Novel Tungstovanadate Wells−Dawson Organic–Inorganic Heteropolyoxometalate Compound: Synthesis and Crystal Structure of [Cu₂(2,2′-bipy)₂(Inic)₂(H₂O)₂][Y(Inic)₂(H₂O)₅]H₃[V₂W₁₈O₆₂]·5.5H₂O (Where 2,2′-bipy = 2,2′-Bipyridine, Inic = γ-Picolinic Acid)

A novel organic–inorganic heteropolyoxometalate compound [Cu2(2,2′-bipy)2(Inic)2(H2O)2][Y(Inic)2(H2O)5]H3[V2W18O62]·5.5H2O (1) was hydrothermally synthesized by reaction of Cu(CH3COO)2·4H2O, Y(NO3)3, V2O5, K9BW11O39, 2,2′-bipyridine, and γ-picolinic acid. The molecular asymmetric unit of 1 consists of one crystallographically independent heteropolyoxoanion [V2W18O62]6−, one dinuclear copper cation [Cu2(2,2′-bipy)2(Inic)2(H2O)2]2+, one nine-coordinated yttrium cation [Y(Inic)2(H2O)5]+, 5.5 water molecules of crystallization, and three protons based on charge balance. The polyoxoanion of 1 retains a classical Wells−Dawson structure. Unexpectedly, the Dawson-type anion with V atoms as heteroatoms has never been reported up to now

Novel Tungstovanadate Wells−Dawson Organic–Inorganic Heteropolyoxometalate Compound: Synthesis and Crystal Structure of [Cu₂(2,2′-bipy)₂(Inic)₂(H₂O)₂][Y(Inic)₂(H₂O)₅]H₃[V₂W₁₈O₆₂]·5.5H₂O (Where 2,2′-bipy = 2,2′-Bipyridine, Inic = γ-Picolinic Acid)

A novel organic–inorganic heteropolyoxometalate compound [Cu2(2,2′-bipy)2(Inic)2(H2O)2][Y(Inic)2(H2O)5]H3[V2W18O62]·5.5H2O (1) was hydrothermally synthesized by reaction of Cu(CH3COO)2·4H2O, Y(NO3)3, V2O5, K9BW11O39, 2,2′-bipyridine, and γ-picolinic acid. The molecular asymmetric unit of 1 consists of one crystallographically independent heteropolyoxoanion [V2W18O62]6−, one dinuclear copper cation [Cu2(2,2′-bipy)2(Inic)2(H2O)2]2+, one nine-coordinated yttrium cation [Y(Inic)2(H2O)5]+, 5.5 water molecules of crystallization, and three protons based on charge balance. The polyoxoanion of 1 retains a classical Wells−Dawson structure. Unexpectedly, the Dawson-type anion with V atoms as heteroatoms has never been reported up to now

Controlled Assembly of Inorganic–Organic Frameworks Based on [SeMo₆O₂₁]^4– Polyanion

The chemical system based on [SeMo₆O₂₁]^4– polyanion and carboxylate ligand has been investigated. According to the inherent nature of organic groups, a series of selenomolybdates with three architectures have been isolated through rational and deliberate synthetic routes by stereospecific addition of different carboxylic acids. Such an approach is potentially interesting for {SeMo₆} cluster, which exhibits a high surface nucleophilicity and is capable of being functionalized by covalently bound carboxylic acids. Investigation of the assemblies reveals that carboxylic acids have good flexibility and conformational freedom, representing the powerful chemical tools to control the polyanion assembly processes

Carboxylate-Functionalized Phosphomolybdates: Ligand-Directed Conformations

The [HPMo₆O₂₁]^2– units and carboxylate linkers can be combined to build novel polyanions by a carefully designed complementary system in self-assembly processes depending only on the number of carboxyl groups and the nature of carboxylic acids. Complexes (NH₄)₅[HPMo₆O₂₁(O₂CC₆H₄OH)₃]·4H₂O (<b>1</b>), (NH₄)₈H₂[(HPMo₆O₂₁)₂(C₂O₄)₃]·13H₂O (<b>2</b>), (NH₄)₂₀[(HPMo₆O₂₁)₄(O₂CCH₂CO₂)₆]·17H₂O (<b>3</b>), and Cs₂(NH₄)₁₀[(HPMo₆O₂₁)₂(HPO₃)­{C₆H₃(CO₂)₃}₂]·5H₂O (<b>4</b>) have been synthesized by a simple one-pot reaction of (NH₄)₆Mo₇O₂₄·4H₂O, H₃PO₃, and carboxylic acid ligands in aqueous solution. Formation of these compounds is critically dependent on the identifying carboxylic acids, which play the important templated role in assembly processes. The stability of these clusters was explored using electrospray ionization mass spectrometry (ESI-MS) and ³¹P NMR spectroscopy, and electron paramagnetic resonance (EPR) experiments further demonstrated the result of the interesting photochromic property

Controlled Assembly of Inorganic–Organic Frameworks Based on [SeMo₆O₂₁]^4– Polyanion

The chemical system based on [SeMo₆O₂₁]^4– polyanion and carboxylate ligand has been investigated. According to the inherent nature of organic groups, a series of selenomolybdates with three architectures have been isolated through rational and deliberate synthetic routes by stereospecific addition of different carboxylic acids. Such an approach is potentially interesting for {SeMo₆} cluster, which exhibits a high surface nucleophilicity and is capable of being functionalized by covalently bound carboxylic acids. Investigation of the assemblies reveals that carboxylic acids have good flexibility and conformational freedom, representing the powerful chemical tools to control the polyanion assembly processes

High-Efficiency Mechanical Energy Storage and Retrieval Using Interfaces in Nanowires

