Layered Crystalline Barium Phenylphosphonate as Host Support for n-Alkylmonoamine Intercalation

Abstract

Layered barium phosphonate, synthesized by combining the metallic salt with a phenylphosphonic acid solution, yielded Ba(HO3PC6H5)2 ·H2O (BaPP), which gives the corresponding anhydrous compound on heating. n-Alkylmonoamines intercalation into the crystalline lamellar precursor resulted in compounds having the general formula Ba(HO3PC6H5)2 ·xH2N(CH2) n CH3 ·(1−x)H2O (n=1–5). The intense infrared bands in the 1160–695 cm−1 interval confirmed the presence of the phosphonate groups attached to the inorganic layer, with sharp and intense peaks in X-ray diffraction patterns for both hydrated and anhydrous compounds. The thermogravimetric curves for both supports showed the release of water molecules and the organic moiety in distinct stages to yield a final Ba(PO3)2residue. An additional amine mass loss steps was observed for the corresponding aminated compounds. One isolated DSC peak found in the layered precursor compound contrasts by its absence in the anhydrous form and the 3P NMR spectrum presented one peak for attached phenylphosphonate groups centered at 12.4 ppm. An increase in carbon and hydrogen percentages for intercalated compounds followed the amine size chain with a corresponding decrease in nitrogen percentage. The interlayer distance (d) correlates linearly with the number of carbon atoms (n c ) of the alkylamine chains, d=1467 + 62n c and d=1688 + 60n c , for the hydrated and anhydrous compounds, respectively, permitting inference of the interlayer distance for an unknown amine.