Transition metals Research Papers - Academia.edu (original) (raw)

- by
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- High Pressure, Transition metals, x-ray magnetic circular dichroism (XMCD)

The activation of CO2 and its hydrogenation to methanol are of much interest as a way to utilize captured CO2. Here, we investigate the use of size-selected Cu4 clusters supported on Al2O3 thin films for CO2 reduction in the presence of hydrogen. The catalytic activity was measured under near-atmospheric reaction conditions with a low CO2 partial pressure, and the oxidation state of the clusters was investigated by in situ grazing incidence X-ray absorption spectroscopy. The results indicate that size-selected Cu4 clusters are the most active low-pressure catalyst for catalytic CO2 conversion to CH3OH. Density functional theory calculations reveal that Cu4 clusters have a low activation barrier for conversion of CO2 to CH3OH. This study suggests that small Cu clusters may be excellent and efficient catalysts for the recycling of released CO2.

- by Stefan Vajda
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- Chemistry, Medicine, DFT calculation, Transition metals

Carbon monoxide is a key C feedstock for the industrial production of hydrocarbons, where it is used to make millions of tonnes of chemicals, fuels, and solvents per annum. Many transition metal complexes can coordinate CO, but the formation of new C-C bonds in well-defined compounds from the scission and subsequent coupling of two or more CO moieties at a transition metal centre remains a challenge. Herein, we report the use of low-coordinate iron(II) complexes for the selective scission and homologation of CO affording unusual squaraines and iron carboxylates at ambient temperature and pressure. A modification of the ligand framework allows for the isolation and structural characterisation of a proposed metallacyclic Fe(II) carbene intermediate. These results indicate that, with the appropriate choice of supporting ligands, it is possible to cleave and homologate carbon monoxide under mild conditions using an abundant and environmentally benign low-coordinate, first row transition...

- by Ana Geer
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- Multidisciplinary, Carbon Monoxide, Transition metals, Nature Communications

Following astonishing growth in the last decade, the field of luminescence thermometry has reached the stage of becoming a mature technology. To achieve that goal, further developments should resolve inherent problems and methodological faults to facilitate its widespread use. This perspective presents recent findings in luminescence thermometry, with the aim of providing a guide for the reader to the paths in which this field is currently directed. Besides the well-known temperature read-out techniques, which are outlined and compared in terms of performance, some recently introduced read-out methods are discussed in more detail. These include intensity ratio measurements that exploit emissions from excited lanthanides levels with large energy differences, dual-excited and time-resolved single-band ratiometric methods, and phase-angle temperature read-outs. The necessity of the extension of theoretical models and a careful re-examination of those currently in use is emphasized. Regarding materials, the focus of this perspective is on dual-activated probes for luminescence intensity ratio (LIR), and transition-metal-ion-activated phosphors for both lifetime and LIR thermometry. Several particularly important applications of luminescence thermometry are presented. These include temperature measurement in catalysis, in-situ temperature mapping for microfluidics, thermal history measurement, thermometry at extremely high temperatures, fast temperature transient measurement, low-pressure measurement via up-conversion nanoparticle emission intensity ratios, evaluation of the photothermal chirality of noble metal clusters, and luminescence thermometry using mobile devices. Routes for the development of primary luminescence thermometry are discussed in view of the recent redefinition of the kelvin.

- by Miroslav Dramicanin
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- Transition metals, Thermal Imaging, Thermometry, Upconversion luminescence

In the present work, thermal degradation behaviors of the Zn (II), Cd(II), and Hg(II) coordination polymers of fumaroyl bis (paramethoxyphenylcarbamide) (fbpmpc) have been investigated by using thermogravimetric (TG) analysis, differential thermal analysis (DTA) and derivative thermogravimetry (DTG) analysis under non-isothermal conditions in nitrogen atmosphere at multiple heating rates. TG–DTA study noteworthy inferred the presence of lattice water in outer sphere of all the polymers. The decomposition was carried out in three-four well-separated stages where involved the loss of water molecules in the first step followed by organic ligand. Furthermore, the kinetics and thermodynamic stabilities of multi-steps thermal degradation were evaluated.

