Gel growth of 3‐methyl‐4‐nitropyridine‐1‐oxide organic crystals: X‐ray and nonlinear optics characterization

1990 ◽  
Vol 68 (1) ◽  
pp. 8-13 ◽  
Author(s):  
P. Andreazza ◽  
F. Lefaucheux ◽  
M. C. Robert ◽  
D. Josse ◽  
J. Zyss
1995 ◽  
Vol 147 (3-4) ◽  
pp. 361-368 ◽  
Author(s):  
N. Horiuchi ◽  
F. Lefaucheux ◽  
M.C. Robert ◽  
D. Josse ◽  
S. Khodja ◽  
...  

Crystals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 89 ◽  
Author(s):  
Jolanta Prywer ◽  
Lesław Sieroń ◽  
Agnieszka Czylkowska

In this article, we report the crystallization of struvite in sodium metasilicate gel by single diffusion gel growth technique. The obtained crystals have a very rich morphology displaying 18 faces. In this study, the habit and morphology of the obtained struvite crystals are analyzed. The crystals were examined and identified as pure struvite by single X-ray diffraction (XRD). The orthorhombic polar noncentrosymmetric space group Pmn21 was identified. The structure of the crystal was determined at a temperature of 90 K. Our research indicates a lack of polymorphism, resulting from the temperature lowering to 90 K, which has not been previously reported. The determined unit cell parameters are as follows a = 6.9650(2) Å, b = 6.1165(2) Å, c = 11.2056(3) Å. The structure of struvite is presented here with a residual factor R1 = 1.2% at 0.80 Å resolution. We also present thermoanalytical study of struvite using thermal analysis techniques such as thermogravimetry (TG), derivative thermogravimetry (DTG) and differential thermal analysis (DTA).


IAWA Journal ◽  
1996 ◽  
Vol 17 (4) ◽  
pp. 393-403 ◽  
Author(s):  
Yuki Kondo ◽  
Tomoyuki Fujii ◽  
Yoshioki Hayashi ◽  
Atsushi Kato

Organic crystals were found in tracheid lumina of some samples of Torreya yunnanensis Chen ' L. K. Fu imported from Yunnan, China. Tracheids with crystals were found in short to long tangential bands along the growth ring boundaries. Because the crystals were rapidly dissolved with ethanol and xylene, cross and tangential sections were mounted in de-ionized water without staining and observed by biological, polarised light, and phase-contrast microscopy. The crystals were sublimated under vacuum during routine sample preparation for conventional SEM and only the peripheral parts remained. With the aid of low vacuum-SEM and modified cryo-SEM procedure, the shape of the crystals was revealed. Some were styloid and large enough to fill tracheid lumina, while others were stacked appearing as slates filling tracheid lumina. X-ray diffraction applied to sections and isolated crystals showed that they were single crystals and orientated along the cell wall. UV spectra on isolated crystals and methanol dissolution of crystals suggested that they were composed of phenolic compounds. Crystals that were recrystallized from methanol were analysed by 1H and l3C nuclear magnetic resonance spectroscopy. These two techniques revealed that the major and minor components were o-methoxy cinnamic acid and o-methoxy cinnamic aldehyde.


Dorothy Hodgkin - as crystallographer, scientist and human being - far surpasses most, and so it is not easy to write about her many-splendoured personality. Instead, my aim here will he to discuss her influence on the growth of X-ray crystallography in India, directly through those who worked with her and indirectly by her travelling all over this country. In such an account, one must be pardoned for some personal element creeping in. In the twenties, India had developed a fairly strong tradition in X-ray physics. The six-week visit of C.V. Raman to Europe in 1921 greatly changed his research interests. On seeing the blue of the Mediterranean he started his researches on the scattering of light in liquids which finally culminated in the discovery of what is now called the Raman Effect. His encounter with Sir William Bragg and his work on naphthalene structure started three lines of research in India. First, Raman fabricated an X-ray tube and was amongst the earliest to use X-ray diffraction as a structural tool to study liquids. He showed that while in large-angle scattering the haloes reflected specific molecular sizes and packing shapes, small-angle scattering was directly related to the statistical fluctuation of density in a liquid. Second, Raman knew that Bragg’s first structure of naphthalene was not consistent with its birefringence, while the second one was. With this as cue he and his school launched extensive studies on the optical and magnetic anisotropy of organic crystals to get vital information on the arrangements of molecules in the crystalline state. Third, one of his students, Kedareshwar Bannerjee, was amongst the earliest to probe into the problem of phase determination by direct methods and for this he used Bragg’s data on naphthalene. Unfortunately, in spite of this early lead, it was not until 1951 that the first crystal structure was solved in India using Fourier methods by Gopinath Kartha. The Indian Institute of Science (IISc) had great hopes of starting a powerful school of X-ray crystallography when G.N. Ramachandran came back from Cambridge. But he went over to Madras, and there he established one of the most renowned Schools of Biophysics. With Gopinath Kartha he solved the structure of collagen.


ChemInform ◽  
2012 ◽  
Vol 43 (48) ◽  
pp. no-no
Author(s):  
M. B. Holcomb ◽  
S. Polisetty ◽  
A. Fraile Rodriguez ◽  
V. Gopalan ◽  
R. Ramesh

CrystEngComm ◽  
2022 ◽  
Author(s):  
Angelo Gavezzotti ◽  
Leonardo Lo Presti ◽  
Silvia Rizzato

The science of organic crystals and materials has seen in a few decades a spectacular improvement from months to minutes for an X-ray structure determination and from single-point lattice energy...


In Part I* of this paper a convenient method of measuring the principal magnetic susceptibilities of single crystals was described, and several organic crystals, among others, were studied by this method. The results were discussed particularly in relation to the structure of the molecules and their orientations in the crystal lattice, and it was shown how a correlation of the principal magnetic susceptibilities of the crystal with those for the individual molecules (obtained from measurements on magnetic double-refraction in the liquid state, or from considerations of molecular structure) gives us useful information regarding the orientations of the molecules in the crystal lattice. Indeed, in favourable cases the molecular orientations may thus be determined much more easily, and some of the parameters defining the orientations also more accurately, than by X-ray methods of analysis. Conversely, where the molecular orientations in the crystal lattice are already known from X-ray studies, a knowledge of the principal magnetic susceptibilities of the crystal enables us to obtain the magnetic constants of the individual molecules, which are of interest. For example, it is thus found that as one proceeds from benzene to naphthalene and from naphthalene to anthracene, the numerical increase in susceptibility that occurs, is directed predominantly along the normal to the plane of the benzene rings


1994 ◽  
Vol 29 (4) ◽  
pp. K59-K61 ◽  
Author(s):  
P. Sureshkumar ◽  
K. Sivakumar ◽  
S. Natarajan
Keyword(s):  

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