The Flavonoids of Combretum quadrangulare: Crystal structures of the Polymorphic Forms of 5-Hydroxy-2-(4'-hydroxy-3',5'-dimethoxyphenyl)-3,7-dimethoxy-4H-1-benzopyran-4-one

1985 ◽  
Vol 38 (8) ◽  
pp. 1177 ◽  
Author(s):  
IR Castleden ◽  
SR Hall ◽  
S Nimgirawath ◽  
S Thadaniti ◽  
AH White
Keyword(s):  
Least Squares ◽  
Crystal Structures ◽  
X Ray Diffraction ◽  
Full Matrix ◽  
X Ray ◽  
Β Phase ◽  
Α Phase ◽  
Polymorphic Forms

The following substituted 2-phenyl-4H-1-benzopyran-4-ones have been isolated from the dried flowers of Combretum quadrangulare Kurz ( Combretaceae ): 5-hydroxy-3,3′,4′,5′,7-pentamethoxy ( combretol ) (1), 3′,5-dihydroxy-3,4′,7-trimethoxy ( ayanin ) (2) and 4′,5-dihydroxy- 3,3′,5′,7-tetramethoxy (3). The last substance (3) was obtained as a mixture of two polymorphic forms (α and β) each of which was characterized by X-ray diffraction. Diffractometer data at 295 K were refined by full matrix least squares to residuals of 0.043 (1181 'observed' reflections) for the α-phase and 0.044 (1421) for the β phase of (3). Crystals of the α-phase of (3) are triclinic, Pī, a 12.663(6), b 9.592(4), c 7.444(4) Ǻ, α 102.48(3), β 101.39(4), γ 91.72(4)°,Z 2. Crystals of the β-phase of (3) are monoclinic P21/n, a 17.139(8), b 12.728(6), c 7.845(7) Ǻ, β 95.07(6)°, Z 4. An unambiguous synthesis of (3) was also achieved.

A REFINEMENT OF THE CRYSTAL STRUCTURES OF (NH4)2TeBr6 AND Cs2TeBr6

1966 ◽  
Vol 44 (8) ◽  
pp. 939-943 ◽  
Author(s):  
A. K. Das ◽  
I. D. Brown
Keyword(s):  
Least Squares ◽  
Crystal Structures ◽  
Diffraction Data ◽  
Bromine Atom ◽  
Three Dimensional ◽  
X Ray Diffraction ◽  
Full Matrix ◽  
X Ray ◽  
Anisotropic Temperature ◽  
Temperature Factors

(NH4)2TeBr6 and Cs2TeBr6 crystals have the cubic K2PtCl6 structure with space group: [Formula: see text] with a0 = 10.728 ± 0.003 Å and 10.918 ± 0.002 Å respectively. The positional coordinate of the bromine atom, and the anisotropic temperature factors of all atoms in the unit cell, have been refined for both crystals by a full matrix least-squares analysis of the three dimensional X-ray diffraction data (R = 0.08). The Te—Br distance, corrected for probable thermal motions of atoms forming the bond, is 2.70 ± 0.01 Å in both crystals.

scholarly journals Crystal structure of Tetraaqua(ethylenediamine)nickel(II) sulfate dihydrate and of Tetraaqua(2,2'-bipyridyl)nickel(II) sulfate dihydrate

1984 ◽  
Vol 37 (5) ◽  
pp. 921 ◽  
Author(s):  
PC Healy ◽  
JM Patrick ◽  
AH White
Keyword(s):  
Crystal Structure ◽  
Water Molecule ◽  
Single Crystal ◽  
Least Squares ◽  
Crystal Structures ◽  
X Ray Diffraction ◽  
Full Matrix ◽  
X Ray ◽  
Oxygen Atoms

The crystal structures of the title compounds, [Ni(OH2)4(en)] [SO4].2H2O, (1), and [Ni(OH2)4(bpy)]- [SO4].2H2O, (2), have been determined by single-crystal X-ray diffraction methods at 295 K, being refined by full matrix least-squares methods to residuals of 0.028,0.031 for 1852, 4323 independent 'observed' reflections respectively. Crystals of (1) are monoclinic, C2/c, a 9.459(4), b 12.192(7), c 12.294(3) �, β 119.84(4)�, Z 4. In the cation, Ni-N is 2.061(2) �; Ni-O (trans to O, N respectively) are 2.106(2), 2.063(2) �. Instead of being enlarged above 90� as predicted from repulsion theory, the angle between the pair of oxygen atoms trans to nitrogen is diminished, being 87 14(7)�. Crystals of (2) are triclinic, P1, a 11.476(5), b 9.351(5), c 7.793(4) �, α 77.63(4), β 83.52(3), γ87.40(4)�, Z 2. In the cation, Ni-N are both 2.063(2) �. Ni-O (trans to N, O respectively) are 2.060(2), 2.O42(2); 2.O80(2), 2�. The short Ni-O distance [2.042(2)�] is associated with the coordination of a trigonal water molecule.