By molecular dynamics simulations, we demonstrate a new concept for mechanical energy storage and retrieval using surface energy as reservoir in body-centered cubic (bcc) tungsten nanowire, achieving a combination of unique features such as large and constant actuation stress (>3 GPa), exceptionally large actuation strain (>30%) and energy density, and >98% energy storage efficiency. The underlying mechanism is a shear-dominant diffusionless transformation akin to martensitic transformation, but driven by surface rather than bulk free energies, and enabled by motion of coherent twin boundary, whose migration has been shown to possess ultralow friction in bcc metals. Aside from energy storage, such surface-energy driven displacive transformations are important for phase transformation and energy-matter control at the nanoscale

Carboxylate-Functionalized Phosphomolybdates: Ligand-Directed Conformations

The [HPMo₆O₂₁]^2– units and carboxylate linkers can be combined to build novel polyanions by a carefully designed complementary system in self-assembly processes depending only on the number of carboxyl groups and the nature of carboxylic acids. Complexes (NH₄)₅[HPMo₆O₂₁(O₂CC₆H₄OH)₃]·4H₂O (<b>1</b>), (NH₄)₈H₂[(HPMo₆O₂₁)₂(C₂O₄)₃]·13H₂O (<b>2</b>), (NH₄)₂₀[(HPMo₆O₂₁)₄(O₂CCH₂CO₂)₆]·17H₂O (<b>3</b>), and Cs₂(NH₄)₁₀[(HPMo₆O₂₁)₂(HPO₃)­{C₆H₃(CO₂)₃}₂]·5H₂O (<b>4</b>) have been synthesized by a simple one-pot reaction of (NH₄)₆Mo₇O₂₄·4H₂O, H₃PO₃, and carboxylic acid ligands in aqueous solution. Formation of these compounds is critically dependent on the identifying carboxylic acids, which play the important templated role in assembly processes. The stability of these clusters was explored using electrospray ionization mass spectrometry (ESI-MS) and ³¹P NMR spectroscopy, and electron paramagnetic resonance (EPR) experiments further demonstrated the result of the interesting photochromic property

One-Dimensional Strain Solitons Manipulated Superlubricity on Graphene Interface

The frictional properties of a uniaxial tensile strained graphene interface are studied using molecular dynamics simulations. A misfit interval statistical method (MISM) is applied to characterize the atomistic misfits at the interface and strain soliton pattern. During sliding along both armchair and zigzag directions, the lateral force depends on the ratio of graphene flake length (L) to strain soliton spacing (Ls) and becomes nearly zero when L is an integer multiple of 3Ls. Furthermore, the strain solitons propagate along the armchair sliding direction dynamically, while fission and fusion are repeatedly evidenced along the zigzag sliding direction. The underlying superlubric mechanism is revealed by a single-atom quasi-static model. The cancellation of lateral force for the contacting atoms exhibits a dynamic balance when sliding along the armchair direction but a quasi-static balance along the zigzag direction. A diagram of flake length with respect to tensile strain (L–ε) is proposed to predict the critical condition for the transition from nonsuperlubricity to superlubricity. Our results provide insights on the design of superlubric devices

Two-Dimensional Polyoxoniobates Constructed from Lindqvist-Type Hexaniobates Functionalized by Mixed Ligands

By introducing mixed ligands into the hexaniobate system, three novel organic−inorganic hybrids, [Cu(en)2]2{[Cu(1,10-phen)][Cu(1,10-phen)(H2O)]Nb6O19}·10.5H2O (1), [Cu(en)2]2{[Cu(2,2′-bipy)][Cu(2,2′-bipy)(H2O)]Nb6O19}·9H2O (2) and [Cu(1,2-dap)2]2{[Cu(2,2′-bipy)][Cu(2,2′-bipy)(H2O)]Nb6O19}·11H2O (3) (en = ethylenediamine, 1,10-phen = 1,10-phenanthroline, 2,2′-bipy = 2,2′-bipydine, 1,2-dap = 1,2-diaminopropane), have been synthesized by the solution diffusion method and characterized by elemental analyses, IR spectra, UV spectroscopy, thermogravimetric analyses, and single-crystal X-ray diffraction. 1, 2, and 3 can be formularized as [Cu(L1)2]2{[Cu(L2)][Cu(L2)(H2O)]Nb6O19}·nH2O (L1 = en for 1 and 2, 1,2-dap for 3, L2 = 1,10-phen for 1, 2,2′-bipy for 2 and 3, n = 10.5 for 1, 9 for 2, 11 for 3), and all exhibit the two-dimensional (2D) network architecture built by [Cu(L1)2]2{[Cu(L2)][Cu(L2)(H2O)]Nb6O19} units and [Cu(L1)2]2+ bridges. 1−3 represent the first 2D architecture with (4,4)-connected topology in polyoxoniobate chemistry. Furthermore, the photoluminescent properties of 1 and 2 have been studied. The magnetic behavior of 1 has been quantitatively investigated and suggests the weak antiferromagnetic exchange interactions

High-Efficiency Mechanical Energy Storage and Retrieval Using Interfaces in Nanowires

By molecular dynamics simulations, we demonstrate a new concept for mechanical energy storage and retrieval using surface energy as reservoir in body-centered cubic (bcc) tungsten nanowire, achieving a combination of unique features such as large and constant actuation stress (>3 GPa), exceptionally large actuation strain (>30%) and energy density, and >98% energy storage efficiency. The underlying mechanism is a shear-dominant diffusionless transformation akin to martensitic transformation, but driven by surface rather than bulk free energies, and enabled by motion of coherent twin boundary, whose migration has been shown to possess ultralow friction in bcc metals. Aside from energy storage, such surface-energy driven displacive transformations are important for phase transformation and energy-matter control at the nanoscale