A novel series of mixed ligand transition metal complexes of Cu(II), Zn(II), Ni(II) and Co(II) have been synthesized from the Schiff base ligand, 3-(naphthalen-1-ylimino)indolin-2-one (achieved by the condensation of isatin and naphthylamine) and 1, 10-phenonthroline. The structural features were corroborated by means of elemental analyses, molar conductance, IR, UV–Vis, 1H NMR and mass spectral studies. The data displays that these complexes have the composition of [MLX] type where X = 1, 10-phenonthroline. The UV–Vis. and magnetic susceptibility data of the complexes suggest a square–planar geometry around the central metal ion. The IR spectral data of the ligand exhibits the presence of iminic group and its complexes manifest that the imine group of the Schiff base coordinate with the metal ion and decreased value of carbonyl group indicates which coordinate to the metal. The proton NMR spectrum of the ligand shows the presence of imine group. The mass spectral data also confirms the metal complexes as [MLX] type. Molar conductance values of the complexes have been found in the range of 5 - 14 ohm−1cm2mol−1, suggesting the non-electrolytic nature of the complexes. The antimicrobial study reveals that copper and cobalt complexes are better antimicrobial agents than the standard drug streptomycin and Nystatin. The copper and cobalt complexes exhibit remarkable antioxidant potential than the other complexes. The catalytic oxidation of styrene by H2O2 was carried out in acetonitrile in the presence of mixed ligand metal complex as catalyst. The result of the catalytic study reveals that the zinc complex effectively catalyses the oxidation of styrene.