Structural Characterization of Two Crystalline Forms of Bis[2-(1,5-dimethyltrazol-3-yl)-1,10-phenanthroline]-iron(II) Perchlorate—a Spin Crossover System

1996 ◽  
Vol 49 (4) ◽  
pp. 497 ◽  
Author(s):  
KH Sugiyarto ◽  
DC Craig ◽  
HA Goodwin
Keyword(s):  
Room Temperature ◽  
Singlet State ◽  
Crystal Packing ◽  
Bulk Sample ◽  
Monoclinic Space Group ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
Quintet State ◽  
Crystalline Forms

At room temperature bis [2-(1,5-dimethyltriazol-3-yl)-1,10-phenanthroline]iron(II) perchlorate has magnetic and Mossbauer spectral properties which indicate that it contains both singlet and quintet state iron(II) in a ratio of approximately 1:2. Two polymorphs were identified in a small batch of crystals grown from acetone/ethanol for crystal structure determination. In polymorph 1 the average iron-nitrogen distance (1.97 Ǻ) is close to the value usually obtained for purely singlet state iron(II) in an [FeN6]2+ system, whereas that for polymorph 2 (2.09 Ǻ) is consistent with the 1:2 ratio of singlet-to-quintet state species. The Mossbauer spectrum of the crystallographic sample is virtually identical to that of the bulk sample. There are small differences in the coordination sphere which could account for the different extent of stabilization of the singlet state in the two polymorphs. The crystal packing differs markedly for the two polymorphs but reveals no obvious rationalization for the spin-state differences. Bis [2-(1,5-dimethyltriazol-3-yl)-1,10-phenanthroline]iron(II) perchlorate , two-thirds water (polymorph 1): monoclinic, space group P 21/c, a 10.766(3), b 25.806(3), c 12.491(4) Ǻ, β 91.17(1)°, Z 4. Bis [2-(1,5-dimethyltriazol-3-yl)-1,10-phenanthroline]iron(II) perchlorate monohydrate (polymorph 2): orthorhombic, space group Pbca, a 16.687(4), b 12.272(2), c 34.305(8) Ǻ, Z 8.

scholarly journals 4-METHYL HYPPURIC ACID: A CASE OF POLYMORPHISM AND SOLVATOMORPHISM

2019 ◽  
Vol 16 (32) ◽  
pp. 812-819
Author(s):  
G. DELGADO ◽  
M. GUILLEN ◽  
A. J. MORA
Keyword(s):  
Pharmaceutical Industry ◽  
Physical Properties ◽  
Crystal Packing ◽  
Solid Material ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Space Group ◽  
Pharmaceutical Ingredients ◽  
Orthorhombic Cell

Polymorphism is known as the ability of a solid material to exist in more than one form or crystal structure, with important applications in the preparation of active pharmaceutical ingredients. Characterization of different polymorphs of the specific metabolite of 4-xylene can contribute to the chemical and pharmaceutical industry. Polymorphism is of particular importance in industrial processes, where different physical properties of polymorphic forms can substantially alter the viability and quality of a manufactured product. This is particularly so for the design and production of drugs in the pharmaceutical industry, as varying physical properties between different polymorphs can affect shelf life and durability, solubility, as well as bioavailability and manufacturing of the drug. The crystallization, spectroscopic and X-ray diffraction characterization of two polymorph and one solvatomorph of 4-methylhippuric acid are presented. These compounds crystallizes in different crystalline systems. Polymorph I (4mH-I) crystalize in an orthorhombic cell with space group P212121. Polymorph II (4mHII) crystallizes in a monoclinic space group P21/c. Solvatomorph (4mH-S) crystallizes in a triclinic P-1 cell. All polymorphs crystallize in neutral form. The crystal packing of the three compounds are governed by hydrogen bonds intermolecular interactions of the type N--H···O and O--H···O forming tridimensional networks.

scholarly journals A variable-temperature study of a phase transition in barbituric acid dihydrate

2005 ◽  
Vol 61 (4) ◽  
pp. 464-472 ◽  
Author(s):  
Gary S. Nichol ◽  
William Clegg
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Barbituric Acid ◽  
Crystal Packing ◽  
Variable Temperature ◽  
Mirror Plane ◽  
Monoclinic Space Group ◽  
Orthorhombic Space Group ◽  
Acta Cryst ◽  
Space Group

