Carbon number-dependent intercalation and interlayer amidation properties of α,ω-alkanediamines for α-titanium (2-carboxyethyl)phosphonate phosphate

Abstract

The uptake of α,ω-alkanediamines H₂N(CH₂)_nNH₂ (n = 2–10) by α-titanium (2-carboxyethyl)phosphonate phosphate, Ti(O₃PCH₂CH₂CO₂H)_1.91(HPO₄)_0.09, has been studied at 25 °C. Each diamine forms one or two intercalated phases in which the amine molecules are arranged as a monolayer with their axes tilted by 54 or 67° relative to the inorganic layer. Diamines with n  7 show a tendency to produce the high and low chain-tilt forms depending on the even and odd number of carbon atoms, respectively, but both forms coexist for n = 6. For shorter chain diamines, on the other hand, only the low-tilt form occurs for n = 3, 4 and 5 and the high-tilt form for n = 2. On heating at 150 °C or above the diammonium-exchanged solids were thermally condensed into the amide form with or without any significant release of the amine guest. The amidation temperature shows a tendency to vary up or down depending on whether the carbon number is even or odd.