FTIR and Raman spectra of Na 2 Cu(SO 4 ) 2 • 2H 2 O and (CH 3 NH 3 ) 2 M(II) (SO 4 ) 2 • 6H 2 O with M (II)؍ Cu, Zn, and Ni are recorded and analyzed. Bands are assigned on the basis of SO 2؊ 4 , CH 3 NH ؉ 3 , and H 2 O vibrations. The lifting of degeneracies of 2 , 3 , and 4 modes and the appearance of 1 and 2 modes in the IR spectra confirm the lowering of symmetry of the SO 2؊ 4 ion from T d to C 1 in all of the title compounds. Bands obtained indicate that the distortion of the SO 2؊ 4 ion in the four crystals are in the order, (
The appearance of NH 3 stretching modes at wavenumbers lower than the values obtained for the free ion indicates the presence of hydrogen bonds between NH 3 and SO 2؊ 4 groups. The appearance of multiple bands in the bending and rocking mode regions and the broad nature of stretching modes show the existence of at least two symmetrically inequivalent water molecules in Na 2 Cu(SO 4 ) 2 • 2H 2 O. The shifting of stretching modes to lower wavenumbers and bending modes to higher wavenumbers of water molecules confirms the existence of strong hydrogen bonds in the crystal which is in agreement with the X-ray data. Bands indicate the presence of strong hydrogen bonds involving water molecules in (CH 3 NH 3 ) 2 Cu(SO 4 ) 2 • 6H 2 O and (CH 3 NH 3 ) 2 Zn(SO 4 ) 2 • 6H 2 O and of lesser strength in (CH 3 NH 3 ) 2 Ni(SO 4 ) 2 • 6H 2 O. 1997 Academic Press EXPERIMENTAL Na Cu(SO ) • 2H O (here after referred to as NaCu) was prepared by dissolving equimolar quantities of