Cobalt Compounds Research Articles

Coordination Compounds of Cobalt(II) Nitrate and Perchlorate with Acetamide and Carbamide: Precursors for the Synthesis of Catalytically Active Tricobalt Tetraoxide

The reactions of cobalt(II) nitrate or perchloride with acetamide (AA) or carbamide (Ur) in an aqueous medium produce coordination compounds [Co(Ur)4](NO3)2 (I), [Co(Ur)6](NO3)2 (II), [Co(AA)4(H2O)2](NO3)2 (III), [Co(AA)4(H2O)2](NO3)2 ∙ 2AA (IV), [Co(Ur)6](ClO4)2, (V), [Co(AA)4(H2O)2](ClO4)2 (VI), and [Co(AA)6](ClO4)2 (VII). The compositions of the isolated complexes are determined by physicochemical methods, and the crystal and molecular structures of compounds II, V, VI, and VII are solved. Specific features of the thermal behavior of all synthesized compounds in a wide temperature range are studied in detail. These compounds are shown to be used as precursors in the preparation of nanosized Co3O4 using self-propagating high-temperature synthesis. The catalytic activity of thus synthesized Co3O4 in the model epoxidation of allyl alcohol is studied.

Enhancing supercapacitor performance through cobalt compounds doping in nickel-vanadium hydrotalcite

Enhancing supercapacitor performance through cobalt compounds doping in nickel-vanadium hydrotalcite

Dual electric field effects boost bifunctional oxygen electrocatalysis

Regulation of the surface microenvironment is crucial for the development of highly active and durable OER/ORR bifunctional catalysts. In this study, a bifunctional m-CoSx@NSC electrocatalyst with dual electric field effects was designed and fabricated by synchronous pyrolysis of organic sulfur-rich cobalt compounds (Co-DC) and melem. The introduction of nitrogen-rich melem effectively induced the conversion of Co-DC and the growth of tentacles to form a hierarchical carbon skeleton. The interfacial micro-electric field between the carbon layer and CoSx active species improves the intrinsic activity and stability of m-CoSx@NSC. Finite element method simulation and in-situ measurements proved that the tentacle-induced external local electric field promotes the formation of Co(OH)2/CoOOH intermediates and mass transfer, thus accelerating the catalytic reaction kinetics. Through the synergistic effect of dual electric fields, the m-CoSx@NSC catalyst demonstrated a low overpotential of 340 mV for OER and a high half-wave potential of 0.85 V for ORR. Furthermore, the m-CoSx@NSC-based ZAB exhibited an open-circuit voltage of 1.42 V, a maximum power density of 87.38 mW cm−2, a specific capacity of 876.17 mAh gZn−1, and a cycling performance of 700 cycles. The synergistic regulation of the internal and external microenvironments provides a novel insight to improve the catalytic reaction kinetics of OER/ORR.

A square planar cobalt(II)-thiosemicarbazone complex. Synthesis, characterization, antiviral and anti-inflammatory potential

Considering the possible antiviral effect of cobalt compounds and known pharmacological potential of thiosemicarbazones, a new combination containing cobalt(II) ions and tetradentate thiosemicarbazone was synthesized and structurally analyzed. In the complex structure (Co1), the cobalt ion is in 2+ oxidation state and is coordinated with ONNO donor set on the thiosemicarbazone backbone. The complex molecule crystallizes in the space group P21/m and the environment of the cobalt center tends to square planar geometry. The inhibitory performance of SARS-CoV-2 and the anti-inflammatory impact of the complex molecule were investigated. It was found that Co1 has high inhibitory effects on the SARS-CoV-2 virus's 3CL main protease enzyme, ACE2:SARS-CoV2 Spike RBD interaction, and IL8. Also, it showed significant anti-inflammatory effects on the release of IL6, IL8, IL10, and TGFβ1 cytokines and wound healing during in vitro TNF-α-induced inflammation. Experimental evidence demonstrates that Co1 diminishes both IL8 gene expression and protein levels. According to in silico and experimental results, it has a drug potential. Assessing the in vivo impacts of Co1 might contribute to understanding its potential as an antiviral and anti-inflammatory agent.

XPS Investigation of Co-Ni Oxidized Compounds Surface Using Peak-On-Satellite Ratio. Application to Co20Ni80 Passive Layer Structure and Composition.

