Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
 
Energy-Transfer Process in Crystals of Chiral and Racemic Double Complex Salts of [Co(ethylenediamine)3][Tb(2,6-pyridinedicarboxylate)3]
Munetaka IwamuraToshiaki TsukudaMakoto Morita
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2007 Volume 80 Issue 6 Pages 1140-1147

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Abstract

Luminescence and energy-transfer reactions in double complex crystals of [Co(en)3][Tb(dpa)3] (en = ethylenediamine, dpa = 2,6-pyridinedicarboxylate) were investigated and compared to single crystals of rac-[Co(en)3rac-[Tb(dpa)3] (double complexes salt of racemic [Co(en)3]3+ and racemic [Tb(dpa)3]3−) and Δ-[Co(en)3rac-[Tb(dpa)3] (chiral [Co(en)3]3+ and racemic [Tb(dpa)3]3− salt). The energy-transfer rate constants from Tb3+ to Co3+ complexes were determined from the time profile of emission intensity of photo-excited TbIII ion in the double complex crystals. The emission decay profiles of rac-[Co(en)3rac-[Tb(dpa)3] were analyzed with single exponential curves. On the other hand, the profiles of Δ-[Co(en)3rac-[Tb(dpa)3] show double-exponential curves. From the X-ray analysis of crystal structures, it was found that there is only one site for [Tb(dpa)3]3− in rac-[Co(en)3rac-[Tb(dpa)3] crystal, and there are two sites in the Δ-[Co(en)3rac-[Tb(dpa)3] crystal, i.e., Δ-[Tb(dpa)3]3− and Λ-[Tb(dpa)3]3− are put in different sites in the crystal. The two rate constants obtained from the double-exponential curve of Δ-[Co(en)3rac-[Tb(dpa)3] are assigned to energy-transfer rates from Δ-[Tb(dpa)3]3− and Λ-[Tb(dpa)3]3− in the crystal. A distance dependence was determined from the obtained energy-transfer rate constants and the Tb–Co distances in the crystals according to a Dexter type electron-exchange mechanism of energy-transfer model. The energy-transfer rate constants in the crystals are comparable in magnitude with energy-transfer rates in quenching experiments in the [Tb(dpa)3]3−–[Co(en)3]3+ aqueous solution.

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© 2007 The Chemical Society of Japan
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