Layered hybrid nickel phyllosilicates and reactivity of the gallery space

Aminated phyllosilicates have been synthesized by a sol–gel process from reactions of nickel ions and three analogous trialkoxysilanes, 3-(trimethoxysilyl)propylamine, N′-[3-(trimethoxysilyl)propyl]ethylenediamine and N′-[3-(trimethoxysilyl)propyl]diethylenetriamine, in aqueous basic medium at 298 and 323 K. The inorganic–organic hybrids SILNix (x = 1–3) were denoted following the above sequence of aminated silanes, varying from one to three amino groups on the organosilanes. The amount of nickel in the SILNix matrices showed the presence of cations in two different environments: (i) octahedral sites and (ii) in the gallery space complexed by amino groups. The thermal stability decreased in the order SILNi1 > SILNi2 ≈ SILNi3. The basal peaks were associated with lamellar distances of 1.64, 2.15 and 2.45 nm for SILNix (x = 1–3), respectively. For the phyllosilicates obtained at room temperature, the values were 1.36 and 1.96 nm for SILNi1* and SILNi2*, respectively. The increased values observed from n = 1 to 3 can be attributed to the presence of organic chains in these new structures, which was confirmed by elemental analysis. The samples showed a peak at 2θ = 60° (d = 0.16 nm) indexed to the 060 reflection, characteristic of trioctahedral phyllosilicates. XRD results and IR spectroscopy suggested nickel hydroxide was not obtained. Reactions of the hybrids with 2-pyridine-carbaldehyde were carried out to evaluate the reactivity of the amino groups in the gallery space.