New series of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) organometallic complexes with hydroxyl benzylidene malonohydrazide ligand have much potential as therapeutic and diagnostic agents. The ligand allows the thermodynamic and kinetic reactivity of the metal ion to be controlled and also provide a scaffold for functionalization. The establishment of structure activity relationships and elucidation of the specification of complexes under conditions relevant to drug testing and formulation are crucial for the further development of promising medicinal applications of organometallic complexes. Specific examples involving the design of metal complexes as anticancer agents are discussed. These complexes have been synthesized and characterized by (1H-NMR, mass, IR, UV-VIS and ESR) spectroscopy, as well as magnetic moments, conductance, elemental and thermal analyses. Molar conductance in DMF solution indicates that, the complexes are non-electrolytes. The ESR spectra of solid Cu(II) complexes (7) and (8) showed isotropic and anisotropic types indicating an octahedral geometry with covalent bond character. However, Co(II) complexes (3) and (4) showed anisotropic type where, g┴ > g|| >2.0023, indicating compressed tetragonal distortion around Co(II) ion. Cytotoxic evolution of the ligand and its complexes have been carried out. Complexes showed enhanced activity in comparison to the parent ligand or standard drug applied.