MS16-P02 Tunable crystal structure and proton conductivity of lanthanide nitrilotris-methylphosphonatesMetal phosphonates are multifunctional solids with remarkable stability and proton conducting properties owing to their structure is usually composed of extended hydrogen-bond networks that favor proton transfer pathways . Moreover, these properties can be enhanced by appropriate modification of the synthesis conditions [2, 3].
In this communication, a new family of isostructural 2D layered compounds based on lanthanide nitrilotris-methylphosphonates is reported. These compounds have been isolated at room temperature and have the general formula Ln[N(CH2)3(PO3H2)2(PO3H)(H2O)]SO4·2H2O (Ln= Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er and Yb). The coordination environment of Ln3+ is composed by eight oxygen atoms from three different ligands and two oxygens from bound waters. This connectivity creates positive charged layers connected to sulfate ions through hydrogen-bonds. These compounds show promising proton conductivity with values ranging between 7.6·10-2 and 3.8·10-2 S·cm-1 at 80 °C and 95% RH and low activation energy corresponding to Grotthuss-type proton transfer mechanism. In addition, a structural transformation occurs at T > 70 °C accompanied by a remarkable enhanced conductivity. Studies on the structure-properties relationships will be discussed.References:
 Metal phosphonate Chemistry: from synthesis to applications. 1st ed., edited by A. Clearfield, K. D. Demadis, RSC-Publishing, Cambridge.
 M. Bazaga-García, G. K. Angeli, K. E. Papathanasiou, I. R. Salcedo, P. Olivera-Pastor, E. R. Losilla, D. Choquesillo-Lazarte, Gary B. Hix, A. Cabeza, K. Demadis. (2016). Inorganic Chemistry, 55, 7414-7424.
 A. Cabeza, P. Olivera-Pastor, R. M. P. Colodrero. (2015). Tailored Organic-Inorganic Materials. Eds. E. Brunet, J. L. Colón, A. Clearfield. Ed. John Wiley & Sons, Inc. Ch. 4, 137-191.
Keywords: metal phosphonates, proton conductivity, crystal structure