Applications of coordination compounds

Coordination compounds have significant practical importance well beyond the laboratory, spanning biology, medicine, water analysis and industrial metal finishing. In biology, several biologically essential natural compounds are themselves metal complexes, playing central roles in ordinary plant and animal life processes: chlorophyll, the light-harvesting pigment present in plants, is a coordination complex of magnesium, and haemoglobin, the oxygen-carrying protein present in blood, is a coordination complex of iron. In medicine, the platinum coordination complex cisplatin (introduced back in section 9.1, and discussed again for its cis/trans isomer difference in section 9.7.1) is used clinically in cancer treatment, while EDTA (the hexadentate ligand introduced in section 9.2.2) is used medically to treat lead poisoning, since it can chelate and help remove toxic Pb2+ ions from the body. To estimate hardness of water: water hardness is specifically caused by dissolved Ca2+ and Mg2+ ions, and because EDTA forms strong, stable complexes with both of these ions, a controlled EDTA titration can be used to measure exactly how much Ca2+ and Mg2+ a water sample contains, i.e. to estimate its hardness. In electroplating: stable coordination complexes dissociate in solution only to a small, controlled extent, so instead of releasing free metal ions all at once, they steadily furnish a slow, CONTROLLED supply of metal ions; keeping the ligands wrapped around the metal atoms in this way also keeps freshly-deposited metal atoms well SEPARATED from one another as they form, which encourages them to buil …