pinecone/core-2020-05-10-deduplication huggingface dataset:
Heteropolyacid-based materials as heterogeneous photocatalysts

Heteropolyacids (HPAs) that are often used as heteropolyanions are cheap and stable compounds that have been extensively used as acid and oxidation catalysts as a result of their strong Brønsted acidity and ability to undergo multielectron-transfer reactions. HPAs, which are very soluble in water and polar solvents, have been also used as homogeneous photocatalysts for the oxidation of organic substrates in the presence of oxygen, but their use in heterogeneous systems is by far desirable. Dispersing HPAs onto solid supports with high surface area is useful to increase their specific surface area and hence (photo)catalytic activity. Moreover, owing to the high energy gap between the HOMO and LUMO positions of the HPAs, these compounds are activated only by UV light. Consequently, only less than 5 % of the solar light can be used in photocatalytic reactions, which restricts the practical application of HPAs. This microreview is oriented to describe the reported literature on the use of HPA-based materials as heterogeneous photocatalysts for environmental purposes, that is, for the complete or partial oxidation or reduction of organic molecules
Bridging the gap : attractive 3c-4e interactions in peri-substituted acenaphthylenes

This work is supported by funding from the EPSRC UKA series of peri-substituted acenaphthylenes that contain mixed halogen-chalcogen functionalities at the 5,6-positions in 1-6 [Acenapyl[X](EPh) (Acenapyl = acenaphthylene-5,6-diyl; X = Br, I; E = S, Se, Te)] and chalcogen-chalcogen moieties in 7-11 [Acenap(EPh)(EPh) (Acenap = acenaphthene-5,6-diyl; E/E = S, Se, Te)] have been prepared from their corresponding acenaphthene analogues A1-A11 by utilising 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) for the dehydrogenation of the ethane backbone. The related dihalide compounds 13 and 14 Acenapyl[XX] (XX = BrBr, II) have also been prepared by following a similar procedure, and 1,2,5,6-tetrabromo-1,2-dihydroacenaphthylene A0 was prepared as an intermediate by following an alternative route to 13. The series of acenaphthylene compounds have remarkably similar molecular structures to their acenaphthene counterparts; they exhibit an expected increase in peri separation as heavier congeners occupy the close peri positions. The presence of the ethene bridge, however, naturally compresses the nearest bay angle as it increases the splay of the exocyclic peri atoms, thereby resulting in a minor increase in separation relative to equivalent acenaphthenes. The structures of 1-11, 13 and 14 are discussed and compared with previously reported analogous naphthalene and acenaphthene compounds. Similar to acenaphthene derivatives, aromatic ring conformations and the location of p-type lone pairs influences the geometry of the peri region. Under appropriate geometric conditions, quasi-linear three-body C-Ph-EZ (E = Te, Se, S; Z = Br/E) fragments provide an attractive component for the EZ interaction. DFT studies confirm the onset of formation of three-center, four-electron bonding, similar in extent to that observed in analogous acenaphthenes, despite an increase in the peri distances.PostprintPeer reviewe
Polyoxometalate multi-electron-transfer catalytic systems for water splitting

The viable production of solar fuels requires a visible-light-absorbing unit, a H2O (or CO2) reduction catalyst (WRC), and a water oxidation catalyst (WOC) that work in tandem to split water or reduce CO2 with H2O rapidly, selectively, and for long periods of time. Most catalysts and photosensitizers developed to date for these triadic systems are oxidatively, thermally, and/or hydrolytically unstable. Polyoxometalates (POMs) constitute a huge class of complexes with extensively tunable properties that are oxidatively, thermally, and (over wide and adjustable pH ranges) hydrolytically stable. POMs are some of the fastest and most stable WOCs to date under optimal conditions. This Microreview updates the very active POM WOC field; it reports the application of POMs as WRCs and initial self-assembling metal oxide semiconductor–photosensitizer–POM catalyst triad photoanodes. The complexities of investigating these POM systems, including but not limited to the study of POM-hydrated metal-ion–metal-oxide speciation processes, are outlined. The achievements and challenges in POM WOC, WRC, and triad research are outlined
Intramolecular π stacking in cationic iridium(III) complexes with phenyl-functionalized cyclometalated ligands : synthesis, structure, photophysical properties, and theoretical studies.

