Fe(III)-doxycycline complexes with diimine ligands: Syntheses, characterization and biological properties

Joshua A Obaleye, Olufunso Olumide Abosede


Three new iron(III) complexes of doxycycline viz: [Fe(dox)2Cl]Cl2 (1), [Febpy(dox)Cl]Cl2 (2) and [Fephen(dox)Cl]Cl2 (3), where dox is doxycycline, bpy is 2,2ʹ-bipyridine and phen is 1,10-phenanthroline, were synthesized and characterized by elemental analysis, electronic absorption, FT-IR, and electrospray ionization mass spectroscopy. Doxycycline and the polypyridyl ligands behave as bidendate ligands; the polypyridyl ligands coordinate through the two diimine nitrogen atoms and doxycycline through enolate and diketoamide oxygen atoms of ring A in a five-coordinate system with chloride atom in the axial position. Their antibacterial and antiplasmodial activities against chloroquine-sensitive Plasmodium falciparum NF54 and their interaction with calf thymus (CT) DNA using electronic titration were investigated. The three complexes showed good activity against strains of Staphylococcus aureus and Klebsiella pneumonia. The complexes bind moderately to CT DNA with binding constants of 5.6 × 104 and 4.8 × 104 for complexes 2 and 3, respectively.


doxycycline; complex, diimine, synthesis, characterization biological activity

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