Intercalation of diamines into zirconium phosphate-phosphite: A layered compound with asymmetric layers

Abstract

Many primary diamines H₂N(CH₂)_nNH₂ (all the members withn ranging from 0 to 12 with the exception ofn =I 1) have been intercalated within the phosphate regions of layered zirconium phosphate-phosphite. As a general rule, intercalation occurs in two steps that are not well differentiated. The first one leads to intercalation compounds in which the diamines are arranged with their alkyl chain oriented parallel to the layers; the second one to the fully intercalated compounds. These latter compounds have composition Zr(HPO₄)_0.7(HPO₃)1,3-yNH₂(CHn2)·NH₂, withy ranging from 0.36 to 0.49 depending on the nature of the diamine. Not all the diamine molecules are thus diprotonated and they show a tendency to reach a y value of 0.5, corresponding to the total occupancy of the crystal sites available for intercalation. Diamines are arranged as a monolayer of extended molecules and an evident even-odd alternation of the interplanar spacing has been observed.

A comparison with the intercalation ofα-zirconium phosphate for the same diamines is also made.