The crystal structure of barbituric acid dihydrate (C4H4N2O3·2H2O) has twice been reported as orthorhombic, space group Pnma, with all atoms (except for CH2 H atoms) lying on the mirror plane [Al-Karaghouli et al. (1977). Acta Cryst. B33, 1655–1660; Jeffrey et al. (1961). Acta Cryst. 14, 881–887]. The present study has found that at low temperatures, below 200 K, the crystal structure is no longer orthorhombic but is non-merohedrally twinned monoclinic, space group P21/n. This phase is stable down to 100 K. Above 220 K the crystal structure is orthorhombic, and between 200 and 220 K the structure undergoes a phase change, with the monoclinic-to-orthorhombic phase transition itself taking place at around 216–217 K. The size of the β angle in the monoclinic structure is temperature dependent; at 100 K β is around 94° and it decreases in magnitude towards 90° as the temperature increases. Although the hydrogen-bonding motifs are the same for both crystal systems, there are significant differences in the crystal packing, in particular the out-of-plane displacement of the two water molecules and the sp 3-hybridized C atom of barbituric acid.

Mono- and difunctional furan-based 1,2,3,5-dithiadiazolyl radicals; preparation and solid state structures of 2,5-[(S2N2C)OC4H2(CN2S2)] and 2,5-[(S2N2C)OC4H2(CN)]

1992 ◽  
Vol 70 (3) ◽  
pp. 919-925 ◽  
Author(s):  
A. Wallace Cordes ◽  
Charles M. Chamchoumis ◽  
Robin G. Hicks ◽  
Richard T. Oakley ◽  
Kelly M. Young ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Crystal Structures ◽  
Monoclinic Space Group ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
The Mean ◽  
Solid State Structures ◽  
Solid State Characterization

The preparation and solid state characterization of the bifunctional radical furan-2,5-bis(1,2,3,5-dithiadiazolyl) 2,5-[(S2N2C)OC4H2(CN2S2)] and the related monofunctional radical 2-cyanofuran-5-(1,2,3,5-dithiadiazolyl) 2,5-[(S2N2C)OC4H2(CN)] are described. The crystal structure of 2,5-[(S2N2C)OC4H2(CN2S2)] is orthorhombic, space group Pna21, and consists of interleaved arrays of dimers, for which the mean interannular [Formula: see text] contact is 3.137 Å. The crystal structure of the monofunctional radical 2,5-[(S2N2C)OC4H2(CN)] is monoclinic, space group P21/n, and consists of a ribbon-like network of dimers (mean interannular [Formula: see text] interconnected by close head-to-tail [Formula: see text] contacts. The dimer units form stacks parallel to z, with a mean interdimer [Formula: see text] separation of 3.956 Å. The similarities and differences between these two crystal structures and those of related benzene-substituted systems are discussed. Keywords: dithiadiazolyl radicals, furan-based diradicals, cyanofuran-based radicals, radical dimers, crystal structures.

Steric Modification of Metal-Phosphorus Bond Lengths: the Preparation, Characterization and CrystalStructures of mer-trans-(PPri3)2(Pme2Ph)-Cl-cis-H2IrIII(1) and mer-trans-(PPri3)2(PMe2Ph)H3IrIII

1995 ◽  
Vol 48 (6) ◽  
pp. 1183 ◽  
Author(s):  
EJ Ditzel ◽  
GB Robertson
Keyword(s):  
Chloride Content ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
X Ray ◽  
Bond Lengths ◽  
Steric Crowding ◽  
Unit Increase

The syntheses and subsequent characterization of the complexes mer -trans-(PPri3)2(Pme2Ph)-Cl-cis-H2IrIII(1) and mer-trans-(PPri3)2(PMe2Ph)H3IrIII (2) by n.m.r. and by low temperature (153�5 K) X-ray diffraction analyses are reported. Crystals of (1) are monoclinic, space group P21/c with a 19.277(2), b 9.020(1), c 17.657(2) Ǻ, β 101.40(1)° and Z 4. Crystals of (2) are orthorhombic, space group P212121, with a 19.373(3), b 18.724(2), c 8.113(1) Ǻ and Z 4. Full-matrix least-squares analyses converged with R = 0.027 and wR = 0.031 for (1) (3243 reflections), and R = 0.030 and wR = 0.038 for (2) (2892 reflections). Consistent with previous observation, the unit increase in chloride content (in place of hydride) in (1) is accompanied by a global lengthening of 0.036 Ǻ (av.) in the Ir -P bond lengths cf. those in (2). Also, because of increased steric crowding (two PPri3 ligands in place of two Pme2Ph), the Ir-PMe2Ph bond in (1) is 0.019(2) Ǻ longer than the chemically equivalent bond in mer-(PMe2Ph)3Cl-cis-H2IrIII. In previously reported complexes in this series metrically similar increases in Ir-PMe2Ph distances result from the replacement of just one Pme2Ph ligand by PPri3.

