Interactions in Lanthanide Systems. I. A Raman and Infrared Study of Aqueous Gadolinium Nitrate

Abstract

Raman spectra of aqueous gadolinium nitrate solutions, and complementary infrared spectra, have been obtained for a wide range of compositions. Detailed intensity analyses indicate that the predominant species in solutions with nitrate:gadolinium ratios less than two is Gd(NO3)2+ (β2 = 4.6 ± 0.2 at 25°C). Small concentrations of a 1:1 species are not excluded but β1 < 0.8. Higher species are significant for ratios of 3 or greater. In systems of low water content evidence is presented for a bridging, polynuclear aggregate which is fragmented by heating or addition of water or nitrate ion. Band assignments are made for the ligand. The nitrate ions in the dinitratogadolinium(III) species are not equivalent: One binds through two oxygen atoms and the other through one.