Present thesis describes the synthesis, characterization and biological screening of sulfonamide ligands; their complexes and five membered heterocyclic ligands (Thiohydantoin ligands); their complexes aiming in search of new candidates to fight with microorganisms. Thanks to metals for being the charm of medicinal and pharmaceutical chemistry since many decades. To extend this search, 20 ligands were synthesized. Ligands containing sulfonamide moieties are prepared by the reaction of ten different amino acids with p-toluene sulfonyl chloride. The compounds are isolated in pure form and checked by TLC. The single crystal structure of the compounds is also reported and dicussed.These compounds were then reacted with transition metals e.g, Zn (II), Sb (III) chloride and Sb (III) bromide and thirty new metal complexes have been synthesized. Further, these sulfonamide derivatives were cyclized in the presence of NH 4 SCN, acetic anhydride and base to form 5-membered heterocyclic ring containing thio group. Forty, new complexes of these thiohydantoins with transition metals e.g. Zn (II), Sb (III) chloride and Sb (III) bromide have been synthesized. All of the synthesized complexes were heat, air and moisture stable after formation, but during the complex formation, moisture and air was avoided to prevent the oxidation of the compounds using standard schlenk line and glove box techniques. The stability profile enhances the link between organometallics and drug design and discovery. Purity of all of the synthesized compounds was conventionally monitored with the help of TLC in different solvent systems. All of the synthesized compounds and their complexes with transition metals were characterized by elemental analysis, FTIR, GC- MS and 1 H NMR , 13 C NMR spectroscopy, the structure was finally confirmed with the help of single crystal structure. All the characterization data is reported in this work and discussed. All the synthesized compounds and their metal complexes were evaluated for their carbonic anhydrase, intestinal alkaline phosphate inhibition, antileshminial, anti oxidant, anticancer and antibacterial activities. The results of these bioassays are also reported and discussed in detail, e.g., the sulfonamide ligands showed excellent carbonic anhydrase activities, while the activity was enhanced 40-60% in case of zinc complexes but the antimony (III) complexes have showed slightly less CA activities. Similarly, the complexes of antimony with sulfonamide ligands have showed excellent antileshminial activities, while the zinc (II) complexes have showed comparatively less activities. Moreover, the results of intestinal alkaline phosphatase activities iiihave proved that the metal complexes of sulfonamide and thiohydantoin ligands have showed increased activities as compared to parent sulfonamide ligands. Additionally, the said complexes also showed enhanced cytotoxic activities against BHK-21 and H-157 cell lines. The antibacterial activity against Gram –ve and Gram +ve bacteria were outstanding in case of metal complexes of the sulfonamides. Results of antibacterial evaluation of all the compounds as percent inhibition against these bacteria are reported and discussed. The activity of different synthesized compounds as percentage inhibition against concentration and time are included and discussed in detail. We can summarize by saying that the newly synthesized ligands and their metal complexes have provided important candidates for drug discovery which can be further improved to be used as drugs with enhanced pharmacological action and lesser side effects.