X-Ray photoelectron spectra of iron trimethylacetate complexes

Bi-, tri-, and hexanuclear iron(II,III) trimethylacetate complexes were studied by X-ray photoelectron spectroscopy. The compounds differed in the number of Fe-O and Fe-N coordination bonds. The Fe 2p, Fe 3p, and N 1s X-ray photoelectron spectra were examined and the role of the ligand in their formation was elucidated. Based on the calculated multiplet splittings, numerous states were discerned in the Fe 2p spectra. This made it possible to reveal a correlation between the magnetic moment and some spectral parameters, such as the relative intensity and energy position of the satellites.     

X-ray photoelectron spectra and structure of polynuclear nickel complexes

Mono- and binuclear nickel complexes of different stoichiometry have been studied by X-ray photoelectron spectroscopy (XPS). The Ni2p, Ni3p, and N1s X-ray photoelectron spectra have been examined, and the role of a ligand in their formation has been determined. As distinct from a low-spin Ni(II) complex, the Ni2p spectra of high-spin Ni(II) compounds show strong satellite lines. For high-spin Ni(II) complexes, which have unpaired 3d electrons, the Ni2p _1/2-Ni2p _3/2 spin-orbit splitting is larger than that for a low-spin Ni(II) compound. The presence or absence of the satellite structure has made it possible to classify these complexes with regard to their magnetic properties. The difference between the Ni2p _3/2 and N1s binding energies has made it possible to estimate the covalence of the metal-ligand bond. The XPS results are consistent with X-ray crystallography data.     

X-ray photoelectron spectra and structure of cobalt compounds with N-heterocyclic ligands

The electronic structure of cobalt complexes with bi-, tri-, and tetradentate ligands and the mutual influence of ligands in them have been studied by X-ray photoelectron spectroscopy. The Co2p, N1s, and O1s photoelectron spectra have been studied. Unlike low-spin Co(III) complexes, the high-spin Co(II) compound exhibits a strong satellite line in the Co2p spectrum. For the high-spin Co(II) compound having unpaired 3d electrons, the Co2p _1/2-Co2p _3/2 spin-orbit splitting is larger than that in the low-spin Co(III) complexes. All cobalt complexes under consideration contain strongly bound dioxygen, which can be considered an inherent structural unit.     

Effect of the nature of axial ligand on the effective charge of the metal center in PcFe(II) complexes

Disubstituted iron phthalocyanine complexes were studied by X-ray photoelectron spectroscopy (XPS). Fe2p _3/2, N1s, and C1s XPS spectra were analyzed, and the role of the ligand in their generation was determined. Assignment of the magnetic properties of phthalocyanine iron complexes was done. Covalence of the metal-ligand bond was determined. The nature of the axial ligand in Pc^tFe affects the electronic state of the central iron atom.     

XPS study of the electronic structure of binuclear 3d transition metal pivalate complexes

Binuclear pivalate complexes of 3d transition metals (manganese, iron, cobalt, and nickel) with the same ligand environment and a lantern structure have been studied by X-ray photoelectron spectroscopy. The M2p, M3s, C1s, O1s, and N1s X-ray photoelectron spectra have been examined. A redistribution of electron density in the OCO group has been revealed. It has been shown that the theory fits the experimental data on the energy separation between the high- and low-spin components in the M3s spectra and between the spin doublet components in the M2p spectra. It has been demonstrated that the iron, cobalt, and nickel complexes are paramagnetic at room temperature, whereas the manganese complex exhibits antiferromagnetic properties. There is a correlation between the size of the 3d subshell of the transition metal atom and the M-O and M-N bond lengths.     

