NDLI: Observation of cation ordering and anion-mediated structure selection among the layered double hydroxides of Cu(II) and Cr(III)

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Jayanthi, K. Kamath, P. Vishnu
Description	Author Affiliation: Jayanthi K ( Department of Chemistry, Central College, Bangalore University, Bangalore 560 001, India. vishnukamath8@hotmail.com.)
Abstract	Highly ordered $Cl^{−}$ and $SO_{4}^{2−}-intercalated$ layered double hydroxides (LDHs) of Cu(II) and Cr(III) are obtained when coprecipitation is carried out at low pH ∼ 5 and elevated temperature (60–80 °C). Precipitation under other conditions results in the formation of a gel. The $SO_{4}^{2−}-LDH$ exhibits weak reflections which could be indexed to the 100 and 101 planes of a supercell corresponding to a = √3 × $a_{o},$ providing direct evidence for cation ordering among LDHs by X-ray diffraction . The ordering of the M(II) and M′(III) in the metal hydroxide layer has been a subject of considerable debate in the LDH literature for the past several years and was earlier probed using short-range techniques such as NMR and EXAFS . Rietveld refinement indicates that the cation -ordered LDH adopts the structure of the 1H polytype (space group P, a = 5.41 Å, c = 11.06 Å). In contrast the $Cl^{−}-intercalated$ LDH adopts the cation -disordered structure of the $3R_{1}$ polytype (space group Rm, a = 3.11 Å, c = 23.06 Å). The $Cl^{−}-LDH$ was used as a precursor to synthesize LDHs with other anions. While $Br^{−}$ and $CO_{3}^{2−}$ (molecular symmetry, $D_{3h})$ select for the $3R_{1}$ polytype, the $XO_{3}^{−}$ (X = Br, I) ions (molecular symmetry, $C_{3v})$ select for the rare $3R_{2}$ polytype. This work demonstrates the role of the intercalated anion in structure selection of the LDH.
ISSN	14779226
Issue Number	36
Journal	Dalton Trans.
Volume Number	42
e-ISSN	13645447
Language	English
Publisher	Royal Society of Chemistry
Publisher Date	2013-09-28
Publisher Place	Great Britain (UK)
Access Restriction	Subscribed
Subject Keyword	Chemistry
Content Type	Text
Resource Type	Article
Subject	Inorganic Chemistry

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