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oai:riuma.uma.es:10630/210202026-02-03T11:32:38Zcom_10630_2254col_10630_37953

Bazaga-García, Montse Papadaki, M. Pérez-Colodrero, Rosario Mercedes Olivera-Pastor, Pascual Losilla, Enrique R. Nieto-Ortega, Belén García-Aranda, Miguel Ángel Choquesillo-Lazarte, Duane Cabeza-Díaz, Aurelio Demadis, Konstantinos D. 2021-03-04T10:27:32Z 2021-03-04T10:27:32Z 2014-12-20 Chem. Mater. 2015, 27, 424−435 https://hdl.handle.net/10630/21020 10.1021/cm502716e The structural and functional chemistry of a family of alkali-metal ions with racemic R,S-hydroxyphosphonoacetate (M-HPAA; M = Li, Na, K, Cs) are reported. Crystal structures were determined by X-ray data (Li+, powder diffraction following an ab initio methodology; Na+, K+, Cs+, single crystal). A gradual increase in dimensionality directly proportional to the alkali ionic radius was observed. [Li3(OOCCH(OH)PO3)-(H2O)4]·H2O (Li-HPAA) shows a 1D framework built up by Li-ligand “slabs” with Li+ in three different coordination environments (4-, 5-, and 6-coordinated). Na-HPAA, Na2(OOCCH(OH)PO3H)(H2O)4, exhibits a pillared layered “house of cards” structure, while K-HPAA, K2(OOCCH(OH)PO3H)(H2O)2, and Cs-HPAA, Cs(HOOCCH(OH)-PO3H), typically present intricate 3D frameworks. Strong hydrogen-bonded networks are created even if no water is present, as is the case in Cs-HPAA. As a result, all compounds show proton conductivity in the range 3.5 × 10−5 S cm−1 (Cs-HPAA) to 5.6 × 10−3 S cm−1 (Na-HPAA) at 98% RH and T = 24 °C. Differences in proton conduction mechanisms, Grothuss (Na+ and Cs+) or vehicular (Li+ and K+), are attributed to the different roles played by water molecules and/or proton transfer pathways between phosphonate and carboxylate groups of the ligand HPAA. Upon slow crystallization, partial enrichment in the S enantiomer of the ligand is observed for Na-HPAA, while the Cs-HPAA is a chiral compound containing only the S enantiomer. eng open access Química inorgánica Tuning Proton Conductivity in Alkali Metal Phosphonocarboxylates by Cation Size-Induced and Water-Facilitated Proton Transfer Pathways journal article