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Three oligonuclear complexes of copper(), [{Cu(Hfsaaep)Cl} 2 ] 1, [{Cu(fsaaep)(H 2 O)} 2 ] 2 and [Cu 3 (fsaaep) 2 ][ClO 4 ] 2 3 have been synthesized, using the unsymmetrical tetradentate Schiff-base ligand 3-[N-2-(pyridylethyl)formimidoyl]salicylic acid, H 2 fsaaep. The crystal structures of complexes 1 and 2 have been solved.That of 1 consists of discrete binuclear entities with copper atoms bridged by two chloride anions. The copper atoms are related by an inversion center and exhibit a slightly distorted square pyramidal stereochemistry. The Cu ؒ ؒ ؒ Cu separation within the binuclear unit is 3.825(2) Å. The structure of 2 consists of neutral centrosymmetric binuclear entities. The copper() ions are bridged by phenolic oxygen atoms, assuming a square-pyramidal geometry. The distance between the copper atoms is 3.0279(4) Å. Variable-temperature magnetic susceptibility measurements indicated a very weak ferromagnetic coupling of the copper() ions in compound 1 (J = 0.15 cm Ϫ1 ) and an antiferromagnetic coupling in compounds 2 and 3 (J = Ϫ617 and Ϫ228 cm Ϫ1 , respectively).

The cobalt ferrite (CoFe2O4) and silver-cobalt ferrite (Ag-CoFe2O4) nanoparticles were obtained through self-combustion and wet ferritization methods using aqueous extracts ofHibiscus rosa-sinensisflower and leaf. X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and magnetic measurements were used for the characterization of the obtained oxide powders. The antimicrobial activity of the cobalt ferrite and silver-cobalt ferrite nanoparticles against Gram-positive and Gram-negative bacteria, as well as fungal strains, was investigated by qualitative and quantitative assays. The most active proved to be the Ag-CoFe2O4nanoparticles, particularly those obtained through self-combustion using hibiscus leaf extract, which exhibited very low minimal inhibitory concentration values (0.031–0.062 mg/mL) against all tested microbial strains, suggesting their potential for the development of novel antimicrobial agents.

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