Cyclometalated ruthenium(II) complexes having acridine moieties have been synthesized and characterized by spectroscopic methods. Protonation of the acridine nitrogen of the ruthenium(II) complexes not only causes dynamic equilibrium with remote N-heterocyclic carbene Ru=C complexes but also generates the NAD(+)-/NADH redox function driven by a proton-coupled two-electron transfer accompanying a reversible C-H bond formation in the pyridinium ring.