Spectroscopic characterization of chosen Ln(III) polyoxometalate complexes with organic counter cations in solid and in non-aqueous solutions

Abstract

Polyoxometalate (POM) compositions containing organic counter cations and SiMo 2W 9O 39 8− polyanion have been synthesized using extraction. Several compounds with counter ions containing phosphorus such as: Ph 3P +CPh 3, Ph 3P +Et, Ph 3P +C 16H 33, Ph 4P +, Bu 4P + were obtained and their Eu(III) complexes synthesized. Luminescence characterization of the europium complexes concerning their intensities, quantum yields and luminescence lifetimes of Eu(III) ion both in DMF solutions and solid are discussed. The complexation study has been carried out analyzing absorption spectra of Nd(III) ion in the range of its hypersensitive transition ( 4I 9/2 → 2H 9/2). Results indicated formation of the Ln(POM) 2 sandwich complexes. Computer-assisted target factor analysis has been applied to evaluate the spectra of Nd(III) in DMSO solutions containing varying amounts of the POM. The conditional formation constants with lg β 12 = 8.6 ± 0.5, lg β 12 = 8.2 ± 0.4 and lg β 12 = 9.6 ± 0.7 were obtained for (Ph 3PEt) 5H 3SiMo 2W 9O 39, (Ph 3PC 16H 33) 7HSiMo 2W 9O 39 and (Ph 3PCPh 3) 6H 3SiMo 2W 9O 39, respectively. Studies have shown significant influence of the counter ion structure on the luminescence properties of Eu(III) in the systems studied. The most intensive luminescence and the highest value of quantum yield were observed in the case of the complex (Ph 3PCPh 3) 7H 6Eu(SiMo 2W 9O 36) 2, containing six phenyl groups in the organic counter cation.