Effect of F Substituents in Thiophenol on the Structure and Properties of µ2-S-(Difluorothiolate)tetranitrosyl Iron Binuclear Complexes

Two new neutral binuclear tetranitrosyl iron complexes of general formula [Fe 2 R 2 (NO) 4 ] with R = 2,4-difluorothiophenyl (complex 1 ) and 3,4-difluorothiophenyl (complex 2 ), donors of nitrogen monoxide (NO), were prepared. The complexes were characterized by single-crystal X-ray diffraction, IR, Mössbauer, EPR spectroscopy, and elemental analysis. The antibacterial activity and cytotoxicity of complex 1 , complex 2 , and previously synthesized [ (NO) 4 ] with R'= 2,4-dichlorothiophenyl (complex 3 ) were studied for the first time. The “amount of NO–biological activity” correlations were analyzed depending on the nature and position of the substituent in the thiophenyl ligand. Complex 2 was found to have antibacterial activity that was four times as high as that of the known antibiotic kanamycin. The anti-biofilm activity of complex 2 was studied; it inhibited 46% of biofilm formation and destroyed 32% of M. Luteus biofilms, surpassing the effects of the reference drugs kanamycin and ampicillin.