Octahedral Cobalt Complexes Research Articles

Chiral octahedral cobalt(III) complex immobilized on Carboblack C as a novel robust and readily available enantioselective voltammetric sensor for the recognition of tryptophan enantiomers in real samples

Enantioselective voltammetric sensors (EVSs) have significant interest in analytical and medicinal chemistry, as they allow for the express analysis and recognition of pharmacologically active components in drugs, as well as the establishment of the enantiopurity of compounds. The most common methods of modifying the electrode surface are through molecular imprinting techniques and the addition of a non-electroactive chiral modifier to the electrode composition. By varying the structure and properties of the chiral modifier, the sensor can be designed to have the highest enantioselectivity for a chosen chiral analyte. In this study, we describe the development of a new type of EVS based on a Carboblack C paste electrode modified with a chiral octahedral cobalt(III) complex for use as a selective enantioselector. It was found that the EVS, prepared from enantiopure Co(III) complexes, can selectively recognize L- and D-tryptophan (Trp) in phosphate buffer solution (PBS) with pH = 6.86. The peak current ratio (iD/iL) between the two enantiomers reached 1.36, demonstrating the effectiveness of the sensor. The experimental results indicate a linear correlation between the peak currents of Trp enantiomers and their concentration in the range from 1.00·10−6 to 5.00·10−4 М, leading to a detection limit of 2.42 µM and 3.30 µM for D- and L-Trp, respectively, when using chiral octahedral Co(III) complex with chloride counter-anion. Next, the EVSs developed demonstrated practical applicability in measuring the concentration of Trp in pharmaceutical samples and human urine and blood plasma. An important advantage of these sensors is the difference in the oxidation potentials between Trp enantiomers (ΔEp=35 mV), which makes it possible to determine Trp enantiomers in their mixtures. Quantum chemical calculations and experimental data show that the octahedral Co(III) complex binds to one of the Trp enantiomers with a stronger affinity, thus increasing its concentration at the electrode surface and promoting its oxidation. The easy preparation of the chiral Co(III) complex from inexpensive commercial materials, its high stability and insolubility in water make it a promising selector for the creation of efficient multifunctional EVSs for the analysis of various aqueous solutions.

Synthesis, characterization, and antibacterial activity studies of two Co(II) complexes with 2-[(E)-(3-acetyl-4-hydroxyphenyl)diazenyl]-4-(2-hydroxyphenyl)thiophene-3-carboxylic acid as a ligand

Two new Cobalt(II) complexes 12 and 13 have been synthesized from 2-[(E)-(3-acetyl-4-hydroxyphenyl)diazenyl]-4-(2-hydroxyphenyl)thiophene-3-carboxylic acid (11) as a novel ligand. These three new compounds were characterized on the basis of their powder X-Ray Diffraction, UV–Vis, IR, NMR, elemental analysis and MS spectral data. DFT/B3LYP mode of calculations were carried out to determine some theorical parameters of the molecular structure of the ligand. The purity of the azoic ligand and the metal complexes were ascertained by TLC and melting points. The analysis of the IR spectra of the polyfunctionalized azo compound 11 and its metal complexes 12 and 13, reveals that the coordination patterns of the ligand are hexadentate and tetradentate respectively. Based on the UV–Vis electronic spectral data and relevant literature reports, the ligand and derived complexes were assigned the E (trans) isomer form. Likewise, octahedral and square-planar geometries were respectively assigned to the cobalt(II) complexes. The broth microdilution method was used for antibacterial assays through the determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The ligand 11 displayed moderate antibacterial activity (MIC = 32–128 μg/mL) against Staphylococcus aureus ATCC25923, Escherichia coli ATCC25922, Pseudomonas aeruginosa and Klebsiella pneumoniae 22. The octahedral cobalt(II) complex 12 showed moderate activity against Pseudomonas aeruginosa (MIC = 128 μg/mL) and Klebsiella pneumoniae 22 (MIC = 64 μg/mL) and none against Staphylococcus aureus ATCC25923 and Escherichia coli ATCC25922, whereas the square-planar complex 13 displayed moderate activity only on Klebsiella pneumoniae 22 (MIC = 64 μg/mL).Graphical abstract

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.

