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Rietveld structure analysis of keatite, a rare, metastable SiO2 polymorph

  • Isabel Grosskreuz ORCID logo and Bernd Marler ORCID logo EMAIL logo
Published/Copyright: May 10, 2023
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Zeitschrift für Kristallographie - New Crystal Structures
From the journal Zeitschrift für Kristallographie - New Crystal Structures Volume 238 Issue 4

Abstract

O24Si12, tetragonal, P43212 (no. 96), a = 7.4462(1) Å, c = 8.5838(4) Å, V = 475.93(3) Å3, Z = 1, R(F) = 0.037, T = 293 K.

CCDC no.: 2259819

Tables 1 and 2 contain details of the measurement method and a list of the atom sites, respectively. Figures 1 and 2 present the crystal structure of keatite and the morphology of the crystals, respectively.

Table 1:

Data collection and handling.

Crystal: Light yellow plates; average size 3 × 3 × 0.1 μm3
Wavelength: Cu Kα radiation (1.54059 Å)
μ: 6.86 cm−1
Diffractometer, scan mode: Siemens D5000, Debye-Scherrer
N(hkl)measured 4767
N(param)refined: 16
Programs: Fullprof 2K [1], VESTA [2]
Table 2:

Fractional atomic coordinates and isotropic displacement parameters (Å2).

Atom x y z U iso
Si1 0.328230 (5) 0.11886 (9) 0.2490 (2) 0.0125 (2)*
Si2 0.4102 (2) 0.4102 (2) 0.00000 0.0125 (2)*
O1 0.4488 (3) 0.1266 (7) 0.4014 (3) 0.0195 (4)*
O2 0.1156 (4) 0.1222 (6) 0.30658 (19) 0.0195 (4)*
O3 0.3593 (5) 0.3017 (4) 0.1526 (2) 0.0195 (4)*
Figure 1: Structural representation of keatite (projection along b).
Figure 1:

Structural representation of keatite (projection along b).

Figure 2: Scanning electron micrograph of keatite.
Figure 2:

Scanning electron micrograph of keatite.

1 Source of material

Fine grained keatite crystals were synthesized according to Ferreira da Silva and Fernández Navarro [3] using a silicate gel prepared from tetraethyl orthosilicate, LiNO3, Cr ( N O 3 ) 3 , water, and heated at 830 K. The reaction mixture consisted of 0.5 Cr2O3: 5 Li2O: 94.5 SiO2. This led to a sample with 94.4 % keatite and two impurity phases: dilithium phyllodisilicate (4.3 %) [4] and quartz (1.3 %). The sample has a light yellow color due to the small chromium content.

2 Experimental details

Scanning electron micrographs were taken using a Zeiss Merlin Gemini 2 electron microscope. The samples were gold coated prior to analysis. For a semi-quantitative chemical analysis, an OXFORD AZtec Energy X-ray microanalysis system attached to the electron microscope was used. The diffractometer used for collecting the powder diffraction data was equipped with a curved germanium (111) primary monochromator and a Braun linear position-sensitive detector (2θ coverage = 6°). The sample was sealed in a glass capillary (0.3 mm in diameter) to avoid a preferred orientation of the crystals. No absorption correction was necessary. Soft distance restraints were used for d(Si–O) = 1.61(1) Å, d(Si–Si) = 3.10(4) Å, d(O–O) = 2.62(2) Å. Isotropic displacement parameters B(iso) for Si and O atoms, respectively, were constrained to be equal. The structures of the two impurity phases were included in the refinement with fixed structural parameters.

