Central Cobalt Atom Research Articles

A new mixed-ligand mononuclear Co(II) complex derived from 4,4,4-trifluoro-1-phenylbutane-1,3-dione and 1,10-phenanthroline: Synthesis, structural elucidation and quantum-computational studies

In this study, a novel mixed-ligand mononuclear Co(II) complex, denoted as {[Co(TFPBD)2(PHE)]DMF}, was synthesized and characterized using single crystal X-ray diffraction analysis. The central cobalt atom coordinated with two 4,4,4-trifluoro-1-phenylbutane-1,3-dione ligands (TFPBD1 and TFPBD2) and a 1,10-phenanthrene (PHE) ligand, adopting a slightly distorted octahedral geometry. Notably, the non-planar characteristics of the ligands led to the manifestation of non-covalent interactions within the molecular structure, further enhanced by the involvement of the lattice DMF solvent. The crystal lattice arrangement in the {[Co(TFPBD)2(PHE)]DMF} complex was a result of diverse non-covalent interactions, including hydrogen bonds, C-F…π, and Π…π stacking interactions, influenced the crystal's stability. Additionally, the study delved into the unique lattice arrangement consisted of pairwise R12(5) ring motifs along with one-dimensional molecular arrays formed along the crystallographic axes. Furthermore, intermolecular C-F…π Cg…Cg interactions resulting in two-dimensional linear molecular arrays along the a- and b-axes. Quantum computational studies using density functional theory (DFT) were employed to examine the complex's electronic structure and stability and reactivity, highlighting electron-rich and electron-deficient regions. Hirshfeld surface analysis (HSA) and Non-covalent interaction analysis confirmed the significance of intermolecular interactions where 2D fingerprint plots emphasized the prominence of CH…F interactions within the crystal structure. These findings contribute significantly to our understanding of mixed-ligand metal complexes and their potential applications in various scientific domains.

The Co-N bond cleavage in the adenosyncobalamin cofactor in advance to glutamate mutase and methylmalonyl-CoA mutase processes

The in vivo experiments show that the adenosylcobalamin cofactor in glutamate mutase and methylmalonyl-CoA mutase processes lose its dimethylbenzimidazole axial ligand before starting the enzymatic processes. Complete active space self-consistent field geometry optimization of the vitamin B12 active forms plus substrates joint models have been performed. These joint models include the adenosylcobalamin cofactor, the carboxyl negative ion model of the studied processes’ active substrates, and the histidine molecule. Partial electronic density is transferred from the highest occupied substrate molecular orbitals to the lowest unoccupied antibonding molecular orbitals, which consist of corrin ring and dimethylbenzimidazole ligand common molecular orbitals during the multi-configurational self-consistent field molecular orbital mixing process. As a result, the Co-N axial bond is permanently elongated during the complete active space self-consistent field geometry optimization until its complete rupture and until the removal of the dimethylbenzimidazole ligand from the central cobalt atom and the corrin ring is complete. The Co-N bond cleavage in the adenosylcobalamin cofactors in the studied processes is running as no energy barrier process under the influence of their active substrates and histidine molecule.

Effective interactions and phase behavior of protein solutions in the presence of hexamine cobalt(III) chloride

It is well established that deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) exhibit a reentrant condensation (RC) phase behavior in the presence of the trivalent hexamine cobalt(III) cations (Hac) which can be important for their packing and folding. A similar behavior can be observed for negatively charged globular proteins in the presence of trivalent metal cations, such as Y3+ or La3+. This phase behavior is mainly driven by charge inversion upon an increasing salt concentration for a fixed protein concentration (cp). However, as Hac exhibits structural differences compared to other multivalent metal cations, with six ammonia ligands (NH3) covalently bonded to the central cobalt atom, it is not clear that Hac can induce a similar phase behavior for proteins. In this work, we systematically investigate whether negatively charged globular proteins β-lactoglobulin (BLG), bovine serum albumin (BSA), human serum albumin (HSA) and ovalbumin (OVA) feature Hac-induced RC. Effective protein–protein interactions were investigated by small-angle X-ray scattering. The reduced second virial coefficient (B2/B2HS) was obtained as a function of salt concentration. The virial coefficient analysis performed confirms the reentrant interaction (RI) behavior for BLG without actually inducing RC, given the insufficient strengths of the interactions for the latter to occur. In contrast, the strength of attraction for BSA, HSA and OVA are too weak to show RC. Model free analysis of the inverse intensity 1/Iq→0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$1/I\\left( {q \ o 0} \\right)$$\\end{document} also supports this finding. Looking at different q-range by employing static (SLS) and dynamic light scattering experiments, the presence of RI behavior can be confirmed. The results are further discussed in view of metal cation binding sites in nucleic acids (DNA and RNA), where Hac induced RC phase behavior.Graphical abstract