Chiral Recognition and Resolution of Phosphoric Acids Using Octahedral Cobalt Complexes

Determining the chirality of phosphoric acids can be a challenging task. In this study, we present a novel approach for the chiral recognition of phosphates using cationic octahedral cobalt complexes. By utilizing 31P NMR spectroscopy, we are able to accurately measure the enantiopurities of chiral phosphoric acids after forming ion pairs with the cobalt complexes. We have successfully applied this method to a variety of chiral phosphoric acids derived from BINOL, H8-BINOL, SPINOL, VAPOL, and VANOL compounds, as well as ATP, and were able to efficiently resolve them in 31P{1H} NMR spectra. Furthermore, we were able to achieve an optical resolution of a phosphoric acid with an enantiomeric excess of greater than 99%.

Hydrogen bonds of a water molecule in the second coordination sphere of amino acid metal complexes: Influence of amino acid coordination

The hydrogen bonds of free and coordinated amino acids with water molecule were studied by analyzing data in the crystal structures from the Cambridge Structural Database (CSD) and by quantum chemical calculations. The CSD data indicate bifurcated NH/O hydrogen bonds and O1/HO hydrogen bonds of coordinated oxygen. The O/HO hydrogen bonds of free zwitterions and non-coordinated carbonyl oxygen (O2/HO) in metal complexes form primarily linear, non-bifurcated hydrogen bonds. Calculated M06L-GD3/def2-TZVPP interaction energies for free zwitterions (glycine, cysteine, phenylalanine and, serine) and water molecule are in the range from −5.1 to −9.6 kcal/mol for NH/O and from −6.9 to −7.6 kcal/mol for O/HO interactions. Coordinated amino acids in neutral octahedral cobalt(III) complexes have NH/O interaction energies ca. -7.4 kcal/mol, independent of the amino acid. The singly and doubly charged complexes have stronger NH/O interactions; the strongest has energy of −16.9 kcal/mol. In the case of O1/HO hydrogen bond, the interaction energy decreases upon coordination; interactions are quite weak for neutral complexes (−2.2 to −2.6 kcal/mol). For O2/HO hydrogen bonds, all amino acids except serine show slightly stronger interaction in singly negative complexes (−6.3 to −8.0 kcal/mol), while interactions are weaker for neutral complexes (−2.8 to −4.4 kcal/mol), comparing to zwitterions.

PH-Switching of the luminescent, redox, and magnetic properties in a spin crossover cobalt(ii) molecular nanomagnet.

The ability of mononuclear first-row transition metal complexes as dynamic molecular systems to perform selective functions under the control of an external stimulus that appropriately tunes their properties may greatly impact several domains of molecular nanoscience and nanotechnology. This study focuses on two mononuclear octahedral cobalt(ii) complexes of formula {[CoII(HL)2][CoII(HL)L]}(ClO4)3·9H2O (1) and [CoIIL2]·5H2O (2) [HL = 4'-(4-carboxyphenyl)-2,2':6',2''-terpyridine], isolated as a mixed protonated/hemiprotonated cationic salt or a deprotonated neutral species. This pair of pH isomers constitutes a remarkable example of a dynamic molecular system exhibiting reversible changes in luminescence, redox, and magnetic (spin crossover and spin dynamics) properties as a result of ligand deprotonation, either in solution or solid state. In this last case, the thermal-assisted spin transition coexists with the field-induced magnetisation blockage of "faster" or "slower" relaxing low-spin CoII ions in 1 or 2, respectively. In addition, pH-reversible control of the acid-base equilibrium among dicationic protonated, cationic hemiprotonated, and neutral deprotonated forms in solution enhances luminescence in the UV region. Besides, the reversibility of the one-electron oxidation of the paramagnetic low-spin CoII into the diamagnetic low-spin CoIII ion is partially lost and completely restored by pH decreasing and increasing. The fine-tuning of the optical, redox, and magnetic properties in this novel class of pH-responsive, spin crossover molecular nanomagnets offers fascinating possibilities for advanced multifunctional and multiresponsive magnetic devices for molecular spintronics and quantum computing such as pH-effect spin quantum transformers.

