negatively charged [CuNa₆Cl₃(PO₄)₄]^7- matrix built by Na-centered polyhedra, PO₄ tetrahedra, and CuO₄Cl pyramids. The composite character of the crystal structure of Na₆Cu₇BiO₄(PO₄)₄[Cl_2.23(OH)_0.77], as well as the way of its self-assembly, are discussed in close connection with the sulfohalite Na₆ClF(SO₄)₂ salt. It is shown that the "host-guest" model of the formation of the tetragonal Na₆Cu₇BiO₄(PO₄)₄[Cl_2.23(OH)_0.77] phase is due to the group-subgroup symmetry relation with the cubic crystal structure of mineral sulfohalite and is also supported by the crystallization condition in excess sodium chloride. The magnetic subsystem of Na₆Cu₇BiO₄(PO₄)₄[Cl_2.23(OH)_0.77] is represented by a dense square-kagomé network of 2Cu1 and 4Cu2 ions, decorated with weakly bonded Cu3 ions. Measurements of magnetization and heat capacity indicate the absence of long-range order up to 2 K, which makes this compound a candidate for a highly demanded spin liquid.

Magnetodielectric detection of magnetic quadrupole order in Ba(TiO)Cu4(PO4)4 with Cu4O12 square cupolas

In vortex-like spin arrangements, multiple spins can combine into emergent multipole moments. Such multipole moments have broken space-inversion and time-reversal symmetries, and can therefore exhibit linear magnetoelectric (ME) activity. Three types of such multipole moments are known: toroidal; monopole; and quadrupole moments. So far, however, the ME activity of these multipole moments has only been established experimentally for the toroidal moment. Here we propose a magnetic square cupola cluster, in which four corner-sharing square-coordinated metal-ligand fragments form a noncoplanar buckled structure, as a promising structural unit that carries an ME-active multipole moment. We substantiate this idea by observing clear magnetodielectric signals associated with an antiferroic ME-active magnetic quadrupole order in the real material Ba(TiO)Cu₄(PO₄)₄. The present result serves as a useful guide for exploring and designing new ME-active materials based on vortex-like spin arrangements.

[A3X][Ga3PS8] (A = K, Rb; X = Cl, Br): promising IR non-linear optical materials exhibiting concurrently strong second-harmonic generation and high laser induced damage thresholds

We have developed a new series of salt-inclusion chalcogenides, which are promising IR-NLO materials exhibiting large second-harmonic generation and high laser-induced damage thresholds.

Mid-far infrared (IR) non-linear optical (NLO) materials are of great importance in military and civil fields. However, commercial IR-NLO crystals (such as AgGaS₂, AgGaSe₂ and ZnGeP₂) do not currently satisfy the requirements of large second-harmonic generation (SHG) and high laser induced damage thresholds (LIDTs), which seriously limits their practical applications. Herein, we have developed a new series of salt-inclusion chalcogenides, [A₃X][Ga₃PS₈] (A = K, Rb; X = Cl, Br), which are constructed from alternate stacking of adamantane-like [Ga₃PS₁₀]^6– cluster layers and cationic [A₃X]²⁺ salt layers. Importantly, they display both large SHG responses of several-fold and high LIDTs for dozens of times that of commercial AgGaS₂, which exhibit the highest LIDTs among the reported IR-NLO materials with a larger SHG conversion efficiency than that of AgGaS₂. These properties together with wide transparent region, type I phase-matching features and congruent-melting behaviors indicate they are promising IR-NLO materials.

Three iodocuprate hybrids symmetrically modulated by positional isomers and the chiral conformation of N-benzyl-methylpyridinium

The successful synthesis and structural analysis of three novel iodocuprate frameworks, [N-Bz-2-MePy]₂[Cu₅I₇] (1), [N-Bz-3-MePy]₂[Cu₅I₇] (2), and [N-Bz-4-MePy][Cu₄I₅] (3), exhibit an excellent structural directing effect of the conformationally chiral N-Bz-MePy⁺.

BaPbSi2O6·BaSO4: the first mixed anionic compound synthesized via BaSO4 salt-inclusion

A novel silicate and sulfate compound, BaPbSi₂O₆·BaSO₄, has been synthesized via BaSO₄ salt-inclusion.

