Ternary complexes containing Copper(II), -Valinate and α, ά-bipyridyl or 1,10-phenanthroline: Synthesis, characterization, ligand substitution and oxidase biomimetic catalytic activity studies

Formation Process of SiF6@Cu2L4 Chiral Cage Pairs in a Glass Vessel: Catechol Oxidation Catalysis and Chiral Recognition

Self-assembly of CuX2 (X- = BF4-, PF6-, and SbF6-) with a pair of chiral bidentate ligands, (1R,2S)-(+)- and (1S,2R)-(-)-1-(nicotinamido)-2,3-dihydro-1H-inden-2-yl-nicotinate (r,s-L or s,r-L), in a mixture solvent including ethanol in a glass vessel gives rise to SiF62--encapsulated Cu2L4 chiral cage products. The SiF62- anion from the reaction of X- with SiO2 of the glass-vessel surface acts as a cage template or cage bridge. One of the products, [SiF6@Cu2(SiF6)(s,r-L)4]·3CHCl3·4EtOH, is one of the most effective heterogeneous catalysts for the oxidation of 3,5-di-tert-butylcatechol. Furthermore, an l-DOPA/d-DOPA pair is recognizable by the cyclic voltammetry (CV) signals of its combination with chiral cages [SiF6@Cu2(BF4)2(s,r- or r,s-L)4]·4CHCl3·2EtOH pair and [SiF6@Cu2(SiF6)(s,r- or r,s-L)4]·3CHCl3·4EtOH pair.

Antimicrobial and Antibiofilm Activity of Copper-Based Metallic Compounds Against Bacteria Related with Healthcare-Associated Infections

Health care-associated infections (HAIs) contribute to a significant rate of morbidity, mortality, and financial burden on health systems. These infections are caused by multidrug-resistant bacteria that produce biofilm as the main virulence factor. This study aimed to evaluate the effect of the copper-based metallic compounds [Cu(phen)(pz)NO₂]Cl (I), [Cu(bpy)(pz)(NO₂)]Cl (II), and [Cu(phen)(INA)NO₂]Cl (III), where phen = phenanthroline, bpy = bipyridine, pz = pyrazinamide, and INA = isonicotinic acid, against planktonic cells and biofilms formation of Staphylococcus aureus, Staphylococcus epidermidis, and Escherichia coli. The susceptibility of the microorganisms was evaluated by minimum inhibitory concentration (MIC), minimum bacterial concentration (MBC), and time-kill curve assay on planktonic cells. The biofilm formation was evaluated by biomass quantification through staining with crystal violet (CV), colony-forming units (CFUs) quantification, and biofilm metabolic activity determination by XTT assay. The compounds showed bacteriostatic and bactericidal activity on all microorganisms analyzed. Regarding the antibiofilm activity, all metallic compounds were able to reduce significantly the biofilm biomass, colony-forming units, and the metabolic activity of remaining cells, varying the efficient concentration according to the strain analyzed. Interestingly, compounds (I), (II) and (III) did not exhibit DNA degradation activity even with up to 100 µM of these metal complexes. On the other hand, complexes (I) and (III) showed a remarkable capacity to cleave DNA upon addition of glutathione, a reducing agent (Cu^II/Cu^I) that leads to reactive oxygen species (ROS) formation. The results presented in this study showed promising antimicrobial and antibiofilm effects.

Tuning the structural and catalytic properties of copper(II)-based complexes containing pyridine-2,6-diimines

Four mononuclear penta coordinated copper(II) chelates, [CuLⁿBr₂] nH₂O, containing the tridentate neutral ligands, pyridine-2,6-diimine (Lⁿ), were prepared via the template technique. Analytical and several physicochemical methods have been used to characterize the prepared metal chelates. Square-pyramidal stereochemistry was described to the current copper(II) complexes. DFT technique has been applied to optimize the structure of the running diimines and their corresponding copper-based compounds. Ligand substitution study performed to link the catalytic potency of the candidate oxidase mimics and their lability characters. Spectral investigations reveal that nature of substituents of the chelated ligands effectively tuning the Lewis acidity of copper(II) centers. Biomimetics of redox proteins specifically containing copper were examined towards the aerobic oxidation of polyphenol. Kinetic studies with the stopped-follow technique showed a close association between the Lewis acidity of the copper(II) nuclei of the prepared chelates and their oxidase-like activity. The catalytic activity of the natural enzyme (catechol oxidase from sweet potatoes) measured and compared with that for the present Cu^II chelates. The thermodynamic parameter drive force (ΔG° or λ) of the performed oxidation processes was determined from the values of redox potential of the chemical species involved in these catalytic reactions. The proposed catalytic reactions pathways have been discussed based on the outcomes of the kinetic investigations.Communicated by Ramaswamy H. Sarma.

Crystal structure of poly[triaqua-bis(μ3-3,3′-((5-carboxylato-1,3-phenylene)bis(oxy))dibenzoato)-tris(1,10-phenanthroline)cobalt(II)], C78H46N6O20Co3

C78H46N6O20Co3, monoclinic, P21/c (no. 14), a = 10.789(4) Å, b = 48.885(18) Å, c = 15.205(4) Å, β = 124.604(19)°, V = 6601(4) Å3, Z = 4, R gt(F) = 0.0539, wR ref(F 2) = 0.1205, T = 293(2) K.

Synthesis and spectroscopic characterization of ternary copper(ii) complexes containing nitrogen and oxygen donors as functional mimics of catechol oxidase and phenoxazinone synthase

Two ternary copper(ii) complexes 1 [(Cu₂Me₄en)₄(EDTA)] and 2 [(CuMe₄en)₂(MIDA)] containing the mixed ligand system of 1,1′,4,4′-tetramethylethylenediamine (Me₄en) (L) and N-methyliminodiacetic (MIDAH₂) (L′) or ethylenediaminetetraacetic acid (EDTAH₄) (L′) were synthesized.