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Publication Type
Journal Article
UWI Author(s)
Author, Analytic
Howell, Robertha C.,; Spence, Kirk V.N.; Kahwa, Ishenkumba A.; White, Andrew J.P.; Williams, David J.
Author Affiliation, Ana.
Chemistry; Faculty of Pure and Applied Sciences
Article Title
The preparation and crystal and molecular structures of new luminescent Schiff-base complexes featuring coupled lanthanide (III) cations
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Journal Title
Journal of the Chemical Society. Dalton Transactions
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Reprint Status
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Date of Publication
1996
Volume ID
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Issue ID
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Page(s)
961-968
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Notes
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Abstract
The reaction between salicylaldehyde, diethylenetriamine and lanthanide (III) (Ln3 +) nitrates in refluxing methanol produced new acyclic dimeric Schiff-base compounds [{LnL7 (NO3)}2] (H2L7 is the 2:1 Schiff-base condensation product of salicylaldenhyde and diethylenetriamine) in which the coupled Ln3+ ions are bridged by phenolate groups and separated by a short LnLn distance of ca. 3.81 . In contrast with lanthanide (III) dinuclear macrocyclic compounds of Schiff bases studied previously where the ligand negative charge to Ln3+ cation ratio is 1:1, chelate L7 feature a shorter Ln3+Ln3+ separtion, greater stability and enhanced electronic coupling among Ln3+-Ln3+ ion pairs. For example, [{LnL7(NO3)}2] complexes readily yielded intact dimeric species such as [{EuL7}2]+ and [Eu2L7 2(NO3)]+ during fast atom bombardment mass spectrometric analyses and exhibit Eu3+ - Eu3+ and Tb3+ -Tb3+ energy migration while macrocyclic analogues do not. However, like other phenolate Schiff-base with the temperature evolution of the Eu3+ (5D0) and Tb3+ (5D4) luminescence decay rates. Heteropair Eu3+ - Dy3+ interactions are observed; assuming a dominant dipole-dipole Eu3+ Dy3+ energy transfer mechanism the coupling constant is ca. 7 x 1-52 m6s-1....
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