Soft routes to inorganic frameworks via assembly of molecular building blocks

The assembly of mononuclear and polynuclear molecular building blocks has been investigated as a route to extended metal oxide structures. Various [MX[subscript(y)]]ⁿ⁻ (X = Cl, OMe, OH) and [(RO)M’M₅O₁₈]³⁻ (R = MeO, M’ = Sn, M = W) building blocks have been synthesised. Controlled hydrolysis has been explored for transition and main group metal hexahalides [MCl₆]ⁿ⁻ M=Ti, Sn using ¹⁷O enriched water. An attempted synthesis of [Me₃NCH₂Ph] [Sn(OMe)₆] gave the dinuclear product [Me₃NCH₂Ph] [Sn₂(OMe)₉]. Variable temperature ¹H NMR studies revealed exchange between terminal and bridging alkoxides and the limiting spectrum is consistent with solid state structure. 2,6-lutidinium hydrochloride was synthesised and used to chlorinate the metal alkoxides {M(OR)[subscript(n)]} (M = Nb). A route to monochloro niobium alkoxide {NbCl(OMe)₄} was developed and variable temperature ¹H NMR spectroscopy studies of {NbCl(OMe)₄} in different solvents revealed exchange between bridging and terminal alkoxides and also suggested the presence of different structural isomers in solution. A novel heterometallic Lindqvist type of POM containing Sn has been successfully synthesised by using controlled hydrolytic aggregation. A mixture of (TBA)₂WO₄, WO(OMe)₄ and {Sn(O[superscript(t)] Bu)₄} was partially hydrolysed in a non-aqueous solvent to give (TBA)₃[(MeO)SnW₅O₁₈] (1). ¹¹⁹Sn NMR INEPT and selective tin decoupled proton NMR experiments have been carried out to determine the axial and equatorial ²J {¹¹⁹Sn*¹⁸³W} coupling constants and to estimate ³J{¹¹⁹Sn¹H} and ³J{¹¹⁷Sn¹H} coupling constants. The electrochemistry of (1) was studied by cyclic voltammetry (CV), and was shown to undergo a reversible one electron reduction close to the solvent limit. Hydrolysis of [(MeO)SnW₅O₁₈]³⁻ produced [(OH)SnW₅O₁₈]³⁻ (2) which is stable in the solid state but in solution undergoes a condensation reaction to give [(µ- O)(SnW₅O₁₈)₂]⁶⁻ (3). The chloro stannotungstate [ClSnW₅O₁₈]³⁻ (4) was also obtained during the synthesis of (1) and (2). Compounds (2) and (4) are crystallographically isostructural and Sn hetero site was disordered over all six metal positions in both anions. The redox properties of (4) were studied by CV and showed an irreversible reduction peak at -1.67 V. Compound (4) is stable in air and did not react with H₂O or PhOH but did react with MeOH or NaOMe to give (1). It also reacted with diisopropylamine (DIPA) to produce the H-bonded aggregate [(Prⁱ₂NH₂)₂(µ-O)(SnW₅O₁₈)₂]⁴⁻. The adduct structure is related to a recently characterised titanium analogue [(µ-O)(TiW₅O₁₈H)₂]⁴⁻ , which forms the H-bonded THF adduct [(µ-O)(TiW₅O₁₈H)₂(THF)]⁴⁻ . 2D-¹H EXSY NMR studies of the mixtures of (1) and MeOH did not show any exchange peaks between (1) and methanol which demonstrates that exchange is slow but reactivity studies of (1) have been carried out with various alcohols and phenols to give substituted products. Sterically smaller alkyl groups gave trans disordered structures, but no disorder is present in structures of anion with bulkier aliphatic alkoxide and aryloxide groups. Hydrogen bonding was observed between the POM cage and pendant phenolic OH groups All the alkyl and aryloxido derivatives have been characterised by single crystal X-Ray diffraction, ¹H and multinuclear NMR spectroscopy, infrared spectroscopy and CHN analysis. Preliminary studies to explore the immobilisation of metal alkoxides [Ti(OPrⁱ )₄] and (1) on ~30% OH functionalised Si(111) surfaces have been carried out. The attempted covalent immobilisation of (1) to Si(111) surfaces appeared to be successful from Atomic Force Microscopy (AFM) measurements

An evaluation of human protein-protein interaction data in the public domain

BACKGROUND: Protein-protein interaction (PPI) databases have become a major resource for investigating biological networks and pathways in cells. A number of publicly available repositories for human PPIs are currently available. Each of these databases has their own unique features with a large variation in the type and depth of their annotations. RESULTS: We analyzed the major publicly available primary databases that contain literature curated PPI information for human proteins. This included BIND, DIP, HPRD, IntAct, MINT, MIPS, PDZBase and Reactome databases. The number of binary non-redundant human PPIs ranged from 101 in PDZBase and 346 in MIPS to 11,367 in MINT and 36,617 in HPRD. The number of genes annotated with at least one interactor was 9,427 in HPRD, 4,975 in MINT, 4,614 in IntAct, 3,887 in BIND and <1,000 in the remaining databases. The number of literature citations for the PPIs included in the databases was 43,634 in HPRD, 11,480 in MINT, 10,331 in IntAct, 8,020 in BIND and <2,100 in the remaining databases. CONCLUSION: Given the importance of PPIs, we suggest that submission of PPIs to repositories be made mandatory by scientific journals at the time of manuscript submission as this will minimize annotation errors, promote standardization and help keep the information up to date. We hope that our analysis will help guide biomedical scientists in selecting the most appropriate database for their needs especially in light of the dramatic differences in their content