XPS data processing for cobalt and nickel core-level peaks can be complicated. This is especially true when analyzing a mixture of oxide/oxyhydroxide/hydroxide compounds of these metals. The objective of this study is to develop a method for decomposing XPS spectra of 2p core levels for nickel and cobalt-oxidized compounds. This methodology was then employed to study the passivation layer of the Co20Ni80 alloy. The analysis of Ni2p and Co2p photo peaks using a homemade code based on core-level peak structure and satellites enables us to determine the chemical composition of the surface layer, knowledge of which is particularly important because it is directly linked to the anticorrosive properties it confers on the surface of the oxidized alloy. The XPS analysis, coupled with sequential ion sputtering, revealed that the passive layer of the Co20Ni80 alloy is heterogeneously covered with either oxidized cobalt compounds or oxidized nickel compounds. The method used also demonstrates that the chemical heterogeneity is associated with the thickness heterogeneity of the passive layer.

Surface Engineering of Anodic WO3 Layers by In Situ Doping for Light-Assisted Water Splitting.

This study presents a novel approach to fabricating anodic Co-F-WO3 layers via a single-step electrochemical synthesis, utilizing cobalt fluoride as a dopant source in the electrolyte. The proposed in situ doping technique capitalizes on the high electronegativity of fluorine, ensuring the stability of CoF2 throughout the synthesis process. The nanoporous layer formation, resulting from anodic oxide dissolution in the presence of fluoride ions, is expected to facilitate the effective incorporation of cobalt compounds into the film. The research explores the impact of dopant concentration in the electrolyte, conducting a comprehensive characterization of the resulting materials, including morphology, composition, optical, electrochemical, and photoelectrochemical properties. The successful doping of WO3 was confirmed by energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy, photoluminescence measurements, X-ray photoelectron spectroscopy (XPS), and Mott-Schottky analysis. Optical studies reveal lower absorption in Co-doped materials, with a slight shift in band gap energies. Photoelectrochemical (PEC) analysis demonstrates improved PEC activity for Co-doped layers, with the observed shift in photocurrent onset potential attributed to both cobalt and fluoride ions catalytic effects. The study includes an in-depth discussion of the observed phenomena and their implications for applications in solar water splitting, emphasizing the potential of the anodic Co-F-WO3 layers as efficient photoelectrodes. In addition, the research presents a comprehensive exploration of the electrochemical synthesis and characterization of anodic Co-F-WO3, emphasizing their photocatalytic properties for the oxygen evolution reaction (OER). It was found that Co-doped WO3 materials exhibited higher PEC activity, with a maximum 5-fold enhancement compared to pristine materials. Furthermore, the studies demonstrated that these photoanodes can be effectively reused for PEC water-splitting experiments.

Square-planar iron imido complexes containing strong-field pincer ligands as models for active species in catalytic nitrene transfer

Treatment of the iron(I) precursor, [Fe(N2)(tBuPNP)] (tBuPNP = anion of 2,5-bis(di-tert-butylphosphinomethyl)pyrrole), with mesitylazide (mesityl = 2,4,6-trimethylphenyl) results in the formation of a new four-coordinate iron imido complex, [Fe(NMes)(tBuPNP)], which serves as a model for reactive metal-nitrene intermediates in catalytic C–H amination. The solid-state structure of the complex exhibits a rare square-planar geometry about the iron center with a nearly linear imido unit. In analogy to similar compounds of cobalt, the electronic structure of [Fe(NMes)(tBuPNP)] is assigned as low-spin Fe(II) ferromagnetically coupled to a nitrene radical giving an overall S = 3/2 groundstate. A similar imido species was detected spectroscopically by treatment of [Fe(N2)(tBuPNP)] with 1-adamantylazide, however, use of the less bulky nitrene source phenylazide results in formation of the tetrazido species, [Fe(κ2-N4Ph2)(tBuPNP)]. Unexpectedly, [Fe(NMes)(tBuPNP)] proved recalcitrant toward nitrene transfer reactions involving weak C–H bonds, but did react readily with CO to generate [Fe(CO)2(tBuPNP)]. The reactivity of the new imido species in the context of its unique geometry and electronic structure is discussed.

Cobalt(III)-Macrocyclic Scaffolds with Anti-Cancer Stem Cell Activity.

