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aUniversity of Osnabrück, Fachbereich Physik, 49069 Osnabrück, Germany

A. ROSCA1, M. HOSSU2, D. RUSU3,* , N. JOO1, M. RUSU1,* , L. DAVID2

Affiliation

  1. “Babes-Bolyai” University, Faculty of Chemistry, 400028, Cluj Napoca, Romania
  2. “Babes-Bolyai” University, Faculty of Physics, 400084 Cluj-Napoca, Romania
  3. “Iuliu Hatieganu” University Faculty of Pharmacy, 400032 Cluj-Napoca, Romania

Abstract

The sandwich-type K6[Si(VO)Mo2W9O39]·14H2O (1) and K10[Si2(VO)MoW16O61] ·18H2O (2) complexes were prepared and investigated by means of elemental analysis and spectroscopic methods (FT-IR, UV, VIS, EPR). The analysis of the coordination mode of the vanadium ions was made by comparing the FT-IR spectra of the complexes 1 and 2 with those of the ligands K7[SiMo2W9O39] ·14H2O and K12[Si2MoW16O61]·19H2O respectively. The stretching vibration of the terminal W=Ot bonds is shifted towards higher wavenumbers in the FTIR spectra of the complexes, which indicates the involving of the terminal oxygen from W=Ot bonds in the coordination to the vanadium ions. The opposite shift of as(W-Oe-W) and as(W-Oc-W) vibrations bands shows the co-ordination of each vanadium ion at oxygen atoms from the belt region. The UV electronic spectra of the ligands and complexes exhibit two strong and broad change transfer bands at 200 nm and 250 nm, assigned to W-Ot (1) and W-Ob-W (2) transitions respectively. The visible electronic spectra in aqueous solution are typically for VIV ions in Oh distorted local symmetry. The powder EPR spectra of both complexes are axial and exhibits eight hyperfine components both in the perpendicular and the parallel bands, due to the hyperfine coupling of the unpaired electron..

Keywords

Heteropolyoxometolates, Keggin structure, Dawson structure.

Submitted at: Nov. 15, 2006
Accepted at: March 15, 2007

Citation

A. ROSCA, M. HOSSU, D. RUSU, N. JOO, M. RUSU, L. DAVID, aUniversity of Osnabrück, Fachbereich Physik, 49069 Osnabrück, Germany, Journal of Optoelectronics and Advanced Materials Vol. 9, Iss. 3, pp. 572-576 (2007)