- by Ratiram Chaudhary
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- Coordination Chemistry, Kinetics, Transition metals, Thermal Analysis

Ultrasonic velocity measurements, density measurements and viscometric studies were conducted for the drug buspironehydrochloride (0.01–0.1 M) at three different concentrations (0.1, 0.05 and 0.025 M) at 298.15 K/1 atm. The buspirone hydrochlo-ride was prepared in aqueous solutions of Cu(II) and Co(II) metal ion. The experimental data were used to determine acousticalparameters, such as isentropic compressibility, intermolecular free length, specific acoustic impedance, relative association, freevolume, internal pressure, viscous relaxation time, Gibb’s free energy, attenuation coefficient, Rao’s constant, and Wada’s constant.The viscosity data were analysed using the Jones–Dole equation, and the values of the Falkenhagen coefficient A and Jones–DoleB-coefficient were calculated. The outcomes were expressed in terms of the molecular interactions and the variations in parametersunder varying solute concentrations. Concluding remarks regarding intermolecular interactions are provided.

- by Brajendra Kusmariya
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- Chemistry, Inorganic Chemistry, Physical Chemistry, Density
- by Abu Zafur Ziauddin Ahmed
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- Physics, Transition metals, Electrical Resistivity
- by Yusuf Abdirahman
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- Nanoparticles, Nanotechnology, Transition metals, Nanoscience

Islet Amyloid Polypeptide (IAPP), also known as amylin, is a 37-amino-acid peptide hormone that is secreted by pancreatic islet β-cells. Amylin is complementary to insulin in regulating and maintaining blood glucose levels in the human body. The misfolding and aggregation of amylin is primarily associated with type 2 diabetes mellitus, which is classified as an amyloid disease. Recently, the interactions between amylin and specific metal ions, e.g., copper(II), zinc(II), and iron(II), were found to impact its performance and aggregation processes. Therefore, the focus in this review will be on how the chemistry and structural properties of amylin are affected by these interactions. In addition, the impact of amylin and other amyloidogenic peptides interacting with metal ions on the cell membranes is discussed. In particular, recent studies on the interactions of amylin with copper, zinc, iron, nickel, gold, ruthenium, and vanadium are discussed.

- by Mariusz Jaremko
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- Coordination Chemistry, Diabetes, Diabetes mellitus, Transition metals

Helmut Sies established the concept of oxidative stress in 1985.
However, it took some time to introduce this concept into
pathology, where investigators count on formalin-fixed
paraffin-embedded tissue sections. I sought out antigens for
this purpose based on an oxidative stress-induced rat renal
carcinogenesis model, which revealed that 8-hydroxy-2′-
deoxyguanosine and 4-hydroxy-2-nonenal-modified proteins
are ideal. These two monoclonal antibodies successfully
revealed the involvement of oxidative stress in numerous human diseases, including carcinogenesis and atherosclerosis.
Shigeru Okada established the aforementioned ferric
nitrilotriacetate (Fe-NTA)-induced rat renal carcinogenesis
model, which thus far has answered many questions regarding
the presence of target genes in oxidative stress-induced carcinogenesis and the sites that are susceptible to oxidative stress in the genome. Particularly, the similarity of genomic alterations between Fe-NTA-induced renal cancer and human cancers suggests that excess iron plays a role also inhuman carcinogenesis. Furthermore, excess iron is amajor pathology in asbestosinduced mesothelioma, including chrysotile. Despite an analogy to asbestos, multi-wall carbon nanotubes were distinct in that diameter is another responsible factor for mesothelial carcinogenesis. Recently, non-thermal plasma emerged as a candidate for medical intervention for wounds and cancers via manipulating oxidative stress. Counteracting excess iron is a promising preventive strategy for major diseases.

