Pa. Tanner et al., Synthesis, structure and spectroscopy of rare earth hypophosphites: 3. Ytterbium hypophosphite, POLYHEDRON, 19(7), 2000, pp. 863-870
Yb(H2PO2)(3) crystallizes in space group C2/m. Planar rectangular arrays of
Yb3+ ions are doubly bridged by hypophosphite ions in the b direction and
singly bridged in the c direction, giving rise to a stacking of corrugated
layers in the crystal structure. The YbO6 site symmetry is C-2h, but not fa
r from D-4h. The vibrational spectra of the hypophosphite anion have been i
nterpreted in detail using unit cell group analysis and are shown to be con
sistent with the crystallographic data. The 10 K electronic absorption spec
trum confirms the presence of two nonequivalent Yb3+ ions situated at centr
osymmetric sites in the unit cell. For the first time, the two-centre trans
itions in the vibronic sidebands have been assigned to the excitation of in
dividual unit cell group modes, showing a one-to-one correspondence with th
e vibrational spectra. The importance of moiety mode-hypophosphite mode cou
plings, and of Yb3+ -hypophosphite interactions of the type quadrupole-dipo
le, or higher, is indicated in the interpretation of the intensities of the
cooperative vibronic transitions. (C) 2000 Elsevier Science Ltd All rights
reserved.