Cobalt(III) compounds with tetradentate ligands have been widely employed to deliver cytotoxic and imaging agents into cells. A large body of work has focused on using cobalt(III)-cyclam scaffolds for this purpose. Here, we investigate the cytotoxic properties of cobalt(III) complexes containing 14-membered macrocycles related to cyclam. A breast cancer stem cell (CSC) in vitro model was used to gauge efficacy. Specifically, [Co(1,4,7,11-tetraazacyclotetradecane)Cl2]+ (1) and [Co(1-oxa-4,8,12-triazacyclotetradecane)Cl2]+ (2) were synthesised and characterised, and their breast CSC activity was determined. The cobalt(III) complexes 1 and 2 displayed micromolar potency towards bulk breast cancer cells and breast CSCs grown in monolayers. Notably, 1 and 2 displayed selective potency towards breast CSCs over bulk breast cancer cells (up to 4.5-fold), which was similar to salinomycin (an established breast CSC-selective agent). The cobalt(III) complexes 1 and 2 were also able to inhibit mammosphere formation at low micromolar doses (with respect to size and number). The mammopshere inhibitory effect of 2 was similar to that of salinomycin. Our studies show that cobalt(III) complexes with 1,4,7,11-tetraazacyclotetradecane and 1-oxa-4,8,12-triazacyclotetradecane macrocycles could be useful starting points for the development of new cobalt-based delivery systems that can transport cytotoxic and imaging agents into breast CSCs.

Mechanism of Nanoparticle Formation under Reduction of Oxygen-Containing Cobalt(II) Compounds with Hydrogen

Mechanism of Nanoparticle Formation under Reduction of Oxygen-Containing Cobalt(II) Compounds with Hydrogen

Chromium-Induced High Covalent Co-O Bonds for Efficient Anodic Catalysts in PEM Electrolyzer.

The proton exchange membrane water electrolyzer (PEMWE), crucial for green hydrogen production, is challenged by the scarcity and high cost of iridium-based materials. Cobalt oxides, as ideal electrocatalysts for oxygen evolution reaction (OER), have not been extensively applied in PEMWE, due to extremely high voltage and poor stability at large current density, caused by complicated structural variations of cobalt compounds during the OER process. Thus, the authors sought to introduce chromium into a cobalt spinel (Co3O4) catalyst to regulate the electronic structure of cobalt, exhibiting a higher oxidation state and increased Co-O covalency with a stable structure. In-depth operando characterizations and theoretical calculations revealed that the activated Co-O covalency and adaptable redox behavior are crucial for facilitating its OER activity. Both turnover frequency and mass activity of Cr-doped Co3O4 (CoCr) at 1.67V (vs RHE) increased by over eight times than those of as-synthesized Co3O4. The obtained CoCr catalyst achieved 1500mA cm-2 at 2.17V and exhibited notable durability over extended operation periods - over 100h at 500 mA cm-2 and 500h at 100 mA cm-2, demonstrating promising application in the PEMWE industry.

CARBON NANOSTRUCTURES OBTAINING FROM POLYMER MATERIALS

As part of the expansion of raw material base used in the development of technological and productive methods for the synthesis of carbon nanostructures (CNS) and solving the problem of environmentally friendly and economical polymer recycling, the results of investigation of microwave (MW) catalytic pyrolysis of macromolecular compounds from the range of polystyrene, polypropylene, polyethylene terephthalate, polyvinyl alcohol are presented. The information about existing approaches to solving these problems is briefly considered, and the prospects for MW processing of polymers are shown. The process was carried out by microwave treatment of a mixture of polymer raw materials acting as a carbon donor and substances-precursors of metal catalysts – cobalt and nickel compounds, their mixtures, as well as metal iron and nickel. Graphite and carbon fiber were used as temperature regulator. Experiments have demonstrated that effective conversion of the studied compounds occurs only in the presence of MW energy absorbers-converters, regardless of the nature of metal catalyst precursor. According to electron microscopy data, the resulting materials are a mixture of carbon nanostructures of disordered morphology with the predominant content of carbon nanotubes (CNTs) in the reaction products for experiments with polystyrene, polypropylene and polyethylene terephthalate. The use of polypropylene and polyvinyl alcohol leads to the production of carbon nanostructures containing only a small amount of CNTs. X-ray phase analysis data confirm the formation of multi-walled carbon nanotubes as the main structural component of the obtained carbon nanomaterials. It has been suggested that transformation pathways of the investigated hydrocarbons are similar, despite the difference in pyrolysis temperatures, which may be related to the simultaneous processes of polymer cracking, carbonization of decomposition products and CNS synthesis due to the rapid growth of reaction mass temperature during microwave treatment. The efficiency of different precursors of catalytic systems based on transition metals in the processes examined is substantiated. It has been shown that the high carbon content in feedstock promotes the formation of carbon nanostructures, but is not decisive for carbon nanotubes obtaining. For citation: Zaritovskii A.N., Kotenko E.N., Grishchuk S.V. Carbon nanostructures obtaining from polymer materials. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 5. P. 99-106. DOI: 10.6060/ivkkt.20246705.6957.