The syntheses of two new heteroleptic cationic iridium complexes containing 2,6-diphenylpyridine (Hdppy) and 2,4,6-triphenylpyridine (Htppy) as the cyclometalated ligands, namely, [Ir(dppy)2phen]PF6 (1, phen = 1,10-phenanthroline) and [Ir(tppy)2phen]PF6 (2), are described. The X-ray crystal structure of 2 reveals a distorted octahedral geometry around the Ir center and close intramolecular face-to-face π–π stacking interactions between the pendant phenyl rings at the 2-position of the cyclometalated ligands and the NN ancillary ligand. This represents a new π–π stacking mode in charged Ir complexes. Complexes 1 and 2 are green photoemitters: their photophysical and electrochemical properties are interpreted with the assistance of density functional theory (DFT) calculations. These calculations also establish that the observed intramolecular interactions cannot effectively prevent the lengthening of the Ir–N bonds of the complexes in their metal-centered (3MC) states. Complexes 1 and 2 do not emit light in light-emitting electrochemical cells (LECs) under conditions in which the model compound [Ir(ppy)2phen]PF6 (3) emits strongly. This is explained by degradation reactions of the 3MC state of 1 and 2 under the applied bias during LEC operation facilitated by the enhanced distortions in the geometry of the complexes. These observations have important implications for the future design of complexes for LEC applications
Structural and Physical Properties of (EDO-TTF-Cl)_2XF_6 (X = As, Sb): Geometrical Aspects for Monosubstituted EDO-TTF (EDO-TTF = 4,5-ethylenedioxytetrathiafulvalene)

Compounds of the formula (EDO-TTF-Cl)_2XF_6 (EDO-TTF-Cl = 4-chloro-4',5'-ethylenedioxytetrathiafulvalene, X = As, Sb) were prepared to examine the substituent size effect on the packing structure of the donor molecules. In these salts, a head-to-tail type donor stacking was observed. Although the AsF6 salt is a quasi-one-dimensional dimer Mott insulator, the SbF_6 salt shows quasi-one-dimensional metallic behavior. Detailed crystal structure analyses revealed the correlation between the anion size and the intermolecular slipping among the donor molecules. The donor morphology, which plays an important role in the overlapping mode selectivity, is characterized by the magnitude and configuration of the out-of-plane substituent size
Oxalate Oxidase Model Studies – Substrate Reactivity

The synthesis and structure of [MnLCl]0.5H2O (1·0.5H2O, HL = 1‐benzyl‐4‐acetato‐1,4,7‐triazacyclononane) is reported. Complex 1 exists as a coordination polymer in the solid state, and the MnII center is bonded to three amine nitrogen atoms, one carboxylate oxygen atom, a chlorido ligand, and an adjacent carboxylate group in a chelating fashion to afford a seven‐coordinate center. The dissolution of 1 in acetonitrile containing excess oxalate (ox) ions results in a monomeric species. When mixtures of 1 and oxalate ions are exposed to oxygen under ambient conditions, a dark pink EPR‐silent species is generated. The pink species is believed to be [MnIII(ox)2]–, which results from the displacement of the ligand L– by an oxalate ion. The decomposition of this species ultimately results in the formation of 1 equiv. of CO2 per oxalate ion consumed, a HCO3– ion, and a MnII species. Further reaction of the resulting MnII species with excess oxalate in the presence of oxygen leads to additional oxalate degradation.MnLCl (HL = 1‐benzyl‐4‐acetato‐1,4,7‐triazacyclononane) is investigated as a structural and functional model for oxalate oxidase. MnLCl effects the catalytic degradation of oxalate ions under ambient conditions. MnLCl is converted to a light‐sensitive intermediate during catalysis. Analysis of the reaction mixture indicates that 1 equiv. of CO2 per oxalate ion is produced along with a HCO3– ion
Binuclear DOTA-based Gd(III) chelates: revisiting a straightforward strategy for relaxivity improvement