- by Shinya Toyokuni
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- Bioinformatics, Chemotherapy, Tumor Immunology, Oxidative Stress
- by Sayandev Chatterjee
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- Electrochemistry, Spectroscopy, Transition metals, Ruthenium Complexes

Although it has been almost twenty years since the discovery of the now classic and widely-used Brust–Schiffrin two-phase method (BSM) for synthesizing organothiol-stabilized metal, chiefly Au, nanoparticles (NPs), details in terms of the metal NP formation mechanism have not yet been fully unravelled. It had long been accepted that Au ions form polymerized species with organothiol molecules before being reduced and forming zero valence Au0 NPs in the BSM synthesis. But recent studies have discovered that the BSM is fundamentally an inverse micelle based process in which the phase transferring surfactant TOAB (tetraoctylammonium bromide) first forms inverse micelles inside the organic phase where water and transferred Au ions are loosely encapsulated, with a structure that can be expressed as [TOA][AuX4] (X=Cl− and/or Br−). It turns out that this inverse micelle structure and the water it encapsulates play key roles in the formation of Au NPs. In this chapter, we will review and discuss in various degrees of detail the relevant chemistry involved in the BSM synthesis of alklychalcogenolate-stabilized metal NPs and highlight the similarity and difference when ligands containing different chalcogen elements (S, Se, or Te) are used as the starting source of the NP-stabilizing agents.

Prion diseases are a group of rare neurodegenerative disorders that develop as a result of the conformational conversion of normal prion protein (PrPC) to the disease-associated isoform (PrPSc). The mechanism that actually causes disease remains unclear. However, the mechanism underlying the conformational transformation of prion protein is partially understood—in particular, there is strong evidence that copper ions play a significant functional role in prion proteins and in their conformational conversion. Various models of the interaction of copper ions with prion proteins have been proposed for the Cu (II)-binding, cell-surface glycoprotein known as prion protein (PrP). Changes in the concentration of copper ions in the brain have been associated with prion diseases and there is strong evidence that copper plays a significant functional role in the conformational conversion of PrP. Nevertheless, because copper ions have been shown to have both a positive and negative effect on prion disease onset, the role played by Cu (II) ions in these diseases remains a topic of debate. Because of the unique properties of paramagnetic Cu (II) ions in the magnetic field, their interactions with PrP can be tracked even at single atom resolution using nuclear magnetic resonance (NMR) spectroscopy. Various NMR approaches have been utilized to study the kinetic, thermodynamic, and structural properties of Cu (II)-PrP interactions. Here, we highlight the different models of copper interactions with PrP with particular focus on studies that use NMR spectroscopy to investigate the role played by copper ions in prion diseases.

- by Mariusz Jaremko
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- Biomolecular NMR, Protein NMR spectoscopy, NMR Spectroscopy, Solid State NMR

Several trace elements are essential micronutrients and are required for various body functions.
The relationship between chronic liver disease and trace heavy metal contents in blood are debatable and have
not been understood clearly. The present study was carried out to determine Cu, Fe, Mn, Cd, Zn, Ni and Co
concentration in blood sera of viral hepatitis patients. Sixty patients (thirty with chronic HBV and thirty with
HCV) and thirty healthy individuals were selected for this study. This study showed that Zn, Cu, Fe, Ni, Co,
Mn and Cd Concentration in serum of chronic HBV were 88.28μg/dL, 434.5μg/dL, 3.44μg/dL, 3.26μg/dL,
77.14μg/dL, 4.28μg/dL and 2.30μg/dL respectively whereas in patients with chronic HCV, these concentrations
were 95.9μg/dL, 464.68μg/dL, 3.08μg/dL, 3.84μg/dL, 69.24μg/dL, 3.79μg/dL and 1.69μg/dL respectively. In
healthy individuals these concentration were found to be 74.52μg/dL, 382.8μg/dL, 2.84μg/dL, 2.67μg/dL,
95.87μg/dL, 5μg/dL and 2.15μg/dL respectively. These results indicate that Cu, Fe, Mn and Cd were present
in higher concentration in the sera of hepatitis patients as compared to healthy controls whereas Zn, Ni and
Co shows opposite trend. Moreover, a good correlation was observed between copies/ml (viral load) and serum
metal’s concentration.

