scholarly journals Role of halogen substituents in a series of polymorphic 2,5-diamino-3,6-dicyanopyrazine derivatives with highly flexible groups

2017 ◽  
Vol 232 (5) ◽  
pp. 395-405 ◽  
Author(s):  
Yoko Akune ◽  
Risa Hirosawa ◽  
Atsushi Koseki ◽  
Shinya Matsumoto
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Electrostatic Interactions ◽  
Crystal Structure Analysis ◽  
Stable Form ◽  
Thermally Stable ◽  
Close Packed Structure ◽  
Packed Structure ◽  
Stable Forms ◽  
Metastable Forms

AbstractThe crystal structures of the ortho-X-benzyl derivatives, where X=F, Cl, Br, I, and Me, of 2,5-bis(N,N-dibenzylamino)-3,6-dicyanopyrazine dyes (C34H24N6X4) were analysed to evaluate the effect of a systematic series of structures on the occurrence of polymorphism. Detailed crystal structure analysis indicated that the thermally stable forms of the polymorphic derivatives (Cl and Br derivatives) were close-packed, whereas those of the non-polymorphic derivatives (F and I derivatives) were stabilised by an intermolecular interaction involving the ortho-substituents. In the thermally metastable forms of the polymorphic derivative, halogen-halogen and halogen-nitrogen interactions contributed to the stabilisation of these crystals in the same way as the thermally stable form of the non-polymorphic derivatives. This indicated that the ease of polymorph occurrence would require an appropriate balance between the crystal energy of the close-packed structure and that of the crystal structure generated mainly by the electrostatic interactions involving the halogens in these halogenated pyrazine derivatives. In addition, the similar tendency of the occurrence of polymorphs in these halogenated pyrazine derivatives was found in 19 sets of halogenated compounds having known crystal structures of F, Cl, Br and I derivatives including at least one polymorphic derivative in the crystal structure database.

scholarly journals Understanding complex phase transition mechanism by crystal structure analysis

2014 ◽  
Vol 70 (a1) ◽  
pp. C1704-C1704
Author(s):  
Kristīne Krūkle-Bērziņa ◽  
Andris Actiņš
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Single Crystal ◽  
Crystal Structures ◽  
Diffraction Data ◽  
Crystal Structure Analysis ◽  
Stable Form ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transition Mechanism

Xylazine hydrochloride (2-(2,6-xylidino)-5,6-dihydro-4H-1,3-thiazine hydrochloride) is an adrenergic α-agonist used as a sedative, analgesic, and muscle relaxant in veterinary medicine. It has four polymorphous forms (A, Z, M and X), monohydrate (H), hemihydrate and solvates with dichloromethane and 2-propanol. It has been reported that the polymorph X is thermodynamically the least stable of these polymorphs, while the A is the most stable form at temperatures above 500C. The X forms only in H dehydration process, and at elevated temperature X transforms to polymorph A [1]. The crystal structures of the polymorphs A and X as well as hydrate H have been reported. Crystal structure of A and X have been determined from the powder X-ray diffraction data (PXRD), whereas that of hydrate have been determined from single crystal X-ray diffraction data [2-3]. In this study structure of A have been determined from single crystal data and compared to that determined by PXRD data. Crystal structures of A, X and H have been compared and analysed. Molecule conformation in crystal structure of all three forms is the same and molecular packing is similar. However, that in monohydrate H and polymorph X is basically the same and the only difference is the inclusion of the water molecules next to the chlorine anions, whereas relative xylazine moiety orientation and arrangement of the chlorine anions is different in the structure of polymorph A. The structural similarity or differences between all three forms noted above were also approved by the 2D-fingerprint plots of the Hirshfeld surfaces. Analysis of all three form crystal structures allowed to better understand complex solid-state phase transition from xylazine hydrochloride polymorph X to polymorph A during and after the dehydration of it monohydrate H.

scholarly journals E. S. Fedorov Promoting the Russian-German Scientific Interrelationship

Minerals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 181 ◽  
Author(s):  
Peter Paufler ◽  
Stanislav K. Filatov
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Structure Analysis ◽  
Crystalline State ◽  
Crystal Structure Analysis ◽  
Present Knowledge ◽  
Personal Contact ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Impact

At the dawn of crystal structure analysis, the close personal contact between researchers in Russia and Germany, well documented in the “Zeitschrift für Krystallographie und Mineralogie”, contributed significantly to the evolution of our present knowledge of the crystalline state. The impact of the Russian crystallographer E. S. Fedorov upon German scientists such as A. Schoenflies and P. Groth and the effect of these contacts for Fedorov are highlighted hundred years after the death of the latter. A creative exchange of ideas paved the way for the analysis of crystal structures with the aid of X-ray diffraction.