Synthesis, Infrared Spectroscopic Characterization and Antimicrobial Studies of Co(III) Dimethylglyoximato Complexes with Aniline and Aniline-derived Axial Ligands

Complexes with cobalt(III) have been used as models in the study of vitamin B12 chemistry. In this study, cobalt(III) complexes with dimethylglyoxime as equatorial ligand and aniline or substituted aniline as well as thiocyanate ion as axial ligands have been synthesized and characterized based on melting point, conductivity, solubility and infrared (IR) spectral studies. The complexes are formulated as [Co(Hdmg)2(B)(SCN)] where Hdmg is dimethylglyoximato, B = aniline (A), 4-bromoaline (4BrA), 2- nitroaniline (2NA), 4-nitroaniline (4NA) or 4-anisidine (4PA). The complexes were formed in low yields (33 – 37 %) except [Co(Hdmg)2(A)(SCN)] which was obtained in significant yield (65 %). The percentage yield of the synthesized cobaloximes follows the order A > 4NA > 4PA > 4BrA = 2NA. They are of various colours, soluble or slightly soluble in the solvents used and have melting points in the range (77 – 120 0C). The data from IR spectra indicated that the coordination compounds coordinated via the nitrogen of the ligands. Further supportive fact of the coordination of the ligands to the metal ions was deduced from the emergence of new bands due to v(M-N) in the metal complexes. In the proposed octahedral coordination sphere of the central cobalt atom, four coordination sites in the equatorial positions are occupied by nitrogen atoms of two dimethylglyoximate monoanions, and the other two sites are occupied by atoms of monodentate neutral ligands and thiocyanate anion. The measured molar conductance showed that the complexes are non-electrolytes, except [Co(Hdmg)2(4BrA)(SCN)] which has conductivity of 149 Scm2 mol-1, hence electrolytic in nature. The in vitro antibacterial potency of the complexes were assayed against some strains of bacteria such as MRSA (Methicillin Resistance Staphylococcus) Staphylococcus aureus, Bacillus subtilis, Streptococcus pneumoniae, and the Gram negative bacteria, Salmonella typhi, Klebsiella pneumoniae, Escherichia coli, and Pseudomonas aeruginosa. The results of the antimicrobial assay uncovered that the complexes have more potency than their free ligands but less than that of the standard drug (Gentamicin)

Perfluorinated Phthalocyanines on Cu(110) and Cu(110)-(2 × 1)O: The Special Role of the Central Cobalt Atom

Interface properties of CoPcF16 on Cu(110) and Cu(110)-(2 × 1)O were investigated by X-ray photoemission spectroscopy (XPS), ultraviolet photoemission spectroscopy (UPS), X-ray absorption spectrosc...

Synthesis, X-ray crystal structure and BVS calculation of Co(II) complex of pyrimidine derived Schiff base ligand: Approached by Hirshfeld surface analysis and TDDFT calculation

A new Co(II) complex [Co(L)(Cl)2]•(MeOH)2 (1) has been synthesized using a symmetrical Pyrimidine derived Schiff base ligand 2,2′-((2E,2′E)-2,2′-(butane-2,3-diylidene)bis(hydrazin-1-yl-2-ylidene))bis(4,6-dimethylpyrimidine) (L) and characterized by single crystal X-ray crystallography analysis. The solid-state structure of 1 is pseudooctahedral with two methanol molecules outside the coordination sphere. The said complex is stabilized through various intermolecular H-bonding incorporating non coordinated solvent methanol molecules. Bond Valence Sum (BVS) calculation confirms that the central cobalt atom in 1 exists as ‘+2′ oxidation state instead of ‘+3′. Hirshfeld surface analysis is performed to determine the intermolecular interactions and the crystal packing of the title complex. The 2D fingerprint plots associated with the Hirshfeld surface clearly present each significant interaction involved in the structure, by quantifying them in an effective visual manner. The electronic transition of complex 1 was recorded in methanol solvent and the electronic distribution of HOMO−LUMO can be rationalized theoretically (through time-dependent density functional theory (TDDFT)).