Coordination Compounds of Cobalt(II) Nitrate and Perchlorate with Acetamide and Carbamide: Precursors for the Synthesis of Catalytically Active Tricobalt Tetraoxide

Coordination Compounds of Cobalt(II) Nitrate and Perchlorate with Acetamide and Carbamide: Precursors for the Synthesis of Catalytically Active Tricobalt Tetraoxide

Exposure to cobalt metal (without tungsten carbide) and some cobalt compounds: a literature review

Cobalt is a natural metallic element with extensive applications across multiple industries, and a critical metal for lithium-ion battery production. Cobalt's only known biological function is its role as a metal component of vitamin B12. Other cobalt compounds have been described as toxic to the environment and the human body following excessive exposure. The International Agency for Research on Cancer (IARC) has classified cobalt, including cobalt metal and soluble cobalt(II) salts, as Group 2A, meaning it is probably carcinogenic to humans. This review aims to present a comprehensive overview of historical and current sources of cobalt in diverse exposure settings, along with its various intake routes. An extensive literature search was conducted between September 2021 and January 2022, analysing over 300 publications. The primary goal of these studies was to identify cobalt sources, intake routes, and exposure pathways. Workers may be exposed to various cobalt compounds and metal powders primarily through inhalation, but exposure can also occur via skin contact or ingestion. For the general population, food typically arises as the predominant source of cobalt exposure. Furthermore, exposure may occur through ambient air, tobacco smoke, and medical implants.

Content of heavy metals in bottom sediments of drained Kakhovka Reservoir

The article highlights the ecological danger of the destruction of the Kakhovka HPP dam and the draining of the Kakhovka Reservoir. The results of experimental studies of the content of mobile compounds and gross forms of heavy metals in five samples of bottom sediments taken from the bottom of drained reservoirs taken on the territory of the Kushugum community of the Zaporizhia district of the Zaporizhia region. Two samples were taken from the bottom of the former flood zone (Balabyne village), 2 samples — from the bottom of the former limestone quarry, which was connected to the floodplain of the Dnipro (Kushugum village) and 1 sample taken from the open area of the Kakhovka Reservoir (Malokaterynivka village). Based on the results of the research, it was established that the maximum permissible limit (for soil) of mobile compounds of lead (from 2.0 to 4.1 times), zinc (from 2.4 to 5.4 times), cadmium (from 1.9 to 2.5 times) was exceeded. and nickel (from 1.04 to 2.2 times) in all investigated bottom sediment samples. Exceeding the MPC (soil) for the content of gross forms of lead was found in five bottom sediment samples (from 1.1 to 1.5 times). Exceedings of the MPC of the soil by the content of gross forms of cadmium and manganese and mobile compounds of copper, nickel, cobalt and manganese were not detected. The maximum limit for the content of mobile compounds of iron and gross forms of zinc, copper, nickel, cobalt and iron is not regulated. The highest degree of contamination of bottom sediments by the content of: mobile compounds and gross forms of lead and nickel was found in samples taken from the bottom of a former limestone quarry (Kushugum village, Zaporizhzhia region); zinc — in a sample taken from the bottom of the former flood zone in the territory of the town of Balabyne and a sample taken from the open area of the Kakhovka Reservoir in the territory of the town of Malokaterynivka; cadmium — in the samples taken from the bottom of the former limestone quarry in the territory of the town of Balabyne and the sample taken from the open area of the Kakhovka Reservoir in the territory of the town of Malokaterynivka. According to the results of the correlation analysis, an extremely strong dependence was established between the content of mobile compounds of heavy metals and their gross forms — for cobalt (r=0.96), cadmium (r=0.92), nickel (r=0.91), lead (r=0.88) and zinc (r=0.84).

