Late 3d Transition Metals Research Articles

Interaction of Nitric Oxide with Late 3d Transition Metals: Dissociation and Metal Oxidation

Interaction of Nitric Oxide with Late 3d Transition Metals: Dissociation and Metal Oxidation

Dry Reforming of Methane to Syngas Mediated by Rhodium-Cobalt Oxide Cluster Anions Rh2CoO.

Dry reforming of methane (DRM) to syngas is an important route to co-convert CH4 and CO2. However, the highly endothermic nature of DRM induces the thermocatalysis to commonly operate at high temperatures that inevitably causes coke deposition through pyrolysis of methane. Herein, benefiting from the mass spectrometric experiments complemented with quantum chemical calculations, we have discovered that the bimetallic oxide cluster Rh2CoO- can mediate the co-conversion of CH4 and CO2 at room temperature giving rise to two free H2 molecules and two adsorbed CO molecules (COads). The only elementary step requiring the input of external energy (e.g., high temperature) is desorption of COads from the reaction intermediate Rh2CoOC2O2-. The doping effect of Co has also been clarified that the Co could tune the charge distribution and orbital energy of the active metal Rh, enabling the enhancement of cluster reactivity toward C-H activation, which is essential to facilitating the DRM to syngas. This work not only underlines the importance of temperature control over elementary steps in practical thermocatalysis but also identifies a promising active species containing the late 3d transition metal to drive DRM to syngas. The findings could provide novel insights into design of bimetallic catalysts for co-conversion of CH4 and CO2 at low temperatures.

Super-correlation consistent composite approach (s-ccCA) for the late 3d and 4d transition metals: Impact of higher-order excitations on thermochemical prediction

Resonant 2 Photon Ionization (R2PI) spectroscopy and its ability to achieve thermochemical energies with unprecedented accuracy and extraordinarily small uncertainties has enabled the emergence of a new level of ab initio composite methodologies. The super correlation consistent Composite Approach (s-ccCA) includes coupled cluster terms with up to pentuple excitations has been used to achieve excellent agreement with R2PI for 3d and 4d transition metal thermochemistry. For system size increases, a continued fraction approximant has been examined to address the CCSDTQP contribution.

Defect engineering of 1T′ MX 2 (M = Mo, W and X = S, Se) transition metal dichalcogenide-based electrocatalyst for alkaline hydrogen evolution reaction

The alkaline electrolyzer (AEL) is a promising device for green hydrogen production. However, their energy conversion efficiency is currently limited by the low performance of the electrocatalysts for the hydrogen evolution reaction (HER). As such, the electrocatalyst design for the high-performance HER becomes essential for the advancement of AELs. In this work, we used both hydrogen (H) and hydroxyl (OH) adsorption Gibbs free energy changes as the descriptors to investigate the catalytic HER performance of 1T′ transition metal dichalcogenides (TMDs) in an alkaline solution. Our results reveal that the pristine sulfides showed better alkaline HER performance than their selenide counterparts. However, the activities of all pristine 1T′ TMDs are too low to dissociate water. To improve the performance of these materials, defect engineering techniques were used to design TMD-based electrocatalysts for effective HER activity. Our density functional theory results demonstrate that introducing single S/Se vacancy defects can improve the reactivities of TMD materials. Yet, the desorption of OH becomes the rate-determining step. Doping defective MoS2 with late 3d transition metal (TM) atoms, especially Cu, Ni, and Co, can regulate the reactivity of active sites for optimal OH desorption. As a result, the TM-doped defective 1T′ MoS2 can significantly enhance the alkaline HER performance. These findings highlight the potential of defect engineering technologies for the design of TMD-based alkaline HER electrocatalysts.

Metalating 5-Methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile (ROY): Understanding the Denticity and Speciation of Complexes of the ROY Anion.