The need for MRI contrast agents with improved relaxivity maintains the development of new Gd(III) chelates an intensive and demanding field of research. In this work we introduce the new dimeric chelators bis(DOTA-AHA)adipate and bis(DOTA-AHA)1,3-phenyldiacetate  (L2 = bis(1,4,7,10-tetraazacyclododecane-1-((6-amino)hexanoic)-4,7,10-triacetic acid)adipate and L3 = bis(1,4,7,10-tetraazacyclododecane-1-((6-amino)hexanoic)-4,7,10-triacetic acid)1,3-phenyldiacetate, respectively), based on the bifunctional ligand DOTA-AHA (L1 = 1,4,7,10-tetraazacyclododecane-1-((6-amino)hexanoic)-4,7,10-triacetic acid). Their Gd(III) chelates were studied by variable temperature 1H NMRD and 17O NMR spectroscopy in order to measure the relaxivity and the parameters that govern it. The exchange of inner-sphere water from the monomer GdL1 and from the two binuclear chelates Gd2L2 and Gd2L3 is very similar (298kex ≈ 6.5 x106 s-1) and slightly faster than on [Gd(DOTA)H2O]- (298kex = 4.1 x 106 s-1). All three compounds form weakly bound aggregates with equilibrium constants 298K of 2.9, 15.6 and 14.6 for GdL1, Gd2L2 and Gd2L3, respectively. Even if the aggregates contain only 10 to 15% of the total amount of Gd(III) ions a marked increase in relaxivity between 30 and 100 MHz is observed.
Furthermore the distance between the two Gd(III) centers in the binuclear compounds has been determined by double electron-electron resonance (DEER) experiments and by molecular modelling studies affording comparable distances. The linkers between the chelating moieties allow Gd(III)-Gd(III) distances of circa 3.0 nm for completely stretched linker conformation and ≤ 1.9 nm for the conformation with the metal centers at closer distance. These metal to metal distances by themselves cannot explain the considerably long tumbling times of chelates in solution. Only a model consistent with some level of aggregation for the binuclear chelates in aqueous solution could satisfactorily explain our results.The authors thank the Foundation for Science and Technology (FCT–Portugal) for
financial support through the NMR Portuguese network (Bruker 400 Avance III-Univ
Minho); FCT and FEDER (European Fund for Regional Development)-
COMPETE/QREN/EU for financial support through the research unity PEstC/QUI/UI686/2013
and the PhD grant attributed to André Fontes
(SFRH/BD/63676/2009) also financed by the POPH and FSE. SK and LH thank the
Swiss National Science Foundation for financial support.info:eu-repo/semantics/publishedVersio
Synthesis and characterization of fluorinated β-ketoiminate zinc precursors and their utility in the AP-MOCVD growth of ZnO:F

A novel family of zinc bis beta-ketoiminate complexes 2b-2h have been synthesized by reaction of the isolated free ligands (1a-h) with dimethylzinc. The isolated zinc complexes were characterized by elemental analysis, NMR spectroscopy, and in the case of 2b-d and 2f-h, the molecular structures of the complexes were determined by single crystal X-ray diffraction which reveals the compounds to be pseudo-octahedral 6-coordinate, monomeric homoleptic complexes in the solid state. TG analysis showed complexes 2b-f all to have residual masses at 400 °C of 10% or less, well below the value for ZnO and thus indicative of volatility. Of these systems 2b [Zn{MeC(O)CHC(NCH2CH2OMe)CF3}2] has been investigated for its utility in the AP-MOCVD growth of F –doped ZnO (ZnO:F) in the absence of additional oxidant at 400 °C on glass and silicon substrates
Thymol Bromination - A Comparison between Enzymatic and Chemical Catalysis

