Neutron diffraction study of ammonium oxalate monohydrate, (NH4)2C2O4.H2O

Padmanabhan, V. M.; Srikantha, S.; Ali, S. M.

doi:10.1107/s0365110x65001251

Cited by 18 publications

(5 citation statements)

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“…Ammonium oxalate monohydrate also called as “oxammite” belongs to a family of organic minerals that were formed as the result of expulsion of heavy metals from fungi, lichens, and plants. , Also, it is also an organic ternary supramolecule, which is composed of ammonium cations, oxalate anions, and water molecules. Over the past decade, there has been tremendous interest in investigating cooperative interactions and mechanical properties of supramolecular motifs under pressure. − Under ambient condition, ammonium oxalate monohydrate crystallizes in the orthorhombic structure with space group P 2 1 2 1 2 which was reported previously. − The Raman spectra and elastic constants properties of ammonium oxalate monohydrate have been investigated in recent decades. − As shown in Figure a, ammonium oxalate monohydrate exhibits a simple sandwich structure and constitutes two different commutative layers that are stacked perpendicularly to the c -axis orientation. As shown in Figure b, in the out-of-plane layer, the oxalate anions and the water molecules are tied together by NH···O hydrogen bonds in infinite zigzag chains parallel to a -axis directions.…”

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confidence: 82%

Negative Linear Compressibility in Organic Mineral Ammonium Oxalate Monohydrate with Hydrogen Bonding Wine-Rack Motifs

Qiao

Wang

Yuan

et al. 2015

J. Phys. Chem. Lett.

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Negative linear compressibility (NLC) is a relatively uncommon phenomenon and rarely studied in organic systems. Here we provide the direct evidence of the persistent NLC in organic mineral ammonium oxalate monohydrate under high pressure using synchrotron X-ray powder diffraction, Raman spectroscopy and density functional theory (DFT) calculation. Synchrotron X-ray powder diffraction measurement reveals that ammonium oxalate monohydrate shows both positive and negative linear compressibility along b-axis before 11.5 GPa. The red shift of the external Raman modes and abnormal changes of several selected internal modes in high-pressure Raman spectra further confirmed the NLC. DFT calculations demonstrate that the N-H···O hydrogen bonding "wine-rack" motifs result in the NLC along b-axis in ammonium oxalate monohydrate. We anticipate the high-pressure study of ammonium oxalate monohydrate may represent a promising strategy for accelerating the pace of exploitation and improvement of NLC materials especially in organic systems.

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confidence: 82%

Negative Linear Compressibility in Organic Mineral Ammonium Oxalate Monohydrate with Hydrogen Bonding Wine-Rack Motifs

Qiao

Wang

Yuan

et al. 2015

J. Phys. Chem. Lett.

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“…However, experimentally the opposite is found: only few exceptions from planarity ( D 2 h ) have been reported so far. If crystal structures with R values >14% are disregarded, only NaHC 2 O 4 ·H 2 O (twist angle of 13°), KHC 2 O 4 (13°), − (NH 4 ) 2 C 2 O 4 ·H 2 O (27°), − (NH 4 ) 2 C 2 O 4 ·H 2 O 2 (28°), and BaC 2 O 4 ·0.5H 2 O (30°) remain to be considered. Evidently, in each of these instances the oxalate is involved in significant bonding interactions, i.e., H-bonds.…”

Section: Introductionmentioning

confidence: 99%

Crystal and Molecular Structures of Alkali Oxalates: First Proof of a Staggered Oxalate Anion in the Solid State

et al. 2003

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The molecular and crystal structures of solvent-free potassium, rubidium, and cesium oxalates have been determined ab initio from high-resolution synchrotron and X-ray laboratory powder patterns. In the case of potassium oxalate K(2)C(2)O(4) (a = 10.91176(7) A, b = 6.11592(4) A, c = 3.44003(2) A, orthorhombic, Pbam, Z = 2), the oxalate anion is planar, whereas in cesium oxalate Cs(2)C(2)O(4) (a = 6.62146(5) A, b = 11.00379(9) A, c = 8.61253(7) A, beta = 97.1388(4) degrees, monoclinic, P2(1)/c, Z = 4) it exhibits a staggered conformation. For rubidium oxalate at room temperature, two polymorphs exist, one (beta-Rb(2)C(2)O(4)) isotypic to potassium oxalate (a = 11.28797(7) A, b = 6.29475(4) A, c = 3.62210(2) A, orthorhombic, Pbam, Z = 2) and the other (alpha-Rb(2)C(2)O(4)) isotypic to cesium oxalate (a = 6.3276(1) A, b = 10.4548(2) A, c = 8.2174(2) A, beta = 98.016(1) degrees, monoclinic, P2(1)/c, Z = 4). The potassium oxalate structure can be deduced from the AlB(2) type, and the cesium oxalate structure from the Hg(99)As type, respectively. The relation between the two types of crystal structures and the reason for the different conformations of the oxalate anion are discussed.

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“…The intensities were corrected for absorption, and a set of observed structure factors with weights for each reflexion was obtained as described in an earlier paper (Padmanabhan, Mehdi All & Srikanta, 1965).…”

Section: Methodsmentioning

confidence: 99%

Neutron diffraction study of sodium thiosulphate pentahydrate, Na2S2O3.5H2O

Padmanabhan¹,

Yadava²,

Navarro³

et al. 1971

Acta Crystallogr Sect B

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A single-crystal neutron-diffraction investigation of sodium thiosulphate pentahydrate, Na2S203.5H20, has been made with three sets of zonal data. The structure was refined by least-squares techniques, with individual temperature factors, to an R value of 8.2%. The geometry of the $203 group and sodium-oxygen framework agree with those of X-ray studies. The positional parameters of some of the atoms differ from those p3stulated from the X-ray and nuclear magnetic resonance studies. The O-H and H-H bond distances and the H-O-H valence angle of all the five water molecules were found to be normal. The hydrogen-bond scheme falls into four classes: two strong water-thiosulphate oxygen, two weak water-thiosulphate oxygen, two water-water, and three water-sulphur hydrogen bonds. From the geometry of its surroundings one of the hydrogen atoms H(9) may be regarded as not participating in hydrogen bonding.

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Neutron diffraction study of ammonium oxalate monohydrate, (NH₄)₂C₂O₄.H₂O

Cited by 18 publications

References 2 publications

Negative Linear Compressibility in Organic Mineral Ammonium Oxalate Monohydrate with Hydrogen Bonding Wine-Rack Motifs

Negative Linear Compressibility in Organic Mineral Ammonium Oxalate Monohydrate with Hydrogen Bonding Wine-Rack Motifs

Crystal and Molecular Structures of Alkali Oxalates: First Proof of a Staggered Oxalate Anion in the Solid State

Neutron diffraction study of sodium thiosulphate pentahydrate, Na2S2O3.5H2O

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