Properties Of Transition Metal Ions Research Articles

Chemical tuning of transition metal upconversion properties

The upconversion properties of Ti2+, Ni2+ and Os4+ doped chloride and bromide host lattices are summarized and discussed. These systems are used to illustrate the field of transition metal based upconversion systems and their perspectives, since most upconversion materials investigated so far involve rare earth ions. Three strategies to tune the upconversion properties of transition metal ions by means of chemistry have been studied. They involve a chemically induced crossover in a metastable intermediate excited state, the use of metal–metal exchange interactions to enhance absorption oscillator strengths, as well as the suppression of efficient multiphonon relaxation channels in heavier halide host lattices.

Alternative configuration interaction expansions for transition metal ions with intermediate oxidation states in crystals: The structure and absorption spectrum of Cs2GeF6:Mn4+

The vertical absorption spectrum of the MnF62− cluster embedded in the Cs2GeF6 host crystal was recently calculated using the averaged coupled pair functional method leading to very large discrepancies with accurate one- and two-photon spectra. The same multiconfigurational expansions had previously been successful in similar systems which involved transition metal impurities in lower oxidation states. In this paper we show that the ligand-to-metal charge transfer configurations become so important in this intermediate oxidation state impurity (and, possibly, non-negligible ligand–ligand weak bonding interactions) that none of the 18 molecular orbitals of F 2p character should be left inactive in the correlation treatment. This requirement can be satisfied in MnF62− because of the higher oxidation state of manganese, which enhances the ligand field splittings in the Mn 3d3 configuration manifold so much that one dominant Mn 3d3 configuration rather than the full Mn 3d3 active space can be used as a single reference for single and double excitations from all occupied ligand 2p orbitals. The results of this work, together with those of previous studies, outline two different alternative truncation schemes of the valence electron correlation which produce the same, necessary, high accuracy in structural and spectroscopic properties of transition metal ions doped in ionic crystals. Whether one or the other should be used depends, basically, on the formal oxidation state of the transition metal impurity.

Quantitative EPR studies of transition metal ions in oxide, aluminosilicate and polymer matrices

The importance of the proper choice of diamagnetic diluent used for preparation of standards for quantitative EPR measurements is shown by the example of CuSO4 and VOSO4 standards. The results of determination of the stability of chemical composition of VOSO4-K2SO4 standards stored for various periods of time, performed by different analytical methods, are compared. The examples are given to illustrate application of quantitative EPR measurements in the studies of structure and properties of transition metal ions dispersed in various matrices. Changes in the coordination sphere of surface transition metal ions occurring upon adsorption of gas molecules, the degree of dispersion of these ions and the extent of Mn+−Mn+ interactions derived from quantitative EPR measurements are described. The results of investigation of the mechanism of adsorption and catalytic reactions occurring on dispersed transition metal ions are presented.

Computer Modeling of the Optical Properties of Transition-Metal Ions in Solids

ABSTRACTComputational methods for modeling the optical properties of substitutional transition-metal impurities in insulating solids, potentially applicable to some scintillator and phosphor materials, are reviewed. Methods considered include crystal-field and semi-empirical ligand-field models; SCF-Xα-SW, SCF-RHF-LCAO, SCF-UHF-LCAO and CI ab initio methods: and ICECAP and HADESR embedded cluster methods with lattice relaxation. A detailed example of the application of the HADESR method to crystal-field spectra of Cr3+ in halide elpasolites is described. In this method, ab initio molecular-orbital calculations with effective core potentials are performed for selected ionic configurations. Simultaneous relaxation of the cluster and surrounding lattice, with mutual pair. potential interactions, is accomplished by a modified lattice statics program. Calculated properties include pressure-dependent optical transition energies, vibration frequencies and radiationless transition rates.

Effect of transition metal chloride additives on the radiolysis of aqueous sodium nitrate

Radiolysis of aqueous sodium nitrate solution was studied as a function of concentration in the range 10−4M to 1M NaNO3. The radiolytic yield of nitrite was found to be linear with dose and concentration. The effect of transition metal chloride additives on the radiolysis of 0.01M NaNO3 resulted in higher and lower yields of nitrite in the presence of cobalt and nickel chlorides, respectively, than that obtained in the pure nitrate system. The reduction of nitrate to nitrite is totally quenched even at very low concentration of copper chloride in the binary mixture. The results are explained on the basis of oxidizing and reducing properties of transition metal ions.

