Luminescence and Generation of Reactive Oxygen Species in Solution by TaBr Clusters.

An intrinsic metal cluster NIR-II emission of the {TaBr} aqua/hydroxocomplexes was determined in aqueous solutions under inert atmosphere. The photoluminescence (PL) is enhanced in DO, and the lifetime scale expands from nanoseconds to microseconds. Possible cluster emission transitions have been assigned and analyzed from a computational perspective.

Optoelectronic properties of octahedral molybdenum cluster-based materials at a single crystal level.

Octahedral molybdenum (Mo) clusters constitute suitable building blocks for the design of promising single crystal materials in the field of optoelectronics. Here, we prepared single crystals composed of hydroxo MoX (X = Br, Cl) cluster complexes interconnected by H-bonding interactions with water molecules and protons. The optoelectronic responses and the absorption and emission spectra of these cluster-based single crystals were acquired upon light irradiation, and they show dependency on the nature of the halogens, with the brominated cluster being the most conductive.

Octahedral Tantalum Bromide Clusters as Catalysts for Light-Driven Hydrogen Evolution.

The development of an efficient hydrogen generation strategy from aqueous protons using sunlight is a current challenge aimed at the production of low-cost, easily accessible, renewable molecular hydrogen. For achieving this goal, non-noble metal containing and highly active catalysts for the hydrogen evolution reaction (HER) are desirable. Octahedral tantalum halide clusters {Ta(μ-X)} (X = halogen) represent an emerging class of such HER photocatalysts.

Octahedral Molybdenum Iodide Clusters Supported on Graphene for Resistive and Optical Gas Sensing.

This paper reports for the first time a gas-sensitive nanohybrid based on octahedral molybdenum iodide clusters supported on graphene flakes (Mo@Graphene). The possibility of integrating this material into two different transducing schemes for gas sensing is proposed since the nanomaterial changes both its electrical resistivity and optical properties when exposed to gases and at room temperature. Particularly, when implemented in a chemoresistive device, the Mo@Graphene hybrid showed an outstanding sensing performance toward NO, revealing a limit of quantification of about 10 ppb and excellent response repeatability (0.

Nanostructured Hybrids Based on Tantalum Bromide Octahedral Clusters and Graphene Oxide for Photocatalytic Hydrogen Evolution.

The generation of hydrogen (H) using sunlight has become an essential energy alternative for decarbonization. The need for functional nanohybrid materials based on photo- and electroactive materials and accessible raw materials is high in the field of solar fuels. To reach this goal, single-step synthesis of {TaBr}@GO (GO = graphene oxide) nanohybrids was developed by immobilization of [{TaBr}Br(HO)]·4HO (i = inner and a = apical positions of the Ta octahedron) on GO nanosheets by taking the advantage of the easy ligand exchange of the apical cluster ligands with the oxygen functionalities of GO.

Enhanced Photocatalytic Activity and Stability in Hydrogen Evolution of Mo Iodide Clusters Supported on Graphene Oxide.

Catalytic properties of the cluster compound (TBA)[MoI(OCCH)] (TBA = tetrabutylammonium) and a new hybrid material (TBA)MoI@GO (GO = graphene oxide) in water photoreduction into molecular hydrogen were investigated. New hybrid material (TBA)MoI@GO was prepared by coordinative immobilization of the (TBA)[MoI(OCCH)] onto GO sheets and characterized by spectroscopic, analytical, and morphological techniques. Liquid and, for the first time, gas phase conditions were chosen for catalytic experiments under UV-Vis irradiation.

Configurational landscape of chiral iron(ii) bis(phosphane) complexes.

The reaction of a chiral [FeH(η2-H2){(R,R)-Me-DuPhos}2]+ ((R,R)-Me-DuPhos = (-)-1,2-bis[(2R,5R)-2,5-dimethylphospholano]benzene) complex with ethers and halides is investigated by NMR techniques. From this study, it is apparent that dihydrogen ligand exchange by poorly-coordinating donor molecules, such as THF or Et2O, is feasible under mild conditions. The cis-[FeH(THF-d8){(R,R)-Me-DuPhos}2]+ complex is identified as the product in THF-d8 solution.

