Synthesis, characterization, molecular modeling and antibacterial activity of N1′, N2′-bis[1-(pyridin-2-yl)ethylidene]oxalohydrazide and its metal complexes

New complexes of N1′,N2′-bis[1-(pyridin-2-yl)ethylidene]oxalohydrazide (H2L) with Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Cd2+, VO2+ and Ag+ have been prepared and characterized. The ligand has 10–12 buffering range and pK’s of 4.62, 7.78 and 9.45. The IR spectra showed the neutral, (mono- or dibasic) bidentate, tridentate or tetradentate of H2L. The molar conductance values, in DMSO, are in the range of nonelectrolytes. An octahedral geometry is proposed for the Cr3+, Mn2+, Fe3+, Ni2+; VO2+ complexes and square–planar for the Co2+ and Cu2+ complexes. The ESR spectra support the mononuclear species for [VO(H2L)SO4−(H2O)2]·H2O and [Cu(H2L)(OAc)2]·H2O. The molecular parameters have been calculated to confirm the geometry of the ligand and its complexes. The ligand and some complexes were screened against Bacillus thuringiensis (Bt) as Gram positive and Pseudomonas aeuroginosa (Pa) as Gram negative bacteria using the inhibitory zone diameter. The data showed no effect for the complexes on Pa bacteria growth except [Ag(H2L)(NO3)]H2O which had a high activity. Cu2+, VO2+ and Ag+ complexes exhibit activity against BT; Cu2+complex is the highest one.

► N1’, N2’-bis[1-(pyridin-2-yl)ethylidene]oxalo-hydrazide as ligand.
► Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Cd2+, VO2+ and Ag+ as complexes.
► Octahedral geometry for the Cr3+, Mn2+, Fe3+, Ni2+ and VO2+ complexes and square-planar for Co2+ and Cu2+.
► Cu2+, VO2+ and Ag+ complexes have activity against BT and the Cu2+ complex had the highest inhibition activity.