Transition Metals Iron Research Articles

Efficient model photosensitizers based on metallocenyl complexes with thiophene-N = N-pyrimidine as π-conjugated bridge and cyanoacrylate as an anchoring group: a density functional theory study.

Eight push-pull systems involving containing four transition metals (iron, ruthenium, cobalt, and nickel), metallocenes as donor groups, cyanoacrylate as electron attractor group, and thiophene-N = N- pyrimidine derivatives as π-conjugated bridges were designed and studied using DFT and TD-DFT methods involving B3LYP and CAM-B3LYP functionals combined with the cc-pVDZ/LANL2DZ basis sets. The main purpose of this work is to determine the effect of metallocene in improving the photosensitization property of such chromophores. This was done by calculating their light-harvesting efficiency LHE as well as other properties employed for DSSC application. The considered dyes were first studied in the gas phase, then in the presence of TiO2 nanoparticles representing the semi-conductor, and finally in the presence of a specific implicit solvent. The presence of iron as metal involved in the metallocene group supplemented by extending the π-conjugated bridge by a cyanovinyl spacer was demonstrated so as to give the most optimal response taking into account the lower cost and toxicity as well as the friendliness to the environment of iron as metal.

Predicted Pressure-Induced High-Energy-Density Iron Pentazolate Salts

Metal-pentazolate compounds as candidates for novel high-energy-density materials have attracted extensive attention in recent years. However, dehydrated pentazolate salts of transition metal iron are rarely reported. We predict two new iron pentazolate salts Fdd2-FeN10 and (No.1)-FeN10 using a constrained crystal search method based on first-principles calculations. We propose that the stable Fdd2-FeN10 crystal may be synthesized from FeN and N2 above 20 GPa, and its formation enthalpy is lower than the reported iron pentazolate salt (marked as (No.2)-FeN10). Crystal (No.1)-FeN10 is composed of iron bispentazole molecules. Formation enthalpy, phonon spectrum and ab initio molecular dynamics calculations are performed to show their thermodynamic, mechanical and dynamic properties. Moreover, the high energy density (3.709 kJ/g, 6.349 kJ/g) and good explosive performance indicate their potential applications as high-energy-density materials.

Clays play a catalytic role in pyrolytic treatment of crude-oil contaminated soils that is enhanced by ion-exchanged transition metals

Pyrolytic treatment of crude-oil contaminated soils offers great potential for rapid remediation without destroying soil fertility with lower energy requirements than incineration. Here, we show that clays impregnated with non-toxic transition metals (iron or copper) can be used as an amendment to decrease the required pyrolytic treatment temperature and time. Amending a weathered crude-oil contaminated soil with 10 % (by weight) of bentonite modified via ion-exchange with Fe or Cu, achieved 99 % removal of residual total petroleum hydrocarbons (TPH) at a pyrolysis temperature of 370 °C with 15-min contact time. Pyrolytic treatment of amended soils at the unprecedentedly low pyrolysis temperature of 300 °C resulted in 87 % TPH removal efficiency with Cu-bentonite and a 93 % with Fe-bentonite. We postulate that the transition metals catalyzed the pyrolysis reactions at lower onset temperatures. This hypothesis is supported by thermogravimetric analysis coupled with mass spectrometry, which revealed the release of hydrogen, methyl and propyl ion fragments (markers of pyrolytic degradation products of crude oil) at lower temperatures than those observed for unamended soil. Overall, this work shows proof of concept that metal-impregnated clays can enhance rapid pyro-catalytic treatment of crude-oil contaminated soils and encourages further work to understand the detailed reaction mechanisms and inform process design.