Supramolecular Anchoring of Octahedral Molybdenum Clusters onto Graphene and Their Synergies in Photocatalytic Water Reduction.

Dihydrogen (H) production from sunlight should become one of the most important energy production means in the future. To reach this goal, low-cost and efficient photocatalysts still need to be discovered. Here we show that red near-IR luminescent metal cluster anions, once combined with pyrene-containing cations, are able to photocatalytically produce molecular hydrogen from water.

Adherence to the follow-up of the newborn exposed to syphilis and factors associated with loss to follow-up.

Introduction: All newborns exposed to syphilis in pregnancy must have outpatient follow-up. The interruption of this follow-up especially threatens those children who were not treated at birth.

Objective: To describe the clinical, epidemiological, and sociodemographic characteristics of pregnant women with syphilis and their newborns, and to investigate the factors associated with the discontinuation of the follow-up.

In Situ Generation of Active Molybdenum Octahedral Clusters for Photocatalytic Hydrogen Production from Water.

The photocatalytic hydrogen evolution reaction (HER) from water under homogeneous and heterogeneous conditions is explored for the {Mo6 Br(i) 8 }(4+) cluster core based unit starting from (TBA)2 [Mo6 Br(i) 8 F(a) 6 ] (TBA=tetra-n-butylammonium; "i" and "a" refer to the face-capping inner and terminal apical ligand, respectively). The catalytic activity of {Mo6 Br(i) 8 }(4+) is enhanced by the in situ generation of [Mo6 Br(i) 8 F(a) 5 (OH)(a) ](2-) , [Mo6 Br(i) 8 F(a) 3 (OH)(a) 3 ](2-) , and [Mo6 Br(i) 8 (OH)(a) 6 ](2-) , which are identified by ESIMS, luminescence, and NMR techniques. Full substitution of F(-) by OH(-) leads to the formation of (H3 O)2 [Mo6 Br(i) 8 (OH)(a) 6 ]⋅10 H2 O; its structure was determined by single-crystal XRD.

Proline cis-trans isomerization and its implications for the dimerization of analogues of cyclopeptide stylostatin 1: a combined computational and experimental study.

Cis and trans proline conformers are often associated with dramatic changes in the biological function of peptides. A slow equilibrium between cis and trans Ile-Pro amide bond conformers occurs in constrained derivatives of the native marine cyclic heptapeptide stylostatin 1 (cyclo-(NSLAIPF)), a potential anticancer agent. In this work, four cyclopeptides, cyclo-(NSTAIPF), cyclo-(KSTAIPF), cyclo-(RSTAIPF) and cyclo-(DSTAIPF), which are structurally related to stylostatin 1, are experimentally and computationally examined in order to assess the effect of residue mutations on the cis-trans conformational ratio and the apparent capacity to form dimeric aggregates.

C3-symmetry Mo3S4 aminophosphino clusters combining three sources of stereogenicity: stereocontrol directed by hydrogen bond interactions and ligand configuration.

A diastereoselective synthesis of proline containing aminophosphino cubane-type Mo3S4 clusters, (P)-[Mo3S4Cl3((1S,2R)-PPro)3]Cl (Cl) and (P)-[Mo3S4Cl3((1S,2S)-PPro)3]Cl (Cl), has been achieved in high yields by reacting the corresponding enantiomerically pure PPro ((R)- and (S)-2-[(diphenylphosphino)methyl]pyrrolidine) ligands with the Mo3S4Cl4(PPh3)3(H2O)2 complex. Circular dichroism, nuclear magnetic resonance and X-ray techniques confirm that the Cl and Cl cluster cations are diastereoisomers which combine three sources of stereogenicity provided by the cluster framework, one carbon atom of the aminophosphine ligand and the nitrogen stereogenic center. The higher stability of the (+) cation is due to stabilizing vicinal ClHN interactions as well as due to the cis-fused conformation of the bicyclic system formed upon coordination of the aminophosphine ligand.

Clinical phenotype clustering in cardiovascular risk patients for the identification of responsive metabotypes after red wine polyphenol intake.

