LAUSR

The solution state of a new antituberculosis drug 1,6-bis(hydrazidomethylsulflnyl)hexane (L) and its complexation with copper(II) were investigated by spectrophotometry, pH-potentiometry (T = 25 °C; at variable ionic strength), and mathematical modeling. The dissociation constants of the protonated and imidol forms of compound L were determined. Complexation reactions in the Cu2+—L system result in mononuclear complexes [CuL]2+ and [CuL2]2+ with the amide form of the ligand provided that the redox reactions are excluded. The most probable (optimized) structures of 1,6-bis(hydrazidomethylsulfinyl)hexane and its complexes were obtained from quantum chemical calculations within the framework of the density functional theory (PBE/6-311G (d) method). Compound L adopts a folded conformation. The coordination site of the 1:1 complex includes six oxygen atoms from two carbonyl groups, two sulfoxide groups, and two water molecules. In the 1:2 complex, each ligand molecule is coordinated in bidentate mode through the carbonyl oxygen atom and the primary amino nitrogen of a hydrazide fragment.