5-Methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile (ROY) is considered to be the most crystalline polymorphic organic molecule discovered to date with 12 fully characterized crystal structures present in the Cambridge Structural Database (CSD). However, metal complexes of ROY have not previously been described. Here, we explore the synthetic chemistry of ROY (denoted as H-ROY hereafter for the purpose of our study) and demonstrate that it can be deprotonated using either NaH or KH and that the resulting sodium and potassium salts of H-ROY can be cleanly isolated. Furthermore, we introduce two new metal complexes of the ROY anion (ROY-) with Co(II) and Ni(II) cations, formed by the reaction of the sodium salt of ROY, Na(ROY), with the respective transition-metal chloride salts. Solid-state X-ray diffraction studies confirm the presence of Co(II) or Ni(II) centers, with the ROY- ligand in a 1:2 ratio forming neutral trinuclear clusters of the forms [Co3ROY6] (Co-ROY) and [Ni3ROY6] (Ni-ROY) in both cases. Here, the ROY- moiety interacts with the metal center through the anionic N atom, an O atom of the -NO2 group, and the N atom of the -CN group. IR and electronic absorption spectroscopies reveal the influence of the Co(II) and Ni(II) centers on the properties of the complexes. Taken together, our results show that the metal complexes of the H-ROY proligand can be prepared with late 3d transition metals. The results of these structural chemistry studies may contribute to resolving polymorphism in H-ROY and related compounds.

Correlation consistent effective core potentials for late 3d transition metals adapted for plane wave calculations.

We construct a new modification of correlation consistent effective core potentials (ccECPs) for late 3d elements Cr-Zn with Ne-core that are adapted for efficiency and low energy cut-offs in plane wave calculations. The decrease in accuracy is rather minor, so that the constructions are in the same overall accuracy class as the original ccECPs. The resulting new constructions work with energy cut-offs at or below ≈400 Ry and, thus, make calculations of large systems with transition metals feasible for plane wave codes. We also provide the basic benchmarks for atomic spectra and molecular tests of this modified option that we denote as ccECP-soft.

Compositional effects on the hydrogen storage properties in a series of refractory high entropy alloys

The possible combinations in the multidimensional space of high entropy alloys are extremely broad, which makes the incremental experimental research limited. As a result, establishing trends with well-known empirical parameters (lattice distortion, valence electron concentration etc.) and predicting effects of the chemical composition change are vital to guide future research in the field of materials science. In this context, we propose a strategy to rationalize the effect of chemical composition change on the hydrogen sorption properties in a series of high entropy alloys: Ti0.30V0.25Zr0.10Nb0.25M0.10 with M = Mg, Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ta and ∅ (corresponding quaternary alloy). All materials are bcc alloys and absorb hydrogen at room temperature forming fcc or pseudo-fcc dihydride phases. The maximum hydrogen storage capacity at room temperature strongly depends on the valence electron concentration (VEC) of the alloys: the capacity is high (1.5–2.0 H/M) for low values of VEC (<4.9) whereas, a drastic fading is observed for VEC ≥4.9 which is the case for alloys with M being a late 3d transition metal. The structural analysis suggests that steric effects might not be responsible for this trend and electronic reasons may be invoked. Increasing the VEC by alloying with late 3d transition metals will fill the unoccupied valence states and the electrons from interstitial hydrogens can no longer be accommodated, which is unfavorable for hydrogen storage. Moreover, the onset temperature of desorption increases almost linearly with VEC for this composition series. These findings suggest that alloys with low VEC are more likely to become promising candidates for hydrogen storage.

Water soluble transition metal [Ni(II), Cu(II) and Zn(II)] complexes of N-phthaloylglycinate bis(1,2-diaminocyclohexane). DNA binding, pBR322 cleavage and cytotoxicity.

To validate the effect of metal ions in analogous ligand scaffolds on DNA binding and cytotoxic response, we have synthesized a series of water-soluble ionic N-phthaloylglycinate conjugated bis(diaminocyclohexane)M2+ complexes where M = Ni(II), Cu(II) and Zn(II) (1-3). The structural characterization of the complexes (1-3) was achieved by spectroscopic {FT-IR, EPR, UV-vis absorption data, 1H NMR, ESI-MS and elemental analysis} and single crystal X-ray diffraction studies, which revealed different topologies for the late 3d-transition metals. The Ni(II) and Zn(II) complexes exhibited an octahedral geometry with coordinated labile water molecules in the P1̄ space group while the Cu(II) complex revealed a square planar geometry with the P21/c space lattice. In vitro DNA-complexation studies were performed employing various complementary biophysical methods to quantify the intrinsic binding constant Kb and Ksv values and to envisage the binding modes and binding affinity of (1-3) at the therapeutic targets. The corroborative results of these experiments revealed a substantial geometric and electronic effect of (1-3) on DNA binding and the following inferences were observed, (i) high Kb and Ksv values, (ii) remarkable cleavage efficiency via an oxidative pathway, (iii) condensation behavior and (iv) good cytotoxic response to HepG2 and PTEN-caP8 cancer cell lines, with copper(II) complex 2 outperforming the other two complexes as a most promising anticancer drug candidate. Copper(II) complexes have been proven in the literature to be good anticancer drug entities, displaying inhibition of uncontrolled-cell growth by multiple pathways viz., anti-angiogenesis, inducing apoptosis and reactive oxygen species mediated cell death phenomena. Nickel(II) and zinc(II) ionic complexes 1 and 3 have also demonstrated good chemotherapeutic potential in vitro and the bioactive 1,2-diaminocyclohexane fragment in these complexes plays an instrumental role in anticancer activity.