- by Safdar Javed
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- Hepatology, Liver diseases, Transition metals, SERUM

Herein, temperature dependencies of emission and emission decay of Zn 2SiO4:Mn2 powder in the range from room temperature to 300 °C is reported. These dependencies allow temperature sensing from luminescence measurements, since Mn2 emission intensity, emission band spectral position, and emission decay are rapidly changing over the entire temperature range. For fluorescence intensity ratio method, measurement that relays on emission intensity changes with temperature, sensitivity of 12.2 is found. In the case of lifetime thermometry, method that relays on emission decay changes with temperature, sensitivity of 0.48 is determined. Both sensitivity values are among the highest ever recorded for inorganic materials.

- by Miroslav Dramicanin and +1
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- Transition metals, Phosphor Thermometry, Luminescence Materials and Their Characterisation

Dalton Transactions Pespective: Enforcing unusually low coordination numbers on transition metals with sterically demanding ligands has long been an area of interest for chemists. Historically, the synthesis of these challenging molecules has helped to elucidate fundamental principles of bonding and reactivity. More recently, there has been a move towards exploiting these highly reactive complexes to achieve a range of transformations using cheap, earth-abundant metals. In this Perspective, we will highlight selected examples of transition metal complexes with low coordination numbers that have been used in catalysis and the activation of small molecules featuring strong bonds (N 2 , CO 2 , and CO).

- by Laurence Taylor
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- Catalysis, Organometallic Chemistry, Transition metals, Small Molecules

Achieving control over coordination geometries in lanthanide complexes remains a challenge to the coordination chemist. This is particularly the case in the field of molecule-based magnetism, where barriers for magnetic relaxation processes as well as tunneling pathways are strongly influenced by the lanthanide coordination geometry. Addressing the challenge of design of 4f-element coordination environments, the ubiquitous Ln(hfac) 3 moieties have been shown to be applicable as Lewis acids coordinating transition metal acetylacetonates facially leading to simple, chiral lanthanide–transition metal heterodinuclear complexes. The broad scope of this approach is illustrated by the synthesis of a range of such complexes LnM: LnM(hfac) 3 (µ 2-acac-O,O,O) 3 (Ln = La, Pr, Gd; M = Cr, Fe, Ga), with approximate threefold symmetry. The complexes have been crystallographically characterized and exhibit polymorphism for some combinations of 4f and 3d metal centers. However, an isostructural set of systems spanning several lanthanides which exhibit spontaneous resolution in the orthorhombic Sohncke space group P2 1 2 1 2 1 is presented here. The electronic structure and ensuing magnetic properties have been studied by EPR spectroscopy and magnetometry. The GdFe, PrFe, and PrCr complexes exhibit ferromagnetic coupling, while GdCr exhibits antiferromagnetic coupling. GdGa exhibits slow relaxation of the magnetization in applied static fields.

