Synthesis, characterization, biological activity of binuclear Co(II), Cu(II) and mononuclear Ni(II) complexes of bulky multi-dentate thiosemicarbazide

• Preparation of Co2+, Ni2+ and Cu2+ complexes of multi-dentate thiosemicarbazide.
• Spectral data revealed that the ligand acts as a bi- or mononegative multi-dentate.
• Isolated Ni2+ and Cu2+ complexes are square-planar while the Co2+ is tetrahedral.
• The thermal behavior and kinetic parameters were determined.
• The compounds were screened for antibacterial and superoxide-scavenging activities.

The chelation behavior of 9,10-dihydro-9,10-ethanoanthracene-11,12-dicarbonyl) bis (N-ethylhydrazine-1-carbothioamide) (H6ETS)(1) towards Co2+, Ni2+and Cu2+ have been studied. The spectral data revealed that the ligand acts as a bi- and/or mono-negative multi-dentate. The isolated Ni(II) and Cu(II) complexes are square-planar while the Co(II) is tetrahedral. EPR spectrum of Cu(II) complex confirmed simulated an axial spin-Hamiltonian exhibiting a four-line pattern with nitrogen super-hyperfine couplings originating from imine hydrazinic nitrogen atoms and possess a significant amount of tetrahedral distortion leading to a pseudo-square-planar geometry with unpaired electron has dx2-y2dx2-y2 ground state. Also, the thermal behavior and kinetic parameters were determined. Furthermore, the title compounds were investigated for their antibacterial activity using inhibition zone diameter and for DNA degradation, superoxide-scavenging activity as well as hydroxyl radicals that generated by the oxidation of cytochrome c in L-ascorbic acid/CuSO4–cytochrome c system.

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