Synthesis and structure of bismuth(III)-containing noncentrosymmetric phosphates, Cs3KBi2M4(PO4)6Cl (M = Mn, Fe). Monoclinic (Cc) and tetragonal (P43) polymorphs templated by chlorine-centered Cl(Bi2Cs) acentric units

Single crystals of three new noncentrosymmetric (NCS) phosphates, α (1) and β (2) forms of Cs(3)KBi(2)Mn(4)(PO(4))(6)Cl and α-Cs(3)KBi(2)Fe(4)(PO(4))(6)Cl (3), were grown in a reactive CsCl/KCl molten-salt media. Their structures were determined by single-crystal X-ray diffraction methods showing that the α form crystallizes in the space group Cc (No. 9), which is in one of the 10 NCS polar crystal classes, m (2/m) while the β form crystallizes in P4(3) (No. 78) of another polar class, 4 (4/m). The unit cell parameters of the α form can be approximately correlated with that of the β form via the 3 × 3 orientation matrix [0.5, 0.5, 0; -0.5, 0.5, 0; 0, 0, 2 sin β]. The structures of these otherwise complicated phosphates exhibit two types of channels with circular and elliptical windows where the Cl-centered Cl(Bi(2)Cs) acentric unit is located. The neighboring acentric units are arranged in a parallel fashion in the α form, resulting in the monoclinic (Cc) lattice, but "antiparallel" in the β form, thus giving the tetragonal (P4(3)) unit cell. 1-3 feature the compatible M-O-P unit that contains four crystallographically independent MO(x) (x = 4, 5) polyhedra, which are connected to the Cl(Bi(2)Cs) acentric unit through one short and one long M(II)···Cl bond. The compositions of 1 and 2 consist of three Mn(2+) (d(5)) and one Mn(3+) (d(4)) per formula unit and that of 3 has three Fe(2+) (d(6)) and one Fe(3+) (d(5)). Bond valence sums reveal that, in the α phase, the trivalent site adopts distorted tetrahedral M(1)(3+)O(4) coordination and, in the β phase, distorted trigonal-bipyramidal M(4)(3+)O(5). Thus far, the iron phase has only been isolated in the α form presumably because of little extra stabilization energy gain if the Fe(2+) d(6) ion were to occupy the M(1)O(4) site. The possible origins pertaining to the structural differences in the α and β forms are discussed.

Synthesis of a New Class of Hybrid Solids via Salt Inclusion

Via salt inclusion methods, we have recently isolated a new class of transitionmetal-containing hybrid solids that consist of a composite structure of covalent and ionic lattices. These new solids can be synthesized by conventional high-temperature, solid-state methods employing reactive molten alkali and alkaline-earth metal halide salts. Single crystal structure studies have revealed fascinating extended salt lattices that exhibit structural directing effects that give rise to a variety of nano-structured covalent oxide frameworks. Depending upon the composition of incorporated salt and the coordination environment of halide anions, resulting covalent lattices range from sheets, clusters, to porous structures. Due to the weak interaction between the two chemically dissimilar lattices, the salt lattice, in some cases, is removable showing reversible salt-intercalation at room temperature. In this report, we will demonstrate the utilities of salt-inclusion reactions in the formation of metal-oxide nanostructures in the selected compound families. We will also give some highlights on the recent discoveries of non-centrosymmetric solids via newly exploited salt-inclusion methods.

Synthesis, Crystal and Band Structures, and Properties of a New Mixed Three-Dimensional Framework Metal Pnictidehalide Semiconductor, (Hg6Sb4)(CdI6)

A new, quaternary mercury and cadmium pnictidehalide semiconductor (Hg6Sb4)(CdI6) (1) has been prepared by the solid-state reaction and structurally characterized by single-crystal X-ray diffraction analysis. Compound 1 crystallizes in the space group R-3c of the rhombohedral system with four formula units in a cell: a=13.3818(9) A, alpha=90.93 degrees, and V=2395.3(3) A3. The crystal structural novelty of 1 derives from the fact that a 3-D mercury antimonide cationic network interpenetrates with an unusual 3-D cadmium iodide octahedral anionic network through the weak covalent interactions between mercury and iodine atoms to form a mixed 3-D framework. Among them, the cationic moiety features a perovskite-like 3-D network while the anionic moiety is characterized by a 3-D I6 octahedral anionic network with two-thirds I6 octahedra being occupied by Cd atoms. The optical properties were investigated in terms of the diffuse reflectance and Fourier transform infrared spectra. The electronic band structure along with density of states calculated by the density functional theory method indicates that compound 1 is a semiconductor with a direct band gap and that the optical absorption of 1 is mainly ascribed to the charge transitions from I-5p and Sb-5p states to Cd-5s and Hg-6s states.