The effect of 4-halogenobenzoate ligands on luminescent and structural properties of lanthanide complexes: experimental and theoretical approaches
No Thumbnail Available
Authors
Monteiro, Jorge H. S. K.
de Bettencourt-Dias, Ana
Mazali, Italo O.
Sigoli, Fernando A.
Issue Date
2015
Type
Citation
Language
Keywords
Alternative Title
Abstract
The ligands 4-fluorobenzoate (4-fba), 4-chlorobenzoate (4-cba), 4-bromobenzoate (4-bba) and 4-iodobenzoate (4-iba) were chosen in order to synthesize europium(III), gadolinium(III) and terbium(III) complexes and compare the effect of halogens on their physical chemistry and luminescent properties. The homobimetallic complex [Eu(4-iba)3(H2O)(dmf)]2 crystallizes in the monoclinic P21/c space group with unit cell parameters a = 8.3987(9) Å, b = 25.314(3) Å, c = 14.1255(17) Å, and β = 105.347(2)°. FTIR spectroscopy indicates that the bidentate bridging mode of the carboxylato ligand was present in all complexes while bidentate chelate and a mixture of bidentate bridging and chelate modes were also found. According to emission spectra profiles and the Judd�"Ofelt parameters the halogen of ligand molecules modifies the chemical environment symmetry around the europium(III) ion in their respective complexes. The complexes [Eu(4-fba)3(H2O)2] and [Eu(4-iba)3(H2O)2] have the highest symmetry around the europium(III) while the complexes [Eu(4-cba)3]·2H2O, [Eu(4-bba)3]·5/2H2O and [Eu(4-iba)3(H2O)(dmf)]2 have the lowest. The different halogens at the para position do not change the covalence degree of Eu�"O bonds significantly, however they play a role in the ligand to metal charge transfer energies. The highest non-radiative energy transfer rates from ligand to europium(III) were found for the complexes [Eu(4-cba)3]·2H2O and [Eu(4-bba)3]·5/2H2O.
Description
Citation
Publisher
License
Copyright Not Evaluated