Different approximation methods were used to predict the quintet lifetime in the substituted complexes. In two of these approaches the Arrhenius equation was invoked to estimate the quintet lifetime based on quintet-singlet potential barriers obtained either by shifting PES by the DFT energy differences, or directly from MECP DFT calculations. In two other, more quantum mechanically based approaches the lifetimes were determined using wave-function overlaps and coupling strengths between the states involved. The correspondence between the calculated quintet lifetimes and those determined from the transient absorption experiments is rather satisfactory, which demonstrates the validity of such approaches towards estimating excited state lifetimes.