Bis-bidentate bridging ligands containing two N,O-chelating pyrazolyl-phenolate units; double helical complexes with Co(II), Cu(II) and Zn(II)

Antimicrobial and Antibiofilm Effect of 4,4'-Dihydroxy-azobenzene against Clinically Resistant Staphylococci

The spread of antibiotic resistance among human and animal pathogens is one of the more significant public health concerns. Moreover, the restrictions on the use of particular antibiotics can limit the options for the treatment of infections in veterinary clinical practice. In this context, searching for alternative antimicrobial substances is crucial nowadays. In this study, 4,4'-dihydroxy-azobenzene (DHAB) was tested for its potential in vitro as an antimicrobial agent against two relevant human and animal pathogens, namely Staphylococcus aureus and Staphylococcus pseudintermedius. The values of minimal inhibitory concentration (MIC) were 64 and 32 mg/L respectively, and they comparable to other azo compounds of probed antimicrobial activity. In addition, the minimal bactericidal concentrations (MCB) were 256 and 64 mg/L. The mechanism by which DHAB produces toxicity in staphylococci has been investigated. DHAB caused membrane damage as revealed by the increase in thiobarbituric acid reactive substances (TBARS) such as malondialdehyde. Furthermore, differential induction of the enzymes peroxidases and superoxide dismutase in S. aureus and S. pseudintermedius suggested their prevalent role in ROS-scavenging due to the oxidative burst induced by this compound in either species. In addition, this substance was able to inhibit the formation of biofilms by both bacteria as observed by colorimetric tests and scanning electron microscopy. In order to assess the relevance of DHAB against clinical strains of MRSA, 10 clinical isolates resistant to either methicillin or daptomycin were assayed; 80% of them gave values of CMI and CMB similar to those of the control S. aureus strain. Finally, cutaneous plasters containing a composite formed by an agar base supplemented with DHAB were designed. These plasters were able to inhibit in vitro the growth of S. aureus and S. pseudintermedius, particularly the later, and this suggests that this substance could be a promising candidate as an alternative to antibiotics in the treatment of animal skin infections, as it has been proven that the toxicity of this substance is very low particularly at a dermal level.

Crystal structure of 4-bromo-2-(1H-pyrazol-3-yl)phenol, C9H7BrN2O

C9H7BrN2O, triclinic, C2/c (no. 15), a = 16.255(3) Å, b = 4.4119(9) Å, c = 25.923(5) Å, β = 107.99(3)°, V = 1768.2(7) Å3, Z = 8, R gt(F) = 0.0450, wR ref(F 2) = 0.0960, T = 150 K.

Four Salamo-type 3d–4f hetero-bimetallic [ZnIILnIII] complexes: syntheses, crystal structures, and luminescent and magnetic properties

A series of [Zn^IILn^III] complexes (Ln = Sm, Eu, Tb and Dy) are synthesized by Salamo-type ligand H₂L. Only [Zn^IISm^III] shows the characteristic transitions of Sm³⁺ ion, indicating the effective energy transfer between the ligand and Sm³⁺ ion.

Crystal structure of 4-chloro-4′,6′-dichloro-2,2′-[propane-1,3-diyldioxybis(nitrilomethylidyne)]-diphenol, C17H14Cl3N2O4

C17H14Cl3N2O4, orthorhombic, Fdd2, a = 32.980(2) Å, b = 24.6827(18) Å, c = 4.4872(3) Å, V = 3652.8(4) Å3, Z = 8, R gt (F) = 0.0783, wR ref (F 2 ) = 0.1862, T = 293(2) K.

Crystal structure of 4-bromo-2-(8-(3-ethoxy-2-hydroxyphenyl)-3,6-dioxa-2,7-diazaocta-1,7-dien-1-yl)phenol, C18H19BrN2O5

C18H19BrN2O5, triclinic, P1̅ (no. 2), a = 9.0429(7) Å, b = 9.5752(11) Å, c = 11.8422(15) Å, α = 70.954(11)°, β = 72.691(8)°, γ = 84.794(8)°, V = 925.33(18) Å3, Z = 2, R gt (F) = 0.0511, wR ref (F 2 ) = 0.0876, T = 173 K.

