Synthesis and antimicrobial activity of a phenanthroline-isoniazid hybrid ligand and its Ag⁺ and Mn²⁺ complexes

Hydrazide ligand, (Z)-N'-(6-oxo-1,10-phenanthrolin-5(6H)-ylidene)isonicotinohydrazide, 1 forms from a 1:1 Schiff base condensation reaction between isoniazid (INH) and 1,10-phenanthroline-5,6-dione (phendione). Ag + and Mn 2+ complexes with 1:2 metal:ligand stoichiometry are prepared: [Ag(1) 2 ]NO 3 , [Ag(1) 2 ]BF 4 and [Mn(1) 2 ](NO 3 ) 2 . Polymeric {[Ag(1)(NO 3 )]} n has 1:1 stoichiometry and forms upon infusion of CH 2 Cl 2 into a DMSO solution of [Ag(1) 2 ]NO 3 . {[Ag(1)(NO 3 )]} n was structurally characterized using X-ray crystallography. Metal-free 1 and its 1:2 complexes exhibit very good, broad-spectrum antimicrobial activity and are not excessively toxic to mammalian cells (A549 lineage).