The character and dynamics of the low-lying excited states of [Ru(X)(X')(CO)(2)(iPr-dab)] (X = X' = Cl or l; X = Me, X' = 1; X = SnPh3, X' = Cl; iPr-dab = N,N'-diisopropyl-1,4-diazabutadiene) were studied experimentally by pico- and nanosecond time-resolved IR spectroscopy (TRIR) and (for X = X' = Cl or l) computationally using density functional theory (DFT) and time-dependent DFT (TD-DFT) techniques. The lowest allowed electronic transition occurs between 390 and 460 nm and involves charge transfer from the Ru(halide)(CO)(2) unit to iPr-dab, denoted (MLCT)-M-1/XLCT (metal-to-ligand/halide-to-ligand charge transfer). The lowest triplet state is well modeled by UKS-DFT-CPCM calculations, which quite accurately reproduce the excited-state IR spectrum in the v(CO) region. It has a (MLCT)-M-3/XLCT character with an intraligand (iPr-dab) (3)pi pi* admixture. TRIR spectra of the lowest triplet excited state show two v(CO) bands that are shifted to higher energies from their corresponding ground-state positions. The magnitude of this upward shift increases as a function of the ligands X and X' [(l)(2) < (Sn)(Cl) < (Me)(l) < (Cl)(2)] and reveals increasing contribution of the Ru(CO)(2) -> dab MLCT character to the excited state. The lowest triplet state of [Ru(Cl)(2)(CO)(2)(iPr-dab)] undergoes a similar to 10 ps relaxation that is followed by CO dissociation, producing cis(CO,CH3CN),trans(Cl,Cl)-[Ru(Cl)(2)(CH3CN)(CO)(iPr-dab)] with a unity quantum yield and 7.2 ns lifetime and without any observable intermediate. To our knowledge, this is the first example of a "slow" CO dissociation from a thermally equilibrated triplet charge-transfer excited state.