CAT1-3 demonstrates the XB-donor effect, emphasising that the activation energy of the reaction is in an inverse relationship with the polarisation of the XB-donor. The energy barriers calculated for the reaction under the catalysis of CAT1, CAT2, CAT4, CAT6, and I 2 were observed to be higher than the un-catalysed reaction, suggesting that the XB-interaction within the O-activated TS1 of the Michael addition is relatively weak and ineffective, contradictory to experimental findings reported in literature. Similar to the unusually low σ-hole observed for CAT6 (as shown in Figure ), the activation energy for CAT6 followed a similar trend, exhibiting the highest activation energy amongst all the iodine-based catalysts (CAT3-8). Although the trend of activation energy remains consistent for both the π-type and Oactivation modes, the π-type activation mode shows energetic data that aligns more closely with experimental observations. Notably, when considering the O-activation mode within the CAT6 and I 2 catalysed TS1, the calculated activation energy suggests that the catalyst has a higher activation energy than the un-catalysed system, implying that both catalysts are not effective (Figure ). In contrast, the energetic data for the π-type activation mode indicate much lower activation energy for CAT6 and I 2 catalysed TS1 (Figure ), suggesting that both catalysts perform better than the un-catalysed reaction, in total agreement with the literature. Relative to the O-activation mode, the energy barriers linked with the πtype activation mode offer theoretical predictions that align more closely with experimental observations. This is evident in the depiction of the robust catalytic activity exhibited by I 2 , as supported by experimental results. In summary of the analysis of the two activation modes, a structural comparison was conducted. The specific focus was on the energy required for the rotation of the dihedral angle α within the bidentate catalytic framework (refer to supporting information, Figure and Table ). This comparison involved extracting the catalyst's structure from the optimised TS1 of the Michael addition reaction and subsequently comparing it structurally and energetically to the monomeric catalyst structure. The results, as presented in Table , indicates that a positive deformation energy suggests the optimised monomeric catalyst is more stable relative to the structure of the catalyst within TS1. In particular, our findings consistently revealed relatively lower deformation energies in the π-type activated systems, indicating a less energetically demanding conformational change from the isolated to the π-type activated substrate-bound state in contrast to the O-activation mode. Interestingly, CAT6 exhibited the highest deformation energy in both the O-activated and π-type activated systems, therefore explaining the unusually high activation energy displayed by CAT6 relative to other iodine-based organocatalysts, as depicted in Figures and.