The catalytic activity of the vanadium-dependent bromoperoxidase isolated from the brown alga Ascophyllum nodosum is compared with the activity of a cheap, commercially available V-catalyst precursor in the bromination of thymol. Organic solvents have been avoided to make the system appealing from a sustainable chemistry point of view. It is noteworthy that, notwithstanding the low solubility of the substrate, the thymol bromination reactions were performed in water, with a safe brominating source, under mild conditions, and with relatively inexpensive reagents. In this regard, the greenness of the systems was evaluated by the estimation of the E-factor value; the result is that the chemical reaction has a lower environmental impact than the enzymatic process, with an E-factor in the range of ecofriendly processes
Facile synthesis of (110)-plane-exposed au microflowers as high sensitive hydrogen peroxide sensors

F. Y. thanks the EPSRC for financial support through a grant to R. E. Morris (No. EP/K005499/1). Z. L. thanks the National Natural Science Foundation of China (No. 51302280), Natural Science Foundation of Qinghai (2014-ZJ-936Q), and Young Scholar Project of Qinghai Institute of Salt Lakes, Chinese Academy of Sciences for support. W. Z. thanks the EPSRC for financial support to the Electron Microscopy Laboratory at St Andrews (No. EP/F019580/1).A flower-like Au microstructure with a dominantly exposed active (110) plane has been prepared by a simple, facile method at room temperature. Various experimental factors that can control the shape of the Au microflowers have been investigated and optimized. Furthermore, the glassy carbon electrode modified with these Au microflowers exhibits high electrochemical activity towards H2O2 reduction. The sensor shows a linear range from 10 μM to 5.53 mM with a detection limit of 2 μM, which can be attributed to the exposed (110) planes and 3D hierarchical structure of the Au microflowers.Publisher PDFPeer reviewe
Photoredox Properties of Homoleptic d6 Metal Complexes with the Electron-Rich 4,4',5,5'-Tetramethoxy-2,2'-bipyridine Ligand

A synthetic procedure leading to 4,4′,5,5′-tetramethoxy-2,2′-bipyridine [(MeO)4bpy] was developed, and the first three metal complexes with this ligand were synthesized. A few ligand precursor compounds, the final ligand, and its homoleptic iron(II) complex were characterized structurally by X-ray diffraction. The combination of cyclic voltammetry, optical absorption, luminescence, and transient absorption spectroscopy provided detailed insight into the electronic structure of the entire series of homoleptic FeII, RuII, and OsII complexes. The ruthenium(II) complex is a more potent photoreductant than the [Ru(bpy)3]2+ parent compound by approximately 0.4 V as confirmed by 3MLCT excited-state quenching experiments with a relatively mild oxidant, 1-chloro-4-nitrobenzene. In the presence of methanesulfonic acid in CH3CN, the photoexcited [Ru{(MeO)4bpy}3]2+ complex is able to undergo proton-coupled electron transfer (PCET) with acetophenone to yield a ketyl radical. Chemically robust and potent photoreductants are of interest for the phototriggering of electron-transfer reactions, for example, in photoredox catalysis, in dye-sensitized solar cells, in fundamental studies of (proton-coupled) electron transfer, or for the generation of solvated electrons
PEGylated DOTA-AHA-based Gd(III) chelates – A relaxometric study