Homoleptic octahedral CoII complexes as precatalysts for regioselective hydroboration of alkenes with high turnover frequencies.

Homoleptic complexes adopting octahedral coordination modes are usually less active in catalysis due to the saturated coordination around metal centers that prevents substrate activation in a catalytic event. In this work, we demonstrated that a homoleptic octahedral cobalt complex (1) of 4'-pyridyl-2,2';6',2''-terpyridine that experienced monoprotonation at the non-coordinating pyridyl moiety upon crystallization could serve as a highly efficient precatalyst for the hydroboration of styrene derivatives with Markovnikov selectivity. The solid-state structure of this precatalyst along with relevant homoleptic CoII and FeII complexes has been characterized by X-ray crystallography. In the solid state, 1 features one-dimensional hydrogen-bonded chains that are further stacked by interchain π⋯π interactions. The newly synthesized complexes (1-3) along with several known analogues (4-6) were examined as precatalysts for the hydroboration of alkenes. The best-performing system, 1/KOtBu was found to promote Markovnikov hydroboration of substituted styrenes with high turnover frequencies (TOFs) up to ∼47 000 h-1, comparable to the most efficient polymeric catalyst [Co(pytpy)Cl2]n reported to date. Although some limitations in substrate scope as well as functional group tolerance exist, the catalyst shows good promise for several relevant hydrofunctionaliation reactions.

Synthesis, Characterization, and Structure of Mixed-Ligand Cobalt (II) Complex with N, O Donor Sites

A mononuclear octahedral mixed-ligand cobalt (II) complex [Co(H2L)(PhCOO)2] (1) has been prepared by using H2L (N,N′-dimethyl-N,N′-bi(2-hydroxy-3,5-di methyl benzyl)-ethylenediamine) as a facially coordinating tetradentate ligand with a N2O2 donor center along with sodium benzoate as an ancillary ligand. Complex 1 has been characterized by a single-crystal X-ray diffraction study, as well as by other spectroscopic tools. The complex crystallizes in the monoclinic space group C2 with a = 31.73(3) Å, b = 7.868(3) Å, c = 19.131(15) Å, and β = 125.25(3)°. The single-crystal X-ray diffraction study shows that in the mononuclear cobalt (II) complex [Co(H2L)(PhCOO)2] (1), the metal center adopts an octahedral environment.

Fine‐Tuning of Structural Distortion and Magnetic Anisotropy by Organosulfonates in Octahedral Cobalt(II) Complexes

Comprehensive SummaryPrecise modulation of the magnetic anisotropy of metal ions remains highly important for the development of high–performance single‐molecule magnets (SMMs). We herein reported the synthetic, structural, spectral, magnetic, and computational studies on four mononuclear CoII complexes in a distorted octahedral environment. The change of the organosulfonate anions triggers significant modification of the distorted octahedral CoN6 coordination sphere, which enables us to tackle the influence of the structural distortion on the magnetic anisotropy in these complexes. Magnetic measurements revealed that the four complexes possess easy–plane magnetic anisotropy with large and positive zero‐field splitting parameters, which decrease with the increasing distortion of the pseudo–octahedral CoII coordination geometry. This correlation was further confirmed by high–frequency/–field EPR (HF–EPR) spectra and theoretical calculations. Dynamic magnetic susceptibility measurements indicate that these complexes both exhibit slow magnetic relaxation under an external dc field, indicating the field‐induced single‐ion magnets (SIMs) of the four complexes. These results indicate that structural distortion plays an important role in the magnetic anisotropy of CoII complexes and should be carefully considered in the design of molecular complexes with high magnetic anisotropy.