Re: Crystal Structures of Pyroaurite and Sjögrenite

1994 ◽  
Vol 38 ◽  
pp. 749-755 ◽  
Author(s):  
A. Olowe
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Structure Analysis ◽  
Crystal Structure Analysis ◽  
Metallic Ions ◽  
Chemical Formula ◽  
Metal Hydroxides ◽  
Space Group ◽  
Previous Discussion ◽  
Positively Charged

Abstract Pyroaurite and sjogrenite belong to the group of sandwiched lamellar metal hydroxides which have a fixed metallic ions MII:MIII ratio for a particular class. Their crystal structure consists of positively charged metal hydroxide blocks intercalated with negatively charged interlayers. The atomic positions for the interlayer are definite for a particular class. The exact chemical formula of the pyroaurite class is determined from crystal structure analysis to be MII 6MIII 2(OH)16-CO3-4.5H2O; it crystallizes in the space group Rm with a = 12.4376 Å and c = 23.4126 Å. Sjogrenite, MII 6 MIII 2(OH)16-CO3-4H2O crystallizes in the space group P63/mcm. The crystallogiraphy and structural relationship between these classes are discussed. Previous discussion on these compounds did not give any conclusion on the exact chemical formula and the atomic positions.

Structures and photochemistry of 1,5-disubstituted dibenzobarrelenes

1996 ◽  
Vol 52 (1) ◽  
pp. 151-158
Author(s):  
R. Jones ◽  
S. J. Rettig ◽  
J. R. Scheffer ◽  
J. Trotter ◽  
J. Yang
Keyword(s):  
Crystal Structure ◽  
Double Bond ◽  
Crystal Structures ◽  
Structure Analysis ◽  
Crystal Structure Analysis ◽  
The Other ◽  
Steric Effects ◽  
Molecular And Crystal Structures ◽  
Electronic And Steric Effects

The effect of 1,5-disubstitution on the photochemistry of 9,10-ethenoanthracene-11,12-diesters has been studied and correlated with the crystal structures determined for several derivatives; photoproduct structures have been established from a crystal structure analysis of one of the products and from NMR correlations. The crystals studied are: (1)-Cl, dimethyl 1,5-dichloro-9,10-dihydro-9,10-ethenoanthracene-11,12-dicarboxylate, C20H14Cl2O4, P21/n; (1)-CN, 1,5-dicyano derivative, C22H14N2O4, P21/n; (1)-CN.0.5p-xylene, C22H14N2O4.0.5C8H10, P21/c; (1)-CN.xxylene, C22H14N2O4.xC8H10, P21/n; (1)-OMe, 1,5-dimethoxy derivative, C22H20O6, P{\bar 1}; (2b)-Cl, C20H14C12O4, dimethyl 1,5-dichloro-4b,8b,8c,8d-tetrahydrodibenzo[a, f]cyclopropa[c,d]pentalene-8c,8d-dicarboxylate, Pna21. The dibenzobarrelene molecules all have geometries and dimensions similar to those of related materials. In particular, the orientations of the two ester groups in each molecule differ, one being in general almost fully conjugated with the C(11)=C(12) double bond and the other almost non-conjugated. Relationships are sought between the ratios of the two regioisomeric photoproducts and molecular and crystal structures; both electronic and steric effects are considered, but no one effect seems to dominate.

Zur Reaktion von [MCl2(PR3)2] (M = Ni, Pd) mit E(SiMe3)2 (E = S, Se) Die Kristallstrukturen von [Ni3S2Cl2(PPh3)4], [Pd3S2Cl2(PPh3)4], INi3Se2(SeSiMe3)2(P(C2H4Ph)3)4] und [Pd3Se2(SeSiMe3)2(PPh3)4] / Reaction of [MCl2(PR3)2] (M = Ni, Pd) with E(SiMe3)2 (E = S, Se) The Crystal Structures of [Ni3S2Cl2(PPh3)4], [Pd3S2Cl2(PPh3)4], [Ni3Se2(SeSiMe3)2(P(C2H4Ph)3)4] and [Pd3Se2(SeSiMe3)2(PPh3)4]

1990 ◽  
Vol 45 (2) ◽  
pp. 127-133 ◽  
Author(s):  
Dieter Fenske ◽  
Holm Fleischer ◽  
Harald Krautscheid ◽  
Jörg Magull
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Structure Analysis ◽  
Crystal Structure Analysis ◽  
X Ray ◽  
Triangular Clusters

[MC12(PR3)2] (M = Ni, Pd) reacts with E(SiMe3)2 (E = S, Se) to form triangular clusters, [Ni3S2Cl2(PPh3)4] (1), [Pd3S2Cl2(PPh3)4] (2), [Ni3Se2(SeSiMe3)2(P(C2H4Ph)3)4] (4) and [Pd3Se2(SeSiMe3)2(PPh3)4] (3). 1-4 have been characterized by X-ray crystal structure analysis. All these compounds contain a triangular M3-core, which is capped by two μ3-E-ligands (E = S in 1, Se in 3 and 4).