3 Comment

Synthetic keatite, also known as “silica K” and originally named “A New Crystalline Silica”, was for the first time obtained in 1954 by hydrothermal treatment of silicic acid by P. P. Keat [5]. According to Keat (and, later, according to [3,6], [7], [8], [9], [10]) an alkaline compound like MOH or M2CO3 (M = Li, Na, K) of low concentration is necessary or at least favourable for a successful synthesis of keatite. Keatite is difficult to synthesize as a pure phase and crystallizes always as very fine-grained material. In 2013 Keatite was also discovered in nature “as a precipitate in the core of ultrahigh-pressure (UHP) clinopyroxene (Cpx) within garnet pyroxenite from the Kokchetav Massif, Kazakhstan” [11]. The structure of keatite was solved by Shropshire et al. in 1959 [12]. The authors had to use quite small single crystals, and only the intensities of (hh0) and (hhl) reflections could be determined. Relying, at that time, on film methods (Weissenberg photographs) the structure could not be refined well. The authors state: “ … the intensity measurements are less reliable than in most structure determinations”. No other structure analysis on keatite has been published, so far. Only powder data were available for the structure analysis presented here. The chemical analysis of 10 individual keatite crystals yielded an average value of Cr/Si = 0.025. Cr is slightly enriched compared to the very low value of the reaction mixture (Cr/Si = 0.005). Li is incorporated in the impurity phase dilithium phyllodisilicate. The X-ray powder data were indexed in the tetragonal crystal system proposing the space group symmetry P43212. The Rietveld refinement not only confirmed the rough structure model published by Keat [5] but led to an improved precision concerning atomic coordinates, bond lengths and bond angles. Cr could not be located in the structure of keatite. Keatite is a metastable SiO2 polymorph and does not appear in the phase diagram (p, T) of the silica polymorphs. Although the structure of keatite contains only two crystallographically independent Si sites, the framework structure is quite complex due to the high symmetry. While the framework structures of most dense silica polymorphs like quartz, tridymite and cristobalite are dominated by 6-rings of interconnected [SiO4/2] tetrahedra, the framework of keatite is predominantly constructed from 5- and 7-rings. The density of keatite calculated from the structure data is 2.516 g/cm3, a value intermediate between the ones of the high-temperature polymorph cristobalite (2.318 g/cm3) and the low temperature polymorph quartz (2.649 g/cm3). The geometrical analysis of the structure gave interatomic distances and bond angles that are typical for dense silica polymorphs.

Corresponding author: Bernd Marler, Institute of Geology, Mineralogy und Geophysics, Ruhr–University Bochum, Universitaetsstrasse 150, 44801 Bochum Germany, E-mail:

Funding source: Deutsche Forschungsgemeinschaft

Award Identifier / Grant number: MA 6641/3–1

Acknowledgements

The authors thank Hermann Gies for helpful discussions. The keatite sample was kindly provided by Brigitte Martin, Bochum.

  1. Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.

  2. Research funding: Deutsche Forschungsgemeinschaft with grant number MA 6641/3–1.

  3. Conflict of interest statement: The authors declare no conflicts of interest regarding this article.

References

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Received: 2023-03-21
Accepted: 2023-04-29
Published Online: 2023-05-10
Published in Print: 2023-08-28

© 2023 the author(s), published by De Gruyter, Berlin/Boston

This work is licensed under the Creative Commons Attribution 4.0 International License.