Structure Elucidation, Hirshfeld Surface Analysis, Molecular Docking and Computational Studies of a Jahn-Teller Distorted Octahedral Cobalt (II) Complex with Saccharin Ligand

A Jahn-Teller distorted octahedral cobalt(II) complex with saccharin and water ligands was synthesized and characterized using single-crystal X-ray diffraction, density functional theory calculation, surface analysis (MEP and Hirshfeld) and molecular docking studies. Co(II) center is six-coordinated in a distorted octahedral arrangement, with the two water O atoms located in the axial positions, and the two water O atoms and the saccharin N atoms located in the equatorial plane. Theoretical molecular modeling was carried out with Density Functional Theory (DFT) using UB3LYP with hybrid function LANL2DZ. To support intra-molecular and inter-molecular bondings in crystal structure, molecular electrostatic potential (MEP) and Hirshfeld surfaces are generated and visualized. The molecular docking analysis was investigated between cobalt complex ligand and the receptor of breast cancer mutant PDB: 3HB5-oxidoreductase.

Co(III) carboxamide complexes as electrocatalysts for water splitting

Water splitting is a promising approach for storing intermittent renewable energies, such as sunlight in the clean chemical bonds as a hydrogen fuel. Two water-soluble octahedral cobalt (III) complexes, [Co(bpb)(OAc)(H2O)], 1, (bpb2− = N,N′-bis[(2-pyridine carboxamide)-1,2-benzene] dianion) and [Co(cbpb)(OAc)(H2O)], 2, (cbpb2− = N,N′-bis[(2-pyridine carboxamide)-4-chloro-1,2-benzene] dianion) were synthesised and characterised by CHN elemental analysis, UV–Vis, FT-IR and single-crystal X-ray diffraction techniques. The two carboxamide ligands had been prepared in the ionic liquid TBAB as an environmentally benign reaction medium. The electrocatalytic water splitting activity of 1 and 2 showed that both complexes are highly active for the water splitting in aqueous solutions. Turn Over Frequency (TOF) values were, for 1 and 2 respectively, 527 and 490 mol of hydrogen in each mole of catalyst per hour at an overpotential of 738 mV (pH = 7.0). Such a performance can be ascribed to the flat ligands, the electroactivity of the metal centre and carboxamide ligands and the ability of losing the axial ligands around the metal-ion centre during the reduction process which provide different reduction pathways for an HER process.

Geometry and electronic structures of cobalt(II) and iron(III) complexes bearing bis(2-pyridylmethyl)ether or alkylbis(2-pyridylmethyl)amine

Bis(2-pyridylmethyl)ether (bpme) was used as a tridentate ligand and coordinated to the cobalt(II) or iron(III) center for the development of new material conversion reaction centers. The structures and properties were investigated and compared to those of corresponding complexes bearing alkylbis(2-pyridylmethyl)amine (Rbpma; R = ethyl, benzyl). Reactions of the bpme ligand with CoIICl2·6H2O gave five-coordinate dichloridocobalt(II) complexes whereas those with FeIIICl3·6H2O afforded hexa-coordinate octahedral trichloridoiron(III) complexes. Octahedral cobalt(II) complexes containing two bpme ligands was isolated as well in a reaction with CoII(CH3COO)2·4H2O. All those complexes were in the high spin state at 295–298 K in the respective coordination geometry. Characteristic geometrical features around the metal center of bpme-containing complexes were discussed in comparisons with the corresponding Rbpma-containing complexes; [CoIICl2(bpme)] (1) was square pyramidal though [CoIICl2(Rbpma)] (R = ethyl; 2, benzyl; 3) was trigonal bipyramidal for five-coordinate compounds, and mer-[CoII(bpme)2](PF6)2 (4) and mer-[FeIIICl3(bpme)] (5) were meridional-type complexes while fac-[FeIIICl3(ebpma)] (6) was a facial-type compound for six-coordinate ones. It is noteworthy that distinctive redox behaviors were revealed in organic solvents.