Electronic and Structural Properties of the Spin Crossover Systems Bis(2,6-bis(pyrazol-3-yl)pyridine)iron(II) Thiocyanate and Selenocyanate

2000 ◽  
Vol 53 (9) ◽  
pp. 755 ◽  
Author(s):  
Kristian H. Sugiyarto ◽  
Marcia L. Scudder ◽  
Donald C. Craig ◽  
Harold A. Goodwin
Keyword(s):  
Hydrogen Bonding ◽  
High Spin ◽  
Room Temperature ◽  
Monoclinic Space Group ◽  
Orthorhombic Space Group ◽  
Triclinic Space Group ◽  
Space Group ◽  
Face To Face ◽  
Bright Yellow ◽  
Electronic And Structural Properties

Essentially high-spin [Fe(bpp)2][NCS]2·2H2O and [Fe(bpp)2][NCSe]2 (bpp = 2,6-bis(pyrazol-3-yl)pyridine) were isolated from an aqueous reaction mixture. Both salts undergo an abrupt transition to low spin below room temperature, that for the thiocyanate occurring in two steps and the high-spin Æ low-spin Æ high-spin cycle being accompanied by hysteresis in both steps. Recrystallization of the salts from nitromethane yielded a mixture from which bright yellow crystals were separated for structure determination. In addition, from the recrystallized selenocyanate, deep red-brown crystals of composition [Fe(bpp)2][NCSe]2·H2O·0.25 CH3NO2 were obtained. Recrystallized [Fe(bpp)2][NCS]2·2H2O and [Fe(bpp)2][NCSe]2 were identified as high spin with average Fe–N distances of 2.16 and 2.17 Å, respectively. In the unit cell of [Fe(bpp)2][NCSe]2·H2O·0.25 CH3NO2, there are four independent iron atoms, three identified as low spin and the fourth as high spin. All salts crystallize in a layer-type array involving edge-to-face and face-to-face aryl–aryl-type interactions. Hydrogen bonding between pyrazole >NH groups, anions and solvate molecules is observed. The structure of the uncoordinated ligand was also determined, the molecule being found in a planar arrangement with thecis–cis configuration for the pyrazolyl groups relative to the central pyridyl and the >NH group being at the N 2 atom. Hydrogen bonding involving the >NH groups leads to stepped stacks of molecules. The principal difference in the geometry of coordinated and free bpp molecules is a contraction in the angles about the interannular bridges in the chelate rings. [Fe(bpp)2][NCS]2·2H2O: triclinic, space group P1–, a 8.302(6), b 8.446(6), c 21.531(13) Å, a 78.78(5), b 82.80(5), g 89.85(4)˚, Z 2. [Fe(bpp)2][NCSe]2: triclinic, space group P1–, a 8.354(4), b 8.409(4), c 19.918(9) Å, a 87.02(3), b 83.15(3), g 88.86(3)˚, Z 2. [Fe(bpp)2][NCSe]2·H2O·0.25 CH3NO2: monoclinic, space group Pn, a 16.425(12), b 20.774(9), c 16.933(14) Å, b 90.91(4)˚, Z 8. Uncoordinated bpp: orthorhombic, space group Pna21, a 8.075(3), b 22.479(9), c 5.525(1) Å, b Z 4.

scholarly journals Darstellung und Charakterisierung der μ3-Oxo-Cluster [Cp3Mo3(CO)4µ-Cl)(µ3-O)] und [Cp3Mo3(µ-CO)3(CO)3(µ3-O)]+ / Synthesis and Characterization of the µ3-Oxo Clusters [Cp3Mo3(CO)4μ-Cl)(μ3-O)] and [Cp3Mo3(μ-CO)3(CO)3(μ3-O)]+

1990 ◽  
Vol 45 (4) ◽  
pp. 508-514 ◽  
Author(s):  
B. Nuber ◽  
W. Schatz ◽  
M. L. Ziegler
Keyword(s):  
Structure Analysis ◽  
Elemental Analysis ◽  
Spectroscopic Data ◽  
Synthesis And Characterization ◽  
Monoclinic Space Group ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
X Ray

[CpMo(CO)3]2 (1) (Cp = cyclopentadienyl) reacts with InCl3 in diglyme to yield the oxo-cluster [Cp3Mo3(CO)4(μ-Cl)(μ3-O)] (2) and the cationic oxo-cluster [Cp3Mo3(μ-CO)3(CO)3(μ3-O)]+ as the salt [Cp3Mo3(μ-CO)3(CO)3(μ3-O)][CpMo(CO)3InCl3] (3). The compounds were characterized by elemental analysis, spectroscopic data and X-ray structure analysis. Compound 2 crystallizes in the orthorhombic space group P212121 with a = 1006.0(3), b = 1244.6(4) and c = 1600.8(5) pm, V = 2004.3 x 106 pm3, Z = 4. Compound 3 crystallizes in the monoclinic space group P 21/m with a = 874.4(8), b = 1407(1) and c = 1500(1) pm, β = 92.95(6) , V = 1843 × 106 pm3, Z = 2.

