Several Coordination Modes of 5-Amino-1,3,4-thiadiazole-2-sulfonamide (hats) with Cu(Ii), Ni(Ii) and Zn(Ii): Mimetic Ternary Complexes of Carbonic Anhydrase-Inhibitor

The coordination properties of 5-amino-1,3,4-thiadiazole-2-sulfonamide (Hats) with Cu(II), Ni(II) and Zn(II) ions, are analyzed. Although the ligand presents several donor atoms, we have only observed three coordination behaviors: (i) as a monodentate ligand through the N-sulfonamido atom, (ii) as a bridging ligand linking the metal ions through the N-sulfonamido and N-thiadiazole atoms and (iii) as a bridging ligand linking metal ions through the N and O atoms of the sulfonamidate group. It is noteworthy that coordination mode (iii) is observed for the first time in heterocyclic sulfonamides complexes. In addition, the conformation of the Hats as counter-ion is analyzed and compared with the conformations that the ligand adopts in metal complexes.