Controllable sensitivity mechanism in an energetic compound of [FeII(Rtrz)6] as a molecular switch

Transition metal iron complexes can be designed for spin crossover compounds with low spin and high spin bistable (LS and HS) states, spin transition can be triggered by external excitation, which regulates stability (sensitivity) and magnetism of complexes. [FeII(Rtrz)6] systems are bulit with the nitrogen-rich group triazole as the ligand, potentially making them high-energy compounds that can be applied in pyrotechnics and especially good candidates as green initiator for weapon systems. In this paper, two kinds of mononuclear complexes [FeIIN6-1,2,4-triazole] (1) and [FeIIN6-1,2,3-triazole] (2) are constructed, and LS ⇌ HS transition occurs by altering the bond lengths of metal ligand at room temperature; therefor, complex 1 and 2 may be spin crossover energetic materials. The ground state of both complexes is the LS state (low sensitivity), and the stable trend is 1 > 2. The spin transport mechanism is calculated by the non-equilibrium Green's function formalism combined with density functional theory. The theoretical results show that both 1 and 2 can be used as molecular switches in a small bias range, but 2 cannot be used when the bias voltage is high. In short, complex 1 is an ideal molecular switch from HS state (high-sensitivity) to LS state (low-sensitivity), acting as a reversible on ⇌ off switch. The spin state transition of complex 1 can be induced with an electric field; therefore, it is expected to control the safety of primary explosives precisely in the long term.

The Role of the Metabolism of Zinc and Manganese Ions in Human Cancerogenesis.

Metal ion homeostasis is fundamental for life. Specifically, transition metals iron, manganese and zinc play a pivotal role in mitochondrial metabolism and energy generation, anti-oxidation defense, transcriptional regulation and the immune response. The misregulation of expression or mutations in ion carriers and the corresponding changes in Mn2+ and Zn2+ levels suggest that these ions play a pivotal role in cancer progression. Moreover, coordinated changes in Mn2+ and Zn2+ ion carriers have been detected, suggesting that particular mechanisms influenced by both ions might be required for the growth of cancer cells, metastasis and immune evasion. Here, we present a review of zinc and manganese pathophysiology suggesting that these ions might cooperatively regulate cancerogenesis. Zn and Mn effects converge on mitochondria-induced apoptosis, transcriptional regulation and the cGAS-STING signaling pathway, mediating the immune response. Both Zn and Mn influence cancer progression and impact treatment efficacy in animal models and clinical trials. We predict that novel strategies targeting the regulation of both Zn and Mn in cancer will complement current therapeutic strategies.

Ambient Availability of Amino Acids, Proteins, and Iron Impacts Copper Resistance of Aspergillus fumigatus

The transition metals iron and copper are required by virtually all organisms but are toxic in excess. Acquisition of both metals and resistance to copper excess have previously been shown to be important for virulence of the most common airborne human mold pathogen, Aspergillus fumigatus. Here we demonstrate that the ambient availability of amino acids and proteins increases the copper resistance of A. fumigatus wild type and particularly of the ΔcrpA mutant that lacks export-mediated copper detoxification. The highest-protecting activity was found for L-histidine followed by L-asparagine, L-aspartate, L-serine, L-threonine, and L-tyrosine. Other amino acids and proteins also displayed significant but lower protection. The protecting activity of non-proteinogenic D-histidine, L-histidine-mediated growth inhibition in the absence of high-affinity copper uptake, determination of cellular metal contents, and expression analysis of copper-regulated genes suggested that histidine inhibits low-affinity but not high-affinity copper acquisition by extracellular copper complexation. An increase in the cellular copper content was found to be accompanied by an increase in the iron content, and, in agreement, iron starvation increased copper susceptibility, which underlines the importance of cellular metal balancing. Due to the role of iron and copper in nutritional immunity, these findings are likely to play an important role in the host niche.

Theoretical insight on mechanically robust graphene-nickel interfaces using chromium-substituted nickel and boron-doped graphene

