Ruthenium-based transition metal complexes, particularly Ru(II) polypyridyl motifs, exhibit attractive photophysical and photochemical properties due to the presence of many excited-state electronic configurations which are governed by ligand coordination. In general, three types of low-lying excited states are present in these complexes, namely metal-to-ligand-charge transfer (MLCT), metal-centered (MC) and ligand-centered (LC) states. Recent two-dimensional spectroscopic studies have pinpointed Ru-N and other vibrational states responsible for internal conversion between different excited states in a Ru-polypyridine complex. The relative energy order of the excited states depends on the ligand field strength and its standard reduction potential. In homoleptic Ru-polypyridyl complexes, polarization-dependent experiments have shown that the excited electron in the initial Franck-Condon state is delocalized over all ligands. However, the interactions of the chromophore with solvent molecules leads to rapid decoherence and localization of the electronic density on one of the ligands. Due to the Ru heavy-atom effect, intersystem-crossing rates in Ru-complexes are large and the triplet excited states are often formed within the first hundred femtoseconds after photoexcitation. The complexes with lowest-energy MLCT states tend to have long excited-state lifetimes and decent photostability, while the presence of close-lying MC states generally shortens the lifetimes and leads to ligand dissociationbased photochemistry. As the ligand conjugation is increased, the long-lived triplet LC states tend to dominate the photophysical behavior of Ru-polypyridyl complexes. Terpyridine (terpy) Ru(II) complexes tend to exhibit relatively short excited-state lifetimes. For example, the lifetime of Ru(terpy)2 2+ is only 250 ps, and this behavior has been attributed to the unfavorable bite angle of the terpy ligand, which weakens the ligand field in Ru-terpy complexes. One consequence of this is weak splitting of d orbitals and a lowering of MC (π(t2g) → *σ(eg)) state energies. For example, variable-temperature emission spectroscopy revealed that the MC state in Ru(terpy)2 2+ is only 0.2 eV above the MLCT (π(t2g) → *π(terpy)) state, while the corresponding energy difference in Ru(bpy)3 2+ is 0.5 eV. These energy differences are also consistent with DFT-calculated values. The lifetime of bis(tridentate) Ru(II) complexes can be improved either using tridentate ligands with improved bite angles or by incorporation of strong -donating ligands. The redistribution of electron density in MLCT excited states often modulates the pKa values of Ru-based complexes, leading to proton-coupled processes. In general, acid/base groups will become either more acidic due to the electronic density depletion at the metal center in the MLCT states, or more basic due to the accumulation of the electronic density at the accepting ligand orbital of the MLCT state. As a consequence, the acid/base groups located on the ligand that is not directly involved in the MLCT state will become more acidic in the excited state. For example, the cyano ligands in Ru(bpy)2(CN)2 possess basic nitrogen atoms with a ground-state pKa value of 0.12. In the Ru(d) → bpy( * ) MLCT state, the pKa value of the protonated cyano group shifts to a value of pKa * =-5.7, reflecting the significant electronic depletion on the neighboring Ru center. On the other hand, the acid/base groups located on the ligand that accepts the electronic density upon MLCT excitation will become more basic. Here, we report an investigation of electronic properties of a Ru-based complex, Ru-bpm, that contains a bipyrimidine ligand capable of accepting electrons and protons under applied potential or visible light photoexcitation (Scheme 1). Electrochemical, spectroscopic, and computational studies were utilized to investigate the ground and excited-state electron and proton transfer chemistry of Ru-bpm. From cyclic voltammetry, we find the presence of metal-centered and ligand-centered PCET processes in anodic and cathodic regions, showing the richness of the redox properties of Ru-bpm. The excited state behavior of Ru-bpm was found to be dominated by a Ru → bpm MLCT state which was surprisingly short-lived (decaying on the picosecond timescale). A detailed pH-dependent study revealed that the most likely reason for the fast excited-state deactivation in Ru-bpm is the formation of a hydrogen-bonded complex with the surrounding solvent molecules which causes an increased rate of nonradiative decay via vibrational energy transfer to the solvent.