[Cp∗Rh(bpy)(H2O)]2+: a versatile tool for efficient and non-enzymatic regeneration of nicotinamide and flavin coenzymes

[Cp∗Rh(bpy)(H2O)]2+ is a versatile tool for the non-enzymatic regeneration of oxidoreductase coenzymes such as NAD(P)H, NAD(P)+, and FADH2. The complex shows high stability and activity over a very broad range of pH (more than 60% activity between pH 3.5 and 9.7) and temperature (exponential increase of activity until at least 69 °C). The regeneration concept is not limited to sacrificial electron donors such as formate or alcohols for regeneration of reduced coenzymes; cheap electrical power as a reagent less source of reduction equivalents can also be used. At 30 °C, the complex has a specific activity of 1.2 U mg−1 for NAD(P)H regeneration and about 1 U mg−1 for FADH2 regeneration with identical KM values for both NAD+ and NADP+ of about 9 μM. In addition, a [Cp∗Rh(bpy)(H2O)]2+/FAD based concept for the regeneration of oxidized nicotinamide coenzymes is proposed.