As one type of versatile functional composites, graphene-embedded metal matrix, particularly for the nickel metal, has received much attention due to the mechanical enhancement effect. For the promising graphene-nickel composite (Gr-Ni), one of major challenges is the intrinsically weak interfaces that leads to undesired mechanical failure. To address this issue, some structural modifications are highly required for re-designing the interface towards mechanical robustness. In this work, cationic substitution for nickel and anionic replacement for graphene are rationally adopted to modify the Gr-Ni interface from a theoretical perspective. It is expected that these modifications could induce electronic coupling and/or chemical bonding effects. Specifically, a series of transition metal atoms, including chromium, manganese, iron, cobalt, and copper, are selected for the partial substitution of nickel matrix, and meanwhile the anionic boron is introduced into graphene framework. By systematic evaluation on the properties of the Gr-Ni interface, it is evidenced that the chromium-substituted nickel matrix delivers the strongest adsorption capability towards the boron-doped graphene. Furthermore, the atomic arrangement states and the substitution concentrations are explored for optimizing binding abilities. These theoretical calculation results shed light on the interfacial enhancement strategy by the effective modulation on the atomic composition over metal-graphene interfaces and offer useful guidelines on the experimental manipulation on mechanically reinforced metal-graphene composites.

Accelerating double pulse all-optical write/erase cycles in metallic ferrimagnets

All-optical switching of magnetic order presents a promising route toward faster and more energy efficient data storage. However, a realization in future devices is ultimately dependent on the maximum repetition rates of optically induced write/erase cycles. Here, we present two strategies to minimize the temporal separation of two consecutive femtosecond laser pulses to toggle the out-of-plane direction of the magnetization of ferrimagnetic rare-earth transition metal alloys. First, by systematically changing the heat transfer rates using either amorphous glass, crystalline silicon, or polycrystalline diamond substrates, we show that efficient cooling rates of the magnetic system present a prerequisite to accelerate the sequence of double pulse toggle switching. Second, we demonstrate that replacing the transition metal iron by cobalt leads to a significantly faster recovery of the magnetization after optical excitation allowing us to approach terahertz frequency of write/erase cycles with a minimum pulse-to-pulse separation of 7 ps.

Are Heavy Fermion Strange Metals Planckian?

Strange metal behavior refers to a linear temperature dependence of the electrical resistivity that is not due to electron–phonon scattering. It is seen in numerous strongly correlated electron systems, from the heavy fermion compounds, via transition metal oxides and iron pnictides, to magic angle twisted bi-layer graphene, frequently in connection with unconventional or “high temperature” superconductivity. To achieve a unified understanding of these phenomena across the different materials classes is a central open problem in condensed matter physics. Tests whether the linear-in-temperature law might be dictated by Planckian dissipation—scattering with the rate —are receiving considerable attention. Here we assess the situation for strange metal heavy fermion compounds. They allow to probe the regime of extreme correlation strength, with effective mass or Fermi velocity renormalizations in excess of three orders of magnitude. Adopting the same procedure as done in previous studies, i.e., assuming a simple Drude conductivity with the above scattering rate, we find that for these strongly renormalized quasiparticles, scattering is much weaker than Planckian, implying that the linear temperature dependence should be due to other effects. We discuss implications of this finding and point to directions for further work.

Fluorescent sensing framework based on mixed-ligand as a highly sensitive probe for selective detection of Fe3+ cations, Cr2O72− and nitrobenzene

Using 4'-(4′-pyridyl)-2,2':6′,2″-terpyridine (PYTPY) and 3,5-bis-(3-carboxy-benzyloxy)-benzoic acid (H3bcb) as ligands and transition metals cadmium (II) and iron (III) synthesized two metal organic frameworks [Cd(H2bcb)2(PYTPY)] (1) and [Fe(H2bcb)2(PYTPY)]n (2). The structure was confirmed and characterized by single crystal X-ray diffraction and elemental analysis. The structure analysis shows that complexes 1 and 2 are further connected through π-π interactions and hydrogen bonds to form a 3D supramolecular network. In addition, complex 1 shows high sensitivity to Fe3+, Cr2O72− and nitrobenzene in solutions containing mixed metal ions, anionic groups and aromatic compounds. Which makes it be a promising crystalline material as luminescent probe to Fe3+ Cr2O72− and nitrobenzene. This property makes complex 1 a potential fluorescence sensor for these chemicals. The present investigation clearly demonstrates selective, recyclable detection of lethal environmental pollutants such as Fe3+, Cr2O72− and NB in aqueous media which has relevance in the context of environmental protection and homeland security. Moreover, complex 2 exhibits weak antiferromagnetic interactions at low temperature. It lays a good foundation for the future research and design of molecular based magnets.