X-ray photoelectron spectra of metal complexes of substituted 2,4-pentanediones

The X-ray photoelectron spectra of 14 complexes of Al³⁺, Cr ³⁺, Fe³⁺, Co³⁺ and Cu²⁺ with 3-X-2,4-pentanedione (X = H, Cl, Br) were determined to analyse the nature of metal-ligand bonding in these complexes. The trend in the position of np photoelectron lines of X-group with a change of metal ion was decided by the relative contribution of metal-toligand and ligand-to-metal charge transfer. The analysis of the satellites in the M(2p_3/2) and M(2p_1/2) spectra suggested that the metal-ligand bond in the chromium(III) complex had higher covalent character than that in the iron(III) complex. The satellite separations in the O(1s) spectra of M(3-Xptdn)₃ were in the range 4.0-4.8 eV: these satellites were assigned to a shake-up transition of Lπ → Lπ^* character. The O(1s) spectra of Fe(3-Xptdn)₃ and A1(3-Xptdn)₃ displayed an additional strong peak to higher energy than that of the main peak (δE = 2.1–3.1 eV) when the samples of complexes were bombarded with argon ions for a longer time.     

An X-ray photoelectron study of the electronic structure of Cu(II) complexes with dia- and paramagnetic derivatives of 2-imidazoline

The electronic structure of free radicals and Cu(II) complexes with the nitronyl nitroxide radical and aminonitrone is studied by X-ray photoelectron spectroscopy (XPS). N1s XPS spectra of nitrogen atoms of Cu(II) complexes with aminonitrones confirm the diamagnetic nature of the ligands. The binding energies of the main peak and the intense satellite structure in the Cu2p _3/2,1/2 spectra of the complexes under study correspond to the Cu(II) state. The structure of the satellite in the Cu2p _3/2,1/2 spectrum depends on the environment of the metal ion.     

X-ray photoelectron spectroscopy study of (Ca1−xLax)MnO2.97 (0.1 ≦ x ≦ 0.4)

The X-ray photoelectron spectroscopy (XPS) of perovskite-type (Ca_1−xLa_x)MnO_2.97 (0.1 ≦ x ≦ 0.4) was measured at room temperature. From the absolute values of the binding energy difference (ΔBE) of Ca2pO1s, La3dO1s, and Mn2pO1s, both the chemical bonding of MnO and CaO become more covalent, and that of LaO becomes more ionic with increasing x. The electron transfer of the MnOMn path is dominant, and the electrical properties are strongly influenced by the decrease of the electron transfer of the MnO(Ca,La)OMn path.     

Contribution de la spectrometrie X à l'étude du manganèse dans les oxydes mixtes de structure spinelle: Analyse du spectre MnKβ et du seuil d'absorption K

Chemical shifts of Kβ_1,3 and Kβ₅ emission bands and X-ray absorption spectra near the K edge have been measured in several manganese spinel oxides with the metal in the formal oxidation states +2, +3, and +4. The position of line MnKβ_1,3 is determined mainly by the valence of manganese. The relative intensity of Kβ′ satellite with respect to the Kβ_1,3 line gives qualitative information about the presence of Mn(II) in mixed oxides. Mn(IV) oxides are characterized by a small chemical shift of the Kβ₅ band unlike Mn(II) and Mn(III) compounds. The first high resolution XANES spectra for these materials were performed at the DCI storage ring at LURE (Orsay, France). The chemical shifts ΔE (K absorption discontinuty) and ΔE_max (main peak) are correlated with the oxidation state of metal. Spectra of Mn³⁺ and Mn⁴⁺ ions in the octahedral environment are characterized by the splitting of 1s → 3d transitions (2 eV). In mixed oxides, the first Mn(II) 1s → 4s-4p transition is observed as a peak (or shoulder) located at 7 eV above the 1s → 3d transition. The study of the X-ray absorption fine structure in the near edge region can be used for qualitative solid-state analysis of mixed oxides such as NiMn₂O₄ or CuMn₂O₄.     

X-ray spectroscopy of lanthanum manganites: Nature of doping holes,correlation effects,and orbital ordering

The Mn3s X-ray photoelectron spectra of manganites were studied. It was shown that for the formal valence of manganese from 3+ to 3.3+, the doping holes are O2p in character; as the valence of manganese increases further, the Mn3d states acquire holes. For La_0.7Sr_0.3MnO₃, the Mn3p-3d resonance spectra provided information about the occupied and unoccupied Mn3d states, and the correlation energy U = 6.7 eV was determined experimentally. An analysis of X-ray dichroism on the L absorption spectra of three-dimensional La_7/8Sr_1/8MnO₃ showed that the cooperative Jahn Teller distortion of the orthorhombic phase at 240 K was related to (x ² ? z ²)/(y ² ? z ²) type orbital ordering.     

