Complex Compounds Of Transition Metals Research Articles

Effect of isothermal annealing on formation of self-assembled nanostructures in manganese spinel ZnMnGaO4

The effects of isothermal annealing on the self-assembled nanostructures of spinel manganese oxide ZnMnGaO4 were investigated using transmission electron microscopy and x-ray diffraction. The checkerboard nanostructures and zigzag nanostructures (named “Sierra” nanostructures) coexisted owing to the chemical phase separation of Mn3+ and Ga3+ ions by isothermal annealing at 575 °C. It was observed that the checkerboard nanostructures were dominant in short-time annealing and that the volume fraction of the Sierra nanostructures became more prominent as the annealing period increase. The interdiffusion of Mn3+ and Ga3+ is indicated to play an important role in gaining the total energy of the system by the reduction in the local strain caused by the formation of nanostructures. These results provide further insights into the fabrication of distinct types of nanostructures in complex transition-metal compounds.

Data analysis regarding the behavior against different kinds of anaerobic germs of three first-row transition metal complex compounds

As most kinds of pathogenic agents tend to develop new resistance mechanisms to the common medicines, innovative solutions for counteracting this alarming situation are lately required. Within this context, the current paper aims to propose as potential antibacterial drugs three complex compounds formed by first-row transition divalent metal ions with a Schiff base, presenting the results of a study regarding the behavior of the Schiff base itself, compared to the ones of these three substances, when tested against different kinds of anaerobic germs.The work has been performed by using Kirby-Bauer disk diffusion method, the results being afterwards computationally processed by appealing to the Python multi-paradigm programming language.

Pivotal Role of Intersite Hubbard Interactions in Fe-Doped α-MnO2

We present a first-principles investigation of the structural, electronic, and magnetic properties of the pristine and Fe-doped $\alpha$-MnO$_2$ using density-functional theory with extended Hubbard functionals. The onsite $U$ and intersite $V$ Hubbard parameters are determined from first principles and self-consistently using density-functional perturbation theory in the basis of L\"owdin-orthogonalized atomic orbitals. For the pristine $\alpha$-MnO$_2$ we find that the so-called C2-AFM spin configuration is the most energetically favorable, in agreement with the experimentally observed antiferromagnetic ground state. For the Fe-doped $\alpha$-MnO$_2$ two types of doping are considered: Fe insertion in the $2 \times 2$ tunnels and partial substitution of Fe for Mn. We find that the interstitial doping preserves the C2-AFM spin configuration of the host lattice only when both onsite $U$ and intersite $V$ Hubbard corrections are included, while for the substitutional doping the onsite Hubbard $U$ correction alone is able to preserve the C2-AFM spin configuration of the host lattice. The oxidation state of Fe is found to be $+2$ and $+4$ in the case of the interstitial and substitutional doping, respectively, while the oxidation state of Mn is $+4$ in both cases. This work paves the way for accurate studies of other MnO$_2$ polymorphs and complex transition-metal compounds when the localization of $3d$ electrons occurs in the presence of strong covalent interactions with ligands.

