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Three new halogenated pyridyl hydrazones,namely 4-chlorobenzaldehyde-4-chloropyridine-2-formyl acylhydrazone (C13H9Cl2N3O,3a),4-bromobenzaldehyde-4-chloropyridine-2-formyl acylhydrazone (C13H9BrClN3O,3b) and 4-iodobenzaldehyde-4-chloropyridine-2-formyl acylhydrazone (C13H9ClIN3O,3c),have been synthesized and characterized by elemental analysis,IR,1H NMR,and single-crystal X-ray diffraction.The X-ray diffraction analysis revealed that 3a~3e crystallize in monoclinic with space group Cc.The units of 3a ~ 3c were linked by intermolecular N-H…X (X =Cl,Br,I) hydrogen bonds into 2D layered structures,which were further extended into 3D networks by a series of π-π stacking interactions.Thermogravimetric analysis showed that all of them possessed higher thermal stabilities.The reactivities toward calf thymus DNA (ct-DNA) and bovine serum albumin (BSA) of 3a~3c were investigated by UV-vis and fluorescent spectroscopy as well as molecular docking simulation.Both theoretical and experimental results indicated that 3a~3c bound to ct-DNA in the mode of minor groove binding,and interacted with BSA through the hydrophobic cavity near TRP213.Besides,the orders of binding affinities of 3a~3c to ct-DNA and BSA were both 3c > 3b > 3a,which were the same as that of antibacterial activities.Thus,the interactions of iodinated acyihydrazone with biological targets were stronger than that of chlorinated and brominated acylhydrazones,which provided a representative case for halogenation of lead compounds in rational drug design.