- by Mauro Perfetti and +1
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- Lanthanide, Chirality, Molecular chirality, Magnetism

A new family of stereo–electronically promoted aluminum and scandium super Lewis acids is introduced based on the state–of–the–art computations. Structures of these molecules are designed to minimize resonance electron donation to central metal atoms in the Lewis acids. Acidity of these species is evaluated based on their fluoride–ion affinities in comparison with antimony pentafluoride reference system. It is demonstrated that introduced changes in the stereochemistry of the designed ligands increase acidity considerably compared with Al and Sc complexes with analogous monodentate ligands. High stability of fluoride complexes of these species makes them ideal candidates to be used as weakly coordinating anions in combination with highly reactive cations instead of conventional Lewis acid – fluoride complexes. Further, interaction of all designed molecules with methane is investigated. All studied acids form stable pentavalent–carbon complexes with methane. Besides, interactions of the strongest acid of this family with very weak bases, namely, H2, N2, carbon oxides, and noble gases were investigated; it is demonstrated that this compound can form considerably stable complexes with the aforementioned molecules. To the best of our knowledge, carbonyl and nitrogen complexes of this species are the first hypothetical four–coordinated carbonyl and nitrogen complexes of aluminum. The nature of bonding in these systems is studied in detail by various bonding analysis approaches.

- by Cina Foroutan-Nejad and +1
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- Chemistry, Computational Chemistry, Organic Chemistry, Physical Chemistry

A new charge percolation mechanism (CPM) of olefin polymerization by supported transition metal (Mt) complexes is presented. The partial reduction or oxidation of Mt takes place during the activation. In all cases, Mt exists in several oxidation states producing irregular charge distribution over the support surface. There is a tendency to equalize the oxidation states by charge transfer from Mt(+2) (donor) to Mt(+4) (acceptor). This cannot be performed since they are highly separated on the support. But, monomer molecules adsorb on the support and produce the clusters with stacked π-bonds. Thus monomer molecules make a π -bond bridge between the donor (D) and acceptor (A). Once a bridge is formed (percolation moment), a charge transfer occurs. D and A equalize their oxidation states simultaneously with the polymerization of the monomer. The polymer chain is desorbed from the support making the surface free for the subsequent monomer adsorption. The whole process is repeated by oxidation-reduction of another A-D pairs. The new CPM is confirmed by experimental data and by computer simulation.

We present spectroscopic measurements looking for the coherent coupling between molecular magnetic centers
and microwave photons. The aim is to find the optimal conditions and the best molecular features to achieve the
quantum strong coupling regime, for which coherent dynamics of hybrid photons-spin states take place. To this
end, we used a high critical temperature YBCO superconducting planar resonator working at 7.7 GHz and at low
temperatures to investigate three molecular mononuclear coordination compounds, namely Cu(mnt) 2 , [ErPc 2 ] -
TBA + and Dy-trensal . Although the strong coupling regime was not achieved in these preliminary experiments,
results provide several hints on how to design molecular magnetic centers to be integrated into hybrid quantum
circuits

- by Mauro Perfetti
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- Hybrid Systems, Lanthanide, Transition metals, Quantum Circuits

The perception that carbon monoxide (CO) is poisonous and life-threatening for mammalian organisms stems from its intrinsic propensity to bind iron in hemoglobin, a reaction that ultimately leads to impaired oxygen delivery to tissues. From evolutionary and chemical perspectives, however, CO is one of the most essential molecules in the formation of biological components and its interaction with transition metals is at the origin of primordial cell signaling. Not surprisingly, mammals have gradually evolved systems to finely control the synthesis and the sensing of this gaseous molecule. Cells are indeed continuously exposed to small quantities of CO produced endogenously during the degradation of heme by constitutive and inducible heme oxygenase enzymes. We have gradually learnt that heme oxygenase-derived carbon monoxide (CO) serves as a ubiquitous signaling mediator which could be exploited for therapeutic purposes. The development of transition metal carbonyls as prototypic carbon monoxide-releasing molecules (CO-RMs) represents a novel stratagem for a safer delivery of CO-based pharmaceuticals in the treatment of various pathological disorders. This review looks back at evolution to analyze and argue that a dynamic interaction of CO with specific intracellular metal centers is the common denominator for the diversified beneficial effects mediated by this gaseous molecule.

