The Eu(III) Ion as Luminescent Probe: Investigation of the Metal-Ion Sites in a Dicyclohexyl-18-crown-6 Complex
✍ Scribed by Dominique Plancherel; Linpei Jin; Romano Massara; Jean-Claude G. Bünzli
- Publisher
- John Wiley and Sons
- Year
- 1987
- Tongue
- German
- Weight
- 466 KB
- Volume
- 70
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
The metal ion sites of the 3 : 2 complex between europium nitrate and the A-isomer of dicyclohexyl-18-crown-6, [Eu(NO,),(DCI 8C6)],[Eu(N03),], have been probed by high-resolution excitation and emission spectra at 296 and 77 K. The [Eu(N0,),l2-anion gives rise to a luminescent spectrum dominated by the SD0+7F, transition. The crystal-field splitting of the 7F, levels is close to that observed for (Phe,As),[Eu(NO,),], pointing to a structurally similar pentakis(nitrat0) species. The CDo+7Fo excitation spectrum of the two crystallographically independent complex cations displays five maxima. A detailed analysis of the corresponding and selectively excited emission spectra leads to the following conclusions. Well differentiated spectra are assigned to different conformations of the complex cation, in which half of the ligand atoms, including 0-atoms, present large thermal motions. The other spectra are very similar and arise from slightly unequivalent [Eu(NO,),(DC 18C6)]+ moieties differing in the conformation of their ethylene bridges. This demonstrates the sensitivity of the Eu(II1) ion as conformational probe in the solid state. ') 2 , Part 29 of the series 'Complexes of Lanthanoid Salts with Macrocyclic Ligands'; Part 28: [l].