CuII hydroxy salts: Characterization of layered compounds by vibrational spectroscopy

Abstract

Copper hydroxy salts with a layer-type structure and general composition Cu2(OH)3X (X = NO3-, CH 3COO- and ClO4-) were synthesized by co-precipitation (nitrate and acetate salts) and ion exchange (perchlorate salt) methods. The isolated polycrystalline solids were characterized by X-ray diffractometry, thermogravimetric analysis and vibrational spectroscopy. A weak band at 336 and 345 cm-1 (Raman spectrum) of the nitrate and perchlorate salts, respectively, was tentatively assigned to the nCu-O (anion). In Cu2(OH)3NO3 the nitrate ion has a C 2v symmetry and, accordingly, a splitting in the E' modes is observed. The same happens to the hydroxy perchlorate salt with the degeneracy breakdown of the F2 modes (free ClO4-) at 630 and 1100 cm-1 leading to band splitting. For the carboxylate salt, the small difference in the energy of VasC-O and vs C-O (Δ=143 cm-1) suggests that hydrogen bonding with neighbor OH group may be present. Nitrate, carboxylate and perchlorate are monocoordinated to copper(II) in the investigated salts. © 2006 Sociedade Brasileira de Química.