59Co Internal field NMR analysis of Co35Fe35Ni30 alloy synthesized via novel low cost chemical reduction technique

We have synthesized ternary cobalt alloy using a chemical reduction process using hydrazine as a reducing agent . X-Ray Diffraction (XRD) measurements shows that the synthesized cobalt ternary alloy exists in the pure face centred cubic (fcc) phase with lattice parameter of 3.5562 ± 5 Å. The SEM micrograph shows that the particles exist in the spherical shape which suggests that the particles are crystallized in fcc phase. The magnetic properties are determined using Vibrating Sample Magnetometry (VSM) and 59Co IFNMR technique. The saturation magnetization (MS) of the synthesized sample is ~80 emu/g, a slightly lower value compared to the pure cobalt metal. 59Co IFNMR technique shows that there is a broad distribution of hyperfine field (~6 T) compared to the pure fcc cobalt metal. Further, from the deconvoluted NMR peaks suggests that the variation in the nearest neighbours to the central cobalt atom leads to the different hyperfine field.

Polynuclear Co(II) Myrtenates with 2,4-Lutidine

The reaction of cobalt(II) chloride with potassium myrtenate (KMyr) followed by addition of 2,3-lutidine in ethanol gives the trinuclear compound [Co3(Myr)6(2,4-Lut)2] (I). The central cobalt(II) atom is linked to each of the two other metal atoms by three myrtenic acid anions. The reaction of a solution of compound I with lithium myrtenate (LiMyr) results in the formation of tetranuclear heterometallic complex [Li2-Co2(Myr)6(2,4-Lut)2] (II). Compound II is composed of two binuclear {LiCo(Myr)3(2,4-Lut)} moieties, in which the lithium(I) atoms are linked to cobalt(II) atoms by bridging myrtenate anions. The lithium atoms are connected by two oxygen atoms of acid anions. Compounds I and II were characterized by X-ray diffraction (CIF files CCDC nos. 1898096 (I), 1898097 (II)).

Synthesis and Physico Chemical Studies of Some Cobalt (II) Complexes with Bromide and Biologically Active Ligands

Eleven cobalt (11) complexes of type [Co(L)6]Br2 (where L=imidazole, pyridine, peperidine, piperazine, indole, benzimidazole, benzotriazole, triazole, quinoline, iso-qunoline, carbazole) have been synthesized and are well characterized by elemental analysis, IR. UV. Mass Spectra and magnetic measurement. All these complexes are soluble in ethanol and the conductance measurement shows that all these complexes are of 1: 2 type electrolyte. The IR spectra indicate the coordination between the central cobalt atom and nitrogen atom of the ligands. In the mass spectra molecular ion peak of these complexes appear at appropriate place. The thermo gravimetric analysis shows the strong bond between the central cobalt atom and bromine atom of the complexes. In the complexes the ligands are loosely attached to the central cobalt atom as these are removed first on heating. Finally considering all the spectral analysis conductance values, thermo gravimetric analysis, conductance values octahedral structure are proposes for these complexes

Theoretical analysis of C-F bond cleavage mediated by cob[I]alamin-based structures.

In the present work, C-F bond cleavage mediated by the super-reduced form of cobalamin (i.e., CoICbl) was theoretically studied at the ONIOM(BP86/6-311++G(d,p):PM6)+SMD level of theory. Dispersion effects were introduced by employing Grimme's empirical dispersion at the ONIOM(BP86-D/6-311++G(d,p):PM6)+SMD level. In the first stage of the study, cobalamin was characterized in terms of the coordination number of the central cobalt atom. The ONIOM(BP86/6-311++G(d,p):PM6) results showed that the base-off form of the system is slightly more stable than its base-on counterpart (ΔE=E base-off-E base-on~-2kcal/mol). The inclusion of dispersive forces in the description of the system stabilizes the base-on form, which becomes as stable as its base-off counterpart. Moreover, in the latter case, the energy barrier separating both structures was found to be negligible, with a computed value of 1.02kcal/mol. In the second stage of the work, the reaction CoICbl+CH3F → MeCbl + F- was studied considering the base-off and the base-on forms of CoICbl. The reaction that occurs in the presence of the base-on form of CoICbl was found to be kinetically more favorable (ΔE ≠=13.7kcal/mol) than that occurring in the presence of the base-off form (ΔE ≠=41.2kcal/mol). Further reaction-force analyses of the processes showed that the energy barrier to C-F bond cleavage arises largely due to structural rearrangements when the reaction occurs on the base-on form of the CoICbl complex, but is mainly due to electronic rearrangements when the reaction takes place on the base-off form of the complex. The latter behavior emerges from differences in the synchronicity of the bond strengthening/weakening processes along the reaction path; the base-on mode of CoICbl is able to decrease the synchronicity of the chemical events. This work gives new molecular-level insights into the role of Cbl-based systems in the cleavage of C-F bonds. These insights have potential implications for research into processes for degrading fluorine-containing pollutants.