The Crystal-Structures of (±)-(E)-2-(1-Amino-Ethylidene)-4,4,6-Trimethylcyclohexane-1,3-Dione [(±)-Aminoangustione] and (E)-2-(1-Aminoethylidene)-4,6,6-Trimethylcyclohex-4-Ene-1,3-Dione (Aminodehydroangustione)

1986 ◽  
Vol 39 (6) ◽  
pp. 923 ◽  
Author(s):  
JR Cannon ◽  
VA Patrick ◽  
AH White
Keyword(s):  
Least Squares ◽  
Crystal Structures ◽  
X Ray Diffraction ◽  
Full Matrix ◽  
X Ray

The crystal structures of (�)-(E)-2-(1-aminoethylidene)-4,4,6- trimethylcyclohexane-1,3-dione [(�)- aminoangustione ] (8) and (E)-2-(1- aminoethylidene )-4,6,6-trimethylcyclohex-4-ene-1,3-dione ( aminodehydroangustione ) (9) have been determined by X-ray diffraction. Diffractometer data at 295 K were refined by full-matrix least-squares to residuals of 0.057 (712 'observed' reflections) for (8) and 0.061 (571) for (9). Crystals of (8) are tetragonal I 41/a, a 21.68(1), c 9.426(6)Ǻ, Z 16; crystals of (9) are orthorhombic Pmab , a 7.077(2), b 11.421(6), c 13.283(4)Ǻ, Z 4.

Crystal structures of trans-Dichloro- and Dibromo-bis(2,6-dimethylpyridine)copper(II)

1977 ◽  
Vol 30 (9) ◽  
pp. 1947 ◽  
Author(s):  
JA Campbell ◽  
CL Raston ◽  
JN Varghese ◽  
AH White
Keyword(s):  
Least Squares ◽  
Crystal Structures ◽  
X Ray Diffraction ◽  
Compound A ◽  
Full Matrix ◽  
X Ray ◽  
Square Planar

The crystal structures of the title compounds have been determined at 295(1) K by X-ray diffraction and refined by full-matrix least squares to residuals of 0.045 and 0.067 for 1224 and 1955 ?observed? reflections respectively. The compounds are isomorphous (triclinic, Pī, Z 1). Dichloro compound: a 8.068(2), b 8.024(2), c 7.646(2) Ǻ, α 93.84(2), β 113.44(2), γ 117.11(2)�. Dibromo compound: a 7.999(2), b 7.921(2), c 7.849(2) Ǻ, α 94.37(2), β 112.85(2), γ 115.99(2)�. The copper atoms are square-planar coordinated with two halide and two base ligands coordinated necessarily trans by virtue of the siting of the molecule on a centre of symmetry. Cu-X, Cu-N are 2.264(2), 2.011(3) (dichloro); 2.425(1), 1.997(4) Ǻ (dibromo). The plane of the lutidine is almost normal to the CuN2X2 plane.

Crystal structures of o-phenylenediarsine oxychloride (a redetermination) and o-phenylenediarsine oxybromide

1975 ◽  
Vol 28 (1) ◽  
pp. 15 ◽  
Author(s):  
JC Dewan ◽  
K Henrick ◽  
AH White ◽  
SB Wild
Keyword(s):  
Least Squares ◽  
Crystal Structures ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Full Matrix ◽  
Space Group ◽  
X Ray ◽  
Limits Of Error

The crystal structures of the title compounds have been established by X-ray diffraction at 295 K, being refined by full-matrix least-squares to residuals of 0.054 (0.051) respectively 2715 (469) reflections with I > σ(I)]. Crystals are monoclinic, space group C2/c, the compounds being isomorphous. Oxychloride: a = 14.534(4), b = 8.337(2), c = 7.653(1)Ǻ, β = 106.48(1)�. Oxybromide: a = 14.884(4), b = 8.360(2), c = 7.726(1)Ǻ, β = 105.30(1)�, Z = 4. With the exception-of the arsenic- halogen distance, the geometries of the two molecules are identical within the limits of error: for the oxychloride As-O-As, 121.8(3); Cl- As-O,98.03(6); Cl-As-C, 97.2(2); O-As-C, 92. 9(2)� ; As-O, 1.787(3); As-C, 1.941(5) Ǻ. As-Cl is 2.222(2) and As-Br 2.381(2) Ǻ.

