The Z-polarization direction is weakly changing the TS barrier energy (Fig. ) and oppositely between the endo and exo isomers. Notably, the difference density in this case (Fig. ) exhibits weaker and asymetric changes to the intermolecular region. Note that the molecule is rotated by 90 degrees about the X-axis in Fig. ,f compared to Fig. for visual clarity. Additionally, the intramolecular density, especially on the bottom molecule (cyclopentadiene) shows a different symmetry compared to those shown in Fig. where the under side of the intramolecular π-bonds are accumulating electron density while the top side are being depleted. Overall, the redistribution of electron density does not facilitate the formation of the two covalent bonds and thus showcases a weaker change to the TS barrier height compared to the X-and Y-polarization directions.