Synthesis, characterisation and anion exchange properties of copper, magnesium, zinc and nickel hydroxy nitrates

Anion exchange reactions of four structurally related hydroxy salts, Cu2(OH)3NO3, Mg2(OH)3NO3, Ni2(OH)3NO3 and Zn3(OH)4(NO3)2 are compared and trends rationalised in terms of the strength of the covalent bond between the nitrate group and the matrix cation. Powder X-ray diffraction (PXRD), Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and elemental analysis are used to characterise the materials. Replacement of the nitrate anions in the zinc and copper salts with benzoate anions is possible although exchange of the zinc salt is accompanied by modification of the layer structure from one where zinc is exclusively six-fold coordinated to a structure where there is both six- and four-fold zinc coordination. Magnesium and nickel hydroxy nitrates, on the other hand, hydrolyse to their respective metal hydroxides.