Examination of excited state optimized geometries of representative T-shaped (1a) and α-diimine (S3) complexes revealed considerable differences in the type and degree of distortion between the two classes. The optimized geometry for the triplet excited state of 1a only subtly distorts from the ground state T-shaped geometry (α = 172°, β = 97° and γ = 91°) toward Y-shaped (α = 150°, β = 112° and γ = 98°). On the other hand, S3 shows a significant geometry change from square planar in the ground state (τ4 = 0.10) toward tetrahedral (τ4 = 0.58). The triplet state geometries and overlaid higher energy SOMO orbitals are illustrated in Figure . The change in bond order between the S0 and T1 states was calculated to decrease by 0.49 and 0.11 for 1a and S3, respectively (see ESI, Table for tabular data). While the bond order change is modest for the (α-diimine)Pd complex, it may be consistent with the notion that bond weakening in these complexes may occur after thermalization from the Franck-Condon state. Unfortunately, extensive efforts to optimize the geometries of the lowest singlet excited state for 1a and S3 were unsuccessful. Considering the experimentally small activation barrier of Pd(II)-C homolysis upon photoexcitation, a conical intersection between the potential energy surfaces between S1 and S0 may exist, which is a documented challenge for TD-DFT calculations. In any case, the optimized triplet states were subsequently used to estimate the free energy of bond weakening.