EFFICIENT FLAME RETARDANTS FOR EPOXY RESINS: SYNTHESIS, STRUCTURE, PROPERTIES

Introduction. In modern conditions, the combustibility of polymers plays a dominant role in the process of the appearance and spread of fires. This is because the extremely wide use of polymeric materials in all areas of the national economy. Due to the organic structure, the high content of carbon and hydrogen that make up the macromolecules of the polymers, they are extremely combustible. Combustion of polymers is accompanied by high temperature and flame propagation rate, as well as significant smoke generation and the release of a large number of toxic combustion products. Therefore, the search for new ways to reduce combustibility is one of the priority tasks in the creation and implementation of new polymer materials in various industries. Purpose. The aim of the work is the synthesis of fundamentally new complex compounds of transition metals, the study of their structure and properties, as well as predicting the possibility of their use to reduce the fire hazard of polymeric materials based on epoxy resins. Metods. Modern research methods are used in the work: X-ray diffraction, differential thermal and thermogravimetric analyzes, the method of quantum chemical calculations and IR spectroscopy. The ignition and self-ignition temperatures were determined by standard methods according to GOST 12.1.044-89 using metrologically certified equipment and calibrated measuring instruments.
 Results. By the direct interaction of the combustible organic amine pepa with inorganic salts of copper(II), a number of chelate complexes were obtained. By methods of x-ray phase analysis and IR spectroscopy, their structure was established. The results of quantum-chemical calculations of the complexation process showed that, as a result of the formation in the pepa–Cu(II) salt system, the chelate complexes [Cu(deta)H2O]SO4·H2O, [{Cu(deta)(H2O)(CO3)}2]·6H2O та [Cu(deta)(eda)]SiF6, the energy state of the chemically bonded pepa changes with respect to free molecules. In addition, the results of thermogravimetric studies and the measured ignition and self-ignition temperatures for pepa and complex compounds clearly showed that the process of bonding a combustible organic amine with a non-combustible inorganic salt into a solid complex ensures a decrease in the combustibility of nitrogen-containing hydrocarbon. All this is an extremely important prerequisite in the implementation of the complex mechanism of flame retardant action of transition metal salts. Conclusion. The results of the studies showed that complex compounds based on transition metal salts, and in particular copper(II), can be successfully used as flame retardants that can effectively reduce the fire hazard of nitrogen-containing synthetic polymers, including those based on epoxy resins.

Complex compounds of transition metals with hydroxyaromatic carboxylic acids as precursors for the synthesis of nanosized metal oxides

Eight complex compounds of MnII, FeII, CoII, NiII and CuII with 2,4,6-trihydroxy benzoic acid and 3,4,5-trihydroxybenzoic acid were synthesized in a crystalline form. Nanosized metal oxide particles obtained by thermal decomposition of the complexes were studied by X-ray powder dif raction analysis and electron microscopy.

Adsorption extraction of nickel (II) from industrial aqueous solutions

A scheme for the primary unit of a technological means for the adsorption extraction of nickel from industrial solutions resulting from the processing of oxidised nickel ores is presented. The solutions comprise an aqueous extract of complex compounds of transition metals from an ore having an initial nickel content of 1-2 %. The traditional stepwise treatment of the solutions is oriented towards sequential precipitation of metals by ammonia water in the form of hydroxides, involving their decantation and filtration, etc., which significantly complicates the process of obtaining the target metal. The adsorption process significantly increases the economic efficiency of the extraction process for this valuable metal. In terms of their properties, carbon sorbents are chemically resistant, able to endure the harsh conditions of high temperature exposure and treatments based on strongly acidic and strongly alkaline solutions. Moreover, such sorbents have a developed porous structure, a significant specific surface area and high mechanical strength. The process of nickel extraction using carbon adsorbents from solutions in a weakly alkaline environment at elevated temperatures is described. The scheme of the nickel (II) ion extraction by adsorption unit is based on the use of a fluidised bed whose operational parameters are calculated directly by studying the sorption of nickel ions. The adsorption extraction of nickel (II) ions facilitates the complete selective separation and derivation of the metal following desorption of a saturated solution making the process suitable for direct electrolytic metal production.

Effect of metal complexation on the nonlinear optical response of a conjugated ligand

Organic nonlinear optical materials are widely investigated materials for fabricating optoelectronic devices. Particularly organic π-conjugated systems as well as transition metal complex compounds are studied in this direction because of the strong electronic coupling between the ligand and the metal, their excellent chemical stability, and their rich photochemical and photophysical properties. In this work, comparative studies of the third-order nonlinear optical susceptibilities of a bipyridine ligand (4-(N,N-dibutylamino)-4′-(5-ethynyl-2,2′-bipyridine)-azobenzene (A) and of the corresponding heteroleptic ruthenium complex (Ru(bpy)2(La)(PF6)2 (B) (La signifies the ligand) are presented. The NLO properties were investigated by means of the Z-scan technique using a 30 ps mode-locked Nd-YVO4 laser at 532 nm with a repetition rate of 10 Hz. Our results show that the introduction of the metal in the organic complex results in a significant modification of the third-order nonlinear optical response.