This study aims to evaluate the robustness of clinical and metabolic phenotyping through, for the first time, the identification of differential responsiveness to dietary strategies in the improvement of cardiometabolic risk conditions. Clinical phenotyping of 57 volunteers with cardiovascular risk factors was achieved using k-means cluster analysis based on 69 biochemical and anthropometric parameters. Cluster validation based on Dunn and Figure of Merit analysis for internal coherence and external homogeneity were employed.

An optimized method for (15)N R(1) relaxation rate measurements in non-deuterated proteins.

(15)N longitudinal relaxation rates are extensively used for the characterization of protein dynamics; however, their accurate measurement is hindered by systematic errors. (15)N CSA/(1)H-(15)N dipolar cross-correlated relaxation (CC) and amide proton exchange saturation transfer from water protons are the two main sources of systematic errors in the determination of (15)N R1 rates through (1)H-(15)N HSQC-based experiments. CC is usually suppressed through a train of 180° proton pulses applied during the variable (15)N relaxation period (T), which can perturb water magnetization.

Self-assembled trityl radical capsules--implications for dynamic nuclear polarization.

A new class of guest-induced, bi-radical self-assembled organic capsules is reported. They are formed by the inclusion of a tetramethylammonium (TMA) cation between two monomers of the stable trityl radical OX63. OX63 is extensively used in dissolution dynamic nuclear polarization (DNP) where it leads to NMR sensitivity enhancements of several orders of magnitude.

Computer-aided design of fragment mixtures for NMR-based screening.

Fragment-based drug discovery is widely applied both in industrial and in academic screening programs. Several screening techniques rely on NMR to detect binding of a fragment to a target. NMR-based methods are among the most sensitive techniques and have the further advantage of yielding a low rate of false positives and negatives.

On the mechanism of Re(I)-carboxylate bond cleavage by perchloric acid: a kinetic and spectroscopic study.

We have studied the reaction between pz-CO(2)-Re(CO)(3)(bpy) and perchloric acid in acetonitrile by following the UV-vis and IR spectral changes in the reaction mixture. A fast equilibrium was found to be established between solvated protons, pz-CO(2)-Re(CO)(3)(bpy), and the protonated intermediate [pz-C(OH)O-Re(CO)(3)(bpy)](+) which finally yields pz-COOH and Re(CO)(3)(bpy)(CH(3)CN)(+) as reaction products. This intermediate has been characterized by UV-vis and IR spectroscopies and by DFT calculations.

Isonicotinic acid hydrazide conversion to Isonicotinyl-NAD by catalase-peroxidases.

Activation of the pro-drug isoniazid (INH) as an anti-tubercular drug in Mycobacterium tuberculosis involves its conversion to isonicotinyl-NAD, a reaction that requires the catalase-peroxidase KatG. This report shows that the reaction proceeds in the absence of KatG at a slow rate in a mixture of INH, NAD(+), Mn(2+), and O(2), and that the inclusion of KatG increases the rate by >7 times. Superoxide, generated by either Mn(2+)- or KatG-catalyzed reduction of O(2), is an essential intermediate in the reaction.

Short-term temperature effect on the HRMAS spectra of human brain tumor biopsies and their pattern recognition analysis.

Object: To investigate the effect of temperature (0 versus 37 degrees C) in the high-resolution magic angle spinning spectroscopy (HRMAS) pattern of human brain tumor biopsies and its influence in recognition-based tumor type prediction. This proof-of-principle study addressed the bilateral discrimination between meningioma (MM) and glioblastoma multiforme (GBM) cases.

Materials And Methods: Forty-three tumor biopsy samples were collected (20 MM and 23 GBM), kept frozen and later analyzed at 0 degrees C and 37 degrees C by HRMAS.

Chiral [Mo3S4H3(diphosphine)3]+ hydrido clusters and study of the effect of the metal atom on the kinetics of the acid-assisted substitution of the coordinated hydride: Mo vs W.

