Enhancing hydride formation and transfer for catalytic hydrogenation via electron-deficient single-atom silver.

Metal hydrides are sensitive to HO and O, which reduces the atom efficiency of the hydride donors. Silver (Ag) is an inexpensive coinage metal; however, its lower activity compared to gold, platinum, and palladium limits its application in catalytic hydrogenation. Here, electron-deficient metallic single-atom Ag (AgSA) was loaded onto γ-AlO using a benzoquinone- and KNO- assisted photolysis approach.

Guest modulating the photoactivity of a titanium-oxide cage.

Two host-guest Ti-oxide clusters, Ti(NH) and TiCs, were synthesized and thoroughly characterized. They possess a rarely seen biloculate structure that encapsulates two NH and Cs guests, respectively. Interestingly, alkali metal cations can exchange places with NH .

Enhancing the photocatalytic performance of a rutile unit featuring a titanium-oxide cluster by Pb doping.

Titanium-oxide clusters (TOCs) are well-defined molecular models for TiO materials and provide the opportunity to study the structure-activity relationships of TiO. Here, we report a new Pb-doped TOC, Ti12Pb2, which resembles a two-layer decker of the {TiTi} structural units of rutile TiO with two Ti ions replaced by two Pb ions. Its electronic structure, photoresponse, and photocatalytic performances were investigated and compared with those of the Ti14 cluster, which is isostructural to Ti12Pb2.

A cryptand-like Ti-coordination compound with visible-light photocatalytic activity in CO storage.

A cryptand-like Ti-coordination compound, namely Ti12Cs, comprising two Ti-salicylate cages and hosting two Cs ions, was synthesized by the solvothermal method. It exhibits strong visible-light absorption with an absorption band edge of 652 nm, attributed to the electron transition from salicylate ligands to Ti ions. Electrochemical impedance, visible-light transient photocurrent response, and photoluminescence spectra confirm that Ti12Cs has excellent visible-light response and charge-separation properties.

Ligation of Titanium-oxide and {Mo} Units for Solar CO Storage.

Two Mo-Ti-mixed oxide clusters, and , which contain the {Mo} unit commonly observed in many polyoxomolybdates, were successfully synthesized. The introduction of a {Mo} dopant into a titanium-oxide cluster (TOC) results in a red shift of the absorption edge, hence leading to a substantial enhancement of visible-light absorption. The band gap electron transition mainly involves the ligand-to-metal charge transfer (LMCT, benzoate-to-Mo) and Mo d-d transition.

Divalent Heterometal Doped Titanium-Oxide Cluster Polymers: Structures, Photoresponse, and Photocatalysis.

Five cluster polymers based on heterometal-doped titanium-oxide cluster (TOC) monomers are reported. The monomers feature Ti-oxide cluster cores and are connected to the divalent closed-shell heterometal anchors by salicylate ligands. The Sr, Ba, and Pb dopants cause the monomers to bind head-to-head and generate linear chains, while the Ca and Cd lead to head-to-tail connections and zigzag chains.

A butterfly-like lead-doped titanium-oxide compound with high performance in photocatalytic cycloaddition of CO to epoxide.

The cycloaddition reaction of CO to epoxides is quite promising for CO capture and storage as well as the production of value-added fine chemicals. Herein, a novel atomically precise lead-doped titanium-oxide cluster with the formula TiPbO(phen)(Ac)(DMF) (denoted as Ti10Pb2; phen = 1,10-phenanthroline; Ac = acetate; DMF = dimethylformamide) was synthesized through a facile solvothermal process, and is a molecular photocatalyst with surface-anchored main-group metal active sites. Its structure was characterized by single-crystal X-ray diffraction and other complementary techniques.

Complexed Semiconductor Cores Activate Hexaniobate Ligands as Nucleophilic Sites for Solar-Light Reduction of CO by Water.

Although pure and functionalized solid-state polyniobates such as layered perovskites and niobate nanosheets are photocatalysts for renewable-energy processes, analogous reactions by molecular polyoxoniobate cluster-anions are nearly absent from the literature. We now report that under simulated solar light, hexaniobate cluster-anion encapsulated 30-Ni -ion "fragments" of surface-protonated cubic-phase-like NiO cores activate the hexaniobate ligands towards CO reduction by water. Photoexcitation of the NiO cores promotes charge-transfer reduction of Nb to Nb , increasing electron density at bridging oxo atoms of Nb-μ-O-Nb linkages that bind and convert CO to CO.

New picolinate-functionalized titanium-oxide clusters: syntheses, structures and photocatalytic H evolution.

