ABSTRACT
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).
Subject(s)
Anti-Bacterial Agents/pharmacology , Ceftriaxone/analogs & derivatives , Ceftriaxone/pharmacology , Coordination Complexes/pharmacology , Schiff Bases/pharmacology , Animals , Anti-Bacterial Agents/chemical synthesis , Anti-Bacterial Agents/toxicity , Artemia/drug effects , Ceftriaxone/toxicity , Coordination Complexes/chemical synthesis , Coordination Complexes/toxicity , Density Functional Theory , Escherichia coli/drug effects , Magnetic Phenomena , Metals, Heavy/chemistry , Metals, Heavy/toxicity , Microbial Sensitivity Tests , Models, Chemical , Molecular Structure , Schiff Bases/chemical synthesis , Schiff Bases/toxicity , Staphylococcus aureus/drug effects , Stereoisomerism , Transition Elements/chemistry , Transition Elements/toxicityABSTRACT
M(II) coordination compounds of Mn, Fe, Co and Ni with a Schiff base (HL) derived from the condensation of cephaclor antibiotic with 1,2-diaminobenzene were synthesized and 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 chloride ions coordinate to the metal ions. Based on these studies, the general formulae [M(L)Cl(H2O)] (M(II)=Mn, Fe, Co, Ni) are proposed for the complexes. The ligand HL behaves as a monoanionic tetradentate NNNO chelating agent.
