Document Detail

Probing the local coordination environment and nuclearity of uranyl(vi) complexes in non-aqueous media by emission spectroscopy.
MedLine Citation:
PMID:  21264387     Owner:  NLM     Status:  Publisher    
We describe the synthesis, solid state and solution properties of two families of uranyl(vi) complexes that are ligated by neutral monodentate and anionic bidentate P[double bond, length as m-dash]O, P[double bond, length as m-dash]NH and As[double bond, length as m-dash]O ligands bearing pendent phenyl chromophores. The uranyl(vi) ions in these complexes possess long-lived photoluminescent LMCT (3)Π(u) excited states, which can be exploited as a sensitive probe of electronic structure, bonding and aggregation behaviour in non-aqueous media. For a family of well defined complexes of given symmetry in trans-[UO(2)Cl(2)(L(2))] (L = Ph(3)PO (1), Ph(3)AsO (2) and Ph(3)PNH (3)), the emission spectral profiles in CH(2)Cl(2) are indicative of the strength of the donor atoms bound in the equatorial plane and the uranyl bond strength; the uranyl LMCT emission maxima are shifted to lower energy as the donor strength of L increases. The luminescence lifetimes in fluid solution mirror these observations (0.87-3.46 μs) and are particularly sensitive to vibrational and bimolecular deactivation. In a family of structurally well defined complexes of the related anion, tetraphenylimidodiphosphinate (TPIP), monometallic complexes, [UO(2)(TPIP)(thf)] (4), [UO(2)(TPIP)(Cy(3)PO)] 5), a bimetallic complex [UO(2)(TPIP)(2)](2) (6) and a previously known trimetallic complex, [UO(2)(TPIP)(2)](3) (7) can be isolated by variation of the synthetic procedure. Complex 7 differs from 6 as the central uranyl ion in 7 is orthogonally connected to the two peripheral ones via uranyl → uranium dative bonds. Each of these oligomers exhibits a characteristic optical fingerprint, where the emission maxima, the spectral shape and temporal decay profiles are unique for each structural form. Notably, excited state intermetallic quenching in the trimetallic complex 7 considerably reduces the luminescence lifetime with respect to the monometallic counterpart 5 (from 2.00 μs to 1.04 μs). This study demonstrates that time resolved and multi-parametric luminescence can be of value in ascertaining solution and structural forms of discrete uranyl(vi) complexes in non-aqueous solution.
Michael P Redmond; Stephanie M Cornet; Sean D Woodall; Daniel Whittaker; David Collison; Madeleine Helliwell; Louise S Natrajan
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-1-24
Journal Detail:
Title:  Dalton transactions (Cambridge, England : 2003)     Volume:  -     ISSN:  1477-9234     ISO Abbreviation:  -     Publication Date:  2011 Jan 
Date Detail:
Created Date:  2011-1-25     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101176026     Medline TA:  Dalton Trans     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
School of Chemistry, The University of Manchester, Oxford Road, Manchester, UKM13 9PL.
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