New Ni(II)-sulfonamide complexes: Synthesis, structural characterization and antibacterial properties. X-ray diffraction of [Ni(sulfisoxazole)2(H2O)4] · 2H2O and [Ni(sulfapyridine)2]

The synthesis, structural characterization, voltammetric experiments and antibacterial activity of [Ni(sulfisoxazole)2(H2O)4] · 2H2O and [Ni(sulfapyridine)2] were studied and compared with similar previously reported copper complexes. [Ni(sulfisoxazole)2(H2O)4] · 2H2O crystallized in a monoclinic system, space group C2/c where the nickel ion was in a slightly distorted octahedral environment, coordinated with two sulfisoxazole molecules through the heterocyclic nitrogen and four water molecules. [Ni(sulfapyridine)2] crystallized in a orthorhombic crystal system, space group Pnab. The nickel ion was in a distorted octahedral environment, coordinated by two aryl amine N from two sulfonamides acting as monodentate ligands and four N atoms (two sulfonamidic N and two heterocyclic N) from two different sulfonamide molecules acting as bidentate ligands. Differential pulse voltammograms were recorded showing irreversible peaks at 1040 and 1070 mV, respectively, attributed to Ni(II)/Ni(III) process. [Ni(sulfisoxazole)2(H2O)4] · 2H2O and [Ni(sulfapyridine)2] presented different antibacterial behavior against Staphylococcus aureus and Escherichia coli from the similar copper complexes and they were inactive against Mycobacterium tuberculosis.