Electronic and Structural Properties of Iron(II) and Nickel(II) Cationic Complexes of 2-(Pyrazin-2-ylamino)-4-(pyridin-2-yl)thiazole

1997 ◽  
Vol 50 (2) ◽  
pp. 129 ◽  
Author(s):  
Bradley J. Childs ◽  
John M. Cadogan ◽  
Donald C. Craig ◽  
Marcia L. Scudder ◽  
Harold A. Goodwin
Keyword(s):  
Room Temperature ◽  
Singlet State ◽  
Monoclinic Space Group ◽  
Counter Anion ◽  
Triclinic Space Group ◽  
Space Group ◽  
A Value ◽  
Complex Salts ◽  
Electronic And Structural Properties ◽  
Continuous Temperature

Complex salts containing the [FeIIN6]2+ derivative of 2-(pyrazin-2-ylamino)-4-(pyridin-2-yl)thiazole (pzaptH) undergo continuous, temperature-induced singlet (1A1) quintet (5T2) transitions with the transition temperature being dependent on the nature of the counter anion and the presence of solvate water, the latter tending to stabilize the singlet state. A transition is also observed for the fluoroborate salt in methanol solution. The extent of stabilization of the singlet state for iron(II) in these complexes is somewhat greater than in those derived from the previously studied 2-(pyridin-2-ylamino)-4-(pyridin-2-yl)thiazole. The crystal structures of [Fe(pzaptH)2] [CF3SO3]2 and [Ni(pzaptH)2] [BF4]2.2H2O have been determined. The average Fe-N distance is 1·985 Å, a value consistent with the essentially low-spin nature of the complex at room temperature, and the average Ni-N distance is 2·089 Å. In both complexes the bridging >NH group is involved in hydrogen bonding to the anions and, in the nickel complex, also to the solvate water. The uncoordinated nitrogen of the pyrazine ring is not hydrogen-bonded. Bis[2-(pyrazin-2-ylamino)-4-(pyridin-2-yl)thiazole]iron(II) triflate: triclinic, space group P -1, a 8·794(5), b 11·082(6), c 17·49(1) Å, α 77·59(4), β 86·80(4), γ 84·21(4)°, Z 2. Bis[2-(pyrazin-2-ylamino)-4-(pyridin-2-yl)thiazole]nickel(II) tetrafluoroborate dihydrate: monoclinic, space group P 21/c, a 8·784(3), b 8·795(2), c 41·16(1) Å, β 94·58(2)°, Z 4.

Preparations, X-ray crystal structures, and spectral studies of seleninyl bis(trifluoromethanesulfonate) and seleninyl bis(acetate)

1988 ◽  
Vol 66 (9) ◽  
pp. 2367-2374 ◽  
Author(s):  
Ramesh Kapoor ◽  
Poonam Wadhawan ◽  
Pratibha Kapoor ◽  
Jeffery F. Sawyer
Keyword(s):  
Crystal Packing ◽  
Spectral Studies ◽  
Monoclinic Space Group ◽  
Coordination Geometry ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
X Ray ◽  
X Ray Crystallography ◽  
Intermolecular Contacts ◽  
Ir And Raman

