Structure-based discovery of small molecules targeting different surfaces of protein-kinase CK2

Protein kinase CK2 is an unfavorable pronostic marker in several cancers and has consequently emerged as a relevant therapeutic target. Several classes of ATP-competitive inhibitors have been identified, showing variable effectiveness. The molecular architecture of this multisubunit enzyme could offer alternative strategies to develop small molecule inhibitors targeting different surfaces of the kinase. Polyoxometalates were identified as original CK2 inhibitors targeting key structural elements located outside the active site. In addition, the CK2 subunit interface represents an exosite distinct from the catalytic cavity that can be targeted by peptides or small molecules to achieve functional effects.     

Qualitative (sunlight) and quantitative (xenon light source) aspects of the photochemistry of [S2W18O62] in the presence of electron donors

The photoelectrochemical properties of the polyoxotungstate anion [S₂W₁₈O₆₂]⁴⁻ dissolved in acetonitrite have been surveyed. Qualitative studies revealed that the rate of oxidation of the electron donor in the presence of sunlight correlated well with the voltammetric peak potential for oxidation of the electron donor at a glassy carbon electrode. Quantitative studies on the photooxidation of tetrahydrofuran, dimethylformamide, triphenylphosphine and ferrocene, as detected at a platinum channel electrode in the presence of a xenon light source, were assigned to a CE mechanism. Simulated fits for the proposed mechanism provide estimates of the reaction rates and data are compared with those obtained previously on the basis of a CECE scheme for the molybdenum analogue.     

Nitrogen‐Doped Porous Molybdenum Carbide and Phosphide Hybrids on a Carbon Matrix as Highly Effective Electrocatalysts for the Hydrogen Evolution Reaction

The efficient evolution of hydrogen through electrocatalysis is considered a promising approach to the production of clean hydrogen fuel. Platinum (Pt)‐based materials are regarded as the most active hydrogen evolution reaction (HER) catalysts. However, the low abundance and high cost of Pt hinders the large‐scale application of these catalysts. Active, inexpensive, and earth‐abundant electrocatalysts to replace Pt‐based materials would be highly beneficial to the production of cost‐effective hydrogen energy. Herein, a novel organoimido‐derivatized heteropolyoxometalate, Mo4‐CNP, is designed as a precursor for electrocatalysts of the HER. It is demonstrated that the carbon, nitrogen, and phosphorus sources derived from the Mo4‐CNP molecules lead to in situ confined carburization, phosphorization, and chemical doping on an atomic scale, thus forming nitrogen‐doped porous molybdenum carbide and phosphide hybrids, which exhibit remarkable electrocatalytic activity for the HER. Such an organically functionalized polyoxometalate‐assisted strategy described here provides a new perspective for the development of highly active non‐noble metal electrocatalysts for hydrogen evolution.     

Fine Tuning Electronic Structure of Catalysts through Atomic Engineering for Enhanced Hydrogen Evolution

An efficient, durable, and low‐cost hydrogen evolution reaction (HER) catalyst is an essential requirement for practical hydrogen production. Herein, an effective approach to facilitate the HER kinetics of molybdenum carbide (Mo₂C) electrocatalysts is presented by tuning its electronic structure through atomic engineering of nitrogen implantation. Starting from the organoimido‐derivatized polyoxometalate nanoclusters with inherent Mo? N bonds, the formation of N‐implanted Mo₂C (N@Mo₂C) nanocrystals with perfectly adjustable amounts of N atoms is demonstrated. The optimized N@Mo₂C electrocatalyst exhibits remarkable HER performance and good stability over 20 h in both acid and basic electrolytes. Further density functional theory calculations show that engineering suitable nitrogen atoms into Mo₂C can regulate its electronic structure well and decrease Mo? H strength, leading to a great enhancement of the HER activity. It could be believed that this ligand‐controlled atomic engineering strategy might influence the overall catalyst design strategy for engineering the activation sites of nonprecious metal catalysts for energy conversions.     

Design and Performance of Rechargeable Sodium Ion Batteries,and Symmetrical Li‐Ion Batteries with Supercapacitor‐Like Power Density Based upon Polyoxovanadates

The polyanion Li₇V₁₅O₃₆(CO₃) is a nanosized molecular cluster (≈1 nm in size), that has the potential to form an open host framework with a higher surface‐to‐bulk ratio than conventional transition metal oxide electrode materials. Herein, practical rechargeable Na‐ion batteries and symmetric Li‐ion batteries are demonstrated based on the polyoxovanadate Li₇V₁₅O₃₆(CO₃). The vanadium centers in {V₁₅O₃₆(CO₃)} do not all have the same V^IV/V redox potentials, which permits symmetric devices to be created from this material that exhibit battery‐like energy density and supercapacitor‐like power density. An ultrahigh specific power of 51.5 kW kg^?1 at 100 A g^?1 and a specific energy of 125 W h kg^?1 can be achieved, along with a long cycling life (>500 cycles). Moreover, electrochemical and theoretical studies reveal that {V₁₅O₃₆(CO₃)} also allows the transport of large cations, like Na⁺, and that it can serve as the cathode material for rechargeable Na‐ion batteries with a high specific capacity of 240 mA h g^?1 and a specific energy of 390 W h kg^?1 for the full Na‐ion battery. Finally, the polyoxometalate material from these electrochemical energy storage devices can be easily extracted from spent electrodes by simple treatment with water, providing a potential route to recycling of the redox active material.     