Role of Transient Co-Subcarbonyls in Ostwald Ripening Sintering of Cobalt Supported on γ-Alumina Surfaces

The stability and mobility of atomic cobalt and of cobalt subcarbonyl species on γ-Al2O3 surfaces have been investigated using density functional theory (DFT) with a view to elucidate possible mobile species on these surfaces, which can act as agents in the Ostwald ripening process. The two most stable alumina surfaces γ-Al2O3(100) and γ-Al2O3(110) were probed at different levels of hydration. The stability of cobalt subcarbonyl species on γ-Al2O3(100) at high partial pressure of CO (10 bar) increases with increasing number of CO ligands attached to the central cobalt atom up to Co(CO)3 but exhibits a more complex behavior on γ-Al2O3(110). The effect of the hydration level on the stability of cobalt subcarbonyls was investigated. The interpretation of the DFT results in a thermodynamic model shows that at equilibrium the main cobalt subcarbonyl species present on the alumina surface at ca. 500K in the presence of CO are Co(CO)3 and Co(CO)4, with Co(CO)3 being the dominant species on dry γ-Al2O3(100) and w...

Synthesis and Structure of Low-valent η4 -Cinnamaldehyde Cobalt Complexes

Three η4-(C=C–C=O) coordination cobalt(I) complexes 1–3 were synthesized by the reactions of cinnamaldehyde, p-fluorocinnamaldehyde, and p-chlorocinnamaldehyde with CoMe(PMe3)4. Complex 4 as η2-(C=C) coordination was prepared by the reaction of chalcone with Co(PMe3)4. The structures of complexes 1–4 were confirmed by single-crystal X-ray diffraction. Although the reactions didn't undergo C–H bond activation and decarbonylation, the formation of complexes 1–4 deepens our understanding of the reactions between α,β-unsaturated aldehyde or ketone with low-valent central cobalt atom.

Adsorption and Intermolecular Interaction of Cobalt Phthalocyanine on CoO(111) Ultrathin Films: An STM and DFT Study

We investigate the adsorption of cobalt phthalocyanine (CoPc) molecules on a thin layer of cobalt oxide grown on Ir(100). To that end we compare the results of low-temperature scanning tunneling microscopy (STM) with those of ab-initio density functional theory (DFT) calculations and reveal the adsorption geometry. We find that the CoPc molecules lie flat on the surface and that their central cobalt atom forms a chemical bond to a substrate oxygen ion. However, this bond contributes only modestly to the adsorption energy, while van-der-Waals forces dominate the potential landscape and determine to a large extend the geometry as well as the distortion of substrate and molecule. Furthermore they lead to attractive molecule-molecule interactions at higher molecular coverages. The DFT calculations predict energetic positions of the molecular orbitals which are compared to scanning tunneling spectroscopy (STS) measurements.

Competition between phosphorus lone pairs and ring π-systems in binding to transition metals: Binuclear diphosphacyclobutadiene cobalt carbonyl derivatives

Metal complexes of the 2,4-di-t-butyl-1,3-diphosphacyclobutadiene ligand have been synthesized by head-to-tail dimerization of t-BuCP: on transition metal sites. In this connection the geometries and energetics of the complete series of binuclear cobalt carbonyl complexes (Me2C2P2)2Co2(CO)n (n=5, 4, 3, 2, 1) of the simpler 2,4-dimethyl-1,3-diphosphacyclobutadiene ligand have been investigated by density functional theory. The lowest energy structures of these complexes have bridging η4,η1-Me2C2P2 ligands donating six electrons to the central Co2 unit through a tetrahapto ring-metal linkage to one cobalt atom and a phosphorus lone pair to the other cobalt atom. For the tetracarbonyl (Me2C2P2)2Co2(CO)4 doubly CO-bridged structures with terminal η4-Me2C2P2 ligands similar to known (η5C5H5)2Fe2(μ-CO)2(CO)2 and (η4-Me4C4)2Co2(μ-CO)2(CO)2 structures lie only ∼5kcal/mol in energy above the η4,η1-Me2C2P2 bridged structures. For the unsaturated (Me2C2P2)2Co2(CO)3 and (Me2C2P2)2Co2(CO)2 systems, structures with one or two bridging η4,η1-Me2C2P2 ligands, respectively, are preferred energetically over isomeric structures with formal CoCo double bonds and CoCo triple bonds, respectively. The lowest energy structure for the monocarbonyl (Me2C2P2)2Co2(CO) is a triplet structure in which a (Me2C2P2)2Co sandwich unit functions as a tridentate ligand to a CoCO unit through a phosphorus atom on each ring as well as the central cobalt atom.

