Spectral, thermal, molecular modeling and biological studies on mono- and binuclear complexes derived from oxalo bis(2,3-butanedionehydrazone)

Background: Hydrazones and their metal complexes were heavily studied due to their pharmacological applications such as antimicrobial, anticonvulsant analgesic, anti-inflammatory and anti-cancer agents. This work aims to synthesize and characterize novel complexes of VO 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , Zr 4+ and Pd 2+ ions with oxalo bis(2,3-butanedione-hydrazone). Single crystals of the ligand have been grown and analyzed. Results: Oxalo bis(2,3-butanedionehydrazone) [OBH] has a monoclinic crystal with P 1 21/n 1 space group. The VO 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , Zr 4+ and Pd 2+ complexes have the formulas: [VO(OBH–H) 2 ]·H 2 O, [Co(OBH) 2 Cl]Cl·½EtOH, [Ni 2 (OBH)Cl 4 ]·H 2 O·EtOH, [Cu(OBH) 2 Cl 2 ]·2H 2 O, [Zn(OBH–H) 2 ], [Zr(OBH)Cl 4 ]·2H 2 O, and [Pd 2 (OBH)(H 2 O) 2 Cl 4 ]·2H 2 O. All complexes are nonelectrolytes except [Co(OBH) 2 Cl]Cl·½EtOH. OBH ligates as: neutral tetradentate (NNOO) in the Ni 2+ and Pd 2+ complexes; neutral bidentate (OO) in [Co(OBH) 2 Cl]Cl·½EtOH, [Zr(OBH)Cl 4 ]·2H 2 O and [Cu(OBH) 2 Cl 2 ]·2H 2 O and monobasic bidentate (OO) in the Zn 2+ and VO 2+ complexes. The NMR ( 1 H and 13 C) spectra support these data. The results proved a tetrahedral for the Zn 2+ complex; square-planar for Pd 2+ ; mixed stereochemistry for Ni 2+ ; square-pyramid for Co 2+ and VO 2+ and octahedral for Cu 2+ and Zr 4+ complexes. The TGA revealed the outer and inner solvents as well as the residual part. The molecular modeling of [Ni 2 (OBH)Cl 4 ]·H 2 O·EtOH and [Co(OBH) 2 Cl]Cl·½EtOH are drawn and their molecular parameters proved that the presence of two metals stabilized the complex more than the mono metal. The complexes have variable activities against some bacteria and fungi. [Zr(OBH)Cl 4 ]·2H 2 O has the highest activity. [Co(OBH) 2 Cl]Cl·½EtOH has more activity against Fusarium. Conclusion: Oxalo bis(2,3-butanedionehydrazone) structure was proved by X-ray crystallography. It coordinates with some transition metal ions as neutral bidentate; mononegative bidentate and neutral tetradentate. The complexes have tetrahedral, square-planar and/or octahedral structures. The VO 2+ and Co 2+ complexes have square-pyramid structure. [Cu(OBH) 2 Cl 2 ]·2H 2 O and [Ni 2 (OBH)Cl 4 ]·H 2 O·EtOH decomposed to their oxides while [VO(OBH–H) 2 ]·H 2 O to vanadium. The energies obtained from molecular modeling calculation for [Ni 2 (OBH)Cl 4 ]·H 2 O·EtOH are less than those for [Co(OBH) 2 Cl]Cl·½EtOH indicating the two metals stabilized the complex more than mono metal. The Co(II) complex is polar molecule while the Ni(II) is non-polar.