Enrique Jaimez, Gary B. Hix and Robert C. T. Slade
A new diphosphonic acid,N,N -(diphosphonomethyl)glycine, has been prepared. The titanium(iv) salt [Ti(dpmg)] of this acid has been characterised by X-ray powder diffraction, thermogravimetry, 31P MAS NMR spectroscopy, isothermal N2 adsorption–desorption and ac conductivity measurements. Phosphorus is present in a mixture of bonded phosphonate and free phosphonic acid groups. The material is both amorphous and porous (BET specific surface area=119 m2 g-1), and its water content is relative humidity (RH)-dependent. Ti(dpmg) is a protonic conductor (at 90% RH and 90 °C, σ=3×10-2 S cm-1), with conductivity exhibiting Arrhenius-type behaviour at constant RH. Conductivity and Arrhenius parameters are strongly dependent on the water content.