Premium
The Eu(III) Ion as Luminescent Probe: Investigation of the Metal‐Ion Sites in a Dicyclohexyl‐18‐crown‐6 Complex
Author(s) -
Plancherel Dominique,
Jin Linpei,
Massara Romano,
Bünzli JeanClaude G.
Publication year - 1987
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19870700717
Subject(s) - chemistry , europium , luminescence , ion , excited state , crystallography , ligand (biochemistry) , crystal structure , spectral line , lanthanide , emission spectrum , metal , ligand field theory , stereochemistry , atomic physics , biochemistry , physics , receptor , optoelectronics , organic chemistry , astronomy
The metal ion sites of the 3:2 complex between europium nitrate and the A ‐isomer of dicyclohexyl‐18‐crown‐6, [Eu(NO 3 ) 2 (DC18C6)] 2 [Eu(NO 3 ) 5 ], have been probed by high‐resolution excitation and emission spectra at 296 and 77 K. The [Eu(NO 3 ) 5 ] 2− anion gives rise to a luminescent spectrum dominated by the 5 D 0 → 7 F 2 transition. The crystal‐field splitting of the 7 F j levels is close to that observed for (Phe 4 As) 2 [Eu(NO 3 ) 5 ], pointing to a structurally similar pentakis(nitrato) species. The 5 D 0 ← 7 F 0 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 O‐atoms, Present large thermal motions. The other spectra are very similar and arise from slightly unequivalent [Eu(NO 3 ) 2 (DC18C6)] + moieties differing in the conformation of their ethylene bridges. This dimonstrates the sensitivity of the Eu(III) ion as conformational probe in the solid state.