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Complexation‐Induced Supramolecular Assembly Drives Metal‐Ion Extraction
Author(s) -
Ellis Ross J.,
Meridiano Yannick,
Muller Julie,
Berthon Laurence,
Guilbaud Philippe,
Zorz Nicole,
Antonio Mark R.,
Demars Thomas,
Zemb Thomas
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201403859
Subject(s) - supramolecular chemistry , amphiphile , metal ions in aqueous solution , van der waals force , chemistry , aqueous solution , aqueous two phase system , micelle , phase (matter) , solvation , metal , ion , chemical physics , molecule , organic chemistry , polymer , copolymer
Combining experiment with theory reveals the role of self‐assembly and complexation in metal‐ion transfer through the water–oil interface. The coordinating metal salt Eu(NO 3 ) 3 was extracted from water into oil by a lipophilic neutral amphiphile. Molecular dynamics simulations were coupled to experimental spectroscopic and X‐ray scattering techniques to investigate how local coordination interactions between the metal ion and ligands in the organic phase combine with long‐range interactions to produce spontaneous changes in the solvent microstructure. Extraction of the Eu 3+ –3(NO 3 − ) ion pairs involves incorporation of the “hard” metal complex into the core of “soft” aggregates. This seeds the formation of reverse micelles that draw the water and “free” amphiphile into nanoscale hydrophilic domains. The reverse micelles interact through attractive van der Waals interactions and coalesce into rod‐shaped polynuclear Eu III ‐containing aggregates with metal centers bridged by nitrate. These preorganized hydrophilic domains, containing high densities of O‐donor ligands and anions, provide improved Eu III solvation environments that help drive interfacial transfer, as is reflected by the increasing Eu III partitioning ratios (oil/aqueous) despite the organic phase approaching saturation. For the first time, this multiscale approach links metal‐ion coordination with nanoscale structure to reveal the free‐energy balance that drives the phase transfer of neutral metal salts.