Carbon dioxide is tightly bound in the [Co(Pyridine)(CO2)](-) anionic complex.

The [Co(Pyridine)(CO2)](-) anionic complex was studied through the combination of photoelectron spectroscopy and density functional theory calculations. This complex was envisioned as a primitive model system for studying CO2 binding to negatively charged sites in metal organic frameworks. The vertical detachment energy (VDE) measured via the photoelectron spectrum is 2.7 eV. Our calculations imply a structure for [Co(Pyridine)(CO2)](-) in which a central cobalt atom is bound to pyridine and CO2 moieties on either sides. This structure was validated by acceptable agreement between the calculated and measured VDE values. Based on our calculations, we found CO2 to be bound within the anionic complex by 1.4 eV.

Energy cascades, excited state dynamics, and photochemistry in cob(III)alamins and ferric porphyrins.

Porphyrins and the related chlorins and corrins contain a cyclic tetrapyrrole with the ability to coordinate an active metal center and to perform a variety of functions exploiting the oxidation state, reactivity, and axial ligation of the metal center. These compounds are used in optically activated applications ranging from light harvesting and energy conversion to medical therapeutics and photodynamic therapy to molecular electronics, spintronics, optoelectronic thin films, and optomagnetics. Cobalt containing corrin rings extend the range of applications through photolytic cleavage of a unique axial carbon-cobalt bond, permitting spatiotemporal control of drug delivery. The photochemistry and photophysics of cyclic tetrapyrroles are controlled by electronic relaxation dynamics including internal conversion and intersystem crossing. Typically the electronic excitation cascades through ring centered ππ* states, ligand to metal charge transfer (LMCT) states, metal to ligand charge transfer (MLCT) states, and metal centered states. Ultrafast transient absorption spectroscopy provides a powerful tool for the investigation of the electronic state dynamics in metal containing tetrapyrroles. The UV-visible spectrum is sensitive to the oxidation state, electronic configuration, spin state, and axial ligation of the central metal atom. Ultrashort broadband white light probes spanning the range from 270 to 800 nm, combined with tunable excitation pulses, permit the detailed unravelling of the time scales involved in the electronic energy cascade. State-of-the-art theoretical calculations provide additional insight required for precise assignment of the states. In this Account, we focus on recent ultrafast transient absorption studies of ferric porphyrins and corrin containing cob(III)alamins elucidating the electronic states responsible for ultrafast energy cascades, excited state dynamics, and the resulting photoreactivity or photostability of these compounds. Iron tetraphenyl porphyrin chloride (Fe((III))TPPCl) exhibits picosecond decay to a metal centered d → d* (4)T state. This state decays on a ca. 16 ps time scale in room temperature solution but persists for much longer in a cryogenic glass. The photoreactivity of the (4)T state may lead to novel future applications for these compounds. In contrast, the nonplanar cob(III)alamins contain two axial ligands to the central cobalt atom. The upper axial ligand can be an alkyl group as in the two biologically active coenzymes or a nonalkyl ligand such as -CN in cyanocobalamin (vitamin B12) or -OH in hydroxocobalamin. The electronic structure, energy cascade, and bond cleavage of these compounds is sensitive to the details of the axial ligand. Nonalkylcobalamins exhibit ultrafast internal conversion to a low-lying state of metal to ligand or ligand to metal charge transfer character. The compounds are generally photostable with ground state recovery complete on a time scale of 2-7 ps in room temperature aqueous solution. Alkylcobalamins exhibit ultrafast internal conversion to an S1 state of d/π → π* character. Most compounds undergo bond cleavage from this state with near unit quantum yield within ∼100 ps. Recent theoretical calculations provide a potential energy surface accounting for these observations. Conformation dependent mixing of the corrin π and cobalt d orbitals plays a significant role in the observed photochemistry and photophysics.

