It is important to consider the different coordination chemical conditions for the photochemical and thermal catalysis reactions. In the former, TEA and NAD + whereas in the latter formate and NAD + compete for coordination to the Rh III center of Rh III HphenPer. Therefore, we conclude that coordination is a relevant and crucial step for the final formation of NADH. In addition, the short-lived nature of the CS state observed in the TA spectra (see Fig. ) representing a pre-active intermediate hamper efficient Rh I formation.