Exploring the geometric space of metal-organic polyhedrons (MOPs) of metal-oxo clusters

Metal organic polyhedra (MOPs) such as coordination cages and clusters are increasingly utilized across many fields, but their geometrically selective assembly during synthesis is nontrivial. When ligand coordination along these polyhedral edges is arranged in an unsymmetrical mode or the bridging ligand itself is nonsymmetric, a vast combinatorial space of potential isomers exists complicating formation and isolation. Here we describe two generalizable combinatorial methodologies to explore the geometrical space and enumerate the configurational isomers of MOPs with discrimination of the chiral and achiral structures. The methodology has been applied to the case of the octahedron {Bi6Fe13L12} which has unsymmetrical coordination of a carboxylate ligand (L) along its edges. For these polyhedra, the enumeration methodology revealed 186 distinct isomers, including 74 chiral pairs and 38 achiral. To explore the programming of these, we then used a range of ligands to synthesize several configurational isomers. Our analysis demonstrates that ligand halo-substituents influence isomer symmetry and suggests that more symmetric halo-substituted ligands counterintuitively yield lower symmetry isomers. We performed mass spectrometry studies of these {Bi6Fe13L12} clusters to evaluate their stability and aggregation behavior in solution and the gas phase showing that various isomers have different levels of aggregation in solution

Aqueous solutions of super reduced polyoxotungstates as electron storage systems

Due to the increasing energy density demands of battery technology, it is vital to develop electrolytes with high electron storage capacity. Polyoxometalate (POM) clusters can act as electron sponges, storing and releasing multiple electrons and have potential as electron storage electrolytes for flow batteries. Despite this rational design of clusters for high storage ability can not yet be achieved as little is known about the features influencing storage ability. Here we report that the large POM clusters, {P5W30} and {P8W48}, can store up to 23 e− and 28 e− per cluster in acidic aqueous solution, respectively. Our investigations reveal key structural and speciation factors influencing the improved behaviour of these POMs over those previously reported (P2W18). We show, using NMR and MS, that for these polyoxotungstates hydrolysis equilibria for the different tungstate salts is key to explaining unexpected storage trends while the performance limit for {P5W30} and {P8W48}, can be attributed to unavoidable hydrogen generation, evidenced by GC. NMR spectroscopy, in combination with the MS analysis, provided experimental evidence for a cation/proton exchange process during the reduction/reoxidation process of {P5W30} which likely occurs due to this hydrogen generation. Our study offers a deeper understanding of the factors affecting the electron storage ability of POMs and provides insights allowing for further development of these materials for energy storage

Effective storage of electrons in water by the formation of highly reduced polyoxometalate clusters

Aqueous solutions of polyoxometalates (POMs) have been shown to have potential as high-capacity energy storage materials due to their potential for multi-electron redox processes, yet the mechanism of reduction and practical limits are currently unknown. Herein, we explore the mechanism of multi-electron redox processes that allow the highly reduced POM clusters of the form {MO3}y to absorb y electrons in aqueous solution, focusing mechanistically on the Wells–Dawson structure X6[P2W18O62], which comprises 18 metal centers and can uptake up to 18 electrons reversibly (y = 18) per cluster in aqueous solution when the countercations are lithium. This unconventional redox activity is rationalized by density functional theory, molecular dynamics simulations, UV–vis, electron paramagnetic resonance spectroscopy, and small-angle X-ray scattering spectra. These data point to a new phenomenon showing that cluster protonation and aggregation allow the formation of highly electron-rich meta-stable systems in aqueous solution, which produce H2 when the solution is diluted. Finally, we show that this understanding is transferrable to other salts of [P5W30O110]15– and [P8W48O184]40– anions, which can be charged to 23 and 27 electrons per cluster, respectively