Synthesis and Structural Studies of Some New Cobalt (II) Complexes with Chloride and Heterocyclic Nitrogen Donor ligands

A new series of cobalt complexes of type [Co(L)6]Cl2 (where L =imidazole, pyridine, piperidine, piperazine, indole, triazole, benzimidazole, benzotriazole, quinoline, iso-quinoline and carbazole) have been synthesized and are well characterized by elemental analysis, IR, UV, Mass spectra and magnetic measurements. The thermal studies of these complexes are also reported. All these complexes are soluble in ethanol and the conductance measurement shows that all the complexes are of 1:2 type electrolyte. The IR spectra show clear indication for coordination between central cobalt atom and nitrogen atom of the ligands. The mass spectra clearly show the molecular ion peak and base peak at appropriate place. On thermo gravimetric analysis, it is found that the metal atom and chlorine are strongly attached to each other. The ligands are loosely attached and are removed first on heating. Finally considering all the spectral analysis, conductance values, thermo gravimetric analysis, octahedral structure are proposed for these complexes

Novel Dinuclear Redox‐isomeric Complexes with a Tetrapodal Pyridine‐based Ligand

AbstractTris‐o‐semiquinonato cobalt complexes react with a tetrapodal pyridine‐derived ligand to form dinuclear cobalt compounds of general formula (OMP)[CoQ2]2, where OMP = 2,2′‐(pyridine‐2,6‐diyl)bis(N1,N1,N3,N3‐tetramethylpropane‐1,3‐diamine), Q = mono‐ or dianion of 3,6‐di‐tert‐butyl‐o‐benzoquinone (complex 1) and it derivatives: 3,6‐di‐tert‐butyl‐4,5‐N,N′‐piperazino‐o‐benzoquinone (complex 2), and 3,6‐di‐tert‐butyl‐4‐Cl‐o‐benzoquinone (complex 3). Single crystal X‐ray crystallography of 1 and 3 indicates two bis‐quinonato cobalt units bound by an OMP ligand, which acts as a bridge. Each central cobalt atom is chelated by one N1,N1,N3,N3‐tetramethylpropane‐1,3‐diamine and two o‐quinonato fragments. The nitrogen atom of the pyridine ring is uncoordinated. All complexes were characterized by NIR‐IR and EPR spectroscopy, precise adiabatic vacuum calorimetry, and by variable‐temperature magnetic susceptibility measurements. All data indicate a reversible thermally driven redox‐isomeric (valence tautomeric) transformation in the solid state for all complexes.

Microwave solid phase synthesis, characterization, and antimicrobial activity of 3,5-diiodo-salicylalidene-glycine-cobalt(II)

One mononuclear complex, C9H7I2NO4Co(II) (I) with 3,5-diiodo-salicylalidene, glycine and Co(CH3COO)2 · 4H2O were microwave solid synthesized. The complex was characterized by X-ray crystallography, UV, IR, ESI-MS, and elemental analyses. In addition, further investigation revealed that the central cobalt(II) atom in complex is five-coordinated by one nitrogen atom and four oxygen atoms. The complex was assayed for antibacterial (B. subtilis, S. aureus, S. faecalis, P. aeruginosa, E. coli, and E. cloacae) activities by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl trtrazolium bromide) method. Complex I showed favorable antimicrobial activity with MICs of 3.125, 6.25, 6.25, 6.25, 3.125, and 6.25 μg/mL against B. subtilis, S. aureus, S. faecalis, P. aeruginosa, E. coli, and E. cloacae, respectively.

Synthesis and Structure of a Penta- and Hexa-Coordinated Tri-Nuclear Cobalt(II) Complex

The tri-nuclear cobalt(II) complex, [(CoL)2(μ-OAc)2Co]·2CHCl3 (H2L = 5,5'-dimethoxy-2,2'-[(ethylene)dioxybis(nitrilome thylidyne)]diphenol), has been synthesised. Its X-ray structure shows it to contain two acetate ions coordinating to the three cobalt(II) atoms through Co–O–C–O–Co bridges, and four μ-phenoxo-oxygen atoms from two [CoL] chelates also coordinating to the central cobalt(II) atom. The complex possesses two penta- and one hexa-coordinated cobalt atoms. The crystal packing of the CoII complex shows that a 2D-layer supramolecular network parallel to the ab-plane is formed through intermolecular C–H···O and C–H···Cl hydrogen bonding interactions.