Three PEGylated derivatives of 1,4,7,10-tetraazacyclododecane-1-((6-amino)hexanoic)-4,7,10-triacetic acid) (DOTA-AHA) with different molecular weights were prepared and characterized. Their Gd(III) chelates were studied in aqueous solution using variable-temperature 1H nuclear magnetic relaxation dispersion (NMRD) and 17ONMR spectroscopy in view of the determination of their relaxivity and the parameters that govern it. The relaxivity  varied from 5.1 to 6.5 mM-1.s-1 (37 ºC and 60 MHz) with the increasing molecular weight of the PEG chain, being slightly higher than that of the parent chelate Gd(DOTA-AHA), due to a small contribution of a slow global rotation of the complexes.
A variable temperature 1H NMR study of several Ln(III) chelates of DOTA-A(PEG750)HA allowed the determination of the isomeric M/m ratio (M = square antiprismatic isomer and m = twisted square antiprismatic isomer, the latter presenting a much faster water exchange) which for the Gd(III) chelate was estimated in circa 1:0.2, very close to that of [Gd(DOTA)]-. This explains why the PEGylated Gd(III) chelate has a water rate exchange similar to that of [Gd(DOTA)]-. The predominance of the M isomer is a consequence of the bulky PEG moiety which does not favor the stabilization of the m isomer in sterically crowded systems at the substituent site, contrary to what happens with less packed asymmetrical DOTA-type chelates with substitution in one of the four acetate C(α) atoms.The authors thank the Foundation for Science and Technology (FCT–Portugal) for financial support through the NMR Portuguese network (Bruker 400 Avance III-Univ Minho); FCT and FEDER (European Fund for Regional Development)-COMPETE/QREN/EU for financial support through the research unity PEst-C/QUI/UI686/2013 and the PhD grant attributed to André Fontes (SFRH/BD/63676/2009) also financed by the POPH and FSE
3‐(Pyridin‐2‐yl)imidazo[1,5‐a]pyridine (Pyridylindolizine) as Ligand in Complexes of Transition and Main‐Group Metals

Producción CientíficaThe coordination of the easily prepared 3‐(pyridin‐2‐yl)imidazo[1,5‐a]pyridine (pyridylindolizine, Py‐indz) ligand to several metal moieties was studied, and its electronic properties, similar to those of the classical ligands 2,2′‐bipyridine (bipy) and 1,10‐phenanthroline (phen), are reported. The new complexes were prepared and fully characterized by X‐ray crystallography and other typical spectroscopic methods if possible. Paramagnetic complexes [Ni(S2X)2(Py‐indz)] X = P(OEt)2 (1), COEt (2); [Ni(acac)2(Py‐indz)] (3, acac = acetylacetonate); [Ni(Py‐indz)3](PF6)2 (4); [Mn2Cl4(Py‐indz)2] (6); and [MnCl2(Py‐indz)2] (7) have the magnetic moment expected for a metallic cation with two or five unpaired electrons. Diamagnetic complexes show NMR spectra with similar patterns with small differences depending on the complex. [M{S2P(OEt)2}2 (Py‐indz)] M = Zn (8), Cd (9) have pentacoordinate and hexacoordinate structures, respectively. Octahedral tin complexes [SnL4(Py‐indz)] L4 = I4 (10), Cl3Ph (11), and Cl2nBu2 (12) have different behaviors in solution; whereas complex 10 is practically insoluble, complex 11 displays the expected pattern in its NMR spectrum, and complex 12 shows dynamic behavior. The Py‐indz ligand is also able to stabilize copper(I) and forms [Cu(PPh3)2(Py‐indz)]BF4 (13). The synthesis of the carbonyl complexes [MBr(CO)3(Py‐indz)] M = Mn (14), Re (15) and [Mo(CO)4(Py‐indz)] (16) was followed by IR spectroscopy in solution. [RuCl·p‐cym(Py‐indz)]PF6 (17, p‐cym = p‐cymene) has the familiar half‐sandwich “three‐legged piano‐stool” geometry.Ministerio de Economía, Industria y Competitividad (Project CTQ2013- 41067-P
Observations on the steric impact of N- and S- donor scorpionate ligands

A comparison is made between the steric influences of a range of zinc hydrotris(pyrazolyl)borates and zinc hydrotris(thio-imidazolyl)borates ([Zn(TpR)Cl], [Zn(TmR)Cl],: R = Me, iPr, Ph tBu)) using inverse cone angle analysis. The study combines the crystallographic analysis of [Zn(TmiPr)Cl] and [Zn(TmPh)Cl] with the data previously deposited with the Cambridge Crystallographic Data Centre. The study suggests that despite efforts to manipulate the reactive pocket around the metal centre in M(TmR) complexes, the incorporation of sterically confining substituents onto the framework has a minimal effect at the metal centre unless the group attached is very large
Hierarchical meso-mesoporous and macro-mesoporous silica templated by mixtures of polyoxyethylene ­fluoroalkyl ether and triblock copolymer