A molecular mechanics and molecular dynamics study of the structural organization of Cu(II), Ni(II), Co(II), and Fe(II) stearates as potential catalysts for in situ upgrading of heavy oil

Metal stearates may show a substantial catalytic effect in the thermal methods of in situ upgrading of heavy oil. Their good solubility in oil makes it possible to efficiently distribute them over oil reservoirs. Furthermore, in situ synthesis of metal oxide and metal sulfide nanoparticles is possible under conditions of steam injection or other thermal treatments. The initial molecular structure and arrangement of molecules of copper, nickel, cobalt, and iron transition metal stearates are elucidated using the molecular mechanics and molecular dynamics methods. All the simulated complexes are arranged into lamellar layers with additional arrangement of aliphatic chains and metal atoms in two-dimensional periodic arrays. According to the molecular dynamics simulation data, the disordering of hydrocarbon chains and the overall molecular organization takes place at high temperatures. The simulated structures can be further used for studying the solubility of the studied metal stearates in hydrocarbons and the mechanisms of nanoparticle formation from them under conditions used for in situ upgrading of heavy oil.

New insights into NO adsorption on alkali metal and transition metal doped graphene nanoribbon surface: A DFT approach

The aim of this article is to investigate the sensing performance of NO gas molecule on the graphene nanoribbon domain for the determination of structural and electronic properties. Effect of an alkali metal (lithium) and a transition metal (iron) on the armchair oriented graphene nanoribbon (ArGNR) surface for the sensing purpose of NO gas has been performed through the quantum mechanics based Density Functional Theory (DFT) calculations. Various configurations of ArGNR doped with Li and Fe atoms such as one-edge doped, center doped, both-edge doped Li-ArGNR and Fe-ArGNR have been simulated, and a detailed comparative study of lithium and iron doping on different configurations of ArGNRs for the adsorption energy, stability analysis, band gap analysis and density of states analysis has been quantitatively evaluated. By comparing the adsorption energy of NO, it is found that Li doping enhances the strength of NO adsorption on the different variants of ArGNR. Computational results predict that the undoped ArGNR is insensitive to the NO gas adsorption with adsorption energy of about −0.41 eV. Our results determine that substitutional doping of Li doping at one edge doped and both-edge doped position increases the adsorption abilities of ArGNRs in these configurations with adsorption energies of approximately −6.92 eV and −9.64 eV that is 16 and 23 times greater than the pristine ArGNR (Pr-ArGNR). Band nature for both type of doping estimates the changing behavior of ArGNRs from semiconductor to metallic transition after the adsorption of NO molecule. It is concluded that the Li doping at one edge and both edge position of ArGNR makes it an excellent potential sensing material for the sensing purpose of NO gas as compared to the Fe doped configurations.

Reactivity and Fe-complexation investigation by computational simulation studies on phenyltetrazole derivatives as mild steel corrosion inhibitors in aqueous acidic medium

B3LYP, B3PW91, CAM-B3LYP, HCTH, ωB97XD, and M06-2X are six hybrid correlation-exchange and meta-GGA functionals, with 6-31G(d,p) basis set for the H, C, N, O and Cl atoms and the LANL2DZ basis set for the Fe atom. Utilized to determine the most favorable to be applied with phenyltetrazole derivatives, namely: 5-phenyl-1H-tetrazole (Ph-T), 5-p-tolyl-1H-tetrazole (Me-Ph-T), 5-(4-methoxyphenyl)-1H-tetrazole (Me-O-Ph-T), 5-(4-chlorophenyl)-1H-tetrazole (Me-O-Ph-T), and 5-(4-chlorophenyl) (Cl-Ph-T). Aside from that, the quintet complexes were the most stable of the spin multiplicities studied. Furthermore, three forms of interactions between Fe and phenyltetrazole compounds are identified using Fukui functions, including Fe-Me/Me-O/Cl, Fe-ϕ, and Fe-N among eleven complexes. The meta-GGA functionals are ideally suited to predict metal–ligand interaction in the complexes investigated, which contain the transition metal iron with unsaturated valences. While the bond energies and enthalpies estimated for the two Fe- Me-O-Ph-T and Fe- Cl-Ph-T complexes are the lowest and almost identical, the two inhibitors investigated act similarly. Furthermore, chemisorption is promoted by the flatness of the Cl-Ph-T and Me-O-Ph-T inhibitors. Moreover, the adsorption energy of the Cl-Ph-T and Me-O-Ph-T inhibitors.(-185.661 and −186.005 kcal/mol, respectively), suggests that they are the most stable and strongest adsorption systems demonstrated by MDS. The discovered dynamic descriptors were in excellent accord with the quantum study's findings.

