Cs4Mo5P2O22: a first Strandberg-type POM with 1D straight chains of polymerized [Mo5P2O23]6- units and moderate second harmonic generation response

Structural characterisation and optical properties of new alkaline earth phosphate CaMg(P4O12) and alkaline alumophosphate Cs3Al4(PO4)5

Two new family members of mixed alkali-earth metal phosphate and aluminophosphate CaMg(P4O12) and Cs3Al4(PO4)5 were prepared from a phosphate system using a high-temperature solution method. The structural analysis results show that two compounds crystallize in the monoclinic space group C2/c and P21/n and feature a three-dimensional (3D) network. The 3D structure of CaMg(P4O12) consists of [CaO6], [MgO6] octahedra and [P4O12] rings, in which the [MgO6] and [P4O12] rings link to form a 3D structure and Ca2+ cations are filled within the structure. Interestingly, for compound Cs3Al4(PO4)5, its structure features 4, 8, and 12-ring channels with [Al2O4O4P2O4], [Al4O8O8P4O8] and [Al6O12O12P6O12] units as BBUs, respectively; the Cs+ cations are located in the cavities. Furthermore, IR spectral analysis and thermal properties are discussed. UV-vis-NIR diffuse reflectance spectroscopy data show that the UV cutoff edges of CaMg(P4O12) are below 200 nm. Remarkably, in order to determine optical properties and the structure-properties relationship, theoretical calculations were adopted. Electronic structure calculations demonstrate that CaMg(P4O12) has an indirect band gap with the value of 5.86 eV, and Cs3Al4(PO4)5 has a direct band gap of 5.21 eV.

K2MgMoP2O10 and K3Mg2MoP3O14: two new molybdophosphates exhibiting different optical anisotropies induced by variable dimensionality of the anion framework

By introducing the d0 metal cation Mo6+ into phosphates, two new molybdophosphates, K2MgMoP2O10 and K3Mg2MoP3O14, were synthesized by spontaneous crystallization, and their structures were determined by single-crystal X-ray diffraction. K2MgMoP2O10 shows a two-dimensional layer composed of the uncommon eight-membered ring [Mo2P2O16] formed by [MoO6] and [PO4], while K3Mg2MoP3O14 shows isolated [MoP3O14] clusters composed of [MoO5] and [PO4]. K2MgMoP2O10 and K3Mg2MoP3O14 have UV cut-off wavelengths of 277 and 271 nm, respectively, which are significantly shorter than those of most recently published molybdophosphates. To the best of our acknowledge, K2MgMoP2O10 exhibits the largest birefringence (a calculated value of 0.187 at 546 nm) among reported alkali metal or alkaline earth metal molybdophosphates, which provides a way to explore new birefringent materials. First-principles analysis of the electronic structure shows that the large birefringence of K2MgMoP2O10 mainly originates from the [MoO6] units.

Constructing Two Cu-Modified Organophosphomolybdates from a Nanocluster to a One-Dimensional Chain for Boosted Visible-Light-Driven Hydrogen Production

Photocatalytic decomposition of water to produce hydrogen H2 is an ideal way to solve energy and environmental problems, and the development of highly efficient polyoxometalate catalysts for photocatalytic hydrogen production has attracted wide attention. Herein, two Cu-modified Strandberg-type organophosphomolybdates were successfully synthesized, [Cu(C8H7N3)(H2O)2]2[(C6H5PO3)2Mo5O15]·4H2O (1) and [Cu(phen)(H2O)][Cu(phen)(H2O)2][(C6H5PO3)2Mo5O15]·2H2O (2) ([(C6H5P)2Mo5O21]Cu2) (C8H7N3 = 2-(1H-pyrazol-3-yl)pyridine, phen = 1,10-phenanthroline). Two Strandberg-type organophosphomolybdates can be used for visible-light-driven hydrogen production. Also, compound 2 exhibits an H2 production rate of 6399 μmol g-1 h-1 after 8 h light exposure in the presence of photosensitization agent [Ir(dtbbpy)(ppy)2][PF6] and TEOA. In addition, cyclic tests showed that compound 2 could be recycled four times without a significant reduction in catalytic performance. This work offers fresh insight into the development of novel polyoxometalates for efficient hydrogen evolution.