Designing, Characterization, DFT, Biological Effectiveness, and Molecular Docking Analysis of Novel Fe(III), Co(II), and Cu(II) Complexes Based on 4-Hydroxy-2H-pyrano[3,2-c]quinoline-2,5(6H)-dione.

The main target of the current framework is the designing and synthesizing of novel iron(III), cobalt(II), and cupper(II) complex compounds emanating from bioactive nucleus, 4-hydroxy-2H-pyrano[3,2-c]quinoline-2,5(6H)-dione ligand, to enhance comprehension as potential antibacterial, antifungal, and antioxidant alternatives by means of using DFT calculations and molecular docking investigation. Thus, the new complexes had been synthesized and characterized using various analytical techniques, including elemental analysis, infrared spectroscopy, mass spectrometry, UV spectroscopy, conductivity, and magnetic testing, as well as thermal analysis. The 4-hydroxy-2H-pyrano[3,2-c]quinoline-2,5(6H)-dione ligand exhibits monobasic bidentate OO donor properties toward the metal core, as shown by its infrared spectroscopic characteristics. The use of thermal analysis techniques allows for the identification and characterization of water molecules present inside the complexes, as well as the determination of their distribution patterns. The molecular structures of free ligand and its metal complex compounds have been verified through the use of density functional theory (DFT) simulations. These simulations also provide a valuable understanding of the quantum chemical characteristics associated with these structures. In vitro experiments were conducted to evaluate the antioxidant, antibacterial, as well as antifungal and the properties of the free ligand and its corresponding complex compounds. DATA revealed that synthesized metal complex compounds have heightened biological efficacy as related to the unbound ligand. Furthermore, molecular docking analysis was done to understand the interactions between the studied compounds and proteins derived from Escherichia coli (pdb ID: 2vf5), Aspergillus flavus (pdb ID: 3cku), and humans (pdb ID: 5IJT), which are considered to be significant in drug design. Lastly, a correlation between in vitro efficacies with molecular docking data was done and analyzed.

Spectroscopic and thermal studies of mixed ligand coordination compounds of cobalt (II) with aspartic and dicarboxylic acids

The synthesis of complex compounds of cobalt (II) ion in the presence of aspartic and dicarboxylic acids has been studied by thermal and spectroscopic methods. Thermal decomposition processes of these compounds are studied on the basis of thermal analysis, and endo- and exoeffects are determined. The decomposition products of the compounds were studied on the basis of mass reduction by the thermogravimetric method. Based on the results of spectroscopic studies, the structural formulas of the synthesized coordination compounds are established.

STABILITY OF COBALT AND NICKEL COMPLEXES OF SUCCINIC AND MALEIC IONS STUDIED BY POTENTIOMETRIC TITRATION, UV-VIS SPECTROPHOTOMETRY AND QUANTUM CHEMICAL CALCULATIONS

In this study, composition and stability of coordination compounds of nickel (II) and cobalt (II) ions with succinate anion (L2-) and maleic anion (Y2-) in aqueous ethanol solutions with the molar concentration of ethanol ranging from 0.0 – 0.3 were studied by UV – Vis spectrophotometry at ionic strength of 0.1 maintained with sodium perchlorate. The result showed that, the formation of mono-ligand complexes of Ni2+ and Co2+ ions with succinate and maleic anions become stronger when the volume of ethanol rises. This may be due mainly to a change in the solvate state of the ligand with increasing ethanol concentration in the solvent. In all surveyed solvents, Co2+ forms less stable complexes than Ni2+ ion corresponding to the Irving-Williams series established for aqueous solutions. Obtained results were compared with literature data for akin compounds. The effect of solvent composition change on the geometry, charge, total electron and free Gibbs energies was studied using the DFT and MP2 levels of theory by using the Polarizable Continuum Model (PCM). The results obtained in this article by UV – Vis spectrophotometry and theoretical calculations were analyzed together with the potentiometric titration results obtained by us earlier for these complexes. The results of theoretical calculations are in good agreement with experimental data.

How the spin state tunes the slow magnetic relaxation field dependence in spin crossover cobalt(II) complexes.