Articles in the same Issue

  1. Frontmatter
  2. New Crystal Structures
  3. Crystal structure of a polymorph of potassium picrate, C6H2KN3O7
  4. The crystal structure of (1E,2E)-1,2-bis(quinolin-2-ylmethylene)hydrazine, C20H14N4
  5. 5-Amino-2-chloro-4-fluoro-N-(N-isopropyl-N-methylsulfamoyl) benzamide, C11H15O3ClFN3S
  6. Crystal structure of trans-N 1,N 8-bis(2-cyanoethyl)-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, C22H42N6
  7. The crystal structure of [N-{[2-(oxy)-4-methoxyphenyl](phenyl)methylidene}alaninato]-diphenyl-silicon(IV) – chloroform (1/1), C29H25NO4Si·CHCl3
  8. Crystal structure of tetracarbonyl-{μ-[N-(diphenylphosphanyl)-N,P,P-triphenylphosphinous amide]}-bis[μ-(phenylmethanethiolato)]diiron (Fe–Fe), C48H39Fe2NO4P2S2
  9. Crystal structure of baryte from Mine du Pradet (France)
  10. The crystal structure of [(2,2′-bipyridine-6-carboxylato-κ3 N,N,O)-(6-phenylpyridine-2-carboxylate-κ2 N,O)copper(II)] monohydrate, C23H17N3O5Cu
  11. Crystal structure of bis(μ-benzeneselenolato)-(μ-[N-benzyl-N-(diphenylphosphanyl)-P,P-diphenylphosphinous amide])-tetracarbonyl diiron (Fe–Fe), C47H37Fe2NO4P2Se2
  12. The crystal structure of diaqua-methanol-κ1 O- (3-thiophenecarboxylato-κO)-(2,2′-dipyridyl-κ2 N,N′)manganese(II) 3-thiophenecarboxylate, C21H22N2O7S2Mn
  13. Crystal structure of catena-poly[tetrakis(butyl)-μ2-2-((oxido(phenyl)methylene)hydrazineylidene)propanoato-κ4 O:O,O′,N-μ2-2-((oxido(phenyl)methylene)hydrazineylidene)propanoato-κ4 O,N,O′:N′-ditin(IV)], C34H50N6O6Sn2
  14. Crystal structure of 4-chloro-N′-[(1E)-(2-nitrophenyl)methylidene]benzohydrazide, C14H10ClN3O3
  15. The crystal structure of 3-(1′-deoxy-3′,5′-O-dibenzy-β-d-ribosyl)adenine dichloromethane solvate, C49H52Cl2N10O6
  16. The crystal structure of (Z)-4-amino-N′-(1-(o-tolyl)ethylidene)benzohydrazide, C16H17N3O
  17. The co-crystal structure of etoricoxib–phthalic acid (1/1), C18H15ClN2O2S·C8H6O4
  18. Crystal structure of (glycinto-κ 2 O,N ′)-[5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane-κ 4 N,N ′,N ″,N ‴]nickel(II) perchlorate monohydrate C18H42ClN5NiO7
  19. The crystal structure of catena-poly[bis(1-ethylimidazole-k1 N)-(μ 2-benzene-1-carboxyl-3,5-dicarboxylato-κ 2 O, O′)zinc(II)], C19H20N4O6Zn
  20. Crystal structure of 3-(thiazol-2-ylcarbamoyl)-7-oxabicyclo[2.2.1]heptane-2-carboxylic acid, C11H12N2O4S
  21. Rietveld structure analysis of keatite, a rare, metastable SiO2 polymorph
  22. Crystal structure of catena-poly[(μ2-isophthalato-k3 O,O′:O″)(4-(4-pyridyl)-2,5-dipyrazylpyridine-k3 N,N′,N″)cobalt(II)] trihydrate C26H22N6O7Co1
  23. Crystal structure of 3,5–di-O-benzoyl-1,2-O-isopropylidene-α–D-ribose, C22H22O7
  24. The crystal structure of fac-tricarbonyl(6-bromo-2,2-bipyridine-κ2 N,N)-(nitrato-κO)rhenium(I), C13H7BrN3O6Re
  25. The crystal structure of (E)-N′-(4-hydroxy-3-methoxybenzylidene)-2-naphthohydrazide monohydrate, C19H18N2O4
  26. The crystal structure of 5,5′-diselanediyl-bis(2-hydroxybenzaldehyde), C14H10O4Se2
  27. The crystal structure of catena-poly[diaqua-m2-dicyanido-κ2 C:N-dicyanido-κ1 C-bis(4-(pyridin-4-yl)benzaldehyde-κ1N)iron(II)-platinum(II), C28H22N6O4PtFe
  28. Redetermination of the crystal structure of 5,14-dihydro-6,17-dimethyl-8,15-diphenyldibenzo(b,i)(1,4,8,11)tetra-azacyclotetradecine, C32H28N4
  29. Crystal structure of poly[(μ3-2-(3,5-dicarboxyphenyl) benzimidazole-6-carboxylato-κ4O:O:O′:O″)lead(II)] monohydrate, C16H10N2O7Pb
  30. The crystal structure of fac-tricarbonyl(2-pyridin-2-yl-quinoline-κ2 N,N′)-(pyrazole-κN)rhenium(I)nitrate, C20H14N4O3ReNO3
  31. Crystal structure of dibromo-dicarbonyl-bis(tricyclohexylphosphine)-osmium(II) dichloromethane solvate, C38H66Br2O2OsP2
  32. Crystal structure of poly[bis(μ 2-2,6-bis(1-imidazoly)pyridine-κ 2 N:N′)copper(II)] diperchlorate dihydrate, C22H22Cl2CuN10O10