Metalloglycomics of tris(2,2′-bipyridyl) cobalt and ruthenium compounds

Metal complexes studied to date under the framework of metalloglycomics belong to the M-NH3 general motif (polynuclear platinum compounds; Werner's complex), acting mainly as cationic hydrogen bonding species toward glycosaminoglycans (GAGs), an interaction termed metalloshielding. In this paper, we expand our studies to substitution-inert octahedral cobalt(III) and ruthenium(II) complexes bearing the non‑hydrogen-donor ligand 2,2′-bipyridine (bpy). We identified by NMR spectroscopy that [Co(bpy)3]3+ binds to the highly sulfated synthetic pentasaccharide, Fondaparinux (FPX), while no major perturbations are found in the presence of [Ru(bpy)3]2+. This result is of significance as both coordination compounds have analogous 3D structures. Although weakly binding to the model GAG, [Ru(bpy)3]2+ completely inhibits the enzymatic cleavage of FPX by the bacterial heparinase II (HepII) enzyme, which is not observed for the Co(III) analog. This observation suggests a direct inhibition of HepII by the Ru compound, through a mechanism that is unrelated to metalloshielding.

Field-induced mononuclear cobalt(ii) single-molecule magnet (SMM) based on a benzothiadiazole-ortho-vanillin ligand

A mononuclear octahedral cobalt(ii) complex based on a unique benzothiadiazole-ortho-vanillin ligand shows slow relaxation of the magnetization under applied dc magnetic fields.

Four and six-coordinated cobalt complexes based on thiosemicarbazone. Formation, experimental and theoretical characterization

The template reaction was performed between benzoylacetone-S-propylthiosemicarbazone and salicylaldehyde in the presence of Co(ClO4)2 and a square planar cobalt(II) complex, [Co(L)] (Co1) where L is a dibasic thiosemicarbazidato ligand was isolated. It was aimed to synthesize the octahedral cobalt complexes by using the co-ligands, pyridine and 2-amino pyridine. An octahedral cobalt(III) complex, [Co(L)(py)2]ClO4 (Co2), with two axial-pyridine ligands was obtained. Reaction with 2-amino pyridine gave an unexpected cobalt(III) centered structure, [Co(L1)]·H2O (Co3), where L1 is a new sixdentate (N4O2) ligand that yielded by the addition of the amino group of pyridine to the L ligand. L1 has tribasic thiosemicarbazidato structure that altered by the participation of an oxygen atom in addition to the amines. Experimental characterizations of three complexes have been completed using IR, NMR, UV–Vis, ESI-MS techniques and X-ray data. In order to better understand the intermolecular interactions of the structures, the Nonlinear Optical (NLO) properties and frontier orbitals (FMO) of the complexes were obtained using the Gaussian 09 program, DFT/B3LYP with 6–31 G (d, p) bas set for the C, N, O, H atoms and with LanL2DZ basic set for Co metal atom.

Exquisite chemistries of meso-pentafluorophenyl and meso-(2,6-dichlorophenyl) dipyrromethanes

meso-Aryl dipyrromethanes are important building blocks to create various practical molecules, and the electron-withdrawing effect of the meso-aryls can play an important role in improving/controlling their reactivities in further reactions: meso-Pentafluorophenyl and meso-(2,6-dichlorophenyl) substituted dipyrromethanes towards the associating dipyrrins and other derivatives have been investigated, in which coordination with different transition metals followed by the dissociation of the metal coordination by interruption of proton and halide ions have been verified. Furthermore, simple DDQ-oxidations of the dipyrromethanes have afforded DDQ-dipyrrin adducts which were delivered to distinctly advanced molecular rearrangements in the presence of acid and base. Vinylene bisdipyrrin compounds, obtained in the reactions of DDQ-dipyrrin adducts with a Lewis base triethylamine, have produced expanded porphyrinoid bis-nickel complexes during the metalation procedure with nickel acetate, while a cobalt metalation of the vinylene bisdipyrrin compounds resulted in an isolation of diamagnetic octahedral cobalt(III) complex. Moreover, meso-pentafluorophenyl and meso-(2,6-dichlorophenyl) dipyrromethanes have been useful platforms to accomplish size-controlled series of meso-aryl-substituted expanded porphyrins and easy separation/purification of selective meso-aryl expanded porphyrins, in which advanced metal complexes and various fascinating properties and reactivities admitting moderate functional molecules have arisen.

