Synthesis, crystal structure, and modelling of a new tetramer complex of europium.
A new compound with the formula [Eu4(ETA)9(OH)3(H2O)3)], where ETA is ethyl 4,4,4-trifluoroacetoacetate, has been synthesized and investigated by photoluminescence spectroscopy. The compound was characterized by means of chemical analysis, vibrational (IR), UV-vis absorption, and luminescence spectroscopies, and X-ray crystallography. The crystal structure of the [Eu4(ETA)9(OH)3(H2O)3)] complex in the solid state, determined by X-ray diffraction analysis, revealed that it crystallizes in the triclinic crystal system, space group P, with four crystallographically independent europium centers. From these structural data, the ground-state geometry of the tetramer has been calculated by using the Sparkle/AM1 model. The emission spectrum shows the characteristic transitions of the Eu3+ ion. The features displayed by the5D0-->7F0 transition in the emission spectrum are consistent with the Eu3+ ion occupying four different sites in chemical environments of low symmetries, in agreement with the X-ray data and the optimized geometry obtained from the Sparkle/AM1 model. These structural results have allowed the theoretical calculation of 4f-4f intensity parameters, including the forced electric dipole and dynamic coupling mechanisms as well as ligand singlet and triplet states, in good agreement with experiment.
Souza
Ana Paula
AP
Departamento de Química Fundamental and Centro de Ciências Exatas e da Natureza, Universidade Federal de Pernambuco, Cidade Universitária, 50590-470 Recife-PE, Brazil.
Paz
Filipe A Almeida
FA
Freire
Ricardo O
RO
Carlos
Luís D
LD
Malta
Oscar L
OL
Alves
S
S
de Sá
Gilberto F
GF