“…As discussed previously, 14 the surface activity of these species can be understood from the fact that they are quite bulky and possess hydrophobic moietes, and tend to be expelled out of water in order to avoid paying the price for their high cavitation energy in water, 37 while still enjoying as much as possible the hydrophilic solvation of their polar moieties. The results are consistent with other computational results, [38][39][40] surface spectroscopy, 41 surface tension measurements at aqueous interfaces, 42 and with the interpretation of kinetic data on assisted anion extraction 43 that support the view that bulky charged species, even lacking the classical amphiphilic topology (e.g., "spherical" cryptates, 44,45 tetrahedral ions like AsPh 4 + and BPh 4 -, 46 or even +3 charged symmetrical complexes like Eu(BTP) 3 3+ where BTP is a 2,6-di(5,6-dialkyl-1,2,4-triazin-3-yl)pyridine ligand), 9 can be surface active. In the case of the studied catalytic reaction, there should be therefore an equilibrium between the bulk aqueous phase where the anionic ligands and their complexes are diluted, and the aqueous interface, where they are more concentrated, without necessarily fully covering the aqueous surface, though.…”