Square planar mononuclear platinum(ii) complexes were synthesized in the presence of neutral bidentate heterocyclic (5-quinoline 1,3,5-tri-substituted pyrazole scaffold) ligands and K 2 PtCl 4  salt. The synthesized compounds were characterized by micro-elemental analysis, FT-IR, UV-vis,  1 H NMR,  13 C NMR, TGA, mass spectrometry and molar conductivity. Their biological activities were investigated by  in vitro  brine shrimp lethality bioassay,  in vitro  antimicrobial study against five different pathogens,  in vivo  cellular level cytotoxicity against  Schizosaccharomyces pombe  cells, and  in vitro  anti-proliferation assay. The binding constant  K  sv ,  K  b ,  K  a  values of the complexes were determined by DNA interaction studies. The gel electrophoresis assay was carried out to examine the effect of the complexes on the DNA nuclease of pUC19 plasmid DNA. The docking energies of the ligands ( L 1 -L 5   ) and complexes ( I-V ) were observed in the range of -265.14 to -284.33 kJ mol -1 . The synthesized Pt(ii) complexes ( I-V ) were screened against the MCF-7 (human breast adenocarcinoma) and HCT-116 (human colon carcinoma) cancer cell lines.