A novel family of cobalt(II) compounds with tridentate pyridine-2,6-diiminephenyl type ligands featuring electron-withdrawing substituents of general formula [Co(n-XPhPDI)2](ClO4)2·S [n-XPhPDI = 2,6-bis(N-n-halophenylformimidoyl)pyridine with n = 4 (1-3) and 3 (4); X = I (1), Br (2 and 4) and Cl (3); S = MeCN (1 and 2) and EtOAc (3)] has been synthesised and characterised by single-crystal X-ray diffraction, electron paramagnetic resonance, and static (dc) and dynamic (ac) magnetic measurements combined with theoretical calculations. The structures of 1-4 consist of mononuclear bis(chelating) cobalt(II) complex cations, [CoII(n-XPhPDI)2]2+, perchlorate anions, and acetonitrile (1 and 2) or ethyl acetate (3) molecules of crystallisation. This unique series of mononuclear six-coordinate octahedral cobalt(II) complexes displays both thermally-induced low-spin (LS)/high-spin (HS) transition and field-induced slow magnetic relaxation in both LS and HS states. A complete LS ↔ HS transition occurs for 1 and 2, while it is incomplete for 4, one-third of the complexes being HS at low temperatures. In contrast, 3 remains HS in all the temperature range. 1 and 2 show dual spin relaxation dynamics under the presence of an applied dc magnetic field (Hdc), with the occurrence of faster- (FR) and slower-relaxing (SR) processes at lower (Hdc = 1.0 kOe) and higher fields (Hdc = 2.5 kOe), respectively. On the contrary, 3 and 4 exhibit only SR and FR relaxations, regardless of Hdc. Overall, the distinct field-dependence of the single-molecule magnet (SMM) behaviour along with this family of spin-crossover (SCO) cobalt(II)-n-XPhPDI complexes is dominated by Raman mechanisms and, occasionally, with additional temperature-independent Intra-Kramer [LS or HS (D > 0)] or Quantum Tunneling of Magnetisation mechanisms [HS (D < 0)] also contributing.

Coordination compounds of cobalt(II) with carboxylate non-steroidal anti-inflammatory drugs: structure and biological profile.

Fourteen cobalt(II) complexes with the non-steroidal anti-inflammatory drugs sodium meclofenamate, tolfenamic acid, mefenamic acid, naproxen, sodium diclofenac, and diflunisal were prepared in the presence or absence of a series of nitrogen-donors (namely imidazole, pyridine, 3-aminopyridine, neocuproine, 2,2'-bipyridine, 1,10-phenanthroline and 2,2'-bipyridylamine) as co-ligands and were characterised by spectroscopic and physicochemical techniques. Single-crystal X-ray crystallography was employed to determine the crystal structure of eight complexes. The biological profile of the complexes was investigated regarding their interaction with serum albumins and DNA, and their antioxidant potency. The interaction of the compounds with calf-thymus DNA takes place via intercalation. The ability of the complexes to cleave pBR322 plasmid DNA at the concentration of 500 μM is rather low. The complexes demonstrated tight and reversible binding to human and bovine serum albumins and the binding site of bovine serum albumin was also examined. In order to assess the antioxidant activity of the compounds, the in vitro scavenging activity towards free radicals, namely 1,1-diphenyl-picrylhydrazyl and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid), and their ability to reduce H2O2 were studied.

Intermetallic charge transfer in MTiF6·6H2O (M = Mn, Fe, Co, and Ni): A study by X-ray photoelectron spectroscopy

The X-ray photoelectron spectra (XPS) of a series of hydrated fluoridotitanates MTiF6∙6H2O (M = Mg, Mn, Fe, Co, Ni) were measured for the first time. The compounds were grown in the form of high-quality single crystals and belong to the extensive ABF6∙6H2O family. Under the action of the XPS experimental conditions (vacuum and X-ray), the process of charge transfer from divalent transition metal to the titanium atom develops, which is described as intermetallic (intervalence) charge transfer (IMCT, IVCT): M2+ + Ti4+ → M3+ + Ti3+. Dehydration and hydrolysis of the studied complexes promote the process of charge transfer through the association of isolated octahedra by an edge or a vertex. The obtained XPS data were compared with those available in the literature, which are rather ambiguous for cobalt compounds. In our case, the binding energy of Co 2p electrons is higher for Co3+ than for Co2+ in an octahedral environment.