Outer-Sphere Water Clusters Tune the Lanthanide Selectivity of Diglycolamides Anna G. Baldwin Alexander S. Ivanov Neil J. Williams Ross J. Ellis Bruce A. Moyer Vyacheslav S. Bryantsev Jenifer C. Shafer 10.1021/acscentsci.8b00223.s001 https://acs.figshare.com/articles/journal_contribution/Outer-Sphere_Water_Clusters_Tune_the_Lanthanide_Selectivity_of_Diglycolamides/6515942 Fundamental understanding of the selective recognition and separation of <i>f</i>-block metal ions by chelating agents is of crucial importance for advancing sustainable energy systems. Current investigations in this area are mostly focused on the study of inner-sphere interactions between metal ions and donor groups of ligands, while the effects on the selectivity resulting from molecular interactions in the outer-sphere region have been largely overlooked. Herein, we explore the fundamental origins of the selectivity of the solvating extractant <i>N</i>,<i>N</i>,<i>N</i>′,<i>N</i>′-tetraoctyl diglycolamide (TODGA) for adjacent lanthanides in a liquid–liquid extraction system, which is of relevance to nuclear fuel reprocessing and rare-earth refining technologies. Complementary investigations integrating distribution studies, quantum mechanical calculations, and classical molecular dynamics simulations establish a relationship between coextracted water and lanthanide extraction by TODGA across the series, pointing to the importance of the hydrogen-bonding interactions between outer-sphere nitrate ions and water clusters in a nonpolar environment. Our findings have significant implications for the design of novel efficient separation systems and processes, emphasizing the importance of tuning both inner- and outer-sphere interactions to obtain total control over selectivity in the biphasic extraction of lanthanides. 2018-06-13 21:29:28 distribution studies metal ions Lanthanide Selectivity inner-sphere interactions Outer-Sphere Water Clusters Tune selectivity extractant N outer-sphere interactions TODGA Complementary investigations importance fuel reprocessing separation systems outer-sphere nitrate ions water clusters biphasic extraction rare-earth refining technologies nonpolar environment lanthanide extraction coextracted water Current investigations block metal ions hydrogen-bonding interactions energy systems outer-sphere region chelating agents donor groups dynamics simulations