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Publication Type
Journal Article
UWI Author(s)
Author, Analytic
Alleyne, Bert D.; Hall, Lincoln A.; Kahwa, Ishenkumba A.; White, Andrew J.; Williams, David J.
Author Affiliation, Ana.
Department of Chemistry
Article Title
Comparative study of the luminescence properties of the europium (III) complexes of the squarate, phenylsquarate, and (Diphenylamino)squarate ligands
Medium Designator
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Connective Phrase
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Journal Title
Inorganic Chemistry
Translated Title
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Reprint Status
Refereed
Date of Publication
1999
Volume ID
38
Issue ID
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Page(s)
6278-84
Language
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Connective Phrase
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Location/URL
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ISSN
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Notes
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Abstract
Reaction of EuCl3.6H20 with 3-phenyl-4-hydroxycyclobut-3-ene-1,2-dione (phenylsquarate) in methanol produces the polymeric complex {Eu(-C6H5C4O3)2(C6H5C4O3)2(CH3OH)2(H2O)2.(CH3OH)}n (1) which crystallizes in the space group P21/n with a = 13.4049(5) , b = 13.7043(7) , c = 18.5026(6) , = 106.351(4), and Z = 4. The Eu(III) ion is eight coordinate with two bridging and two pendant phenylsquarate ligands, the coordination polyhedron being completed by two aqua and two methanol ligands. The emission spectra of 1 and the already reported europium (III) squarate, [Eu(H2O)4]2(C4O4)3 (2), and europium (III) (diphenylamino) squarate, {Eu[-C6H5)2-NC4O3]2[C6H5)2NC4O3][NO3][H2O]4}2.4H2O (3) show emissions dominated by the Eu3+(5D0 7Fj) transitions which are typical for Eu3+ species in low-symmetry sites. For 1 the emission occurs at room temperature and is apparently sensitized by the phenyl substituents on the phenylsquarate ligand groups; for 2 and 3 the emission is only observed at low temperature (77 K). The broad band (370-575 nm) in the excitation spectrum of 3 at 77 K is consistent with excimer formation, which can be attributed to enhanced p-p interactions between the C4- cycles of neighboring phenylsquarate ligand groups whose centroid...centroid separation decreases from 3.630(7) at room temperature (293 K) to 3.565(7) at 96 K. The temperature dependence of the luminescence of all three complexes revealed strong Eu...Eu interactions which keep the energy transport process in the dynamic regime.....
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