Two nanosized titanium-oxide clusters (TOCs), Ti(μ-O)(μ-O)PA (1; PA = 2-picolinate) and Ti(μ-O)PA (2) were synthesized by using 2-picolinic acid and Ti(OPr) in one-pot reactions. Their structures were determined using single-crystal X-ray diffractometry. Although both have the same core composition of TiO, 1 exhibited superior H evolution activity of up to 180 μmol h g, which is nearly eight times faster than 2.

Soluble Complexes of Cobalt Oxide Fragments Bring the Unique CO Photoreduction Activity of a Bulk Material into the Flexible Domain of Molecular Science.

The deposition of metal oxides is essential to the fabrication of numerous multicomponent solid-state devices and catalysts. However, the reproducible formation of homogeneous metal oxide films or of nanoparticle dispersions at solid interfaces remains an ongoing challenge. Here we report that molecular hexaniobate cluster anion complexes of structurally and electronically distinct fragments of cubic-spinel and monoclinic CoO can serve as tractable yet well-defined functional analogues of bulk cobalt oxide.

Effects of organic ammonium cations on the isolation of {Ti} cyclic clusters from water: an O NMR study.

For the preparation of aqueous Ti-oxo clusters (TOCs) without organic ligands, organic ammonium cations (OACs) are important, but the mechanism is obscure. Here, the Ti/SO system was chosen as a model to investigate the roles of OACs. Three {Ti} clusters were isolated from this system with different cationic additives.

Self-Assembly and Ionic-Lattice-like Secondary Structure of a Flexible Linear Polymer of Highly Charged Inorganic Building Blocks.

Among molecular building blocks, metal oxide cluster anions and their countercations provide multiple options for the self-assembly of functional materials. Currently, however, rational design concepts are limited to electrostatic interactions with metal or organic countercations or to the attachment and subsequent reactions of functionalized organic ligands. We now demonstrate that bridging μ-oxo linkages can be used to string together a bifunctional Keggin anion building block, [PNbMoO] (), the diniobium(V) analogue of [PVMoO] ().

Cyclin-Dependent Kinase 5-Dependent BAG3 Degradation Modulates Synaptic Protein Turnover.

Background: Synaptic protein dyshomeostasis and functional loss is an early invariant feature of Alzheimer's disease (AD), yet the unifying etiological pathway remains largely unknown. Knowing that cyclin-dependent kinase 5 (CDK5) plays critical roles in synaptic formation and degeneration, its phosphorylation targets were reexamined in search of candidates with direct global impacts on synaptic protein dynamics, and the associated regulatory network was also analyzed.

Methods: Quantitative phosphoproteomics and bioinformatics analyses were performed to identify top-ranked candidates.

CDK5-mediated phosphorylation and stabilization of TPX2 promotes hepatocellular tumorigenesis.

Background: CDK5, an atypical member of the CDK family, play a significant role in the tumorigenesis of multiple organ, but CDK5 and its substrates in genesis and development of HCC is still unclear.

Methods: Expression of CDK5 in HCC tumor and paired adjacent noncancerous tissues from 90 patients were measured by Western blotting, immunohistochemistry, and real-time PCR. The role of CDK5 in cell function and tumorigenesis was explored in HCC cell lines, ex vivo xenografts and diethylnitrosamine induced HCC model.

Aqueous Isolation of 17-Nuclear Zr/Hf Oxide Clusters during the Hydrothermal Synthesis of ZrO /HfO.

Novel 17-nuclear Zr/Hf oxide clusters ({Zr } and {Hf }) are isolated from aqueous systems. In the clusters, Zr/Hf ions are connected through μ -O, μ -OH, and μ -OH linkages into a pinwheel core which is wrapped with SO , HCOO , and aqua ligands. Octahedral hexanuclear Zr/Hf oxide clusters ({Zr } and {Hf } ) are also isolated from the same hydrothermal system by decreasing the synthesis temperature.

Titanium-Oxide Host Clusters with Exchangeable Guests.

A novel family of water-soluble, polyoxocationic titanium-oxide host-guest clusters are reported herein. They exhibit an unprecedented hexagonal prismatic core structure for hosting univalent cationic guests like K, Rb, Cs and HO. Guest exchange has been studied using Cs NMR, showing the flexible pore of a host permits passage of a comparatively larger cation and giving an equilibrium constant of ca.

Alkali Halide Cubic Cluster Anions ([CsX], X = Cl, Br) Isolated from Water.