Electronic Excitations and Lattice Dynamics of Coordinatively “Unsaturated” Complex Transition Metal Compounds

Single crystal polarized Raman and infrared spectra of the series Na(5)[MO(2)][X] with M = Co(I), Ni(I), and Cu(I) and X = S(2-) and CO(3)(2-), are reported. All phonon modes are assigned to the lattice eigenmodes based on the group theory analysis and first principles lattice dynamics calculations. The energies of the fundamental symmetric and asymmetric vibrations of the [MO(2)](3-) complex are discussed on the basis of their electronic structure and variation in M-O interatomic distances. Electronic Raman scattering and luminescence are observed for the magnetic members of the series (Co(I), d(8), and Ni(I), d(9)). Ligand field theory is employed to account for the electronic effects which originate from states split by spin-orbit coupling.

High-spin complex [FeL2(NCS)2]·H2O [L = 3,5-di(pyrimidin-2-yl)-4H-1,2,4-triazol-4-amine]: Synthesis and properties

Complex [FeL2(NCS)2]·H2O (L = 3,5-di(pyrimidin-2-yl)-4H-1,2,4-triazol-4-amine) was prepared as the first example of complex compounds of transition metals with 3,5-di(pyrimidin-2-yl)-4H-1,2,4-triazol-4-amines. The coordination core of the iron atom is a distorted octahedron FeN6. In the range 80–300 K the complex is high-spin, μeff ∼ 5.3 MB. The parameter of the crystal field splitting, 10Dq, for [FeL2(NCS)2]·H2O is ∼10800 cm−1.

Lanthanide level location in transition metal complex compounds

We will provide a method to place the levels of all trivalent lanthanides with respect to the top of the valence band and bottom of the conduction band in oxides containing transition metal complexes. The method will be applied to CaTiO 3, YVO 4, LaVO 4, CaNb 2O 6, YNbO 4, CaWO 4, YTaO 4, and LaTaO 4, but in principle can be applied to any oxide containing transition metal complexes with lanthanide dopants on either rare earth or alkaline earth sites. Crucial to place the energy levels is the energy for intervalence charge transfer between a lanthanide ( Pr 3 + and Tb 3 + ) and a transition metal ion ( Ti 4 + , V 5 + , Nb 5 + , Mo 6 + , Ta 5 + , W 6 + ) that can be observed in luminescence excitation spectra. The quenching of Pr 3 + emission from the 3 P 0 state and of Tb 3 + emission from the 5 D 3 and 5 D 4 states provides complementary information.

CombiningM- andL-edge resonant inelastic x-ray scattering for studies of3dtransition metal compounds

Resonant inelastic x-ray scattering (RIXS) measurements performed jointly across the ${M}_{2,3}$ and ${L}_{3}$ absorption thresholds are used to study CoO local electronic structure and are supported by model calculations. The high-resolution experimental data provide a precise set of parameters to describe the correlated response of valence electrons. The same core-hole independent set of parameters within the single impurity Anderson model is used to describe both the $M$ $(3p\text{\ensuremath{-}}3d)$ and $L$ $(2p\text{\ensuremath{-}}3d)$ resonances. This work shows that combining $M$ and $L$ scattering data provides an enhanced contrast view of the spectral weights. Measured ${M}_{2,3}$-RIXS spectra are observed to be free of charge-transfer or normal fluorescence contributions. Moreover the cross section of $M$-RIXS final states with change in spin multiplicity is low. Combining this information with $L$-edge studies establishes an appealing means of making a better separation between on-site and intersite (ligand to metal) electronic excitations. Experimental and theoretical features specific to RIXS studies performed at $M$ and $L$ edges are summarized as a basis for future studies on complex transition metal compounds.

