The picrate anion as a versatile chelating counterion for the complexation of alkali and alkaline earth metal cations with ionophores: 'The picrate effect'

The special characteristics of the picrate anion as a versatile counter-ion for cation complexation are demonstrated by crystal structures. On the basis of the experimental data reported in the literature a categorization into different modes of picrate/cation interactions is proposed together with the corresponding nomenclature. The results of the present study and the analysis of the picrate versatile interactions may be used for various scientific and commercial applications since picrate is commonly used as a counter-ion in many systems involving extraction and transport of alkali and alkaline-earth metal cations. The data presented here should also be considered for systems involving picrate as counter ion where high efficiency and selectivity towards specific ion are desired. Such systems may be significantly affected from the high diversity of both the coordination and geometry of the picrate-cation interactions.