An x-ray photoelectron spectroscopic study of some nickel(II) tetraaza macrocyclic complexes

Summary X-ray photoelectron spectra (XPS) of the Ni(2 p_{3/2, 1/2}), N(1s) and Cl(2p) core levels for seven nickel(II) tetraaza macrocyclic complexes and three related macrocycles of the basic cyclam and corrin ring structures are reported. Relative satellite intensities for the Ni(2p_3/2) level are also reported, where observed. The binding energy data for the core levels are interpreted in terms of structural features of these complexes, such as: (i) the conformation of the macrocyclic ring and the concomitant isomerism possibilities, (ii) the existence of “cluster-ions”, formed as a consequence of hydrogen bonding between macrocyclic cation and counter-ion, and (iii) the coordination number of nickel in these complexes. Additional information of chemical significance, which is derived from the binding energy data, concerns the magnetic properties of the complexes and an estimate of the degree of metal-ligand covalency.     

Study of the electronic structure of polynuclear cobalt trimethylacetate complexes by Co3<Emphasis Type="Italic">s</Emphasis> and Co3<Emphasis Type="Italic">p</Emphasis> X-ray photoelectron spectroscopy

The electronic structure of mono-, hexa-, and nonanuclear cobalt trimethylacetate complexes was studied by XPS. The Co3s- and Co3p X-ray photoelectron spectra of the complexes were recorded. The Co3p spectrum of bivalent cobalt was calculated in the isolated-ion intermediate-coupling approximation. Spectrum analysis showed that the [Co(N-Phobsqdi)2(η′-N-Ph-opda)(OOCCMe₃)] complex is a strong-field complex with Co(III) in the diamagnetic state; the [Co(dipy)₂(OOCCMe₃)₂], [Co(dipyam)(OOCCMe₃)₂], and [Co₉(μ₃-OH)₆(μ-OOCCMe₃)₁₂(OCMe₂)₄] are high-spin weak-field Co(II) complexes; and the [Co₆(μ₄-O)₂(OOCCMe₃)₁₀(THF)₄] complex contains both the Co(II) and Co(III) atoms. The energy position of major Co3s- and Co3p spectral maxima were found to be sensitive to the nature of the nearest environment of cobalt atoms. The data correlate well with X-ray crystallographic data.     

XPS studies of charge transfer interactions in some polyphenylacetylene-electron acceptor systems

X-ray photoelectron spectroscopy (XPS) studies have been performed on charge transfer complexes of trans-polyphenylacetylene (PPA). The acceptors used included halogens, such as I₂ and Br₂, and organic electron acceptors, such as 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), chloranil, fluoranil, and 7,7,8,8-tetracyano-p-quinodimethane (TCNQ). Incomplete and relatively weak charge transfer interactions were observed in most of the complexes. These help to account for the relatively low conductivity levels observed in most of the PPA complexes when compared with the corresponding complexes of other conjugated polymers. PPA has also been found to interact with molecular oxygen to some extent in solution. In complexes involving O₂, Br₂, and fluoranil, XPS data suggest that the charge transfer interaction may have proceeded further than the pure formation of molecular charge transfer complexes.     