- by Roberto Motterlini
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- Evolutionary Biology, Inflammation, Drug Discovery, Therapeutics

Full journal version available: doi: 10.1016/j.scriptamat.2018.08.045 This poster presents the preliminary results of our work on Cr-Mo-V-W high-entropy alloy published as "Cr-Mo-V-W: A new refractory and transition metal high-entropy alloy system". For further details, http://unsworks.unsw.edu.au/fapi/datastream/unsworks:57273/bin5cf5882d-409c-485b-b03d-3190d0c72699?view=true Abstract: Cr-Mo-V-W high-entropy alloy (HEA) is studied, with 2553 K equilibrium solidus and high Cr content to promote protective oxide scale formation, suggesting potential applications in hot, oxidising environments. Alloy Search and Predict (ASAP) and phase diagram calculations found a single-phase, body-centred cubic (BCC) solid solution at elevated temperatures, across the range of compositions present within the system - uncommon for a HEA of refractory and transition metals. Density functional theory identified solubility of 22 at.% Cr at solidus temperature, with composition-dependent drive for segregation during cooling. An as-cast, BCC single-phase with the composition 31.3Cr-23.6Mo-26.4 V-18.7 W exhibiting dendritic micro segregation was verified. DOI: 10.1016/j.scriptamat.2018.08.045

Beer freshness is that what makes a good beer pop. Sadly enough, for both brewers and consumers alike, beer is unresistant to the tooth of time. Noticeable staling can already occur 2-3 months from packaging when stored at room temperature. As beer starts to fade, it loses precious aromas and pleasant (hop) bitterness, all while developing unpalatable or harsh off-flavours.
The question is: does this phenomenon really concern the average home brewer?

- by Tuur Mertens
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- Beer (Alcohol Studies), Brewing, Transition metals, Metal chelation
- by Dr. Biplab Kumar Paul and +1
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- Materials Engineering, Transition metals, Dielectrics, Mullite
- by Zahra Badri
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- Computational Chemistry, Theoretical Chemistry, Aromaticity, Metal clusters
- by Lucas Fernández Seivane and +1
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- Anisotropy, Transition metals, Spin-Orbit Coupling, Nanoclusters

We have calculated the electrical resistivity of amorphous transition metals Fe and Ni by using the Diffraction model as proposed by Ziman. The electron–ion interaction is described by a local model pseudopotential, and the static structure factors are taken from the experiment. The d-band effect, a characteristic of the transition metals, is accounted for through the sp–d hybridization effect. Agreement of the calculated results with the available experimental data is found to be remarkably good for both systems.

- by Masud Rana
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- Physics, Materials Science, Transition-Metal Oxides, Mathematical Sciences

The scope and limitations of metal salt Lewis acid catalysts were examined for the selectivity control for the
formation of Friedländer and non-Friedländer product during the reaction involving 2-aminobenzophenone and
ethyl acetoacetate. From a pool of metal halides, tetrafluoroborates, perchlorates, and triflates used as catalyst,
In(OTf)3 emerged as the most effective catalyst for selective/exclusive formation of the Friedländer product. The
generality of the In(OTf)3-catalysed Friedländer reaction was demonstrated by the reaction of differently
substituted 2-aminoarylketones with various carbonyl compounds containing active methylene group (e.g., β-
ketoesters, cyclic/acyclic β-diketones, cyclic/acylic ketones, and aryl/heteroaryl methyl ketones) under solvent-free
conditions affording the desired quinolines in 75-92% yields.

- by ASIM KUMAR, Ph.D. and +1
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- Transition metals
- by Debapriya Chaudhuri
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- Quantum Chemistry, Transition metals, Magnetic Susceptibility, Shanon Entropy
- by Katharina Boguslawski and +1
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- EPR, ESR, EPR Spectroscopy, DFT calculation, Transition metals

The synthesis of a thiourea substituted derivative o f tris( pyr idyl-2-meth yl )amine (TPA) is reported. Tw o of the three pyridine rings are substituted in the 6-positio n with benzoylthiourea groups. Thes e thiourea groups undergo intramol ecular hydrogen bonding to form six- membered rings which leave s one N – H group available to form hydrogen bonds with other molec ules. This reports details how the complexation of this new ligand with transition met al ions yields complexes with differi ng geometries. Seven co-ord inate Mn( II) and Cd( II ), six co-ordinate Ni ( II ) and ﬁve co-o rdinate Co ( II ), Cu( II ) and Zn( II ) complexes have been isolated.

