Ceftriaxone-based Schiff base transition metal(II) complexes. Synthesis, characterization, bacterial toxicity, and DFT calculations. Enhanced antibacterial activity of a novel Zn(II) complex against S. aureus and E. coli.

From the reaction of ceftriaxone 1 antibiotic with 2,6-diaminopyridine 2 a ceftriaxone-based Schiff base (H2L,3) was obtained and its transition metal complexes were synthesized. Spectroscopic and physicochemical techniques, namely, UV-visible, FT-IR, 1H NMR, EPR, mass spectrometry, molar conductance, magnetic susceptibility and density functional theory (DFT) calculations, together with elemental and thermal analyses, were used to find out the binding mode and composition of these complexes. The ceftriaxone-based Schiff base 3 behaves as a monoanionic tridentate N,N,O ligand. Spectral and magnetic data suggest an octahedral geometry for all complexes and the general formulae [M(HL)(OAc)(H2O)2] (M(II) = Mn2+4, Co2+5, Ni2+6, Cu2+7, Zn2+8), are proposed for them. All compounds were screened for antibacterial activity using both the agar disc diffusion method and the minimal inhibitory concentration (MIC). It was found that complex 8 exhibited the most promising bactericidal activity against S. aureus (MIC = 0.0048 µmol/ml) and E. coli (MIC = 0.0024 µmol/ml). It is more active than the free ligand 1 (MIC = 0.0560 µmol/ml for S. aureus and 0.0140 µmol/ml for E. coli). These MIC results were compared with those obtained using similar zinc(II) Schiff base complexes, and with the values obtained using ceftriaxone conjugated with silver and gold nanoparticles (NPs), using earlier published data. Synthesized metal complexes exhibited LC50 values >1000 ppm indicating their nontoxicity against brine shrimp nauplii (Artemia Salina).

Tetradentate metal complexes derived from cephalexin and 2,6-diacetylpyridine bis(hydrazone): Synthesis, characterization and antibacterial activity.

Metal(II) coordination compounds of a hydrazone ligand (HL) derived from the condensation of cephalexin antibiotic with 2,6-diacetylpyridine bis(hydrazone) were synthesized. The hydrazone ligand and mononuclear [ML(H2O)2][PF6] (M(II)=Mn, Co, Ni, Zn) complexes were characterized by several techniques, including elemental and thermal analysis, molar conductance and magnetic susceptibility measurements, electronic, FT-IR, EPR and (1)H NMR spectral studies. The cephalexin 2,6-diacetylpyridine bis(hydrazone) ligand HL behaves as a monoanionic tetradentate NNNO chelating agent. The biological applications of complexes have been studied on two bacteria strains (Escherichia coli and Staphylococcus aureus) by agar diffusion disc method.

Tridentate hydrazone metal complexes derived from cephalexin and 2-hydrazinopyridine: synthesis, characterization and antibacterial activity.

Metal(II) coordination compounds of a tridentate hydrazone ligand (HL) derived from the condensation of cephalexin antibiotic with 2-hydrazinopyridine were synthesized. The hydrazone ligand and mononuclear [ML(OAc)(H2O)] (M(II)=Mn, Co, Ni, Cu, Zn, Ag) complexes were characterized by several techniques, including elemental and thermal analysis, molar conductance and magnetic susceptibility measurements, electronic, FT-IR, EPR and (1)H NMR spectral studies. The cephalexin 2-pyridinylhydrazone ligand HL behaves as a monoanionic tridentate NNO chelating agent. The biological applications of complexes have been studied on three bacteria strains (Escherichia coli, Acinetobacter baumannii and Enterococcus faecalis) by agar diffusion disc method.

Synthesis, characterization and antibacterial activity of a tridentate Schiff base derived from cephalothin and sulfadiazine, and its transition metal complexes.

Metal(II) coordination compounds of a cephalothin Schiff base (H2L) derived from the condensation of cephalothin antibiotic with sulfadiazine were synthesized. The Schiff base ligand, mononuclear [ML(H2O)3] (M(II)=Mn,Co,Ni,Zn) complexes and magnetically diluted dinuclear copper(II) complex [CuL(H2O)3]2 were characterized by several techniques, including elemental and thermal analysis, molar conductance and magnetic susceptibility measurements, electronic, FT-IR, EPR and (1)H NMR spectral studies. The cephalothin Schiff base ligand H2L behaves as a dianionic tridentate NOO chelating agent. The biological applications of complexes have been studied on two bacteria strains (Escherichia coli and Staphylococcus aureus) by agar diffusion disc method.

Synthesis, characterization and antibacterial activity of a Schiff base derived from cephalexin and sulphathiazole and its transition metal complexes.

Metal(II) coordination compounds of a cephalexin Schiff base (HL) derived from the condensation of cephalexin antibiotic with sulphathiazole were synthesized. The Schiff base ligand, mononuclear [ML(OAc)(H2O)2] (M(II)=Mn, Co, Ni, Zn) complexes and magnetically diluted trinuclear copper(II) complex [Cu3L(OH)5] were characterized by several techniques, including elemental and thermal analysis, molar conductance and magnetic susceptibility measurements, electronic, FT-IR, EPR and (1)H NMR spectral studies. The analytical and molar conductance values indicated that the acetate ions coordinate to the metal ions. The Schiff base ligand HL behaves as a monoanionic tridentate NNO and tetradentate NNOO chelating agent in the mono and trinuclear complexes respectively.

Two polymorphs of bis(2-bromophenyl) disulfide.

Colourless crystals of the title compound, bis(2-bromophenyl) disulfide, C(12)H(8)Br(2)S(2), are obtained from the reaction of 2-bromophenylmercaptan with metallic sodium and either zinc chloride or cadmium chloride in methanol. In the presence of Zn(II) ions, the crystals are orthorhombic (space group Pbca, with Z' = 1); with Cd(II) ions present, the product is triclinic (space group (-)P1, with Z' = 4). Both polymorphs exhibit significant intramolecular C-H.S hydrogen bonds. In the orthorhombic form, molecules are linked by intermolecular C-H...Br hydrogen bonds, while in the triclinic form, molecules exhibit Br...Br contacts.