A review on the computational studies of the reaction mechanisms of CO2 conversion on pure and bimetals of late 3d metals.

Despite series of experimental studies that reveal unique activities of late 3d transition metals and their role in microorganisms known for CO2 conversion, these surfaces are not industrially viable yet. An insight into the elementary steps of surface catalytic processes is crucial for effective surface modification and design. The mechanisms of CO2 transformation into CO, through the reverse water gas shift and methane reforming, are being studied. Mechanisms of CO2 methanation is also being explored by the Sabatier reaction into methane. This review covers both experimental and theoretical studies into the mechanisms of CO2 reduction into CO and methane, on single metals and bimetals of late 3d transition metals, i.e. Fe, Co, Ni, Cu and Zn. This paper highlights progress and gaps still existing in our knowledge of the reaction mechanisms. These mechanistic studies reveal CO2 activation and reduction mechanisms are specific to both composition and surface facet. Surfaces with least CO2 binding potential are seen to favour CO and O binding and provide higher barriers to dissociation. No direct correlation has been seen between binding strength of CO2 and its degree of activation. Hydrogen-assisted dissociation is seen to be generally favoured kinetically on Cu and Ni surfaces over direct dissociation except on the Ni (211) surface. Methane production on Cu and Ni surfaces is seen to occur via the non-formate pathway. Hydrogenation reactions have focused on Cu and Ni, and more needs to be done on other surfaces, i.e. Co, Fe and Zn.

Permanganyl Fluoride: A Brief History of the Molecule MnO3 F and of Those Who Cared For It.

Permanganyl fluoride's existence at the stability threshold in the series of oxides and oxide fluorides of the late 3d transition metals is reflected by its experimentally challenging properties and by the difficulties posed in the theoretical description of its bonding characteristics. The history of this molecule is reviewed from early qualitative observations and the growing scattered information on its chemical and physical properties to the accurate determination and interpretation of its molecular structure and spectral features. The still problematic theoretical models for MnO4 − and MnO3F are briefly presented in the broader context of the chemistry of elements in high oxidation states. Short biographies of the scientists engaged in these studies are offered. Related technetium and rhenium compounds are briefly considered for comparison.

Tailoring the properties of 3d transition metal complexes with different N-cycloalkyl-substituted tetrazoles

N-Cycloalkyl-substituted tetrazoles were coordinated with different late 3d transition metal(ii) salts to give moderately sensitive energetic coordination compounds.

Mixed Ionic–Electronic Conductor of Perovskite LixLayMO3−δ toward Carbon‐Free Cathode for Reversible Lithium–Air Batteries

AbstractMixed ionic–electronic conductors (MIECs) can play a pivotal role in achieving high energies and power densities in rechargeable batteries owing to their ability to simultaneously conduct ions and electrons. Herein, a new strategy is proposed wherein late 3d transition metals (TMs) are substituted into a perovskite Li‐ion conductor to transform it into a Li‐containing MIEC. First‐principles calculations show that perovskite LixLayMO3 with late 3d TMs have a low oxygen vacancy formation energy, implying high electron carrier concentrations corresponding to high electronic conductivity. The activation barriers for Li diffusion in LixLayMO3 (M = Ti, Cr, Mn, Fe, and Co) are below 0.411 eV, resulting in high Li‐ion conductivity. The designed perovskites of Li0.34La0.55MnO3−δ experimentally prove to have high electronic (2.04 × 10−3 S cm−1) and Li‐ion (8.53 × 10−5 S cm−1) conductivities, and when applied in a carbon‐free cathode of a Li–air cell, they deliver superior reversibility at 0.21 mAh cm−2 over 100 charge/discharge cycles while avoiding the degradation associated with carbonaceous materials. This strategy enables the effective design of Li‐conducting MIEC and reversible Li–air batteries.

