We have synthesized heterocyclic base adducts [pyridine (py), 2,2’-bipyridine (bipy), 1,10-phenanthroline (Phen), α/β-picoline] of Nickel (II) complexes by the reaction of Nickel (II) chloride with 5-chloro-2-hydroxy acetophenone N(4) methyl thiosemicarbazone in presence of heterocyclic base. Ligand was characterized by 13C, 1H NMR as well as IR, electronic spectra. The synthesized adducts were characterized by IR, ESI-MS, UV-visible, magnetic measurement, molar conductivity, TGA and DSC. The magnetic and spectroscopic data indicate a square planner geometry for the four coordinate and a distorted square pyramidal for five coordinate complexes. The Nickel (II) bipy and Nickel (II) β–pico adducts show higher antioxidant activity.