Six tennolecular reaction systems Comprised Of Ru(4,4'-bis(trifluoromothyl)-2,2'-bipyridine)(3)(2+), phenols with different para substituents,, and pyridine in acetonitrile undergo proton-coupled electron: transfer (PCET) upon photoexcita, non of the metal complex. Five of these six phenols are found photooxidant and a proton to the pyridine base. The kinetics to release it concerted fashion an electron to the ruthenium for this concerted bidirectional PCET process and its relationship to the reaction free energy were compared. to the driving force dependence of reaction kinetics for unidirectional concerted proton electron transfer (CPET) between the same phenols and Ru(2,2'-bipyraZine)(3)(2+), a Combined electron/proton acceptor. The results strongly Support the concept of thermodynamic,equivalence between Separated -electron/proton acceptors and single reagent hydrogen atom acceptors., A key feature of the explored systems is the similarity betweenxriolecules employed : for bi- and unidirectional CPET.