The compounds seleninyl bis(trifluoromethanesulphonate) (1) and seleninyl bis(acetate) (2) have been prepared and characterized by elemental analysis, ir and Raman spectroscopy, and X-ray crystallography. Crystals of 1 are monoclinic, space group P21/n with a = 12.735(1) Å, b = 5.163(4) Å, c = 16.133(2) Å, β = 96.426(8)°, U = 1054 Å3, Dx = 2.48 g cm−3 for Z = 4, R = 0.038 for 1745 observed reflections with I > 2.5σ(I). Those of 2 are orthorhombic, space group Pcab with a = 6,845(3) Å, b = 8.992(2) Å, c = 23.560(9) Å, U = 1450 Å3Dx = 1.95 g cm−3 for Z = 8, R = 0.074 for 1073 observed reflections with I > 3.0σ(I). The primary geometry of the Se atom in SeO(O3SCF3)2 is AX3E with a Se=O distance of 1.571(3) Å and Se—O bond lengths to the CF3SO3 ligands of 1.902(3) and 1.922(3) Å. Completing the overall coordination geometry of the Se atom are 2 intramolecular and 4 intermolecular Se … O contacts which are less than van der Waals limits. The overall coordination geometry is somewhat irregular since the two triflate anions are significantly differently arranged with respect to the SeO3E tetrahedron. The crystal packing consists of layers of interacting molecules. In 2 there is some disorder. However, the major arrangement of the molecule has Se=O and Se—O(1), Se—O(3) distances to the acetate ligands of lengths 1.575(9), 1.847(7), and 1.831(8) Å respectively. The overall geometry of the Se atom in this compound is completed by two intramolecular secondary Se … O contacts involving the second O atoms of both acetates and two intermolecular contacts involving the seleninyl oxygen atom and atom O(2) of an acetate group in two different symmetry related molecules. Overall, the crystal packing consists of essentially centrosymmetric dimeric units linked together through Se=O—Se bridges. A 1:2 adduct of 1 with pyridine has also been prepared and characterised.

Structures of L-valyl-L-glutamine and L-glutamyl-L-valine

1996 ◽  
Vol 52 (6) ◽  
pp. 999-1006 ◽  
Author(s):  
C. H. Görbitz ◽  
P. H. Backe
Keyword(s):  
Hydrogen Bond ◽  
Crystal Packing ◽  
Molecular Geometry ◽  
Side Chain ◽  
Monoclinic Space Group ◽  
Orthorhombic Space Group ◽  
Acta Cryst ◽  
Space Group ◽  
Cell Parameters ◽  
Additional Hydrogen Bond

L-Val-L-Gln crystallizes in the orthorhombic space group P21212 with a = 16.419 (3), b = 15.309 (3) and c = 4.708 (1) Å. The final wR(F o 2) is 0.100 for 2044 independent reflections, R(Fo ) = 0.050 for 1475 reflections with I > 2.0σ(I). L-Glu-L-Val crystallizes in the monoclinic space group P21 with a = 6.487 (2), b = 5.505 (2), c = 16.741 (4) Å and β = 97.22 (2)°. The final wR(F F o 2) is 0.111 for 1920 independent reflections, R(Fo ) = 0.047 for 1576 reflections with I > 2.0σ(I). Molecular geometries are normal, except for a unique eclipsed orientation of the charged amino group of L-Glu-L-Val. Dipeptides with a N-terminal hydrophobic residue and C-terminal hydrophilic residue are shown to have crystal packing patterns fundamentally different from those of dipeptides with the same types of residues in reversed order. Accordingly, the structure of L-Val-L-Glu [Eggleston (1984). Acta Cryst. C40, 1250 –1252] is rather similar to L-Val-L-Gln, but different from its retroanalogue L-Glu-L-Val. Nevertheless, the pairing of hydrogen-bond donors and acceptors is the same for L-Val-L-Glu and L-Glu-L-Val, indicating very distinct hydrogen-bonding preferences. This is the first demonstration of such a coincidence among dipeptide structures. The differences between L-Val-L-Glu and L-Val-L-Gln structures stem from modifications of the molecular geometry and cell parameters due to the formation of an additional hydrogen bond from the extra donor in the L-Gln side chain.

Isobaric and isochoric freezing of CH2BrCl and isostructural relations between CH2Cl2, CH2Br2 and CH2BrCl

2007 ◽  
Vol 63 (6) ◽  
pp. 903-911 ◽  
Author(s):  
Marcin Podsiadło ◽  
Andrzej Katrusiak
Keyword(s):  
High Pressures ◽  
Crystal Packing ◽  
Ambient Pressure ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Potential Surfaces ◽  
Space Group ◽  
Cl Atoms

Bromochloromethane, CH2BrCl, has been temperature-frozen and in situ pressure-frozen and the structure determined by X-ray diffraction at low temperatures of 170 and 100 K at ambient pressure (0.10 MPa), and at high pressures of 1.04 and 1.72 GPa at room temperature (295 K). CH2BrCl exhibits a remarkable polymorphism: at low temperature it crystallizes in the monoclinic space group C2/c (phase I), isostructural to the crystals of CH2Br2. The pressure-frozen crystal of CH2BrCl is orthorhombic, space group Pbcn, and is isostructural to the crystal of CH2Cl2. In both phases I and II the Br and Cl atoms are substitutionally disordered. The freezing temperatures and pressures of simple dihalomethanes have been correlated to their molecular weight and halogen... ˙˙halogen distances. Calculated electrostatic potential surfaces have been related to the different crystal packing of dihalomethanes investigated.

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