  33. The crystal structure of fac-tricarbonyl(N-benzoyl-N,N-cyclohexylmethylcarbamimidothioato-κ2 S,O)-(pyridine-κN)rhenium(I), C23H24N3O4ReS
  34. Crystal structure of (E)-7-fluoro-2-(4-fluorobenzylidene)-3,4-dihydronaphthalen-1(2H)-one, C17H12F2O
  35. Synthesis and crystal structure of 1-((3R,10S,13S, 17S)-3-((2-methoxyphenyl)amino)-10,13-dimethylhexadecahydro-1H-cyclopenta[α]phenanthren-17-yl)ethan-1-one, C28H41NO2
  36. The crystal structure of fac-tricarbonyl((pyridin-2-yl)methanamino-κ2 N,N′)-((pyridin-2-yl)methanamino-κN)rhenium(I) nitrate, C15H16O3N4Re
  37. The crystal structure of (1-(pyridin-2-yl)-N-(pyridin-2-ylmethyl)-N-((1-(4-vinylbenzyl)-1H-benzo[d]imidazol-2-yl)methyl)methanamine-κ 4 N,N′,N″,N‴)tris(nitrato-kO,O′)-erbium(III), C29H27ErN8O9
  38. Crystal structure of tetracene-5,12-dione, C18H10O2
  39. Crystal structure of (3R,3aS,6R,6aR)-6-hexyl-3-methyltetrahydrofuro[3,4-b]furan-2,4-dione, C13H20O4
  40. The crystal structure of N′1,N′3-bis((E)-thiophen-2-ylmethylene)isophthalohydrazide monohydrate, C18H16N4O3S2
  41. Crystal structure of methyl ((4-aminobenzyl)sulfonyl)-L-prolinate, C13H18N2O4S
  42. Crystal structure of (E)-3-(3-methoxybenzylidene)benzofuran-2(3H)-one, C16H12O3
  43. Synthesis and crystal structure (E)-1-(4-bromo-2-hydroxyphenyl)-3-(dimethylamino)prop-2-en-1-one, C11H12BrNO2
  44. Synthesis and crystal structure of (S,E)-4-hydroxy-3-(2-((4aR,6aS,7R,10aS,10bR)-3,3,6a,10b-tetramethyl-8-methylenedecahydro-1H-naphtho[2,1-d][1,3]dioxin-7-yl)ethylidene)dihydrofuran-2(3H)-one, C23H34O5
  45. The crystal structure of N,N′-(1,2-phenylene)bis (2-((2-oxopropyl)selanyl)benzamide), C26H24N2O4Se2
  46. The crystal structure of 1-ethyl-2-nitro-imidazole oxide, C5H7N3O3
  47. The crystal structure of 2-(2-fluorophenyl)naphtho[2,1-d]thiazole, C17H10FNS
  48. Crystal structure of (E)-2,4-di-tert-butyl-6-(((2-fluorophenyl)imino) methyl)phenol, C21H26FNO
  49. Synthesis and crystal structure of 3-methyl-2-(methylthio)-4H-chromen-4-one, C12H12O2S
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  54. The crystal structure of 2-amino-4-carboxypyridin-1-ium perchlorate, C6H7ClN2O6
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  56. The crystal structure of 2,2-bis(3-methoxyphenyl)-1-tosyl-1,2-dihydro- 2λ4,3λ4  -[1,3,2]diazaborolo[4,5,1-ij]quinoline - dichloromethane (1/1)
  57. The crystal structure of catena-poly[bis(6-phenylpyridine-2-carboxylato-κ2 N,O)-(μ2-4,4′-bipyridne-κ2 N:N)cadmium(II)], C34H24N4O4Cd
  58. The crystal structure of 5,7-dinitropyrazolo[5,1-b]quinazolin-9(4H)-one, C10H5N5O5
  59. Crystal structure of rac-1,8-bis(2-carbamoylethyl)-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, C22H46N6O2
  60. The crystal structure of (E)-N ′-(2-bromobenzylidene)-2-naphthohydrazide, C36H26Br2N4O2
  61. The crystal structure of 5-nitronaphthoquinone, C10H5NO4
  62. The crystal structure of (S, R p )-4–benzhydrylideneamino-12-(4-tert-butyl oxazolin-2-yl)[2.2]paracyclophane, C36H36N2O
  63. Synthesis and crystal structure of 2-(2-oxo-2-(o-tolyl)ethyl)-4H-chromen-4-one, C18H14O3
  64. Crystal structure of 2-(thiazol-2-yl)hexahydro-1H-4,7-epoxyisoindole-1,3(2H)-dione, C11H10N2O3S
  65. Crystal structure of N-(diaminomethylene)-1-(dimethylamino)-1-iminiomethanaminium dichloride, C4H13Cl2N5
  66. Crystal structure of poly[(μ3-3, 5-dichloro-2-hydroxy-benzoato-κ4 Cl,O:O′:O″) silver(I)], C7H3AgCl2O3
  67. The crystal structure of tetrakis(1-isopropylimidazole-κ1 N)-[μ2- imidazole-4,5-dicarboxylato-κ4 O,N,O′,N′)]- trioxido-divanadium, C29H41N10O7V2
  68. Crystal structure of catena-[(μ3-bromido)-(1H-1,2,4-triazol-1-yl)benzoato-κ1 N)copper(I)], C9H7BrCuN3O2
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https://doi.org/10.1515/ncrs-2023-0135
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Articles in the same Issue

