The phenomenon of I 2 forming covalent bonds with unsaturated hydrocarbon compounds is a well-established concept and has been extensively observed in the electrophilic iodination of organic compounds using I 2 in appropriate solvents. In the context of iodofluorination of α-β-unsaturated esters, it has been reported that the iodonium cation forms a covalent 4: Structural and electronic features of the I 2 catalyst bound to the transcrotonophenone substrate in the full mechanistic pathway of the Michael addition reaction, compared to the control isolated I 2 catalyst. in a similar fashion to the observations reported herein for the π-type activated TS1 of the I 2 catalysed Michael addition reaction. Compared to other diatomic atoms in the halogen series, I 2 exhibits the lowest thermodynamic barrier for transitioning from I 2 to I -, in line with its relatively low reduction potential. Therefore, the observed conversion of I 2 to I -throughout the π-type activated Michael addition of indole to trans-crotonophenone, as documented in this study, can be considered within the expected behaviour of I 2 upon interaction with the α-β-unsaturated hydrocarbon molecules. The transitional nature of the interaction between I 2 and the α-carbon of the trans-crotonophenone serves as a driving force for the π-type activated Michael addition reaction, playing a crucial role in facilitating the transformation. Furthermore, the physical origin of π-type activated TS1 in the Michael addition reaction was examined using LMO-EDA. The main objective was to gain clarity and justification for the evident preference for the π-type activation mode in the I 2 catalysed reaction. First, the energetic components that contribute to the overall interaction energy between the indole and I 2 activated trans-crotonophenone were in the O-and π-type activation modes (Figure ).