Crystal structures of N,N,N',N'-Tetramethylthiuram monosulphide and Diiodo(N,N,N',N'-tetramethylthiuram monosulphide)mercury(II)

1977 ◽  
Vol 30 (8) ◽  
pp. 1693 ◽  
Author(s):  
BW Skelton ◽  
AH White
Keyword(s):  
Single Crystal ◽  
Least Squares ◽  
Crystal Structures ◽  
Metal Atom ◽  
X Ray Diffraction ◽  
Sulphur Atom ◽  
Full Matrix ◽  
X Ray ◽  
The Common ◽  
Trigonal Prismatic

The crystal structures of the title compounds, Me2NC(S)SC(S)NMe2 (tmtm) and I2Hg(tmtm), have been determined by single-crystal X-ray diffraction at 295 K and refined by full-matrix least squares to residuals of 0.038 and 0.050 respectively for 1080 and 1532 ?observed? reflections. ��� The ligand tmtm is monoclinic, P21/a, a 14.096(4), b 7.457(3), c 10.178(3)Ǻ, β 110.55(3)�, Z4. The complex I2Hg(tmtm) is orthorhombic, P212121, a 12.910(3), b 12.441(3), c 9.863(2) Ǻ, Z4. ��� The structure of the ligand comprises a pair of planar Me2NCS2 fragments linked at the common central sulphur atom with a dihedral of 78.4�. As in the related tetraethylthiuram disulphide, the ?CS2- geometry is very asymmetric: <C=S> 1.657; <C-S> 1.793 Ǻ; <S-C-S> 119.3; <S-C-N> 115.2; <S=C-N> 125.4�; with C-S-C, 103.2(2)�. The metal-atom geometry in I2Hg(tmtm) is pseudo-trigonal prismatic, as in I2Hg(Me2NCS2- S2CNMe2), the prism apex being occupied by a ligand sulphur atom, but considerable changes are observed in the geometry about the metal as a consequence of the change in the ligand ?bite?.

Lewis-Base Adducts of Group-11 Metal(I) Compounds. XXIX. Crystal Structures of Bis(Pyridine-4-carbonitrile)silver(I) Nitrate and Bis(4-benzoylpyridine)Silver(I) Nitrate Monohydrate

1987 ◽  
Vol 40 (9) ◽  
pp. 1603 ◽  
Author(s):  
S Gotsis ◽  
AH White
Keyword(s):  
Single Crystal ◽  
Least Squares ◽  
Crystal Structures ◽  
Complex Cation ◽  
Lewis Base ◽  
X Ray Diffraction ◽  
Full Matrix ◽  
X Ray ◽  
Silver Atoms ◽  
Close Contacts

The crystal structures of the title compounds, [Ag(C6H4N2),] (NO3), (I), and [Ag(C12H9NO)2] (NO3).H2O, (2), have been determined by single-crystal X-ray diffraction methods at ~295 K, being refined by full-matrix least-squares methods to residuals of 0.042 and 0.044 for 1814 and 3434 independent 'observed' reflections respectively. Crystals of (1) and (2) are triclinic P1; for (1) a, 27.954(7), b 6.354(2), c 3.710(1)�, α 87.55(3), β 86.21(2), γ 89.35(2)�, Z 2; for (2), a 17.036(5), b 8.691(3), c 7.849(3) �, α � 107.74(2), β 97 53(2), γ 91 .11(2)�, Z 2. In both structures the formulation is basically a linearly coordinated complex cation/anion as shown above: in (I), Ag-N are 2.214(4), 2.203(4) � with N-Ag-N, 162.2(2)"; in (2), Ag-N are 2.146(3), 2.147(3) �, N-Ag-N, 175.3(1)�. The shortest Ag-O contact is found in (1) at 2.693(4)�. No close contacts are found between the silver atoms and cyano or ketonic ligand substituents.