  1. Frontmatter
  2. New Crystal Structures
  3. Crystal structure of a polymorph of potassium picrate, C6H2KN3O7
  4. The crystal structure of (1E,2E)-1,2-bis(quinolin-2-ylmethylene)hydrazine, C20H14N4
  5. 5-Amino-2-chloro-4-fluoro-N-(N-isopropyl-N-methylsulfamoyl) benzamide, C11H15O3ClFN3S
  6. Crystal structure of trans-N 1,N 8-bis(2-cyanoethyl)-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, C22H42N6
  7. The crystal structure of [N-{[2-(oxy)-4-methoxyphenyl](phenyl)methylidene}alaninato]-diphenyl-silicon(IV) – chloroform (1/1), C29H25NO4Si·CHCl3
  8. Crystal structure of tetracarbonyl-{μ-[N-(diphenylphosphanyl)-N,P,P-triphenylphosphinous amide]}-bis[μ-(phenylmethanethiolato)]diiron (Fe–Fe), C48H39Fe2NO4P2S2
  9. Crystal structure of baryte from Mine du Pradet (France)
  10. The crystal structure of [(2,2′-bipyridine-6-carboxylato-κ3 N,N,O)-(6-phenylpyridine-2-carboxylate-κ2 N,O)copper(II)] monohydrate, C23H17N3O5Cu
  11. Crystal structure of bis(μ-benzeneselenolato)-(μ-[N-benzyl-N-(diphenylphosphanyl)-P,P-diphenylphosphinous amide])-tetracarbonyl diiron (Fe–Fe), C47H37Fe2NO4P2Se2
  12. The crystal structure of diaqua-methanol-κ1 O- (3-thiophenecarboxylato-κO)-(2,2′-dipyridyl-κ2 N,N′)manganese(II) 3-thiophenecarboxylate, C21H22N2O7S2Mn
  13. Crystal structure of catena-poly[tetrakis(butyl)-μ2-2-((oxido(phenyl)methylene)hydrazineylidene)propanoato-κ4 O:O,O′,N-μ2-2-((oxido(phenyl)methylene)hydrazineylidene)propanoato-κ4 O,N,O′:N′-ditin(IV)], C34H50N6O6Sn2
  14. Crystal structure of 4-chloro-N′-[(1E)-(2-nitrophenyl)methylidene]benzohydrazide, C14H10ClN3O3
  15. The crystal structure of 3-(1′-deoxy-3′,5′-O-dibenzy-β-d-ribosyl)adenine dichloromethane solvate, C49H52Cl2N10O6
  16. The crystal structure of (Z)-4-amino-N′-(1-(o-tolyl)ethylidene)benzohydrazide, C16H17N3O
  17. The co-crystal structure of etoricoxib–phthalic acid (1/1), C18H15ClN2O2S·C8H6O4
  18. Crystal structure of (glycinto-κ 2 O,N ′)-[5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane-κ 4 N,N ′,N ″,N ‴]nickel(II) perchlorate monohydrate C18H42ClN5NiO7
  19. The crystal structure of catena-poly[bis(1-ethylimidazole-k1 N)-(μ 2-benzene-1-carboxyl-3,5-dicarboxylato-κ 2 O, O′)zinc(II)], C19H20N4O6Zn
  20. Crystal structure of 3-(thiazol-2-ylcarbamoyl)-7-oxabicyclo[2.2.1]heptane-2-carboxylic acid, C11H12N2O4S
  21. Rietveld structure analysis of keatite, a rare, metastable SiO2 polymorph
  22. Crystal structure of catena-poly[(μ2-isophthalato-k3 O,O′:O″)(4-(4-pyridyl)-2,5-dipyrazylpyridine-k3 N,N′,N″)cobalt(II)] trihydrate C26H22N6O7Co1
  23. Crystal structure of 3,5–di-O-benzoyl-1,2-O-isopropylidene-α–D-ribose, C22H22O7
