One-pot synthesis, characterization, photocatalytic activity and biological studies of Co(II), Ni(II) and Cu(II) complexes of a tetraazamacrocyclic Schiff base

Abstract

Template condensation between pentane-1,5-dial and triethylenetetramine in the presence of divalent metal salts in methanolic solution resulted in mononuclear 15-membered tetraazamacrocyclic Schiff base metal complexes, [M(C₁₁H₂₂N₄)X₂], where M = Co(II), Ni(II) and Cu(II), X = Cl⁻ and C₁₁H₂₂N₄ is the tetradentate macrocyclic ligand. The bonding and overall geometry of the complexes are inferred through elemental analysis, FT-IR, UV–vis, ¹H/¹³C NMR, ESI-mass, molar conductance, magnetic susceptibility and TG measurements. On the basis of the absorption bands in UV–vis spectra and magnetic moment analyses, a six-coordinate octahedral geometry is proposed for all the metal complexes. The formulation of the metal chelates is compatible with the thermal decomposition profiles. Photocatalytic efficiency of the macrocyclic Ni(II) complex was studied using solar water-splitting. The in vitro antimicrobial activity of metal complexes has been tested against certain bacterial and fungal species. The scavenging ability of DPPH free radicals was used to test the antioxidant activity of the complexes. In addition, MTT assay was used to assess the cytotoxicity of Cu(II) chloro complex against L929 mouse fibroblast cell lines.

Keywords:

• Schiff base macrocycles
• one-pot synthesis
• template condensation
• photocatalytic efficiency
• biological applications

Acknowledgements

The authors acknowledge CLIF, BIOVENT INNOVATIONS PVT. LTD. (KUBIIC) and Department of Chemistry, University of Kerala, Kariavattom Campus; SAIF, IIT-Bombay, Kochi and Chennai; Department of Chemistry, Mahatma Gandhi College, Thiruvananthapuram; NIIST, Thiruvananthapuram, Kerala for availing the research facilities. The financial assistance from University of Kerala, Thiruvananthapuram is gratefully acknowledged for Junior Research Fellowship.

Disclosure statement

No potential conflict of interest was reported by the authors.