In chemistry, a redox switch is a molecular device, which has two subunits, a functional component and a control component. The "control subunit" is redox-active, meaning that it can exist in either of two redox states. The "functional" component could have a variety of readouts, such as fluorescence, the binding of a substrate, or catalytic activity. The key feature of such redox switches is that the functional component is influenced by the control subunit. One of many examples of a redox switch consists of an anthracene substituent to a copper-thiacrown ether (14-ane-4) coordination complex. When in the cupric oxidation state, the anthracene does not fluoresce. When in the cuprous state, the assembly is highly fluorescent.[1] Several redox switches have been produced from ferrocenecarboxylic acid, which can be conjugated to a number of functional components. 1,1'-Diaminoferrocene has been incorporated into various diamide and diimine ligands, which form catalysts that exhibit redox switching.[2]