Mn(II)-monosubstituted polyoxometalates as candidates for contrast agents in magnetic resonance imaging

Two mono-substituted manganese polyoxometalates, K(6)MnSiW(11)O(39) (MnSiW(11)) and K(8)MnP(2)W(17)O(61) (MnP(2)W(17)), have been evaluated by in vivo and in vitro experiments as the candidates of potential tissue-specific contrast agents for magnetic resonance imaging (MRI). T1-relaxivities of 12.1mM(-1)s(-1) for MnSiW(11) and 4.7 mM(-1)s(-1) for MnP(2)W(17) (400 MHz, 25 degrees C) were higher than or similar to that of the commercial MRI contrast agent (GdDTPA). Their relaxivities in BSA and hTf solutions were also reported. After administration of MnSiW(11) and MnP(2)W(17) to Wistar rats, MR imaging showed longer and remarkable enhancement in rat liver and favorable renal excretion capability. The signal intensity increased by 74.0+/-4.9% for the liver during the whole imaging period (90 min) and by 67.2+/-5.3% for kidney within 20-70 min after injection at 40+/-3 micromol kg(-1) dose for MnSiW(11). MnP(2)W(17) induced 71.5+/-15.1% enhancement for the liver in 10-45 min range and 73.1+/-3.2% enhancement for kidney within 5-40 min after injection at 39+/-3 micromol kg(-1) dose. In vitro and in vivo study showed MnSiW(11) and MnP(2)W(17) being favorable candidates as the tissue-specific contrast agents for MRI.     

The use of polyoxometalates in charge transfer salts

Several Organo/mineral charge transfer salts based on the polyoxometalates anions with the Keggin and Lindquist structures have been prepared with organic radical cations derived from TTF (Tetrathiafulvaalene) by the electrocrystallization technique. Electron transfer from the organic units to the anionic part has been evidenced in the [(TTF)₆(HPM₁₂O₄₀)(Et₄N), M=Mo, W] salts leading to the first radical cation salt with delocalized paramagnetic centers on the polyoxmetalate. Additionally, a metallic state has been observed in (BEDT-TFF)₅VW₅O₁₉, 5H₂O (BEDT=Bisethyleneditithio) containing substituted Lindquist anion.TMTTF Tetramethyltetrathiafulvalene - TMTSF Tetramethyl-tetraselena Fulvalene - BEDT-TTF or ET Bis (Ethylenedithiotetrathiafulvalene) - TPTTF Tetraphenyltetrathiafulvalene - DMDPTTF Dimethyldiphenyl-TTF - Et⁴N=(C²H⁵)N Tetraethylammonium - MDT-TTF Methylenedithiotetrathiafulvalene - DMET-TTF Dimethyl Ethylene Dithio Tetrathiafulvalene - M(dmit)² Bis-[bis(dimercapto-dithiol-thione)metal(II)]     

Keggin polyoxometalates-supported assembly of 2D supramolecular isomers: Synthesis, crystal structures and characteristics of two novel hybrid host-guest complexes

Two novel hybrid host-guest architectures based on metal-organic fragments and Keggin polyoxometalates, namely [α-Cu₁₂(trz)₈][PMo₁₂O₄₀] · H₂O (1) and [β-Cu₁₂(trz)₈][PMo₁₂O₄₀] · 2H₂O (2) (trz = 1,2,4-triazole), have been prepared under hydrothermal conditions and characterized by single-crystal X-ray diffraction (XRD), elemental analysis, powder XRD, ESR, FT-IR, UV-Vis, and thermogravimetric analysis (TGA). The [Cu₁₂(trz)₈]⁴⁺ hosts in compounds 1 and 2 are two-dimensional (2D) supramolecular isomers, which present 4⁴ topology based on Cu₄(trz)₄ cyclic units and 6³ topology based on Cu₃(trz)₃ cyclic units, respectively. The metalmacrocyclic Cu₈(trz)₈ and Cu₉(trz)₉ rings represent the largest examples in the coordination chemistry of 1,2,4-triazole. 2D metal-organic fragments and Keggin anions both are connected via hydrogen bonds and Cu?O short contacts to form interesting 3D host-guest architectures of 1 and 2.     

Two new polyoxometalate-based hybrids: Structural transformation played by a secondary bridging ligand

Two new Keggin polyoxometalate-based compounds, [Ag₄(phnz)₆(SiW₁₂O₄₀)] (phnz = phenazine) (1) and [Ag(phnz)_1.5][Ag(phnz)(pz)][{Ag₂(phnz)(pz)(H₂O)}(SiW₁₂O₄₀)] (2) (pz = pyrazine), have been hydrothermally synthesized. Compound 1 is a discrete cluster in which the [SiW₁₂O₄₀]⁴⁻ (SiW₁₂) anion symmetrically connects two dinuclear Ag₂(phnz)₃ fragments. All Ag^I in 1 adopt a trigonal geometry. By introducing the secondary bridging ligand “pz” into the above system, compound 2 was obtained. Compound 2 contains three kinds of silver complex subunits: [Ag₂(phnz)(pz)(H₂O)]²⁺, [Ag₂(phnz)₃]²⁺ and [Ag(phnz)(pz)]⁺. The first one extends to a wave-like chain with SiW₁₂ anions as bi-dentate suspenders, and the last two are counter cations. Furthermore, Ag^I ions in 2 exhibit three kinds of coordination modes. Their electrochemistry properties have also been studied.