Electronic structure of ZrCuSiAs and ZrCuSiP by X-ray photoelectron and absorption spectroscopy

The electronic structures of quaternary pnictides ZrCuSiPn (Pn=P, As) were analyzed by X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge spectroscopy (XANES). Shifts in the core-line XPS and the XANES spectra indicate that the Zr and Cu atoms are cationic, whereas the Si and Pn atoms are anionic, consistent with expectations from simple bonding models. The Cu 2p XPS and Cu L-edge XANES spectra support the presence of Cu¹⁺. The small magnitudes of the energy shifts in the XPS spectra suggest significant covalent character in the Zr-Si, Zr-Pn, and Cu-Pn bonds. On progressing from ZrCuSiP to ZrCuSiAs, the Si atoms remain largely unaffected, as indicated by the absence of shifts in the Si 2p_3/2 binding energy and the Si L-edge absorption energy, while the charge transfer from metal to Pn atoms becomes less pronounced, as indicated by shifts in the Cu K-edge and Zr K, L-edge absorption energies. The transition from two-dimensional character in LaNiAsO to three-dimensional character in ZrCuSiAs proceeds through the development of Si-Si bonds within the [ZrSi] layer and Zr-As bonds between the [ZrSi] and [CuAs] layers.     

Thermal behavior of manganese(II) complexes with pyridine-2,3-dicarboxylic acid

In this study, we analyzed influence of the type of the syntheses used: hydrothermal and non-hydrothermal on pyridine-2,3-dicarboxylic acid (2,3pydcH₂) coordination fashion. Two manganese(II) complexes: [Mn(H₂O)₃(2,3pydc)] _n (1) and [Mn(H₂O)₆][Mn(2,3pydcH)₃]₂ (2) were successfully synthesized from the non-hydrothermal reaction system containing organic ligand and different Mn(II) salts. The received complexes have been prepared and characterized by spectroscopic (IR, Raman), structural (X-ray single crystal), and thermogravimetric methods. The results of the crystal study give some evidence that ligand exhibits various topological structures and interesting properties. Pyridine-2,3-dicarboxylic acid acts as monodicarboxylate N,O-chelating anion (complex 2) or a doubly deprotonated three-dentate-N,O,O?? dicarboxylate ion (complex 1). In the [Mn(H₂O)₆][Mn(2,3pydcH)₃]₂ the coordination geometry around Mn(1) ion can be considered as being distorted octahedron {MnN₃O₃}. The Mn(2) cation possesses the same coordination polyhedron (octahedral). We have also analyzed influence of furnace atmosphere on the thermal behavior and the kind of final product. The sample of (1) decomposes in four stages in N₂ (368?C1073?K) and the final residue is MnO₂. The thermogram of (2) exhibits three main distinct decomposition steps (383?C973?K). A residue of MnO is remained. In both air and nitrogen atmosphere, Mn(II) complexes (1) and (2) keep unchanged over all steps of decomposition. Only the final residues are different (Mn₂O₃ are formed). The course of pyrolysis and molecular structure of the complexes lead to the same conclusion about the strength of metal?Cligand bonds. On the basis of the above results, it is concluded that the thermal stability of the manganese(II) compounds is slightly different.     

Electronic structure and luminescent properties of antimony(III) complex compounds with nitrogen containing outer-sphere organic cations

X-Ray photoelectron (XPS) and luminescent spectroscopy have been used to investigate complex compounds of antimony(III) halides with nitrogen containing organic bases. Inequality of bonds of amine and imine groups was found by XPS to disappear when complexes of antimony(III) with N,N′-diphenylguanidine (Dphg) were formed. The appearance of N1s symmetric line when transiting from Dphg to the cation N,N′-diphenylguanidine ( Dphg⁺) in complex compounds of antimony(III) testifies to this. The study performed demonstrates that electron density increment on the antimony(III) central atom (complexing agent) results in the bathochromic shift ³P₁ → ¹ S ₀ of the luminescence band of antimony(III) ion.     