Melting properties by X-ray absorption spectroscopy: common signatures in binary Fe\u2013C, Fe\u2013O, Fe\u2013S and Fe\u2013Si systems

X-ray absorption spectroscopy (XAS) is a widely used technique to probe the local environment around specific atomic species. Applied to samples under extreme pressure and temperature conditions, XAS is sensitive to phase transitions, including melting, and allows gathering insights on compositional variations and electronic changes occurring during such transitions. These characteristics can be exploited for studies of prime interest in geophysics and fundamental high-pressure physics. Here, we investigated the melting curve and the eutectic composition of four geophysically relevant iron binary systems: Fe–C, Fe–O, Fe–S and Fe–Si. Our results show that all these systems present the same spectroscopic signatures upon melting, common to those observed for other pure late 3d transition metals. The presented melting criterion seems to be general for late 3d metals bearing systems. Additionally, we demonstrate the suitability of XAS to extract melt compositional information in situ, such as the evolution of the concentration of light elements with increasing temperature. Diagnostics presented in this work can be applied to studies over an even larger pressure range exploiting the upgraded synchrotron machines, and directly transferred to time-resolved extreme condition studies using dynamic compression (ns) or fast laser heating (ms).

3 d Transition Metal-Catalyzed Hydrogenation of Nitriles and Alkynes.

Selective hydrogenation of nitriles and alkynes is crucial considering the vast applications of reduced products in industries and in the synthesis of bioactive compounds. Particularly, the late 3d transition metal catalysts (manganese, iron, cobalt, nickel and copper) have shown promising activity for the hydrogenation of nitriles to primary amines, secondary amines and imines. Similarly, semihydrogenation of alkynes to E- and Z-alkenes by 3d metals is adequately successful both via the transfer hydrogenation and by using molecular hydrogen. The emergence of 3d transition metals in the selective synthesis of industrially relevant amines, imines and alkenes makes this protocol more attractive. Herein, we provide a concise overview on the late 3d transition metal-catalyzed hydrogenation of nitriles to amines and imines as well as semihydrogenation of alkynes to alkenes.

Rhodium-containing oxide-hydrides: covalently stabilized mixed-anion solids.

The first rhodium-containing oxide-hydride phases, LaSrCo0.5Rh0.5O3H and La0.5Sr1.5Mn0.5Rh0.5O3H, have been prepared via topochemical anion exchange. This clearly demonstrates the ability of rhodium, a late 4d transition metal, to kinetically stabilize oxide-hydride lattices, reinforcing the paradigm of covalent stabilization of transition-metal oxide-hydride phases.

Synthesis of Thin-Film Metal Pyrites by an Atomic Layer Deposition Approach.

Late 3d transition metal disulfides (MS2 , M=Fe, Co, Ni, Cu, Zn) can crystallize in an interesting cubic-pyrite structure, in which all the metal cations are in a low-spin electronic configuration with progressive increase of the eg electrons for M=Fe-Zn. These metal pyrite compounds exhibit very diverse and intriguing electrical and magnetic properties, which have stimulated considerable attention for various applications, especially in cutting-edge energy conversion and storage technologies. The synthesis of the metal pyrites is certainly very important, because highly controllable, reproducible, and reliable synthesis methods are virtually essential for both fundamental materials research and practical engineering. In this Concept, a new approach of (plasma-assisted) atomic layer deposition (ALD) to synthesize the thin-film metal pyrites (FeS2 , CoS2 , NiS2 ) is introduced. The ALD synthesis approach allows for atomic-precision control over film composition and thickness, excellent film uniformity and conformality, and superior process reproducibility, and therefore it is of high promise for uniformly conformal metal pyrite thin-film coatings on complex 3D structures in general. Details and implications of this ALD approach are discussed in this Concept, mainly from a conceptual perspective, and it is envisioned that, with this new ALD synthesis approach, a significant amount of new studies will be enabled on both the fundamentals, and novel applications of the metal pyrite materials.

Methylsemicarbazide as a Ligand in Late 3d Transition Metal Complexes.

Most ignition and initiation systems nowadays still contain poisonous chemicals such as lead styphnate and lead azide but also chromates and other compounds of high concern. Therefore, methylsemicarbazide (1, MSC), which can be prepared in a one-step reaction and in an extraordinary high yield of 95 %, has been evaluated as ligand in energetic coordination compounds. For the first time 25 new transition metal complexes (Mn2+ , Ni2+ , Co2+ , Cu2+ , and Zn2+ ) using methylsemicarbazide (1) as the ligand were prepared and comprehensively analyzed by, for example, XRD, IR, EA, UV/Vis and DSC/DTA/TGA. Many show a strong energetic character, which can be tuned by using different anions such as Cl- , SO42- , NO3- , ClO4- , picrate or styphnate. Selected compounds were additionally evaluated as lead-free primary explosives in initiation tests (nitropenta filled detonators) and in laser ignition systems. Especially compound 7 showed very promising results during these tests and could be a potential candidate for future applications.