Cerium-Encapsulated SbIII-SeIV-Templating Polyoxotungstate for Electrochemically Sensing Human Multidrug Resistance Gene Segment

A tower-like SbIII-SeIV-templating polyoxotungstate [H2N(CH3)2]12Na7H3[Ce0.5/Na0.5(H2O)5]2[SbSe2W21O75]2·50H2O (1) was synthesized, whose skeleton is assembled from two prolonged lacunary Dawson [SbSe2W21O75]13- units and two [Ce0.5/Na0.5(H2O)5]2+ linkers. The uncommon [SbSe2W21O75]13- unit can be viewed as a combination of one [SeW6O21]2- group grafted onto a trivacant Dawson [SbSeW15O54]11- subunit. The conductive composite 1-Au@rGO containing 1, gold nanoparticles, and reduced graphene oxide (rGO) was conveniently prepared, using which the 1-Au@rGO-based electrochemical genosensor was constructed for detecting human multidrug resistance gene segment. This work enriches structural types of dual-heteroatom-inserted polyoxometalates and promotes the application of polyoxometalates in genosensors.

Proton-Rich POM-Type K12Mo8O20(HPO4)8(PO4)Cl with Ion-Exchange Capabilities

A proton-rich POM-type molybdenum phosphate K₁₂Mo₈O₂₀(HPO₄)₈(PO₄)Cl was successfully obtained. It crystallizes in a noncentrosymmetric tetragonal space group of P-4 (No. 81) with the unit cell parameters of a = 9.6580(4) Å, c = 14.2607(10) Å, and Z = 1. The occurrence and positions of the light element H in the structure are inferred from single-crystal X-ray diffraction and confirmed by DFT calculations. The hydrogen atoms are found to form hydroxyl bonds with O atoms from P(2)O₄ and P(3)O₄ constituting the [Mo₄P₄O₂₆H₄]^4- layers but are only weakly bound to the isolated P(3)O₄ group through hydrogen bonds. The title compound presents a POM-type framework of corrugated [Mo₄P₄O₂₆H₄]^4- layers with four K⁺ ions and mixed ions (K₄Cl³⁺ and isolated PO₄^3-) orderly imbedding in the interlayer spaces with distances of 5.0396 (1) and 5.5966 (3) Å, respectively. The proton-rich nature and the structure feature were further verified by a series of experiments including ¹H, ⁷Li, and ³¹P MAS NMR spectra, IR spectroscopy, and thermal analysis. Moreover, the weak bonding and large interlayer spaces make K⁺ and H⁺ ions susceptible to exchange with ions of Cs⁺, Ba²⁺, Zn²⁺, Pb²⁺, Cu²⁺, and Ni²⁺ commonly presented in chemical pollutants or nuclear wastes. In addition, the title compound shows a small second-harmonic generation signal, consistent with its noncentrosymmetric structure.

A6Mo2P4O19 (A = Rb, Cs) and Rb2MoP2O9: new molybdophosphates with distinct polyanionic configurations

The exploration of A-Mo-P-O (A = Rb, Cs) systems has allowed several new Mo(V) phosphates, Rb₂MoP₂O₉, Rb₆Mo₂P₄O₁₉ and Cs₆Mo₂P₄O₁₉, to be synthesized through the spontaneous nucleation method. Single-crystal X-ray diffraction analysis reveals that the identical stoichiometry compounds Rb₂MoP₂O₉ and Cs₂MoP₂O₉ belong to different space groups C2/c and Pbca, respectively. Both compounds consist of dissimilar 1D [Mo-O-P]_∞ chains with different repeated building units, while monovalent cations fill in spaces to form 3D structures. However, Rb₆Mo₂P₄O₁₉ and Cs₆Mo₂P₄O₁₉ are isostructural and crystallize in the same space group of P2₁/c. They exhibit a 3D framework structure with 0D Mo₂O₅O₆P₄O₈ groups, which are separated by Rb/Cs atoms. Interestingly, structural relationships between the different monophosphates of the A-Mo-P-O (A = Rb, Cs) systems are presented in which distinct polyanionic configurations appear owing to the A/P ratios, as well as the size of the univalent cations. Further, detailed structural comparisons, optical properties and theoretical calculations are also discussed.

Assembly of a coordination polymer with sulphate-capped pentamolybdate units and copper: Synthesis, Structure, Magnetic and Catalytic studies

A new coordination polymer based upon the sulphate-capped pentamolybdate unit has been synthesized from the reaction of {Mo3S7Br6}2- with copper(II) bromide and pyridine, in DMF. The as-synthesized compound, formulated as...