The molybdenum(IV) cluster hydrides of formula [Mo(3)S(4)H(3)(diphosphine)(3)](+) with diphosphine = 1,2-(bis)dimethylphosphinoethane (dmpe) or (+)-1,2-bis-(2R,5R)-2,5-(dimethylphospholan-1-yl)ethane ((R,R)-Me-BPE) have been isolated in moderate to high yields by reacting their halide precursors with borohydride. Complex [Mo(3)S(4)H(3)((R,R)-Me-BPE)(3)](+) as well as its tungsten analogue are obtained in optically pure forms. Reaction of the incomplete cuboidal [M(3)S(4)H(3)((R,R)-Me-BPE)(3)](+) (M = Mo, W) complex with acids in CH(2)Cl(2) solution shows kinetic features similar to those observed for the related incomplete cuboidal [W(3)S(4)H(3)(dmpe)(3)](+) cluster.

Polychlorinated trityl radicals for dynamic nuclear polarization: the role of chlorine nuclei.

Polychlorinated trityl radicals bearing carboxylate substituents are water soluble persistent radicals that can be used for dynamic nuclear polarization. In contrast to other trityl radicals, the polarization mechanism differs from the classical solid effect. DFT calculations performed to rationalize this behaviour support the hypothesis that polarization is transferred from the unpaired electron to chlorine nuclei and from these to carbon by spin diffusion.

The role of solvent on the mechanism of proton transfer to hydride complexes: the case of the [W(3)PdS(4)H(3)(dmpe)(3)(CO)](+) cubane cluster.

The kinetics of reaction of the [W(3)PdS(4)H(3)(dmpe)(3)(CO)](+) hydride cluster (1(+)) with HCl has been measured in dichloromethane, and a second-order dependence with respect to the acid is found for the initial step. In the presence of added BF(4) (-) the second-order dependence is maintained, but there is a deceleration that becomes more evident as the acid concentration increases. DFT calculations indicate that these results can be rationalized on the basis of the mechanism previously proposed for the same reaction of the closely related [W(3)S(4)H(3)(dmpe)(3)](+) cluster, which involves parallel first- and second-order pathways in which the coordinated hydride interacts with one and two acid molecules, and ion pairing to BF(4) (-) hinders formation of dihydrogen bonded adducts able to evolve to the products of proton transfer.

Unprecedented solvent-assisted reactivity of Hydrido W3CuS4 cubane clusters: the non-innocent behaviour of the cluster-core unit.

Opening the cluster core: Substitution of the chloride ligand in the novel cationic cluster [W(3)CuS(4)H(3)Cl(dmpe)(3)](+) (see figure; dmpe=1,2-bis(dimethylphosphino)ethane) by acetonitrile is promoted by water addition. Kinetic and density functional theory studies lead to a mechanistic proposal in which acetonitrile or water attack causes the opening of the cluster core with dissociation of one of the Cu--S bonds to accommodate the entering ligand.Reaction of the incomplete cuboidal cationic cluster [W(3)S(4)H(3)(dmpe)(3)](+) (dmpe=1,2-bis(dimethylphosphino)ethane) with Cu(I) compounds produces rare examples of cationic heterodimetallic hydrido clusters of formula [W(3)CuClS(4)H(3)(dmpe)(3)](+) ([1](+)) and [W(3)Cu(CH(3)CN)S(4)H(3)(dmpe)(3)](2+) ([2](2+)).

Use of high-pressure freeze fixation and freeze fracture electron microscopy to study the influence of the phospholipid molar ratio in the morphology and alignment of bicelles.

The high-pressure freeze fixation and freeze fracture electron microscopy techniques were combined with the (31)P nuclear magnetic resonance to study the morphological transitions of two different dimyristoyl-phosphatidilcholine/dihexanoyl-phosphocholine aggregates by the effect of temperature. Through these techniques, the relationship between magnetic alignment and the morphology of alignable and non-alignable aggregates was evaluated. The micrographs related to the non-alignable dimyristoyl-phosphatidilcholine/dihexanoyl-phosphocholine sample presented rounded objects at a temperature below the dimyristoyl-phosphatidilcholine phase transition (T(m)) and, above this temperature an increase of viscosity was followed by the appearance of large elongated aggregates.