Tunable crystal structure and proton conductivity of lanthanide nitrilotrismethylphosphonates

Salcedo, Inés R.; Pérez-Colodrero, Rosario Mercedes; Hix, Gary B.; Cabeza-Díaz, Aurelio; Bazaga-García, Montse; Ramírez-Losilla, Enrique; Olivera-Pastor, Pascual

Abstract

Metal 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 [1]. 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.

Tunable crystal structure and proton conductivity of lanthanide nitrilotrismethylphosphonates

Author: Salcedo, Inés R.,Pérez-Colodrero, Rosario Mercedes,Hix, Gary B.,Cabeza-Díaz, Aurelio,Bazaga-García, Montse,Ramírez-Losilla, Enrique,Olivera-Pastor, Pascual

Year: 2018

Source: https://riuma.uma.es/xmlui/bitstream/10630/16552/7/Abstract_IRS-tunablecrystal.pdf

Tunable c ys al s uc u e and p o on conduc i i y o lan hanide ni ilo is-
me hylphosphona es.
Inés R. Salcedo1, Au elio Cabeza 1, Mon se Bazaga-Ga cía1, Rosa io M. P. Colod e o2,
Ga y Hix2, En ique R. Losilla1, Pascual Oli e a-Pas o 1.
1. Depa amen o Química Ino gánica, C is alog a ía y Mine alogía. Facul ad de
Ciencias. Uni e sidad de Málaga. Málaga, Spain
2. Wol e hamp on School o Sciences. Facul y o Science and Enginee ing. Uni e si y
o Wol e hamp on. Wol e hamp on, Uni ed Kingdom.
email: [email p o ec ed]
Me al phosphona es a e mul i unc ional solids wi h ema kable s abili y and p o on
conduc ing p ope ies owing o hei s uc u e is usually composed o ex ended
hyd ogen-bond ne wo ks ha a o p o on ans e pa hways [1]. Mo eo e , hese
p ope ies can be enhanced by app op ia e modi ica ion o he syn hesis condi ions [2,
3].
In his communica ion, a new amily o isos uc u al 2D laye ed compounds based on
lan hanide ni ilo is-me hylphosphona es is epo ed. These compounds ha e been
isola ed a oom empe a u e and ha e he gene al o mula
Ln[N(CH2)3(PO3H2)2(PO3H)(H2O)]SO4·2H2O (Ln= P , Nd, Sm, Eu, Gd, Tb, Dy, Ho, E
and Yb). The coo dina ion en i onmen o Ln3+ is composed by eigh oxygen a oms
om h ee di e en ligands and wo oxygens om bound wa e s. This connec i i y
c ea es posi i e cha ged laye s connec ed o sul a e ions h ough hyd ogen-bonds.
These compounds show p omising p o on conduc i i y wi h alues anging be ween
7.6·10-2 and 3.8·10-2 S·cm-1 a 80 °C and 95% RH and low ac i a ion ene gy
co esponding o G o huss- ype p o on ans e mechanism. In addi ion, a s uc u al
ans o ma ion occu s a T > 70 °C accompanied by a ema kable enhanced
conduc i i y. S udies on he s uc u e-p ope ies ela ionships will be discussed.
Re e ences:
[1] Me al phosphona e Chemis y: om syn hesis o applica ions. 1s ed., edi ed by A.
Clea ield, K. D. Demadis, RSC-Publishing, Camb idge.
[2] M. Bazaga-Ga cía, G. K. Angeli, K. E. Papa hanasiou, I. R. Salcedo, P. Oli e a-
Pas o , E. R. Losilla, D. Choquesillo-Laza e, Ga y B. Hix, A. Cabeza, K. Demadis.
(2016). Ino ganic Chemis y, 55, 7414-7424.
[3] A. Cabeza, P. Oli e a-Pas o , R. M. P. Colod e o. (2015). Tailo ed O ganic-
Ino ganic Ma e ials. Eds. E. B une , J. L. Colón, A. Clea ield. Ed. John Wiley & Sons,
Inc. Ch. 4, 137-191.
Keywo ds: me al phosphona es, p o on conduc i i y, c ys al s uc u e.