Herein we report the syntheses and the X-ray structure of [CsX] (X = Cl, Br) clusters, the first binary cluster anions isolated in bulk crystal structures. They were obtained by electrostatic capture and face-directed recognition of the prenucleation [CsCl] clusters from water solutions, using [M(OH)(OH)] (M = Zr or Hf) as the counter cations. These compounds have been thoroughly characterized with a variety of techniques including vibrational spectroscopy and superionic conductivity analysis.

Effects of Substitutional Dopants on the Photoresponse of a Polyoxotitanate Cluster.

In this paper, using a simple method, 17 isostructural polyoxotitanates (POTs) were synthesized, including the pristine [Ti12O16(O(i)Pr)16], the monodefected [Ti11O13(O(i)Pr)18], and the heterometal-doped [Ti11O14(O(i)Pr)17(ML)] (M = Mg, Ca, Zn, Cd, Co, or Ni; L = Cl, Br, I, or NO3). The electronic structures of these POTs were determined by UV-vis spectroscopy and DFT calculations. Upon UV irradiation of the POTs, electron spin resonance showed the formation of Ti(III) under anaerobic conditions and superoxide (O2(•-)) in the presence of O2.

Water-Soluble Pentagonal-Prismatic Titanium-Oxo Clusters.

By using solubility control to crystallize the prenucleation clusters of hydrosol, a family of titanium-oxo clusters possessing the {Ti18O27} core in which the 18 Ti(IV)-ions are uniquely connected with μ-oxo ligands into a triple-decked pentagonal prism was obtained. The cluster cores are wrapped by external sulfate and aqua ligands, showing good solubilities and stabilities in a variety of solvents including acetonitrile and water and allowing their solution chemistry being studied by means of electrospray ionization mass spectroscopy, (17)O NMR, and vibrational spectroscopy. Furthermore, this study provides new titanium oxide candidates for surface modifications and homogeneous photocatalysis.

A Post-Functionalizable Iso-Polyoxotitanate Cage Cluster.

During solvothermal alcoholysis of a mixture of TiI4 and Ti(O(i)Pr)4, a {I@Ti22} cage cluster encapsulating an OH and iodide guests is crystallized. The {I@Ti22} host-guest cluster surface is postfunctionalizable with catecholate and carboxylate ligands. The synthetic details, structural characterization, spectroscopic properties of the obtained cages clusters are provided.

Counteranion-Stabilized Titanium(IV) Isopolyoxocationic Clusters Isolated from Water.

A novel titanium(IV) oxo cluster comprised solely of Ti, O, and H atoms, [Ti6(Oμ)8(OtH2)20](8+) (Ti6) was synthesized in high yield via controlled hydrolysis and condensation of TiX4 (X = Cl, Br) in the presence of TBAX (TBA = tetrabutylammonium; X = Cl, Br) from water, while reactions of TiI4 and TBAI yielded [Ti8O12(OH2)24](8+) (Ti8). The structures and compositions of the clusters were determined by single-crystal X-ray crystallography, powder X-ray diffraction, inductively coupled plasma atomic emission spectrometry, and energy-dispersive spectrometry. Ti6 is comprised of six-coordinated titanium(IV) atoms bridged with μ2-O atoms, structurally similar to a typical Lindqvist polyoxometalate.

Small Titanium Oxo Clusters: Primary Structures of Titanium(IV) in Water.

For sol-gel synthesis of titanium oxide, the titanium(IV) precursors are dissolved in water to form clear solutions. However, the solution status of titanium(IV) remains unclear. Herein three new and rare types of titanium oxo clusters are isolated from aqueous solutions of TiOSO4 and TiCl4 without using organic ligands.

The roles of Cdk5-mediated subcellular localization of FOXO1 in neuronal death.

Deficiency of cyclin-dependent kinase 5 (Cdk5) has been linked to the death of postmitotic cortical neurons during brain development. We now report that, in mouse cortical neurons, Cdk5 is capable of phosphorylating the transcription factor FOXO1 at Ser249 in vitro and in vivo. Cellular stresses resulting from extracellular stimulation by H2O2 or β-amyloid promote hyperactivation of Cdk5, FOXO1 nuclear export and inhibition of its downstream transcriptional activity.

CDK5 activator protein p25 preferentially binds and activates GSK3β.

Glycogen synthase kinase 3β (GSK3β) and cyclin-dependent kinase 5 (CDK5) are tau kinases and have been proposed to contribute to the pathogenesis of Alzheimer's disease. The 3D structures of these kinases are remarkably similar, which led us to hypothesize that both might be capable of binding cyclin proteins--the activating cofactors of all CDKs. CDK5 is normally activated by the cyclin-like proteins p35 and p39.