- by Niklaas Buurma and +1
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- Coordination Chemistry, Transition metals, Tripodal Ligands, Anion Binding
- by Aleksey Kuznetsov
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- Engineering, Computational Chemistry, Chemical Physics, Porphyrins

In this study, we have performed a thorough examination of density functional theory (DFT) and time-dependent (TD) DFT to investigate the structural and optoelectronic properties of 3d-transition metals (Cu, Fe, Mn, Ni, V and Zn)-doped pentacene π-conjugated organic molecule. The HOMO energy level of Ni-doped pentacene is − 6.17 eV wide, i.e., about 1.31 eV greater and more negative than pentacene. The bandgap of the pentacene considerable decreases from 2.20 eV to 1.32, 1.35 and 0.37 eV, for Mn, Zn and V-doped pentacene structures, respectively, which affords an efficient charge transfer from HOMO to LUMO. The HOMO-LUMO energy gap is higher (4.44 eV, for Ni-doped pentacene), implying that the kinetic energy is higher and high chemical reactivity. We have examined, additionally, the reactivity and absorption properties of individual undoped and 3d-transition metals-doped pentacene. Pentacene has the largest vertical ionization potential (6.18 eV), corresponding to the highest chemical stability. Our results suggest that the new 3d-transition metals-doped pentacene may significantly contribute to the efficiency of solar cells.

- by İskender Muz
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- Transition metals, Band Gap, Pentacene, TDDFT

We explored the Fe rich side of the (Mn,Fe)2(P,Ge) magnetocaloric system. The transition temperature of this system is extremely easy to tune with careful manipulation of Fe and Ge content as well as stoichiometrical proportions, which give rise to the real possibility of lowering theprice of this compound and thus make it economically viable for practical magnetocaloric applications. Novel and unexpected magnetic properties observed in this system suggest na exciting potential for permanent magnet application in a limited concentration range.

- by Mausumi Ray
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- Reaction Mechanisms, Silicon, DFT calculation, Transition metals
- by Lucas Fernández Seivane and +1
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- Transition metals, Spin-Orbit Coupling

The chromatographic behavior of alkaline earth metals, Cu(II), Mn(II), Co(II), Zn(II), Ni(II), Pb(II), and Cd(II) on a chelating aminomethylphosphonic acid-functionalized silica column was studied in eluants with high ionic strength to suppress ion exchange. Unusual variations were found in plots of capacity factor against pH demonstrating changes in retention order, suggesting a change in the coordination of metal ions from O,O to N,O,O chelation. Increased affinity of the chelating ion exchanger to heavy metals and in particular Mn(II) was observed at low pH. Examples are shown of high-efficiency separations of groups of metal species with varying retention orders at different pH values, including a separation of eight metal species in under 16 min. These characteristics make aminophosphonate chelating substrates a useful and more versatile phase for high-performance chelation ion chromatography than iminodiacetate phases

Angle-resolved valence-band resonant-photoemission of nickel metal has been measured close to the 2p core-level thresholds with synchrotron radiation. The well-known 6-eV correlation satellite has an intensity enhancement of about two orders of magnitude at resonance. The angular dependence of the photoemission intensity has been studied as function of photon energy and provides unambiguous evidence for interference effects all the way up to the resonance maximum. The observation of different angular asymmetries,, ...

