Modulating extraction and retention of fluorinated β-diketonate metal complexes in perfluorocarbons through the use of non-fluorinated neutral ligands

Extraction of metal ions into perfluorocarbon solvents using fluorinated ligands has shown promise in a number of applications ranging from catalysis to biomedical imaging. However, the speciation of the extracted metal complexes is poorly understood hindering the design and implementation of new fluorous extraction systems. The extraction of s-, p-, d-, and f-block metal ions from the aqueous phase to the fluorous phase (perfluoro-15-crown-5 ether) with a fluorinated acetylacetonate pro-ligand was investigated and the speciation of the extracted metal complexes characterized, including coordinatively saturated mononuclear and polynuclear species and coordinatively unsaturated mononuclear species. The leaching of these species back into aqueous media was studied along with the effects of synergistic extraction using a combination of fluorinated acac and nonfluorinated neutral ligands. Our findings indicate that formation of coordinatively saturated mononuclear metal complexes in the fluorous phase is essential for retaining extracted species and suggest an important role for synergistic extraction for metal ions that do not form these types of metal complexes with acac ligands alone.