Lipophilic cage ligands: synthesis, spectroscopic properties and applications

Macropolycyclic lipophilic ligands, capable of solubilizing inorganic salts in non polar organic solvents, can be efficiently used as anion activators or ion carriers through membranes. In this context we recently reported the synthesis of new lipophilic ligands 6 assisted by the template effect of sodium cation. Due to the high rigidity imposed by the short bridging chains ligands 6 form very stable sodium complexes in non—polar media, even when very hydrophilic and poorly polarizable anions are involved. This makes it easy to perform base—promoted reactions: e.g. carbanion formation from very weak carbon acids under phase-transfer conditions. X-Ray analysis of a sodium perchlorate complex showed that the cation is embedded in a on—symtric cubic cage. The assignment of all resonances of H and C NMR spectra was achieved by using two-dimensional techniques. At room temperature the free ligan1d3 is in a fast conformational equilibrium as shown by a C NMR investigation at variable temperature. However, in the sodium perchlorate complex only the portion of the molecule on the side of the alkyl group is affected by lowering the temperature, while the remaining part showed no conforma— tional change down to -60°C. Ligands 6 were obtained by continuous extraction with n-hexane from an aqueous solution of their methoxide or fluoride sodium complexes. This allowed the preparation an the+ stuy of complexes with different metal cations, as K , Ag , Cu etc..