  24. The crystal structure of fac-tricarbonyl(6-bromo-2,2-bipyridine-κ2 N,N)-(nitrato-κO)rhenium(I), C13H7BrN3O6Re
  25. The crystal structure of (E)-N′-(4-hydroxy-3-methoxybenzylidene)-2-naphthohydrazide monohydrate, C19H18N2O4
  26. The crystal structure of 5,5′-diselanediyl-bis(2-hydroxybenzaldehyde), C14H10O4Se2
  27. The crystal structure of catena-poly[diaqua-m2-dicyanido-κ2 C:N-dicyanido-κ1 C-bis(4-(pyridin-4-yl)benzaldehyde-κ1N)iron(II)-platinum(II), C28H22N6O4PtFe
  28. Redetermination of the crystal structure of 5,14-dihydro-6,17-dimethyl-8,15-diphenyldibenzo(b,i)(1,4,8,11)tetra-azacyclotetradecine, C32H28N4
  29. Crystal structure of poly[(μ3-2-(3,5-dicarboxyphenyl) benzimidazole-6-carboxylato-κ4O:O:O′:O″)lead(II)] monohydrate, C16H10N2O7Pb
  30. The crystal structure of fac-tricarbonyl(2-pyridin-2-yl-quinoline-κ2 N,N′)-(pyrazole-κN)rhenium(I)nitrate, C20H14N4O3ReNO3
  31. Crystal structure of dibromo-dicarbonyl-bis(tricyclohexylphosphine)-osmium(II) dichloromethane solvate, C38H66Br2O2OsP2
  32. Crystal structure of poly[bis(μ 2-2,6-bis(1-imidazoly)pyridine-κ 2 N:N′)copper(II)] diperchlorate dihydrate, C22H22Cl2CuN10O10
  33. The crystal structure of fac-tricarbonyl(N-benzoyl-N,N-cyclohexylmethylcarbamimidothioato-κ2 S,O)-(pyridine-κN)rhenium(I), C23H24N3O4ReS
  34. Crystal structure of (E)-7-fluoro-2-(4-fluorobenzylidene)-3,4-dihydronaphthalen-1(2H)-one, C17H12F2O
  35. Synthesis and crystal structure of 1-((3R,10S,13S, 17S)-3-((2-methoxyphenyl)amino)-10,13-dimethylhexadecahydro-1H-cyclopenta[α]phenanthren-17-yl)ethan-1-one, C28H41NO2
  36. The crystal structure of fac-tricarbonyl((pyridin-2-yl)methanamino-κ2 N,N′)-((pyridin-2-yl)methanamino-κN)rhenium(I) nitrate, C15H16O3N4Re
  37. The crystal structure of (1-(pyridin-2-yl)-N-(pyridin-2-ylmethyl)-N-((1-(4-vinylbenzyl)-1H-benzo[d]imidazol-2-yl)methyl)methanamine-κ 4 N,N′,N″,N‴)tris(nitrato-kO,O′)-erbium(III), C29H27ErN8O9
  38. Crystal structure of tetracene-5,12-dione, C18H10O2
  39. Crystal structure of (3R,3aS,6R,6aR)-6-hexyl-3-methyltetrahydrofuro[3,4-b]furan-2,4-dione, C13H20O4
  40. The crystal structure of N′1,N′3-bis((E)-thiophen-2-ylmethylene)isophthalohydrazide monohydrate, C18H16N4O3S2
  41. Crystal structure of methyl ((4-aminobenzyl)sulfonyl)-L-prolinate, C13H18N2O4S
  42. Crystal structure of (E)-3-(3-methoxybenzylidene)benzofuran-2(3H)-one, C16H12O3
  43. Synthesis and crystal structure (E)-1-(4-bromo-2-hydroxyphenyl)-3-(dimethylamino)prop-2-en-1-one, C11H12BrNO2
  44. Synthesis and crystal structure of (S,E)-4-hydroxy-3-(2-((4aR,6aS,7R,10aS,10bR)-3,3,6a,10b-tetramethyl-8-methylenedecahydro-1H-naphtho[2,1-d][1,3]dioxin-7-yl)ethylidene)dihydrofuran-2(3H)-one, C23H34O5
