Electronic Structure Of Metal Ions Research Articles

Two-Dimensional NiCo2S4 Nanosheets Deliver Efficient Oxygen Evolution Reaction

Introduction: The development of cost-effective and efficient catalysts plays a pivotal role in the realization of hydrogen production through electrochemical water splitting. Method: In this study, two-dimensional NiCo2S4 nanosheets weresynthesized usinga hydrothermal method followed by a sulfidation process. Results: The resulting materials were thoroughly characterized to understand their morphology and structure. The findings indicate that the NiCo2S4 nanosheets exhibit exceptional electrical conductivity and a high density of pores, which facilitate electrolyte infiltration and interfacial charge transfer during electrochemical reactions. Furthermore, the incorporation of S2− modulates the electronic structure of metal ions, reducing the oxidation potential of metal sites and promoting the surface reconstruction of the electrode to form active species. Electrochemical tests conducted in a 1 M KOH solution using the synthesized catalyst as the working electrode demonstrate an overpotential of merely 280 mV and 300 mV at a current density of 20 mA cm−2 and 40 mA cm−2 , respectively, which are much lower than those of NiCo-LDH electrodes (360 mV and 410 mV). Conclusion: Furthermore, the NiCo2S4 electrode delivers a remarkably low Tafel slope of 47.9 mV dec−1 . This investigation presents a novel approach to the development of efficient transition metal-based electrocatalysts.

Pressure Effect on Zero-Field Splitting Parameter of Hemin: Model Case of Hemoproteins under Pressure.

We experimentally studied the pressure dependence of the zero-field splitting (ZFS) parameter of hemin (iron(III) protoporphyrin IX chloride), which is a model complex of hemoproteins, via high-frequency and high-field electron paramagnetic resonance (HFEPR) under pressure. Owing to the large ZFS, the pressure effect on the electronic structure of iron-porphyrin complexes has not yet been explored using EPR. Therefore, we systematically studied this effect using our newly developed sub-terahertz EPR spectroscopy system in the frequency range of 80-515 GHz, under magnetic fields up to 10 T and pressure up to 2 GPa. We observed a systematic shift of the resonance fields of hemin upon pressure application, from which the axial component of the ZFS parameter was found to increase from D = 6.9 to 7.9 cm-1 at 2 GPa. In contrast to the previous methods used to study proteins under pressure, which mainly focused on conformational changes, our HFEPR technique can obtain more microscopic insights into the electronic structures of metal ions under pressure. In this sense, our technique provides novel opportunities to study the pressure effects on biofunctional active centers of versatile metalloproteins.

Using a Combination of Experimental and Computational Methods To Explore the Impact of Metal Identity and Ligand Field Strength on the Electronic Structure of Metal Ions

In this exercise, students apply a combination of techniques to investigate the impact of metal identity and ligand field strength on the spin states of three d5 transition-metal complexes: Fe(acac)3, K3[Fe(CN)6], and Ru(acac)3, where acac– is acetylacetonate. Students first use crystal field theory to predict the most likely spin state based on the metal identity (3d versus 4d metal) and the ligand field strength of the acac– and CN– ligands (weak-field versus strong-field ligands). Next, students use density functional theory (DFT) to determine the geometries and the energies of the high- and low-spin electronic configurations of each complex, allowing them to predict the most energetically favorable configuration and to compare their computed geometries with X-ray structural data. Finally, students experimentally determine the magnetic susceptibility and spin state of each complex and compare these results with their predictions. This combined application of basic chemical principles, computational chemistry, and experimental measurement provides students with practical insight into the application of complementary methods to better understand chemical properties.

Delocalization of 4f Electrons in Gadolinium Oxide on the Nanometer Scale

Some metals such as silver are known to become strong reducers on the nanometer scale. Electron energy-loss spectroscopy (EELS) shows that modifications of the electronic structure of metal ions also arise in nanoparticles of gadolinium oxide. Indeed, the oxygen K and gadolinium N4,5 edges present modifications for particles size below 1.5 nm which are the signature of an hybridization of the initially atomiclike Gd 4f states with the valence band and especially the O p states. These modifications evidence that, like in metals, electron delocalization from metal sites also occurs in oxides on the nanometer scale.

Solution thermodynamics of rare-earth metal ions – physicochemical study–

The results of the studying of interactions in multicomponent systems "polyvinyl alcohol (PVA) – rare-earth element ion – nitrate of sodium – water" are represented. It is established that for rubidium (I) ions temperature and ionic strength is render destroying action, and for yttrium (III) ions the influence of these factors has return character which is connected with features of an electronic structure of metal ion. It is revealed that a dominating role of non-electrostatic formation composed, hence, the formation of donor-acceptor connection of "metal – ligand" occurs through atom of oxygen.

ChemInform Abstract: Metal Ion Effects in Isotopic Hydrogen Exchange in Biologically Important Heterocycles

The binding of metal ions to heteroatomic centers of biomolecules has been utilized as a probe of metal ion effects in living systems. This article focuses on the effect of N-coordination by transition metals, especially Pt(II), Co(III), Cr(III), on isotopic C(2)−H or C(8)−H exchange of imidazoles, thiazoles, and purines. The usual reactivity trend, protonated ≫ metalated ≫ neutral substrate, is excepted for Cr(III)/1-methylimidazole, where Cr(III) activates stronger than H+. An interplay of factors is considered, including metal-to-ligand back-bonding, electronic structure of metal ions, and differences in crystal field stabilization energy.

Metal Ion Effects in Isotopic Hydrogen Exchange in Biologically Important Heterocycles

The binding of metal ions to heteroatomic centers of biomolecules has been utilized as a probe of metal ion effects in living systems. This article focuses on the effect of N-coordination by transition metals, especially Pt(II), Co(III), Cr(III), on isotopic C(2)-H or C(8)-H exchange of imidazoles, thiazoles, and purines. The usual reactivity trend, protonated >> metalated >> neutral substrate, is excepted for Cr(III)/1-methylimidazole, where Cr(III) activates stronger than H(+). An interplay of factors is considered, including metal-to-ligand back-bonding, electronic structure of metal ions, and differences in crystal field stabilization energy.

Electronic Configuration in Electrodeposition from Aqueous Solutions: I . The Effect of Ionic Structures

Consideration of electronic structures of metal ions in aqueous solutions indicates that metals are electrodeposited from ions in which coordinate linkages involve only orbitals of the outermost electronic shell. When coordination involves the penultimate shell also, that is, with Taube's “inner orbital” complexes, the metal is not electrodeposited. Apparently the energy required to break such hybridization exceeds that required for cathodic discharge of hydrogen from these solutions. Platinum metals are exceptions, probably because of extraordinary stability of the metallic state for these elements; deposition, however, requires high activation, as shown by over‐ potentials and low current efficiencies. Between different oxidation states, electrolytic oxidation or reduction is irreversible if the electronic configuration must be changed significantly. Irreversible deposition is observed for transition metals or when the ion is bound in a hydrolyzed aggregate. Since inner orbital hybridization is associated with a lack of substitutional lability of the coordinated groups, whereas lability of outer orbital complexes probably results from formation of a dissociation interm iate, it is likely that such an intermediate is also important in the cathode process. These considerations are used to account for and extend the Piontelli electrolytic classification of metals. In considering the effects of anions, it is shown that aquo complexes are reduced with highest irreversibility, which is attributed to high activity of water; the influence of halide ions may be labilization by the trans effect.