IR AND X-RAY-POWDER DIFFRACTION STUDIES ON BA2ME(HCOO)(6)CENTER-DOT-4H(2)O (ME = CO, NI, ZN)

It has been established that the double salts Ba2Me(HCOO)(6) . 4 H2O ( Me = Co, Ni, Zn) are isostructural with Ba2Cu(HCOO)(6) . 4 H2O (trincl inic space group P1 = C-i(1)). The infrared spectra of the double salt s and their deuterated analogues have been recorded and the internal m odes of the formate groups and the water molecules are reported. The a nalysis of the infrared spectra indicates that some of the internal fo rmate modes (nu(3) and nu(4)) reflect the existence of three crystallo graphically independent formate ions. The comparatively large frequenc y separations between the asymmetric and symmetric C-O stretching mode s is a criterion for the different C-O bond lengths within each format e groups. The number and the positions of the bands in the high freque ncy range (4000-2300 cm(-1)) are evidence for the existence of two ine quivalent water molecules. The appearance of four uncoupled O-D modes in the spectra of the isotopically dilute samples shows that the water molecules are asymmetric. The librational modes of the water molecule s are discussed as well.