Extended Members of the Layered Rare‐Earth Hydroxide Family, RE₂(OH)₅NO₃·nH₂O (RE = Sm, Eu, and Gd): Synthesis and Anion‐Exchange Behavior

Three new layered rare‐earth hydroxides (LRHs), RE(OH) 2.5 (NO 3 ) 0.5 · x H 2 O (RE = Gd, Eu, and Sm), have been prepared by a hydrothermal reaction. These materials correspond to the extended members of the RE 2 (OH) 5 NO 3 · n H 2 O (RE = the rare‐earth series) family. Although it has been suggested that the LRH structure seems to be kinetically favored by yttrium or (the second half of) the small rare‐earth ions, an appropriate control of pH conditions for the hydrothermal reaction could extend this family to the larger rare‐earth ions in the present study. The ion‐exchange reactions between NO 3 – and diverse organic anions (a series of organic carboxylates, 1‐alkanesulfonates, and alkylsulfates) were successfully carried out in the gallery of layered rare‐earth hydroxides, RE 2 (OH) 5 NO 3 · n H 2 O (RE = Gd, Eu, and Sm). The FTIR spectra of the LRH hosts and some selected organic anion‐exchanged derivatives clearly revealed the absence of nitrate and the appearance of characteristic bands attributed to carboxylate and sulfonate groups after the exchange reactions. Despite a large expansion of interlayer spacing, the layered gadolinium hydroxide and the long alkyl chain anion‐exchanged derivative showed a similar paramagnetic behavior.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)