Synthesis, characterization, and biological activities of zinc, cadmium, copper, and nickel complexes containing meta -aminophenyl benzimidazole

Abstract

ZnX₂, CdX₂, CuX₂, and NiX₂ (X = Cl⁻, Br⁻, , or ) react with meta-aminophenyl benzimidazole in 1 : 2 mole ratio at reflux in methanol to give Zn₂Cl₄L₃ · 2H₂O, ZnBr₂L₂(OH₂), [Zn(OClO₃)L₃]ClO₄ · 3H₂O, CdCl₂L(OH₂), Cd₂Br₄L₃ · 2H₂O, Cd(ONO₂)₂L₂ · 2H₂O, [Cu₂Cl₄L₃] · 2H₂O, Cu₂Br₄L₃, [Cu(OClO₃)L₂]₂(ClO₄)₂, [NiCl₂L(OH₂)] · 2H₂O, [NiBrL₃]Br · 3H₂O, and [Ni(OClO₃)L₃]ClO₄ · H₂O. These complexes were characterized by elemental analysis, melting point, TGA, conductivity, magnetic moment measurements, IR, far-IR, NMR, electronic, and mass spectral studies. Based on these studies, Zn₂Cl₄L₃ · 2H₂O and Cd₂Br₄L₃ · 2H₂O were assigned binuclear structures while [Zn(OClO₃)L₃]ClO₄ · 3H₂O, CdCl₂L(OH₂), Cd(ONO₂)₂L₂ · 2H₂O, [NiCl₂L(OH₂)] · 2H₂O, and [NiBrL₃]Br · 3H₂O were mononuclear with tetrahedral geometry. The copper complexes were binuclear and exhibit strong antiferromagnetic coupling at room temperature. Square pyramidal geometry was proposed for halo complexes of copper and ZnBr₂L₂(OH₂) and square-planar geometry for perchlorato complexes of copper and nickel. All the synthesized compounds were screened for antimicrobial activities.

Keywords:

• m-APB
• NMR spectra
• Complexes
• Biological activity

Acknowledgements

Authors wish to thank “CESEM” award project under Vision Group on Science and Technology, Government of Karnataka, India. SAIF, CDRI, Lucknow, for elemental analyses and mass spectra. SAIF, IIT, Bombay, and STIC, Cochin University for TGA. SAIF, NMR Research Centre, Indian Institute of Science, Bangalore, for NMR spectra. Central Instrumentation Facility, Pondicherry University, for far-IR spectra. Dr Vasanthacharya, SSCU, Indian Institute of Science, Bangalore, for magnetic susceptibility measurements and SAIF, IIT, Madras, for variable temperature magnetic susceptibility measurement. Spectroscopy/Analytical Test Facility, IISc, Bangalore, for ESI-MS. B. Roopashree thanks JSSATE, Bangalore, and JSSMVP, Mysore, for encouraging doctoral studies.