An unexpected Schiff base-type Ni(II) complex: synthesis, crystal structures, fluorescence, electrochemical property and SOD-like activities

An unexpected Schiff base-type Ni(II) complex, [Ni(L(2))2]⋅CH3OH (HL(2) = 1-(2-{[(E)-3, 5-dibromo-2-hydroxybenzylidene]amino}phenyl)ethanone oxime), has been synthesized via complexation of Ni(II) acetate tetrahydrate with HL(1) (2-(3,5-dibromo-2-hydroxyphenyl)-4-methyl-1,2-dihydroquinazoline 3-oxide) originally. HL(1) and its corresponding Ni(II) complex were characterized by IR, (1)H NMR spectra, as well as by elemental analysis, UV-Vis and emission spectroscopy, respectively. Crystal structures of the ligand and complex have been determined by single-crystal X-ray diffraction. Each complex links two other molecules into an infinite 1-D chain via intermolecular hydrogen bonding interactions. Moreover, the electrochemical property of the nickle complex was studied by cyclic voltammetry. In addition, SOD-like activities of HL(1) and Ni(II) complex were also investigated.

A novel trinuclear cobalt(II) complex derived from an asymmetric Salamo-type N2O3 bisoxime chelate ligand: synthesis, structure and optical properties

A novel trinuclear Co(II) complex, {[CoL(PrOH)]2Co(H2O)}·PrOH, has been synthesized with 6-ethoxy-6'-hydroxy-2,2'-[ethylenedioxybis(nitrilomethylidyne)]diphenol (H3L), and characterized by elemental analyses, FT-IR, UV-Vis, molar conductance and X-ray crystallographic analysis. Two n-propanol molecules and one water molecule coordinate to three Co(II) ions and four μ-phenoxo oxygen atoms from two [CoL(CH3CH2CH2OH)] units also coordinating to Co(II) ion. All the penta-coordinated Co(II) ions of the Co(II) complex have a slightly distorted trigonal bipyramidal coordinated polyhedron. Meanwhile, the μ-phenoxo bridges play important roles in assembling Co(II) ions and L(3-) units, which is different from the normal trinuclear Co(II) complexes with the Salamo-type ligands reported early.

Synthesis, crystal structure and spectral properties of a supramolecular trinuclear nickel(II) complex with 5-methoxy-4'-bromo-2,2'-[ethylenedioxybis(nitrilomethylidyne)]diphenol

A novel trinuclear Ni(II) complex [{NiL(n-PrOH)(μ-OAc)}2Ni]·n-PrOH·H2O with an asymmetric Salamo-type ligand, 5-methoxy-4'-bromo-2,2'-[ethylenedioxybis(nitrilomethylidyne)]diphenol (H2L), has been synthesized and characterized by elemental analyses, IR, UV/Vis and fluorescence spectra and molar conductance measurement. The crystal structure of the Ni(II) complex has been determined by single-crystal X-ray diffraction. Two acetate groups coordinating to three Ni(II) ions through NiOCONi bridges and four μ-phenoxo oxygen atoms from two [NiL(n-PrOH)] units also coordinating to Ni(II) ions. In the Ni(II) complex, two n-propanol molecules are coordinated to the two terminal Ni(II) ions having slightly distorted octahedral coordination geometries and form a trinuclear structure, There are also one non-coordinated n-propanol and one non-coordinated water molecule. In the crystal structure, the Ni(II) complex is linked by intermolecular hydrogen bonds into an infinite 1D supramolecular chain-like structure.

An unexpected cobalt(III) complex containing a Schiff base ligand: Synthesis, crystal structure, spectroscopic behavior, electrochemical property and SOD-like activity

An unexpected mononuclear Co(III) complex, [Co(L2)2·(CH3COO)]·CH3OH (HL2=1-(2-{[(E)-3,5-dichloro-2-hydroxybenzylidene]amino}phenyl)ethanone oxime), has been synthesized via complexation of Co(II) acetate tetrahydrate with HL1 originally. The plausible reaction mechanism for the formation of quinazoline-type ligand was proposed. HL1 and its corresponding Co(III) complex were characterized by IR, as well as by elemental analysis and UV-vis spectroscopy. The crystal structure of the complex has been determined by single-crystal X-ray diffraction. Each complex links two other molecules into an infinite 1-D chain via intermolecular hydrogen bonding interactions. Moreover, the electrochemical properties of the cobalt(III) complex were studied by cyclic voltammetry and X-ray photoelectron spectrum (XPS). In addition, superoxide dismutase-like activities of HL1 and Co(III) complex were also investigated.