We report here the synthesis of different kinds of hierarchical porous silica materials by using mixtures of an amphiphilic block copolymer (Pluronic P123) and a nonionic fluorinated surfactant. In particular, we have taken advantage of the difference in polarities between the two compounds to design dual-mesoporous materials through the cooperative templating mechanism (CTM). We have undertaken a complete study of this system by varying the composition of the mixed micelles and the synthesis conditions. We have shown that both the dual-mesoporosity and the mesopore ordering are favored when materials are prepared with fluorine-rich and P123-rich micelles. However, when the P123-rich micelles predominate, the mesostructure is less organized and the dual-porosity depends on the P123 content. In addition, concentrated emulsions were formed by incorporating perfluorodecalin (PFD) in the surfactant mixture, and hierarchical macro-mesoporous materials were prepared by combining the CTM and the emulsion templating mechanism
Facile synthesis of cooperative acid-base catalysts by clicking cysteine and cysteamine on an ethylene-bridged periodic mesoporous organosilica

A periodic mesoporous organosilica (PMO) that contains ethylene bridges was functionalized to obtain a series of cooperative acid-base catalysts. A straightforward, single-step procedure was devised to immobilize cysteine and cysteamine on the support material by means of a photoinitiated thiol-ene click reaction. Likewise, PMO materials capped with hexamethyldisilazane (HMDS) were used to support both compounds. This resulted in different materials in which the amine site was promoted by carboxylic acid groups, surface silanol groups, or both. The catalysts were tested in the aldol reaction of 4-nitrobenzaldehyde and acetone. It was found that silanol groups have a stronger promoting effect on the amine than the carboxylic acid group. The highest turnover frequency (TOF) was obtained for an amine-functionalized material that contained only silanol promoting sites. The loading of the active sites also had a significant effect on the activity of the catalysts, which was rationalized on the basis of a computational study
A systematic study on the preparation and hydrogen storage of Zeolite 13X templated microporous carbons

Author's manuscript version.This is the pre-peer reviewed version of the following article: Yang, Z., Xiong, W., Wang, J., Zhu, Y. and Xia, Y. (2016), A Systematic Study on the Prep­aration and Hydrogen Storage of Zeolite 13X-Templated Microporous Carbons. European Journal of Inorganic Chemistry, which has been published in final form at doi: 10.1002/ejic.201501180.A systematic study on chemical vapour deposition (CVD)-based synthesis strategies (single CVD process, double CVD process and a combination of liquid impregnation and a CVD process) for the nanocasting of zeolite-templated porous carbon materials with commercially available zeolite 13X as hard template and ethylene, furfuryl alcohol, acetonitrile and/or vinyl cyanide as carbon precursor is presented. The results indicated that the combination of liquid impregnation and CVD is superior to the single or the double CVD processes in producing carbon materials with high surface area, high pore volume and high microporosity. The combination of liquid impregnation with furfuryl alcohol and CVD with ethylene generates carbon materials with the highest surface area of 2841 m2/g, a pore volume of 1.54 cm3/g and a hydrogen-uptake capacity of 6.3 wt.-% (at –196 °C and 20 bar). Under the studied conditions, the porous carbon materials exhibit variable structural ordering and tuneable textural properties with surface areas of 1600–2850 m2/g, pore volumes of 1.0–1.8 cm3/g and hydrogen-uptake capacities in the range of 3.4–6.3 wt.-% (at –196 °C and 20 bar). Notably, linear relationships between the hydrogen-uptake capacity and the total surface area, the micropore volume and the micropore surface area were found for the studied porous carbons, and this implies an important role of the total surface area, the micropore volume and the micropore surface area in the hydrogen adsorption.Royal SocietyRoyal Academy of EngineeringBayu Oversea Intelligence Plan of Chongqin