Origin of the chemical shift in X‐ray absorption near‐edge spectroscopy at the Mn K‐edge in manganese oxide compounds

The absorption edge in Mn K‐edge X‐ray absorption spectra of manganese oxide compounds shows a shift of several electronvolts in going from MnO through LaMnO₃ to CaMnO₃. On the other hand, in X‐ray photoelectron spectra much smaller shifts are observed. To identify the mechanisms that cause the observed chemical shifts, 1s ionization as well as 1s → “4p” transition energies have been determined by electronic structure calculations on embedded Mn ions and embedded MnO₆ clusters. Systematic variation of the cluster geometry and the cluster embedding showed that the chemical shifts are predominantly determined by two effects: the changes in the Mn 3d occupation and the changes in the Madelung potential. The large chemical shift in the 1s → 4p transition energies between different materials occurs because the two effects do not compensate each other. The chemical shifts obtained for the embedded MnO₆ clusters agree reasonably with the experimental shifts. The small sensitivity to the material observed for the Mn 1s ionization energies is explained by the near cancellation of the effects of the Madelung potential and the 3d occupation of the Mn ion. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2003     

Electronic structure of lanthanum transition-metal oxyarsenides LaMAsO (M = Fe,Co, Ni) and LaFe1−xM′xAsO (M′ = Co,Ni) by X-ray photoelectron and absorption spectroscopy

The electronic structures of the quaternary oxyarsenides LaMAsO (M = Fe, Co, Ni) were examined with X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge spectroscopy (XANES). Interpretation of the metal 2p_3/2 and arsenic 3d_5/2 binding energies, as well as a satellite feature in the Co 2p XPS spectrum, suggests charges that are much less extreme than expected (i.e., not M²⁺ and As^3?) because of the strong covalent character within the M–As bonds. As M is varied, the differing degrees of charge transfer from M to As atoms within these bonds are manifested by shifts in the As 3d_5/2 binding energies and changes in the As K-edge intensities. This charge transfer is isolated within the [MAs] layer and does not influence the O 1s and La 3d XPS spectra. Fitting the experimental valence band spectra of these oxyarsenides LaMAsO yielded electron populations of states that support the formal charge assignment [La³⁺O^2?][M²⁺As^3?]. The mixed-metal series LaFe_1?xM′_xAsO (M′ = Co, Ni) was examined by XANES; analysis of the metal K- and L-edges, as well as of the Co 2p XPS satellite feature, revealed that no metal–metal charge transfer takes place.     

Synthesis and crystal structures of Manganese(IV) complexes with tridentate schiff bases

The complexes with the formulae [Mn(L¹)₂] · 0.5H₂O (I) and [Mn(L²)₂] (II), where L¹ and L² are the dianionic form of 2,4-dichloro-6-[(2-hydroxyethylimino)methyl]phenol and 2-{[1-(3-ethoxy-2-hydroxyphenyl)methylidene]amino}-2-methylpropane-1,3-diol, respectively, were obtained and characterized by elemental analysis and IR spectroscopy. The crystal structures of complexes I and II were determined using X-ray diffraction. The crystal of I is orthorhombic space group Fdd2: a = 24.170(2), b = 32.021(3), c = 11.352(2) Å, V = 8785.9(19) ų, Z = 8. The crystal of II is monoclinic space group C2/c: a = 13.931(4), b = 18.381(5), c = 12.444(5) Å, β = 121.980(3)°, V = 2702.9(15) ų, Z = 4. The Mn atom in each of the complexes is in an octahedral coordination.     

The X-ray photoelectron spectra of inorganic molecules: VI. Compounds containing rhenium-oxygen and rhenium-halogen bonds: rhenium 4f,chlorine 2p and oxygen 1s binding energies and their co

Rhenium 4f, chlorine 2p and oxygen 1s binding energies have been recorded for a series of coordination complexes of rhenium(V) and rhenium(VII) containing rhenium-oxygen bonds. Related studies on the rhenium(III) acetates Re₂(OAc)₄X₂(X = Cl, Br) and on several adducts of the rhenium chlorides (Re 4f and Cl 2p binding energies only) are also reported. Chemical shift data are related where possible to the molecular structures of the complexes. Correlations between rhenium 4f binding energies and oxidation state are of diagnostic value only in distinguishing the high oxidation state species (rhenium(V) and (VII)). Differences in rhenium 4f_{$\text{7}\text{2}$} and oxygen 1s binding energies [δ(O1s, Re 4f_{$\text{7}\text{2}$})] may be useful in probing the nature of the rhenium-oxygen bonds.