Syntheses, crystal structures of Ni(II), Ag(I)-enoxacin complexes, and their antibacterial activity

Two metal-enoxacin complexes, [Ni(H-Ex)2(H2O)2](NO3)2 (1) and Ag2(H-Ex)4(NO3)2 (2) (where H-Ex = enoxacin, Ex = deprotonated enoxacin), have been synthesized and characterized by elemental analysis, infrared spectroscopy, and single crystal X-ray diffraction. Complex 1 is composed of a [Ni(H-Ex)2(H2O)2]2+ core with two uncoordinated nitrates. The Ni(II) lies on the inversion site in a slightly distorted octahedral environment. Complex 2 is a binuclear silver(I) complex, in which two Ag(I) ions are bridged by a weakly bonding bidentate [image omitted]. The coordination modes of enoxacin are monodentate for 2 and bidentate for 1. In addition, 1 and 2 were screened for their activities against several bacteria and showed activities similar to that of free enoxacin; the test compounds were more active against Gram-negative bacteria than Gram-positive bacteria.