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Periodic Behavior of Lanthanide Coordination within Reverse Micelles.
MedLine Citation:
PMID:  23296409     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Trends in lanthanide(III) (Ln(III) ) coordination were investigated within nanoconfined solvation environments. Ln(III) ions were incorporated into the cores of reverse micelles (RMs) formed with malonamide amphiphiles in n-heptane by contact with aqueous phases containing nitrate and Ln(III) ; both insert into pre-organized RM units built up of DMDOHEMA (N,N'-dimethyl-N,N'-dioctylhexylethoxymalonamide) that are either relatively large and hydrated or small and dry, depending on whether the organic phase is acidic or neutral, respectively. Structural aspects of the Ln(III) complex formation and the RM morphology were obtained by use of XAS (X-ray absorption spectroscopy) and SAXS (small-angle X-ray scattering). The Ln(III) coordination environments were determined through use of L(3) -edge XANES (X-ray absorption near edge structure) and EXAFS (extended X-ray absorption fine structure), which provide metrical insights into the chemistry across the period. Hydration numbers for the Eu species were measured using TRLIFS (time-resolved laser-induced fluorescence spectroscopy). The picture that emerges from a system-wide perspective of the LnO interatomic distances and number of coordinating oxygen atoms for the extracted complexes of Ln(III) in the first half of the series (i.e., Nd, Eu) is that they are different from those in the second half of the series (i.e., Tb, Yb): the number of coordinating oxygen atoms decrease from 9 O for early lanthanides to 8 O for the late ones-a trend that is consistent with the effect of the lanthanide contraction. The environment within the RM, altered by either the presence or absence of acid, also had a pronounced influence on the nitrate coordination mode; for example, the larger, more hydrated, acidic RM core favors monodentate coordination, whereas the small, dry, neutral core favors bidentate coordination to Ln(III) . These findings show that the coordination chemistry of lanthanides within nanoconfined environments is neither equivalent to the solid nor bulk solution behaviors. Herein we address atomic- and mesoscale phenomena in the under-explored field of lanthanide coordination and periodic behavior within RMs, providing a consilience of fundamental insights into the chemistry of growing importance in technologies as diverse as nanosynthesis and separations science.
Authors:
Ross J Ellis; Yannick Meridiano; Renato Chiarizia; Laurence Berthon; Julie Muller; Laurent Couston; Mark R Antonio
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-1-7
Journal Detail:
Title:  Chemistry (Weinheim an der Bergstrasse, Germany)     Volume:  -     ISSN:  1521-3765     ISO Abbreviation:  Chemistry     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2013-1-8     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9513783     Medline TA:  Chemistry     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Affiliation:
Chemical Sciences & Engineering Division, Argonne National Laboratory, Argonne, IL 60439 (USA). rellis@anl.gov.
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