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Proton and Deuteron Exchange in TTB‐Like Na 1.2 Nb 1.2 W 0.8 O 6 : Structural Characterization and Spectroscopic Study
Author(s) -
Sanjuán M. Luisa,
Kuhn Alois,
Azcondo M. Teresa,
GarcíaAlvarado Flaviano
Publication year - 2008
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200700706
Subject(s) - chemistry , orthorhombic crystal system , crystallography , raman spectroscopy , tetragonal crystal system , deprotonation , neutron diffraction , octahedron , proton , deuterium , superstructure , ion , crystal structure , atomic physics , physics , organic chemistry , quantum mechanics , optics , oceanography , geology
Proton‐ and deuteron‐exchange reactions have been performed on Na 1.2 Nb 1.2 W 0.8 O 6 with the tetragonal tungsten bronze (TTB) structure. Na + /H + and Na + /D + ion exchange occurs when aqueous nitric acid solutions are used as the exchanging agent. Up to two out of the three Na + ions are readily exchanged to yield crystalline powder samples. The ion‐exchange reaction proceeds topotactically, in other words the basic TTB structure is retained, although X‐ray and electron diffraction reveal that the exchange process produces an orthorhombic supercell which possesses a true unit cell based on a ≈ 2√2 a TTB , b ≈ √2 a TTB , c = 2TTB. The nature of the hydrogenated species has been analyzed by means of IR and Raman spectroscopy on both parent and exchanged compounds. The results are interpreted in terms of short M–O (M = Nb or W) bonds formed through the trapping of two protons or deuterons close to the oxygen ions of the [MO 6 ] octahedra. The band assigned to the short M–O bonds disappears after deprotonation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)