  45. The crystal structure of N,N′-(1,2-phenylene)bis (2-((2-oxopropyl)selanyl)benzamide), C26H24N2O4Se2
  46. The crystal structure of 1-ethyl-2-nitro-imidazole oxide, C5H7N3O3
  47. The crystal structure of 2-(2-fluorophenyl)naphtho[2,1-d]thiazole, C17H10FNS
  48. Crystal structure of (E)-2,4-di-tert-butyl-6-(((2-fluorophenyl)imino) methyl)phenol, C21H26FNO
  49. Synthesis and crystal structure of 3-methyl-2-(methylthio)-4H-chromen-4-one, C12H12O2S
  50. Crystal structure of dithieno[2,3-d:2′,3′-d′]benzo[1,2-b:4,5-b′]dithiophene-5,10-dione, C14H4O2S4
  51. The crystal structure of dimethyl 2,2ʹ-((adamantane-1,3-diylbis(4,1-phenylene)) bis(oxy))diacetate, C28H32O6
  52. The crystal structure of N-(6-chloro-2-methyl-2H-indazol-5-yl)acetamide, C10H10ClN3O
  53. Crystal structure of triaqua-(5-bromoisophthalato-κ1 O)-(2,2′-bipyridine-κ2 N:N′)nickel(II) hydrate, C18H19BrN2NiO8
  54. The crystal structure of 2-amino-4-carboxypyridin-1-ium perchlorate, C6H7ClN2O6
  55. The crystal structure of catena-poly[5-aminonicotinic acid-k1 N-m2-bromido-copper(I)], Cu(C6N2H6O2)Br
  56. The crystal structure of 2,2-bis(3-methoxyphenyl)-1-tosyl-1,2-dihydro- 2λ4,3λ4  -[1,3,2]diazaborolo[4,5,1-ij]quinoline - dichloromethane (1/1)
  57. The crystal structure of catena-poly[bis(6-phenylpyridine-2-carboxylato-κ2 N,O)-(μ2-4,4′-bipyridne-κ2 N:N)cadmium(II)], C34H24N4O4Cd
  58. The crystal structure of 5,7-dinitropyrazolo[5,1-b]quinazolin-9(4H)-one, C10H5N5O5
  59. Crystal structure of rac-1,8-bis(2-carbamoylethyl)-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, C22H46N6O2
  60. The crystal structure of (E)-N ′-(2-bromobenzylidene)-2-naphthohydrazide, C36H26Br2N4O2
  61. The crystal structure of 5-nitronaphthoquinone, C10H5NO4
  62. The crystal structure of (S, R p )-4–benzhydrylideneamino-12-(4-tert-butyl oxazolin-2-yl)[2.2]paracyclophane, C36H36N2O
  63. Synthesis and crystal structure of 2-(2-oxo-2-(o-tolyl)ethyl)-4H-chromen-4-one, C18H14O3
  64. Crystal structure of 2-(thiazol-2-yl)hexahydro-1H-4,7-epoxyisoindole-1,3(2H)-dione, C11H10N2O3S
  65. Crystal structure of N-(diaminomethylene)-1-(dimethylamino)-1-iminiomethanaminium dichloride, C4H13Cl2N5
  66. Crystal structure of poly[(μ3-3, 5-dichloro-2-hydroxy-benzoato-κ4 Cl,O:O′:O″) silver(I)], C7H3AgCl2O3
  67. The crystal structure of tetrakis(1-isopropylimidazole-κ1 N)-[μ2- imidazole-4,5-dicarboxylato-κ4 O,N,O′,N′)]- trioxido-divanadium, C29H41N10O7V2
  68. Crystal structure of catena-[(μ3-bromido)-(1H-1,2,4-triazol-1-yl)benzoato-κ1 N)copper(I)], C9H7BrCuN3O2
  69. The crystal structure of (E)-4-fluoro-N′-(1-(2-hydroxyphenyl)propylidene)benzohydrazide, C16H15FN2O2
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