ChemInform Abstract: Change of Properties of Transition Metal Ions and the Role of the Support as a Function of Catalyst Preparation

ChemInform Abstract: Change of Properties of Transition Metal Ions and the Role of the Support as a Function of Catalyst Preparation

Complexation between 3-methylorotic (3-methyluracil-6-carboxylic) acid dianion and divalent metal cations. The slow acid dissociation of transition metal complexes and its possible relevance to orotic acid phosphoribosylation

3-Methylorotic (3-methyluracil-6-carboxylic) acid dianion gives 1 : 1 complexes with divalent metal ions. Their stability constants were determined by u.v. spectroscopy for Ca2+, Mg2+, Co2+, Ni2+, and Cu2+. The kinetics of formation of these complexes was investigated by T-jump relaxation in the alkaline pH range. The rate constants thus determined for complexation by Ca2+, Mg2+, Co2+, and Cu2+, show that it fits the Eigen mechanism. Complex dissociation was studied by the stopped-flow technique in the acidic pH range. Surprisingly, the observed first-order rate constants for transition metal ions (Co2+, Ni2+, and Cu2+) are found to be dependent on the final acidity. These results indicate a mechanism involving the slow protonation of these complexes (kH+ < 104 l mol–1s–1). A possible explanation of the inhibiting properties of transition-metal ions in the enzyme-catalysed syntheses of 6-carboxyuridine 5′-monophosphate is inferred.

Crystal field theory and magnetic properties of transition metal ions in amorphous compounds

The aim of this letter is to show that a number of experimentally gathered data on magnetic properties of amorphous paramagnetic compounds can be interpreted in terms of a very simple structural model for these systems. To the Authors ' knowledge, the present approach, though only providing a clue to the problem, is applied here for the first time to the case of amorphous compounds. The splitt ing of the free-ion ground state of transit ion metal ions in aggregate systems, and the related magnetic properties, are greatly influenced by the local symmetry of the environment of the ion. The magnetic properties of typical amorphous compounds containing transit ion metal ions can then be interpreted in terms of the symmetry of short-range order structures which are present in these materials, even in the absence of any long-range order. Complex amorphous systems containing relatively large amounts of transit ion metal ions can be, for instance, aluminosilicate (~) or alkaliborate (~) glasses into which transition metal oxides, principally Fe.,0a, are doped. Other amorphous materials can be obtained by inciting and quenching transit ion metal oxides (CoO (a), MR0 (3), Fe20 a (4), Ti02-Ti~08 (~)) with phosphorus pentoxide P~O 5. Typically these compounds show a paramagaetic behaviour down to 4 K. In some cases only a partial amorphicity of the compound can be obtained. This feature can be controlled by inspection through X-ray diffraction and also by comparison of the magnetic behaviour of samples with crystalline ones with similar compositions. In any case, a large part of the obtained compounds arc definitely in complete amorphous phase within the limits of experimental techniques.

Toward a theory of the spectral and magnetic properties of transition metal ions occupying low-symmetry sites in metalloproteins. Application of the angular overlap model to distorted tetrahedral tetrachlorocobaltate(2-) ions

Toward a theory of the spectral and magnetic properties of transition metal ions occupying low-symmetry sites in metalloproteins. Application of the angular overlap model to distorted tetrahedral tetrachlorocobaltate(2-) ions

有機イオウ化合物に対する遷移金属イオンの抽出反応特性

有機イオウ化合物に対する遷移金属イオンの抽出反応特性

Gyromagnetic Factors and Spin—Orbit Coupling in Ligand Field Theory

It has been customary to compute the effect of spin—orbit coupling on the magnetic properties of transition metal ions in crystals with the expression taken over from atomic spectroscopy, although this expression is valid only in a spherically symmetric field. In the present work, we show how the use of a spin—orbit interaction Hamiltonian derived from the Bethe—Salpeter approximation to the relativistic Breit equation for a partly covalent complex leads to a dependence of the gyromagnetic factor on the spin—orbit coupling parameter of the ligand atoms. We develop an expression of g for a d8-ion in a cubic field and apply it to the case of KNiF3. The calculated g values agree very well with experimental results. Other differences between our expression and those found by other authors are discussed.

Trigonal or Tetragonal Distortions and the Magnetic Properties of Transition Metal Ions with Triply Orbitally Degenerate Ground Terms

Trigonal or Tetragonal Distortions and the Magnetic Properties of Transition Metal Ions with Triply Orbitally Degenerate Ground Terms

The magnetic properties of transition metal ions in asymmetric ligand fields. Part 3.—The behaviour of some t52g complexes

Download options Please wait... Article information DOI https://doi.org/10.1039/TF9615700204 Article type Paper Download Citation Trans. Faraday Soc., 1961,57, 204-209 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions The magnetic properties of transition metal ions in asymmetric ligand fields. Part 3.—The behaviour of some t52g complexes B. N. Figgis, Trans. Faraday Soc., 1961, 57, 204 DOI: 10.1039/TF9615700204 To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author B. N. Figgis

The magnetic properties of transition metal ions in asymmetric ligand fields. Part 2.—Cubic field3T2terms.

The magnetic properties of transition metal ions in asymmetric ligand fields. Part 2.—Cubic field₃T₂terms.

Magnetic properties of transition metal ions in asymmetric ligand fields. Part 1.—Cubic field A and E terms

Magnetic properties of transition metal ions in asymmetric ligand fields. Part 1.—Cubic field A and E terms

929. The effects of crystal fields on the properties of transition-metal ions

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