5-Hydroxy-7-methoxy-2-phenyl-4H-1-benzopyran-4-one (Tectochrysin) and 2,5-Dihydroxy-7-methoxy-2-phenyl-2,3-dihydro-4H-1-benzopyran-4-one: Isolation From Uvaria rufas and X-Ray Structures

1989 ◽  
Vol 42 (12) ◽  
pp. 2289 ◽  
Author(s):  
K Chantrapromma ◽  
C Pakawatchai ◽  
BW Skelton ◽  
AH White ◽  
S Worapatamasri
Keyword(s):  
Least Squares ◽  
Crystal Structures ◽  
X Ray Diffraction ◽  
Full Matrix ◽  
X Ray

5-Hydroxy-7-methoxy-2-phenyl-4H-1-benzopyran-4-one ( tectochrysin ) (1), 5-hydroxy-7,8-di-methoxy-2-phenyl-4H-1-benzopyran-4-one (7-0-methylwogonin) (2), 5-hydroxy-6,7-dimethoxy-2-phenyl-4H-1-benzopyran-4-one (6,7-O,O-dimethylbacaiein) (3) and 2,5-dihydroxy-7-methoxy-2-phenyl-4H-1-benzopyran-4-one (4) have been isolated from the roots of Uvaria rufas Blume. The crystal structures of (1) and (4) have been determined by X-ray diffraction methods from diffractometer data at 295 K and refined by full matrix least squares. Crystals of (1) are monoclinic P21/c, a 10.l28(3), b 15.289(5), c 8.215(4) �,β 92.39(3)� Z 4; R 0.045 for No 874 'observed' reflections; crystals of (4) are monoclinic P21/c, a 12.299(4), b 6.489(3), c 16.579(6) �, β 90.24(3)� Z 4; R 0.051 for No 1016.

On the molecular geometry of 1,2-Di(9-anthryl)ethanes. Crystal structures of two crystalline modifications of 1,2-Bis(10-acetoxy-9-anthryl)ethane

1982 ◽  
Vol 35 (11) ◽  
pp. 2357 ◽  
Author(s):  
H Becker ◽  
SR Hall ◽  
BW Skelton ◽  
AH White
Keyword(s):  
Single Crystal ◽  
Crystal Structures ◽  
Molecular Conformation ◽  
Molecular Geometry ◽  
X Ray Diffraction ◽  
Crystalline Phases ◽  
Molecular Conformations ◽  
X Ray ◽  
Β Phase ◽  
Α Phase

In order to define molecular conformations, the crystal structures of two crystalline phases of 1,2- bis(10-acetoxy-9-anthryl)ethane have been determined by single-crystal X-ray diffraction methods at 295 K. Both phases are monoclinic, P21/c. For the 'α'-phase, a 7.609(2), b 14.469(3), c 11.358(3) � β, 96.39(2)�, Z 2. The final residual was 0.034 for 1341 'observed' reflections; the molecule is centrosymmetric about a crystallographic inversion centre. For the 'β'-phase, a 31.264(15), b 5.248(3), c 15.718(6) �,β 97.84(3)�, Z 4, the final residual was 0.052 for 972 'observed' reflections. In this structure two independent, centrosymmetric molecules are found. In both α- and β-form, the molecular conformation is thus 'stretched' rather than 'eclipsed'. The packing patterns of the two modifications have been correlated with their crystal luminescence properties.

Mechanical Alloying Behavior in the Nb-Si, Ta-Si, and Nb-Ta-Si Systems

1988 ◽  
Vol 133 ◽  
Author(s):  
K. S. Kumar ◽  
S. K. Mannan
Keyword(s):  
High Temperature ◽  
Mechanical Alloying ◽  
Mechanical Milling ◽  
Room Temperature ◽  
Crystalline Compound ◽  
X Ray Diffraction ◽  
X Ray ◽  
Β Phase ◽  
Α Phase

ABSTRACTThe mechanical alloying behavior of elemental powders in the Nb-Si, Ta-Si, and Nb-Ta-Si systems was examined via X-ray diffraction. The line compounds NbSi2 and TaSi2 form as crystalline compounds rather than amorphous products, but Nb5Si3 and Ta5Si3, although chemically analogous, respond very differently to mechanical milling. The Ta5Si3 composition goes directly from elemental powders to an amorphous product, whereas Nb5Si3 forms as a crystalline compound. The Nb5Si3 compound consists of both the tetragonal room-temperature α phase (c/a = 1.8) and the tetragonal high-temperature β phase (c/a = 0.5). Substituting increasing amounts of Ta for Nb in Nb5Si3 initially stabilizes the α-Nb5Si3 structure preferentially, and subsequently inhibits the formation of a crystalline compound.

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