INFRARED STUDY ON THE HYDRATION OF MN2+, FE2+, CO2+, LA3+, ND3+, DY3+, AND YB3+ IONS IN DILUTE AQUEOUS-SOLUTION

OD stretching vibration spectra of Mn2+, Fe2+, Co2+, La3+, Nd3+, Dy3+, and Yb3+ perchlorates in dilute (0.2-0.4 M) aqueous solution were obtained using infrared spectroscopy. Intensities, bandwidths, and peak positions of the hydrated cation bands are reported. The currently studied first-row transition-metal ions all have a similar effect on the coordinated water (HDO) molecules and give rise to OD stretching vibration bands at 2427 (2) cm-1. Qualitatively similar spectra were obtained for the trivalent lanthanide perchlorate solutions, with a single OD band from cation-perturbed HDO molecules. This implies that the lanthanide ions only perturb the nearest-neighboring water molecules, which thus constitute the primary hydration shell, and to a similar extent as do the divalent cations. The obtained hydration numbers for the lanthanide ions are 7.8 (6) (La), 8.0 (6) (Nd), 8.7 (6) (Dy), and 8.8 (6) (Yb).