Deformation Modes and Anomalous Strengthening of Ni3X -Type Intermetallic Compounds with the Geometrically Close-Packed Structure

2005 ◽  
Vol 502 ◽  
pp. 145-150 ◽  
Author(s):  
Yukichi Umakoshi ◽  
Koji Hagihara ◽  
Takayoshi Nakano
Keyword(s):  
Plastic Deformation ◽  
Crystal Structures ◽  
Intermetallic Compounds ◽  
Deformation Behavior ◽  
Deformation Characteristics ◽  
Close Packed Structure ◽  
Plastic Deformation Behavior ◽  
Packed Structure ◽  
Deformation Modes

Plastic deformation behavior including anomalous strengthening of Ni3X-type compounds with D019, D0a and D024 structure were examined and summarized, focusing on the correlation between deformation characteristics and features of their crystal structures.

1-Thiooxamat, NH2C(O)C(S)O , und 2-Thiooxamat, NH2C(S)CO2 als Liganden in Übergangsmetall-Komplexen. Die Strukturen von [Fe(2-thiox)2(H2O)2], [Zn(2-thiox)2(H2O)] und [Zn(1-thiox)2(H2O)]·H2O/ 1-Thiooxamate, NH2C (O)C(S)O– , and 2-Thiooxamate, NH2C(S)CO2–, as Ligands in Transition Metal Complexes. Crystal Structures of [Fe(2-thiox)2(H2O)2], [Zn(2-thiox)2(H2O)] and [Zn(1-thiox)2(H2O)]·H2O

1985 ◽  
Vol 40 (8) ◽  
pp. 1068-1072 ◽  
Author(s):  
Johannes Bertels ◽  
Rainer Mattes
Keyword(s):  
Crystal Structure ◽  
Transition Metal ◽  
Metal Complexes ◽  
Crystal Structures ◽  
Structure Analysis ◽  
Transition Metal Complexes ◽  
Crystal Structure Analysis

AbstractTransition metal complexes of the ligands 1-thiooxamate and 2-thiooxam ate have been prepared. According to crystal structure analysis of Fe(2-thiox)2(H2O)2, Zn(2-thiox)2(H2O) and Zn(1-thiox)2(H2O)2 these ligands act as O .S-donors and form pentaatomic chelaterings. Both Zn-complexes are trigonal-bipyramidally coordinated.

scholarly journals Crystal structure of a calcium(II)–pyrroloquinoline quinone (PQQ) complex outside a protein environment

2020 ◽  
Vol 76 (12) ◽  
pp. 1051-1056
Author(s):  
Henning Lumpe ◽  
Peter Mayer ◽  
Lena J. Daumann
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Crystal Structures ◽  
Pyrroloquinoline Quinone ◽  
Crystal Structure Analysis ◽  
Hydrogen Bond Network ◽  
Alcohol Dehydrogenases ◽  
Bond Network ◽  
Similarities And Differences ◽  
Protein Environment

Pyrroloquinoline quinone (PQQ) is an important cofactor of calcium- and lanthanide-dependent alcohol dehydrogenases, and has been known for over 30 years. Crystal structures of Ca–MDH enzymes (MDH is methanol dehydrogenase) have been known for some time; however, crystal structures of PQQ with biorelevant metal ions have been lacking in the literature for decades. We report here the first crystal structure analysis of a Ca–PQQ complex outside the protein environment, namely, poly[[undecaaquabis(μ-4,5-dioxo-4,5-dihydro-1H-pyrrolo[2,3-f]quinoline-2,7,9-tricarboxylato)tricalcium(II)] dihydrate], {[Ca3(C14H3N2O8)2(H2O)11]·2H2O} n . The complex crystallized as Ca3PQQ2·13H2O with Ca2+ in three different positions and PQQ3−, including an extensive hydrogen-bond network. Similarities and differences to the recently reported structure with biorelevant europium (Eu2PQQ2) are discussed.

scholarly journals Three differently coloured polymorphs of 3,6-bis(4-chlorophenyl)-2,5-dipropyl-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione

2019 ◽  
Vol 75 (3) ◽  
pp. 414-422
Author(s):  
Hee-Soo So ◽  
Shinya Matsumoto
Keyword(s):  
Crystal Structure ◽  
Crystal Structure Analysis ◽  
The Other ◽  
Stable Form ◽  
Bonding System ◽  
Hydrogen Bonding System ◽  
Crystallization Conditions ◽  
Polymorphic Forms ◽  
The Difference ◽  
Packing Effect

In this paper, the conformational polymorphism of a chlorinated diketopyrrolopyrrole (DPP) dye having flexible substituents in a non-hydrogen-bonding system is reported. The propyl-substituted DPP derivative (PR3C) has three polymorphic forms, each showing a different colour (red, orange and yellow). All polymorphs could be obtained concomitantly under various crystallization conditions. The results of the crystal structure analysis indicate that PR3C adopts different conformations in each polymorph. The packing effect caused by the difference in the arrangement of neighbouring molecules was found to play an important role in the occurrence of the observed polymorphism. The thermodynamic stability relationship between the three polymorphs was identified by thermal analysis and indicates that the yellow polymorph is the thermally stable form. The results indicate that the yellow form and orange form are enantiotropically related, and the other polymorph is monotropically related to the others.

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