While ion-pairs 1 and 2 are in slow exchange on the NMR time scale, diffusion is an even slower process, and the diffusion of each species influences the diffusion of all others related by the equilibria shown. As mentioned in the introduction, ESI would not be possible unless excess ions (of the charge under study) are present at the charged droplet interface. In polar media, one can thus expect that OSIP 1 will be in exchange with solvated cations (and anions) and since the [Cp2ZrMe2AlMe2] + cation has a much smaller size, the averaged dimensions of ionpair 1 will be significantly reduced compared to the situation in toluene. The effect will even be seen for ISIP 2 but to a lesser extent as it is indirectly coupled to the third equilibrium.