Neuroprotective Effect of Quercetin during Cerebral Ischemic Injury Involves Regulation of Essential Elements, Transition Metals, Cu/Zn Ratio, and Antioxidant Activity.

Cerebral ischemia results in increased oxidative stress in the affected brain. Accumulating evidence suggests that quercetin possesses anti-oxidant and anti-inflammatory properties. The essential elements magnesium (Mg), zinc (Zn), selenium (Se), and transition metal iron (Fe), copper (Cu), and antioxidants superoxide dismutase (SOD) and catalase (CAT) are required for brain functions. This study investigates whether the neuroprotective effects of quercetin on the ipsilateral brain cortex involve altered levels of essential trace metals, the Cu/Zn ratio, and antioxidant activity. Rats were intraperitoneally administered quercetin (20 mg/kg) once daily for 10 days before ischemic surgery. Cerebral ischemia was induced by ligation of the right middle cerebral artery and the right common carotid artery for 1 h. The ipsilateral brain cortex was homogenized and the supernatant was collected for biochemical analysis. Results show that rats pretreated with quercetin before ischemia significantly increased Mg, Zn, Se, SOD, and CAT levels, while the malondialdehyde, Fe, Cu, and the Cu/Zn ratio clearly decreased as compared to the untreated ligation subject. Taken together, our findings suggest that the mechanisms underlying the neuroprotective effects of quercetin during cerebral ischemic injury involve the modulation of essential elements, transition metals, Cu/Zn ratio, and antioxidant activity.

An overview of the active sites in transition metal electrocatalysts and their practical activity for hydrogen evolution reaction

Locating the active sites and understanding the reaction mechanism are crucial for the design and preparation of higher hydrogen evolution activity catalysts. If these theoretical knowledges can be combined with practical large-scale hydrogen production, the development of electrochemical water splitting will be further promoted. In this review, we have first summarized the active sites of recent reported HER catalysts, including transition metals molybdenum, iron, nickel, cobalt and noble metal-based materials. At the same time, the mechanisms of hydrogen evolution followed by each catalyst and corresponding strategies for improving their catalytic activity are also discussed. In addition, from the point of practical application, the testing conditions, achievements already made and challenges that to be faced for each type of material are also proposed. The implementation of this work is helpful for researchers to master the electrocatalyst from a deeper perspective (including hydrogen adsorption energy, water adsorption energy, water dissociation energy, active surface and active site.), thus promoting the development of water electrolysis.

An N4-Tetradentate Hydrazone Ligand That Binds in a Neutral, Mono- and Bisdeprotonated Form to Iron(II) and Zinc(II) Metal Ions

The coordination chemistry of butane-2,3-dione bis (2′-pyridylhydrazone) towards the divalent first-row transition metals zinc and iron has been explored. Depending upon the conditions, the ligand in the six complexes was found to be either neutral, mono, or doubly deprotonated. The zinc(II) and iron(II) complexes were fully characterized by elemental analysis, mass spectrometry, and X-ray diffraction methods.

Indication of Strongly Correlated Electron Transport and Mott Insulator in Disordered Multilayer Ferritin Structures (DMFS).