Carbon monoxide is a key C 1 feedstock for the industrial production of hydrocarbons, where it is used to make millions of tonnes of chemicals, fuels, and solvents per annum. Many transition metal complexes can coordinate CO, but the formation of new C−C bonds in well-defined compounds from the scission and subsequent coupling of two or more CO moieties at a transition metal centre remains a challenge. Herein, we report the use of low-coordinate iron(II) complexes for the selective scission and homologation of CO affording unusual squaraines and iron carboxylates at ambient temperature and pressure. A modification of the ligand framework allows for the isolation and structural characterisation of a proposed metallacyclic Fe(II) carbene intermediate. These results indicate that, with the appropriate choice of supporting ligands, it is possible to cleave and homologate carbon monoxide under mild conditions using an abundant and environmentally benign low-coordinate, first row transition metal.

- by Laurence Taylor
- •
- Carbon Monoxide, Transition metals, Fisher-Tropsch

The magnetic properties of the pentacoordinate [M II (Me 4 cyclam)N 3 ] + (Me 4 cyclam = tetramethylcyclam;N 3 = azido;M= Ni, Co) complexes were investigated. Magnetiza-tion and EPR studies indicate that they have an easy plane of magnetization with axial anisotropy parameters D close to 22 and greater than 30 cm À1 for the Ni and Co complexes ,r espectively.A bi nitio calculations reproduced the experimental values of the zero-field splitting parameters and allowedt he orientationof the anisotropy tensor axes with respectt ot he molecular frame to be determined. For M = Ni, the principal anisotropy axis lies along the NiÀN azido direction perpendicular to the Ni(Me 4 cyclam)m ean plane,w here-as for M = Co it lies in the Co(Me 4 cyclam) mean plane and thus perpendicular to the CoÀN azido direction.T hese orienta-tions match one of the possible solutions experimentally provided by single-crystal cantilever torque magnetometry. To rationalize the geometry and its impact on the orientation of the anisotropy tensora xis, calculations were carried out on modelc omplexes [Ni II (NCH) 5 ] 2 + and[ Co II (NCH) 5 ] 2 + by varyingt he geometry between square pyramidal and trigo-nal bipyramidal. The geometryo ft he complexes was found to be the result of ac ompromise between the electronic configuration of the metal ion and the structure-orienting effecto ft he Me 4 cyclam macrocycle. Moreover, the orientation of the anisotropy axes is mainlyd ependent on the geometry of the complexes.

- by Mauro Perfetti
- •
- Transition metals, Cobalt, Nickel, Torque
- by Phillip Pendleton
- •
- Kinetics, Ionic Liquid, Ionic Liquids, Transition metals

Dramatic change in the crystal structure was observed upon electrochemical delithiation. As a result Rh atoms migrate cooperatively and the structure transforms from layered to that, containing small rutile and bigger ramsdelite... more

- by Olesia Karakulina and +1
- •
- Materials Science, Lithium Batteries, Transmission Electron Microscopy, Electron Diffraction

1. Спосіб одержання сорбенту для вилучення іонів перехідних металів з розчинів взаємодією силікагелю і зшивального агента з наступною обробкою отриманого модифікованого силікагелю комплексоутворюючим агентом, який відрізняється тим, що як... more

- by Olena Andrianova
- •
- Sorbents, Transition metals

X-ray absorption spectra of gas-phase VOCl3 and CrO2Cl2 have been measured in the metal L2,3-edge and O
K-edge regions. The assignment of the spectral features is based on the relativistic two-component ZORA
TDDFT approach. The calculations provide results in excellent agreement with the experimental spectra and
prove the importance of including both configuration mixing and spin-orbit coupling in the theoretical
description to obtain a reliable simulation of the transition metal L2,3-edge. The calculations are extended
also to the MnO3Cl molecule to discuss the spectral variations along the series of the oxychlorides both in
the metal L2,3 and ligand O K spectra

- by Mausumi Ray
- •
- Reaction Mechanisms, Silicon, DFT calculation, Transition metals