**2.6 Ni(II) complexes**

Ni(II) and its complexes of 3-Methoxy-salicylaldehyde-4(N)-substituted thiosemicarbazones exhibits strong anti-oxidant property with strong radical scavenging ability. Some of the complexes shows better anticancer activity against lung cancer cell lines (A549) than the ligand and cisplatin [11]. N(4)-substituted thiosemicarbazone and its Ni(II) complexes Anti-cancer activity was tested against human breast cancer cell lines (MCF-7). All the complexes shows moderate activity compared to commercial anti-cancer drug, cisplatin [65].

Ni(II) and its complexes of dinucleating bis(thiosemicarbazones) were tested for cytotoxic activity against human cancer cell lines (A549 and HepG2). One of the nickel complex shows better activity against A549 cell line than cisplatin drug [66].

2-Hydroxy-1-naphthaldehydethiosemicarbazone; salicylaldehyde-4(N) ethylthiosemicarbazone; 2-hydroxy-1-naphtha ldehyde-4(N)-ethyl TSC and Ni(II) complexes were tested for cytotoxic activity against human cancer cell lines (A549 and HepG2). One of the nickel complex shows better activity against A549 cell line than cisplatin drug [67]. Ortho-Naphthaquinone thiosemicarbazone; ortho-Naphthaquinone semicarbazone Anti-cancer activity and its Ni(II) complexes were tested against MCF-7 human breast cancer cell lines and results revealed that semicarbazone and nickel complexes were more active than thiosemicarbazone ligand [68].

*p*-Fluorobenzaldehdye thiosemicarbazones and its nickel complexes shows remarkable inhibition activity against human leukemic cell line U937 (**Figure 5**) [69].

**Figure 5.** *Cytotoxic activity of Ni(II) complexes of thiosemicarbazones.*
