Infrared and Raman spectroscopic and theoretical studies of nonaaqua complexes of trivalent rare earth metal ions

Mink, János and Skripkin, Mikhail Yu and Hajba, László and Németh, Csaba (2005) Infrared and Raman spectroscopic and theoretical studies of nonaaqua complexes of trivalent rare earth metal ions. SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY, 61 (7). pp. 1639-1645. ISSN 1386-1425

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Abstract

Mini-Symposium on Molecular and Biomolecular Spectroscopy held in Honour of James R Durig Location: Kansas City, MO Date: APR 28-29, 2005 Abstract: Infrared (IR), far-infrared (far-IR) and Raman spectra have been recorded of the hydrated lanthanide(III) trifluoromethanesulfonates, [Ln(OH2)(9)](CF3SO3)(3), (Ln=La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu), and also for the deuterated [La(OD2)(9)](CF3SO3)(3) compound. This has enabled complete assignments of all seven metal-oxygen stretching modes for the first time. Force constant calculations have been performed for an LnO(9)(3+) moiety, with a tricapped trigonal prismatic oxygen atom arrangement in D-3h point group symmetry. The lanthanide contraction in reflected in continuously increasing trends for the averaged Ln-O stretching frequencies and force constants with increasing inverse of ionic radii. The stretching force constants increased from 0.81 to 1.16 Ncm(-1) for the LnO(6) prism in the series from La to Lu, while those for the capping LnO(3) bonds increased from 0.49 to 0.65 Ncm(-1). The Ln-O stretching force constants showed a smooth correlation with the Ln-O bond distances to the prism oxygen atoms, while the correlation to the Ln-O capping oxygen atoms has a different shape, reflecting the increased ligand-ligand repulsion with decreasing lanthanide ion size.

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