Synthesis, spectral, thermal and biological studies on N−(2,4-dinitro-phenyl)-2-mercaptoacetohydrazide and its metal complexes

• VO2+, Co2+, Ni2+, Cu2+, Zn2+ and Cd2+ complexes of N−(2,4-dinitrophenyl)-2-mercaptoacetohydrazide.
• Octahedral, tetrahedral and square-pyramid stereochemistries for the complexes.
• The antimicrobial activity of the ligand and its complexes.
• Stoichiometry and stability constants of the complexes in solution.

Complexes of VO2+, Cr3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+ and Hg2+ ions with N−(2,4-dinitrophenyl)-2-mercaptoacetohydrazide (H2L) have been prepared and characterized on the basis of elemental analysis, molar conductance, thermal (TGA, DTGA), spectral (IR, NMR, UV–Visible, MS) and magnetic measurements. The IR spectra show that H2L behaves in a mononegative and/or binegative bidentate manner. The sulfate bridged the two complex molecules in [Cu(HL)(H2O)2(½SO4)]⋅3H2O. The acetate functions as a monodentate in [Ni(HL)(OAc)(H2O)3] and [Cr(HL)(OAc)2(H2O)(EtOH)]. Different stereochemistries are proposed: octahedral for Cr(III), Ni(II), Hg(II) and [Cu(HL)(H2O)2(SO4)0.5]⋅3H2O, square-based pyramid for [VO(HL)2]⋅EtOH, square-planar for [Co(L)(EtOH)(H2O)]⋅H2O, [Cu(L)(H2O)2] and tetrahedral for [Zn(L)(EtOH)(H2O)], [Cd(L)(EtOH)(H2O)] and [Cu2(HL)(H2O)6]Cl3⋅H2O according to the data of electronic spectra and magnetic measurements. The TGA data support the formula and indicate the outer and inner solvents as well as the final residue. The thermodynamic parameters are calculated using the Coats–Redfern and Horowitz–Metzger methods. H2L and [Zn(L)(EtOH)(H2O)] showed the highest cytotoxic activity while H2L has a higher antioxidant activity than ascorbic acid. The ionization constant of the ligand and the stability constant of the Cu(II)H2L in absence and presence of hexamine buffer were calculated.

Structure of [VO(HNMAH)2]⋅EtOH.Figure optionsDownload as PowerPoint slide