Coupling d⁶ Ir(III) and d⁸ Pt(II) Chromophores

Two classes of widely studied luminescent metal complexes are octahedral d⁶ (i.e., Ir³⁺) and square planar d⁸ (i.e., Pt²⁺) polypyridyl complexes, which have distinctly different photophysics and photoreactivity. In this study we report a series of d⁶–d⁸ Ir^III–Pt^II hybrid complexes arising from coordination of metalloligands IrL₂(benzene-1-thioether-2-thiolate) or Ir­(L)₂(benzene-1,2-dithiolate) anion [L = 2-phenylpyridine (ppy), 2-(2,4-difluorophenyl)­pyridine (dfppy), or 1-phenylisoquinoline (piq)] to Pt­(terpy)²⁺ (terpy = 2,2′:6′,2″-terpyridine). X-ray crystal structures of the Ir–Pt complexes show the IrL₂ and Pt­(terpy) chromophores are cofacially oriented with interplanar distances of 3.268–3.442 Å. Density functional theory (DFT) calculations show that the highest occupied molecular orbital and the lowest unoccupied molecular orbital are localized in the IrL₂ and the Pt­(terpy), respectively. All the complexes display a low-energy absorption band (λ_max = 460–534 nm, ε_max = (0.75–2.13) × 10³ M^–1 cm^–1), which is attributed to interchromophore-charge-transfer (<b>ICCT</b>) transition, according to time-dependent DFT calculations. The ³ICCT excited state is emissive, giving long-lived phosphorescence that reaches as low as near-infrared (λ_max = 668–710 nm, τ = 0.17–0.79 μs)

Gallium(III)-Containing, Sandwich-Type Heteropolytungstates: Synthesis, Solution Characterization, and Hydrolytic Studies toward Phosphoester and Phosphoanhydride Bond Cleavage

The gallium(III)-containing heteropolytungstates [Ga4(H2O)10(β-XW9O33)2](6-) (X = As(III), 1; Sb(III), 2) were synthesized in aqueous acidic medium by reaction of Ga(3+) ions with the trilacunary, lone-pair-containing [XW9O33](9-). Polyanions 1 and 2 are isostructural and crystallized as the hydrated sodium salts Na6[Ga4(H2O)10(β-AsW9O33)2]·28H2O (Na-1) and Na6[Ga4(H2O)10(β-SbW9O33)2]·30H2O (Na-2) in the monoclinic space group P21/c, with unit cell parameters a = 16.0218(12) Å, b = 15.2044(10) Å, c = 20.0821(12) Å, and β = 95.82(0)°, as well as a = 16.0912(5) Å, b = 15.2178(5) Å, c = 20.1047(5) Å, and β = 96.2(0)°, respectively. The corresponding tellurium(IV) derivative [Ga4(H2O)10(β-TeW9O33)2](4-) (3) was also prepared, by direct reaction of sodium tungstate, tellurium(IV) oxide, and gallium nitrate. Polyanion 3 crystallized as the mixed rubidium/sodium salt Rb2Na2[Ga4(H2O)10(β-TeW9O33)2]·28H2O (RbNa-3) in the triclinic space group P1̅ with unit cell parameters a = 12.5629(15) Å, b = 13.2208(18) Å, c = 15.474(2) Å, α = 80.52(1)°, β = 84.37(1)°, and γ = 65.83(1)°. All polyanions 1-3 were characterized in the solid state by single-crystal XRD, FT-IR, TGA, and elemental analysis, and polyanion 2 was also characterized in solution by (183)W NMR and UV-vis spectroscopy. Polyanion 2 was used as a homogeneous catalyst toward adenosine triphosphate (ATP) and the DNA model substrate 4-nitrophenylphosphate, monitored by (1)H and (31)P NMR spectroscopy. The encapsulated gallium(III) centers in 2 promote the Lewis acidic synergistic activation of the hydrolysis of ATP and DNA model substrates at a higher rate in near-physiological conditions. A strong interaction of 2 with the P-O bond of ATP was evidenced by changes in chemical shift values and line broadening of the (31)P nucleus in ATP upon addition of the polyanion.status: publishe

Suspicious Actions Detection System Using Enhanced CNN and Surveillance Video

Suspicious pre- and post-activity detection in crowded places is essential as many suspicious activities may be carried out by culprits. Usually, there will be installations of surveillance cameras. These surveillance cameras capture videos or images later investigated by authorities and post-event such suspicious activity would be detected. This leads to high human intervention to detect suspicious activity. However, there are no systems available to protect valuable things from such suspicious incidents. Nowadays machine learning (ML)- and deep learning (DL)-based pre-incident warning alarm systems could be adapted to monitor suspicious activity. Suspicious activity prediction would be based on human gestures and unusual activity detection. Even though some methods based on ML or DL have been proposed, the need for a highly accurate, highly precise, low-false-positive and low-false-negative prediction system can be enhanced by hybrid or enhanced ML- or DL-based systems. This proposed research work has introduced an enhanced convolutional neural network (ECNN)-based suspicious activity detection system. The experiment was carried out and the results were claimed. The results are analyzed with the Statistical Package for the Social Sciences (SPSS) tool. The results showed that the mean accuracy, mean precision, mean false-positive rate, and mean false-negative rate of suspicious activity detections were 97.050%, 96.743%, 2.957%, and 2.927% respectively. This result was also compared with the convolutional neural network (CNN) algorithm. This research work can be applied to enhance the pre-suspicious activity alert security system to avoid risky situations