Immobilization of metal complexes on a carbon electrode was successfully carried out via their ligand, of which the functional group on the opposite side of the central metal ion is covalently bonded to the carbon electrode. This method is viewed as a ligand grafting method. The functional group is primary or secondary amine, but not tertiary amine. As metal complexes, Os(bpy)(2)Cl-2 (bpyequivalent to4,4'-bipyridyl), Ru(bpy)(2)Cl-2, and Os(phen)(2)Cl-2 were used, and as ligands, which act as a bridge between the complex and the carbon electrode, 4-aminopyridine and 4-aminoethylpyridine, were used. Two ligand grafting methods were developed: in one, a ligand by itself was first grafted on carbon through electrochemical cation radical formation in ethanol solution, and then metal complex was refluxed with ligand-grafted carbon to generate metal complex grafted carbon. A second method is for the metal complex to be directly bonded to carbon by the electrochemical cation radical formation.