Understanding the Origin of the Chiral Recognition of Esters with Octahedral Chiral Cobalt Complexes

AbstractHere, we report a combined experimental and computational study to understand the chiral recognition of cationic cobalt complexes with esters. The cationic cobalt complexes were synthesized by stereoselective assembly of ligands to the cobalt center. The tetradentate N2O2 ligand was used to control the metal‐centered chirality, and the bidentate diamine ligand played an important role in the chiral discrimination of esters by 1H NMR spectroscopy. The phenyl rings of the cobalt complexes additively enhanced the chiral discrimination. The opposite chiralities of the N2O2 ligand and bidentate diamine ligand constituted a well‐matched combination, which was further demonstrated by computational analysis of 1 : 2 binding models of the cationic cobalt complex and 1‐phenylethyl acetate.

An octahedral cobalt(iii) complex based on cheap 1,2-phenylenediamine as a bifunctional metal-templated hydrogen bond donor catalyst for fixation of CO2 with epoxides under ambient conditions

An octahedral cobalt(iii) complex based on cheap 1,2-phenylenediamine operates as an efficient bifunctional hydrogen bond donor catalyst in cycloaddition of epoxides with CO2 under ambient conditions and solvent- and co-catalyst-free conditions.

Modulation of amyloid-β aggregation by metal complexes with a dual binding mode and their delivery across the blood-brain barrier using focused ultrasound.

One of the key hallmarks of Alzheimer's disease is the aggregation of the amyloid-β peptide to form fibrils. Consequently, there has been great interest in studying molecules that can disrupt amyloid-β aggregation. While a handful of molecules have been shown to inhibit amyloid-β aggregation in vitro, there remains a lack of in vivo data reported due to their inability to cross the blood–brain barrier. Here, we investigate a series of new metal complexes for their ability to inhibit amyloid-β aggregation in vitro. We demonstrate that octahedral cobalt complexes with polyaromatic ligands have high inhibitory activity thanks to their dual binding mode involving π–π stacking and metal coordination to amyloid-β (confirmed via a range of spectroscopic and biophysical techniques). In addition to their high activity, these complexes are not cytotoxic to human neuroblastoma cells. Finally, we report for the first time that these metal complexes can be safely delivered across the blood–brain barrier to specific locations in the brains of mice using focused ultrasound.

Cobalt(II)/(III) complexes bearing a tetradentate thiosemicarbazone: Synthesis, experimental and theoretical characterization, and electrochemical and antioxidant properties

New cobalt complexes, Co1 and Co2, were synthesized starting from acetylacetone‐S‐methylthiosemicarbazone. The square planar cobalt(II) and octahedral cobalt(III) complexes were characterized by FT‐IR, UV–visible, 1H NMR, and X‐ray diffraction spectroscopies and mass spectrometry. Frontier orbitals of the complexes were theoretically obtained to better understand the complex structures and intermolecular interactions. The electrochemical behaviors of Co1 and Co2 were investigated and the results were evaluated by comparing with each other and with similar published compounds to determine their possible usage in various electrochemical technologies, such as energy storage devices, electrocatalysts, and electrosensors. Metal‐based oxidation at around 0 V and metal‐based reduction at around −1.0 V indicated that these complexes are valuable for the proposed applications. By determining the trolox equivalent antioxidant capacity and the radical scavenging activity of the cobalt complexes, the compatibility between the antioxidant qualification, redox, and theoretical calculation results was discussed.