Haem peroxidases are a class of metalloenzyme that catalyse the oxidation of substrates using hydrogen peroxide. To understand their behaviour a range model complexes have recently been studied. The structures

of two of these complexes are shown below. 7The key step in catalytic cycle involving haem peroxidase involves cleaving of the O-0 bond in H2O2. The reaction occurs about 800 times faster with compound 7 than compound 8.Assuming that the binding of H2O2 to haem is similar to that of small molecules such as 02, explain why both compounds 7 and8 can bind small molecules such as H2O2 and suggest why compound 7 is a better catalyst than compound 8.