Nitric oxide, superoxide and hydrogen peroxide are small molecules which have versatile biological functions and are of industrial and environmental interest. Coordination of these small molecules to transition metal centres significantly affects their behaviour. In particular, the redox potentials of these molecules can be tuned, depending on the electronic properties of the metal. These redox reactions are important not only in physiological processes, but also in chemical catalysis; therefore, understanding the mechanisms of the elementary reaction steps behind these complex processes is of fundamental importance. 

In this Dalton Transactions Perspective, Rudi van Eldik and Ivano Ivanovic-Burmazovic, from the University of Erlangen-Nürnberg, Germany, describe their recent work in this area. The authors have applied low temperature and high pressure kinetic and thermodynamic techniques in order to shed more light on the mechanisms of the reaction steps involved in the activation of nitric oxide, superoxide and various peroxides. 

Activation of NO and peroxide by Fe(III) complexes is discussed, in addition to the catalytic and stoichiometric dismutation of superoxide by Mn(II)-based mimetics of the superoxide dismutase (SOD) metalloenzyme. The authors aim to characterise these metal-superoxide adducts as this will provide a greater understanding of these systems and allow tuning of their reactivity towards different organic substrates of industrial and biological interest.