Preferential Solvation of an Asymmetric Redox Molecule

The fundamental correlations between solubility and solvation structure for the electrolyte system comprising N-(ferrocenylmethyl)-N,N-dimethyl-N-ethylammonium bistri-fluoromethylsulfonimide (Fc1N112-TFSI) dissolved in a ternary carbonate solvent mixture is analyzed using combined NMR relaxation and computational methods. Probing the evolution of the solvent solvent, ion solvent and ion ion interactions with an increase in solute concentration provides a molecular level understanding of the solubility limit of the Fc1N112-TFSI system. An increase in solute concentration leads to pronounced Fc1N112-TFSI contact-ion pair formation by diminishing solvent solvent and ion solvent type interactions. At the solubility limit, the precipitation of solute is initiated through agglomeration of contact ion pairs due to overlapping solvation shells.