ChemInform Abstract: Complex Compounds of Transition Metals with the Coordination Center MN4

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Chlorine Kβ X-ray emission spectra from selected transition-metal complex compounds

Abstract The chlorine K β emission fluorescence spectra of 16 selected transition-metal complex compounds were measured with a high-resolution two-crystal vacuum spectrometer and presented along with the chlorine K absorption-edge spectra of these compounds, reported previously. The compounds studied include the 3 d transition-metal complex compounds MnCl 2 · 4H 2 O, FeCl 2 · n H 2 O, CoCl 2 · 6H 2 O, NiCl 2 ·6H 2 O, CuCl 2 · 2H 2 O, [Co(NH 3 ) 6 ]Cl 3 , [CoCl(NH 3 ) 5 ]CL 2 , and trans -[CoCl 2 (NH 3 ) 4 ]Cl; the 4 d transition-metal complex compounds [Ru(NH 3 ) 6 ]Cl 3 , K 3 RuCl 6 , (NH 4 ) 3 RhCl 6 and K 2 PdCl 6 ; and the 5 d transition-metal complex compounds (NH 4 ) 2 OsCl 6 , (NH 4 ) 2 IrCl 6 , (NH 4 ) 3 IrCl 6 , and (NH 4 ) 2 PtCl 6 . The Cl K β emission exhibits either a line-shape spectrum or a broad spectrum with a low-energy shoulder. The compounds are classified into three groups according to observed values for the half-widths of the Cl Kβ emission spectra, which range from 1.4 to 4.3 eV. Combining the emission data with those of the absorption allows us to estimate the energy separation of the molecular orbital levels for the 4 d and 5 d transition-metal complex compounds.

The Distribution of Charge in Complex Compounds

The charges on metal atoms and ligands in complex compounds of transition metals may be calculated theoretically or measured empirically, but there is no reliable method of doing either. This review is concerned mainly with two experimental methods, dipole moment measurement and X-ray photoelectron spectroscopy, applied to tertiary phosphate and such complexes of the heavier transition metals. It is concluded that the charge is rarely greater than ±0.3e and that some so-called neutral or positive ligands, e.g. N2 or NO+, may carry more negative charge in a complex than formally anionic ligands such as H−. Small ligands of high formal charge, e.g. O2−, NR2−, and N3−, appear to carry no more negative charge than Cl−, but monoanionic ligands vary greatly in their capacity to contribute to the dipole moments. The ligands NO, CO, PF3, CH, and H− are all nearly neutral to slightly negative, whereas pyridines, tertiary phosphanes, etc. are the most strongly positively charged.

Photoelectron spectroscopic study of surface complexes on Fe(110)

Chemisorption of CO, PF 3 and CNCH 3 on a Fe(110) single crystal surface was studied by means of ultraviolet photoelectron spectroscopy. The results suggest that the mechanism of chemisorption is similar to the bond formation in corresponding transition metal complex compounds.

The theory of electron transfer transitions in complexes with conjugated ligands

In this paper the electron transfer transitions in complex compounds of transition metals with ligands containing a conjugated system of double bonds a

Splittings ofd n-terms in strong complex fields of trigonal and rhombic symmetries

The properties of complex compounds of transition metals can be substantially characterized by thed-electrons. In the present paper all the strong-field configurations arising through the influence of strong fields of trigonal and rhombic symmetries fromdn (n=1, 2, ..., 10) configurations are given. Owing to the effect of strong fields these strong-field configurations split. The symmetries and the multiplicites of the splitting products have been determined by the group theory. To classify the splitting products a new method was developed which, because of its group-theoretical basis, is exact.