Models for Unsymmetrical Active Sites in Metalloproteins: Structural, Redox, and Magnetic Properties of Bimetallic Complexes with MII-(μ-OH)-FeIII Cores.

Bimetallic complexes are important sites in metalloproteins but are often difficult to prepare synthetically. We have previously introduced an approach to form discrete bimetallic complexes with MII-(μ-OH)-FeIII (MII = Mn, Fe) cores using the tripodal ligand N,N',N″-[2,2',2″-nitrilotris(ethane-2,1-diyl)]tris(2,4,6-trimethylbenzenesulfonamido) ([MST]3-). This series is extended to include the rest of the late 3d transition metal ions (MII = Co, Ni, Cu, Zn). All of the bimetallic complexes have similar spectroscopic and structural properties that reflect little change despite varying the MII centers. Magnetic studies performed on the complexes in solution using electron paramagnetic resonance spectroscopy showed that the observed spin states varied incrementally from S = 0 through S = 5/2; these results are consistent with antiferromagnetic coupling between the high-spin MII and FeIII centers. However, the difference in the MII ion occupancy yielded only slight changes in the magnetic exchange coupling strength, and all complexes had J values ranging from +26(4) to +35(3) cm-1.

Modeling σ-Bond Activations by Nickel(0) Beyond Common Approximations: How Accurately Can We Describe Closed-Shell Oxidative Addition Reactions Mediated by Low-Valent Late 3d Transition Metal?

Accurate modelings of reactions involving 3d transition metals (TMs) are very challenging to both ab initio and DFT approaches. To gain more knowledge in this field, we herein explored typical σ-bond activations of H-H, C-H, C-Cl, and C-C bonds promoted by nickel(0), a low-valent late 3d TM. For the key parameters of activation energy (ΔE‡) and reaction energy (ΔER) for these reactions, various issues related to the computational accuracy were systematically investigated. From the scrutiny of convergence issue with one-electron basis set, augmented (A) basis functions are found to be important, and the CCSD(T)/CBS level with complete basis set (CBS) limit extrapolation based on augmented double-ζ and triple-ζ basis pair (ADZ and ATZ), which produces deviations below 1 kcal/mol from the reference, is recommended for larger systems. As an alternative, the explicitly correlated F12 method can accelerate the basis set convergence further, especially after its CBS extrapolations. Thus, the CCSD(T)-F12/CBS(ADZ-ATZ) level with computational cost comparable to the conventional CCSD(T)/CBS(ADZ-ATZ) level, is found to reach the accuracy of the conventional CCSD(T)/A5Z level, which produces deviations below 0.5 kcal/mol from the reference, and is also highly recommendable. Scalar relativistic effects and 3s3p core-valence correlation are non-negligible for achieving chemical accuracy of around 1 kcal/mol. From the scrutiny of convergence issue with the N-electron basis set, in comparison with the reference CCSDTQ result, CCSD(T) is found to be able to calculate ΔE‡ quite accurately, which is not true for the ΔER calculations. Using highest-level CCSD(T) results of ΔE‡ in this work as references, we tested 18 DFT methods and found that PBE0 and CAM-B3LYP are among the three best performing functionals, irrespective of DFT empirical dispersion correction. With empirical dispersion correction included, ωB97XD is also recommendable due to its improved performance.

Facile Synthesis of Nano-Alloy Particles for the Oxygen Evolution Reaction

We report a facile method for the infiltration of late 3d transition metals into nanoporous carbon. This method allows for the deposition of Ni, Fe, and Co, as well as their binary alloys, NiFe, NiCo, and FeCo. Utilizing NH3-saturated water nanodroplets adsorbed within nanoporous carbon, metal precursors are precipitated as metal hydroxides with high dispersion. Following deposition, the MOx-carbon composites are reduced in 5% H2 atmosphere and then alloyed at 1100 °C in Ar. The resulting metal and alloy loaded carbon composites demonstrate excellent activity and stability for the alkaline oxygen evolution reaction (OER). The NiFe, and NiCo alloy composites both require an overpotential less than 400 mV after 2 hours under alkaline OER conditions in saturated O2.