These catalysts feature a nitrogen atom positioned at the centre of a tetrahedron formed by carbon atoms, with three sterically hindered faces, resulting in a single accessible face for anion interaction, thereby facilitating the establishment of ion pairs (Figure ). The successful use of electrostatic interactions between the ammonium cation and the counterion holds significant promise The introduction of a second interaction point, such as a hydrogen bond (HB) donor, has been reported to influence the ion pairing process in PTCs and competes with the establishment of a HB interaction. As a result, two distinct modes of activation for these bifunctional PTCs have been proposed, wherein the catalyst can act either through ion-pair formation or hydrogen bonding.