RbMo2P3O14 with large birefringence mainly induced by highly distorted [MoO6] in uncommon [Mo2P3O14]∞ layers

The introduction of d⁰ transition metal Mo⁶⁺ cations into a phosphate generates a new acentric molybdophosphate, RbMo₂P₃O₁₄. It shows uncommon [Mo₂P₃O₁₄]_∞ layers composed of isolated [MoO₆] octahedra and [P₃O₁₀] groups. To the best of our acknowledge, it exhibits the largest birefringence (a calculated value of 0.166 at 546 nm) among reported molybdophosphates. In addition, it also possesses a shorter UV cut-off edge (about 250 nm) than other molybdates and molybdophosphates, indicating that it can be used as a birefringent crystal in the UV optical region. First-principles electronic structure analysis suggests that the large birefringence mainly originates from highly distorted [MoO₆].

Extended Condensed Ultraphosphate Frameworks with Monovalent Ions Combine Lithium Mobility with High Computed Electrochemical Stability

Extended anionic frameworks based on condensation of polyhedral main group non-metal anions offer a wide range of structure types. Despite the widespread chemistry and earth abundance of phosphates and silicates, there are no reports of extended ultraphosphate anions with lithium. We describe the lithium ultraphosphates Li₃P₅O₁₄ and Li₄P₆O₁₇ based on extended layers and chains of phosphate, respectively. Li₃P₅O₁₄ presents a complex structure containing infinite ultraphosphate layers with 12-membered rings that are stacked alternately with lithium polyhedral layers. Two distinct vacant tetrahedral sites were identified at the end of two distinct finite Li₆O₁₆^26– chains. Li₄P₆O₁₇ features a new type of loop-branched chain defined by six PO₄^3– tetrahedra. The ionic conductivities and electrochemical properties of Li₃P₅O₁₄ were examined by impedance spectroscopy combined with DC polarization, NMR spectroscopy, and galvanostatic plating/stripping measurements. The structure of Li₃P₅O₁₄ enables three-dimensional lithium migration that affords the highest ionic conductivity (8.5(5) × 10^–7 S cm^–1 at room temperature for bulk), comparable to that of commercialized LiPON glass thin film electrolytes, and lowest activation energy (0.43(7) eV) among all reported ternary Li–P–O phases. Both new lithium ultraphosphates are predicted to have high thermodynamic stability against oxidation, especially Li₃P₅O₁₄, which is predicted to be stable to 4.8 V, significantly higher than that of LiPON and other solid electrolytes. The condensed phosphate units defining these ultraphosphate structures offer a new route to optimize the interplay of conductivity and electrochemical stability required, for example, in cathode coatings for lithium ion batteries.

Synthesis, structure and characterization of three new Mg-containing phosphates with deep-UV cut-off edges

Three new Mg-containing phosphates, AMg₂P₃O₁₀ (A = Li, Cs) and Rb₂MgP₂O₇, have been successfully synthesized using a high-temperature solution method.

Li2ZnGeS4: a promising diamond-like infrared nonlinear optical material with high laser damage threshold and outstanding second-harmonic generation response

A promising IR nonlinear optical material Li₂ZnGeS₄ with a diamond-like configuration and high optical performance is reported.

K2TeP2O8: a new telluro-phosphate with a pentagonal Te–P–O layer structure

We report a new telluro-phosphate K₂TeP₂O₈ with an analogously pentagonal [TeP₂O₈]²⁻ layer structure.

Remarkable multimember-ring configurations in a new family of Na7MIISb5S12 (MII = Zn, Cd, Hg) exhibiting various three-dimensional tunnel structures

A new series of thioantimonates featuring the newly discovered trimer (M^II/Sb)₃S₉ and 12 + 12-MR configurations are verified as potential IR birefringent materials.

NaBaMIIIQ3 (MIII = Al, Ga; Q = S, Se): first quaternary chalcogenides with isolated edge-sharing (MIII2Q6)6− dimers

New series of quaternary chalcogenides with firstly discovered isolated edge-sharing (MIII2Q₆)⁶⁻ dimers showing obvious optical anisotropy were reported.

Synthesis of crystalline molybdenum oxides based on a 1D molecular structure and their ion-exchange properties

Crystalline molybdotellurate based on a 1D molecular structure exhibits interesting ion-exchange properties with both inorganic and organic cations.

