Synthesis and Voltammetric Behavior of Loracarbef Metal Complexes

Loracarbef (HL), a second generation cephalosporin antibiotic, possesses various donor sites for interaction with transition metal ions such as Cu(II), Co(II), Fe(III) and Ru(III) to form complexes of the type [M(Cl)(HL)(H2O)]Cl (M: Cu(II), Co(II)] and [M(Cl)2(HL)(H2O)2]Cl (M: Fe(III), Ru(III)] with metal:ligand (M:L) molar ratio 1:1. These complexes were prepared and characterized by physicochemical and spectroscopic methods. UV-Vis, IR and mass spectra suggest that HL potentially acts as a bi-dentate ligand, with spectroscopic properties of these complexes changing in response to pH changes. The HL ligand and the resulting metal complexes gave intense emissions (δmax = 376 nm) upon irradiation by Ultra-Violet light. The photoluminescence quantum yields and long excited-state lifetimes of the ligand and its complexes were calculated. The HL ligand has a photoluminescence quantum yield of 52% and a long excited-state lifetime of 4.88 ns. The photoluminescence intensities and quantum yields of the metal complexes were dramatically reduced with respect to that of the HL ligand upon complexation with various metals. Also, the magnetic properties of the complexes were measured and the electrochemical behavior of these synthesized complexes was studied over a glassy carbon electrode in various buffer solutions using cyclic voltammetry. The peak current and peak potential of the complex depend on pH, initial potential, and scan rate. The complexes were screened for antibacterial activity against several bacteria and yeast, and results were compared with the activity of the uncomplexed antibiotic. The synthesized compounds were found to have remarkable bactericidal and fungicial properties. It is interesting that copper, iron and ruthenium complexes were very effective against all microorganisms.