T. M. Ivanova

X-ray photoelectron spectra of polynuclear manganese complexes

Manganese trimethylacetate complexes with different ligand environments were studied by X-ray photoelectron spectroscopy (XPS). Changes in the Mn 2p, C 1s, O 1s, and N 1s X-ray photoelectron spectra caused by the substitution of Mn → N coordination bonds for Mn → O coordination bonds were examined. In the spectra of manganese trimethylacetate complexes, the satellite component was identified, which is evidence of the high-spin state of manganese atoms. An increase in the magnetic moment of the manganese complexes, both with the oxygen and mixed oxygen-nitrogen environment, is accompanied by an increase in the spin-orbit splitting, the difference in Eb between the satellite and the Mn 2p3/2 line, and the ratio between the integrated intensities of the satellite and the Mn 2p3/2 line (I sat3/2/I Mn 2p3/2). The XPS data made it possible to determine the measure of covalence of the metal-ligand bond. The XPS results are consistent with X-ray crystallography data.

XPS study of the electronic structure of heterometallic complexes [Fe2MO(O2CCH3)6(H2O)3] · 3H2O (M = Co, Ni)

Heterometallic compounds of general formula [Fe2IIIMIIO(O2CR)6(H2O)3] · 3H2O (R = CH3, M = Co, Ni; R = CCl3, M = Co, Ni) have been studied by XPS. The compounds have been identified as high-spin complexes with metal atoms in oxidation states M(II) and M(III). Analysis of the XPS data revealed the tendency of the XPS pattern and magnetic parameters of molecules to change with a change in the electronic nature of metal atoms. The assignment is based on the degree of covalence of the M-O bond. In chloro-substituted heterocomplexes, electron density delocalization on the metal atoms with metal-to-ligand charge transfer through three bonds (M-O-C-C) is observed. The substitution in terminal groups leads to the change in the electron density distribution between the carboxylate and terminal groups.

XPS study of the electronic structure of heterometallic complexes Fe2MO(Piv)6(HPiv)3 (M = Ni, Co)

Heterometallic complexes Fe2MO(Piv)6(HPiv)3 (M = Ni, Co) have been studied by XPS. The complexes are identified as high-spin complexes with metal atoms in oxidation states M(II) and M(III). A change in the ligand environment of metal atoms has an effect on both the energetic state of metal atoms and the XPS pattern. The substitution of a Co atom for the nickel atom in the heterometallic complexes changes the XPS pattern of iron and their magnetic state. For the Fe2MO(Piv)6(HPiv)3 complexes, quantum-chemical calculations have been performed at the density functional theory (DFT) level. In combination with XPS and magnetochemistry data, the quantum-chemical calculation demonstrates that the Fe, Ni, and Co atoms in the trinuclear complexes are in the high-spin local state and that the ground state is dominated by antiferromagnetic exchange interaction.

Study of the electronic structure of polynuclear cobalt trimethylacetate complexes by Co3s and Co3p 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.

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 Ni2p1/2-Ni2p3/2 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 Ni2p3/2 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 of heterometallic 3d-metal carboxylate complexes

The electronic structure and magnetic states in the heterometallic hexanuclear complex Mn4IIFe2III (μ4-O)2(Piv)10 · MeCN4 have been studied by X-ray photoelectron spectroscopy (XPS). The substitution of two Mn atoms for two Fe atoms in the hexanuclear complex was found to have an effect on the patterns of iron and manganese X-ray photoelectron spectra. XPS data are evidence of the high-spin paramagnetic state of MnII and FeIII atoms, as well as of the ligand-metal charge transfer upon complex formation. In the heteroatomic complex, the degree of bond covalence increased for both the manganese and iron atoms. The results obtained are in good agreement with X-ray diffraction data.

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.

Fe3s X-ray photoelectron spectra of polynuclear iron complexes

Specific features of the electronic structure and spin magnetic state of iron atoms in bi-, tri-, and hexanuclear iron trimethylacetate complexes were studied by X-ray photoelectron spectroscopy. A correlation was found between the ionicity (of the spin state of iron atoms) and Fe3s binding energies, exchange splitting of the final photoionization state, and the energy position and intensity of charge-transfer satellites. Nonequivalent iron states were identified in tri- and hexanuclear complexes. The overall magnetic moment of the complexes was found to decrease with an increase of the individual magnetic moments of iron atoms, which is evidence of complicated mutual orientation of atomic magnetic moments in the complexes.

X-ray photoelectron spectra of some Ni mono-and polynuclear complexes

The core-level photoelectron spectra for Ni(bpy)2(OOCCMe3)2, Ni2(H2O)bpy2(OOCCMe3)4, Nibpy(OOCCMe3)2, Ni(C10H4(CH3)2N(SO2C6H4(CH3), Ni2(2,4-Lut)2(OOCCMe3)4, and (2,4-Lut is 2,4-lutidine) are reported and discussed, and the role of ligands in their appearance is determined. X-ray irradiation of some complexes was found to induce removal of some pyridyl rings and oligomerization both at room and liquid nitrogen temperature. The dependence of composition on temperature was used to find correlation between ligand surrounding and the spectra.

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). Fe2p3/2, 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 PctFe affects the electronic state of the central iron atom.