Structure comparison and optical properties of Na7Mg4.5(P2O7)4: a sodium magnesium phosphate with isolated P2O7 units

The crystal structure of Na₇Mg_4.5(P₂O₇)₄ comprises a parallelogram channel composed of corner/edge-sharing isolated [P₂O₇] dimers and a Na(2)O₅ polyhedra to form a 3D framework and has an ultraviolet (UV) cut-off edge of about 210 nm.

A new method for the preparation of a [Sn2(H2PO2)3]Br SHG-active polar crystal via surfactant-induced strategy

A new SHG-active polar crystal, [Sn₂(H₂PO₂)₃]Br, was prepared by surfactant-induced strategy.

Enhancing optical anisotropy of crystals by optimizing bonding electron distribution in anionic groups

Contrivable deep-UV coherent light from an originally non-phase-matchable crystal was achieved by optimizing bonding electron distribution in anionic groups.

The first quaternary diamond-like semiconductor with 10-membered LiS4rings exhibiting excellent nonlinear optical performances

New DLS–Li₄HgGe₂S₇with novel 10-MR LiS₄rings and excellent performances(concurrently large SHG coefficient and impressive LDT) is reported.

Nonlinear optical response mechanism of noncentrosymmetric lead borate Pb6[B4O7(OH)2]3with three crystallographically independent [B4O7(OH)2]4−chains

Pb₆[B₄O₇(OH)₂]₃features three unique [B₄O₇(OH)₂]⁴⁻chains while lead cations and π-conjugated BO₃groups make contribution to the nonlinear optical effect.

Chiral polyoxomolybdate-based hybrid compounds obtained by spontaneous resolution: syntheses, structures and non-linear optical properties

By spontaneous resolution, two chiral hybrid 2D architectures [MMo₆O₂₁(glycine)₃]²⁻ (M = Te 1, Se 2) were obtained, which show an SHG efficiency of about 3.5 and 3.7 × KDP.

Experimental and theoretical studies on the linear and nonlinear optical properties of lead phosphate crystals LiPbPO4

LiPbPO₄achieved a desired balance between UV transparency (232 nm) and high nonlinear optical (NLO) activity (about 3 × KDP).

Ultrathin inorganic molecular nanowire based on polyoxometalates

The development of metal oxide-based molecular wires is important for fundamental research and potential practical applications. However, examples of these materials are rare. Here we report an all-inorganic transition metal oxide molecular wire prepared by disassembly of larger crystals. The wires are comprised of molybdenum(VI) with either tellurium(IV) or selenium(IV): {(NH4)2[XMo6O21]}n (X=tellurium(IV) or selenium(IV)). The ultrathin molecular nanowires with widths of 1.2 nm grow to micrometre-scale crystals and are characterized by single-crystal X-ray analysis, Rietveld analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, thermal analysis and elemental analysis. The crystals can be disassembled into individual molecular wires through cation exchange and subsequent ultrasound treatment, as visualized by atomic force microscopy and transmission electron microscopy. The ultrathin molecular wire-based material exhibits high activity as an acid catalyst, and the band gap of the molecular wire-based crystal is tunable by heat treatment.

Theoretical exploration to the cation effect on the second-order nonlinear optical properties of Strandberg-type polyoxometalates

The combination of cations with octahedral coordinated d0 transition metal ions has been proved to be an effective way for designing new polar materials. So we investigate the second-order nonlinear optical (NLO) properties of Strandberg-type polyoxometalates (POMs) with alkali metal cations M 6 Mo 5 X 2 O 23 ( M = K +, Rb +, Cs +; X = P , As ) and M 4 M o5 X 2 O 21 ( M = K +, Rb +, Cs +; X = S , Se , Te ) by density functional theory (DFT) method. The calculated results show that this kind of Strandberg-type POMs possesses remarkably large molecular second-order NLO polarizability, especially for the Cs 6 Mo 5 P 2 O 23 (system Ic), which has a computed β0 value of 12526 a.u. and might be an excellent second-order NLO material. Moreover, the cations have important impact on the second-order NLO polarizabilities. Therefore, a careful choice of appropriate cations may allow the control of the second-order NLO response on these Strandberg-type POMs, which may provide a new route to design efficient NLO materials.

Temperature-induced racemic compounds and chiral conglomerates based on polyoxometalates and lanthanides: syntheses, structures and catalytic properties

Four new species, originated from [Co₂Mo₁₀H₄O₃₈]⁶⁻ and lanthanides by adjusting the reaction temperature, are reported, which act as Lewis acid–base catalysts toward the cyanosilylation reaction.