Electron tunneling in ferritin and between ferritin cores (a transition metal (iron) oxide storage protein) in disordered arrays has been extensively documented, but the electrical behavior of those structures in circuits with more than two electrodes has not been studied. Tests of devices using a layer-by-layer deposition process for forming multilayer arrays of ferritin that have been previously reported indicate that strongly correlated electron transport is occurring, consistent with models of electron transport in quantum dots. Strongly correlated electrons (electrons that engage in strong electron-electron interactions) have been observed in transition metal oxides and quantum dots and can create unusual material behavior that is difficult to model, such as switching between a low resistance metal state and a high resistance Mott insulator state. This paper reports the results of the effect of various degrees of structural homogeneity on the electrical characteristics of these ferritin arrays. These results demonstrate for the first time that these structures can provide a switching function associated with the circuit that they are contained within, consistent with the observed behavior of strongly correlated electrons and Mott insulators.

Influence on structural, electronic and optical properties of Fe doped ZnS quantum dot: A density functional theory based study

AbstractIn this paper, the tunability of the fluorescence capacity of ZnS quantum dot (QD) after the effective doping of transition metal iron (Fe) have been studied. The structural, electronic, and optical properties have been optimized for pure and Fe doped ZnS QDs by using local density approximation in density functional theory framework. The optimized lattice volumes show a reasonable agreement with previously obtained experimental and theoretical data for both the doped and un‐doped system. As Fe is doped to ZnS, the crystal system transforms from cubic to tetragonal structure with an increased lattice volume compared to the pure system and exhibits a narrow band gap with a negative value. Moreover, the absorption peak is broadened in the ultraviolet to the blue (visible) region and it shows a low intense peak in the infrared region. These results indicate the increase of fluorescence capacity that may be expected to apply for rapid detection of virus‐like as SARS CoV‐2.

CO activation by the heterobinuclear transition metal-iron clusters: A photoelectron spectroscopic and theoretical study

Spectroscopic characterization of CO activation on multiple metal-containing catalysts remains an important and challenging goal for identifying the structure and nature of active site in many industrial processes such as Fischer-Tropsch chemistry and alcohol synthesis. Here, we use mass-selected photoelectron velocity-map imaging spectroscopy and quantum chemical calculations to study the reactions of CO molecules with several heterobinuclear transition metal-iron clusters M–Fe (M = Ti, V, Cr). The mass spectra reveal the favorable formation of MFe(CO)4− with relatively high thermodynamic stability. The MFe(CO)4− (M = Ti, V, Cr) complexes are established to have a metal–Fe bonded M–Fe(CO)4 structure with C3v geometry. While the positive charge and unpaired electrons are mainly located on the M atom, the natural charge of Fe(CO)4 is about −2e. The MFe(CO)4− (M = Ti, V, Cr) can be seen as being formed via the interactions between the M+ fragment and the [Fe(CO)4]2− core, which satisfies the 18-electron rule. The CO molecules are remarkably activated in these MFe(CO)4−. These results shed insight into the structure–reactivity relationship of heterobinuclear transition metal carbonyls and would have important implications for understanding of CO activation on alloy surfaces.

The Role of Metal Ions in Fungal Organic Acid Accumulation.

Organic acid accumulation is probably the best-known example of primary metabolic overflow. Both bacteria and fungi are capable of producing various organic acids in large amounts under certain conditions, but in terms of productivity-and consequently, of commercial importance-fungal platforms are unparalleled. For high product yield, chemical composition of the growth medium is crucial in providing the necessary conditions, of which the concentrations of four of the first-row transition metal elements, manganese (Mn2+), iron (Fe2+), copper (Cu2+) and zinc (Zn2+) stand out. In this paper we critically review the biological roles of these ions, the possible biochemical and physiological consequences of their influence on the accumulation of the most important mono-, di- and tricarboxylic as well as sugar acids by fungi, and the metal ion-related aspects of submerged organic acid fermentations, including the necessary instrumental analytics. Since producing conditions are associated with a cell physiology that differs strongly to what is observed under “standard” growth conditions, here we consider papers and patents only in which organic acid accumulation levels achieved at least 60% of the theoretical maximum yield, and the actual trace metal ion concentrations were verified.