To establish a solid basis for investigating a series of XB-based organocatalytic scaffolds, we conducted a comprehensive analysis of the electronic properties of a diverse range of monodentate and bidentate XB-donors (I 2 and CAT1-8, Scheme 1). In accordance with the σ-hole theory 14 the electronic properties of catalysts were investigated through MEP calculations. First, we compared the relative V max of the MEP in a series of bidentate XBdonor catalysts, exhibiting different XB-donor atoms, as illustrated in Figure (CAT1-3). As anticipated, the size of the σ-hole was in direct correlation with the polarisability of the XB-donor atom. The iodine atom being the most polarisable of all assessed XB donor atoms, possessed the highest V max and thus the largest σ-hole (see supporting information Figure -S10). Subsequently, an in-depth examination of the effect of the substituent on the σ hole was performed, maintaining a constant XB-donor atom while varying the catalytic scaffolding. The investigation focused primarily on evaluating factors such as denticity, substituent placement, and electron-withdrawing capacity of different catalytic scaffolding (Figure ). The correlation between elemental composition and the size of the σ-hole was observed for both homoatomic I 2 and heteroatomic CAT4. Notably, the heteroatomic CAT4 displayed a larger V max compared to the former, attributed to a more pronounced polarisation effect within the catalytic scaffolding. The polarisation effect was further investigated in CAT3, CAT5 and CAT6, where the electron-withdrawing capacity of the scaffolding was varied. In the case of replacing the imidazolium moiety with the more electron-withdrawing benzimidazolium group (CAT3 to CAT5) V max for the σ-hole increased slightly from 0.267 a.u. to 0.271 a.u. However, the opposite effect was observed upon the incorporation of a trifluoromethyl group ortho to the benzimidazolium moieties as seen in CAT6, resulting in a reduced V max of 0.263 a.u. Consequently, CAT7 and CAT8 were computationally suggested, in order to explore the impact of the placement of the trifluoromethyl group within the catalytic scaffolding, resulting in an overall increase in V max (Figure and Figure ). In general, the trend discussed for the MEP analysis translated into the energy barriers calculated for TS1 of the Michael addition of indole to trans-crotonophenone (Figure ).