Crystal structure of hexa(3,5-dicarboxypyridine)potassium tetrabromoaurate(III)

The title complex has been prepared, and characterized by X-ray crystallography. The crystals are rhombohedral, space groupR32, witha=20.954(5),c=9.753(1) Å,Z=3, andR _F =0.070 for 680 observed MoK reflections. The structure consists of a packing of hexa(3,5-dicarboxypyridine) potassium cations and tetrabromoaurate(III) anions. The potassium atom is surrounded by equivalent oxygen atoms to form a KO₆ octahedron with a very short K-O distance of 2.56(1) Å. The AuBr ₄ ^– group exhibits orientational disorder with a mean bond length of 2.38(1) Å. Two symmetric strong hydrogen bonds (linear OHO and bent NHN) are found in the crystal structure. The nearly planar organic ligands are interlinked by hydrogen bonds to form parallel sheets which approximately correspond to the (003) family of planes. The potassium atoms lying in between these sheets connect them into a three-dimensional network.On leave from Central Laboratory, Nankai University, Tianjin, China.     

Cyclodipeptides: Structure and conformation of cyclo(tyrosyl-prolyl)

The structure and conformation of the cyclodipeptide, cyclo(Tyrosyl-Prolyl), cyclo(Tyr-Pro) have been investigated with X-ray crystallographic and spectroscopic methods. Two conformations of cyclo(Tyr-Pro) crystallized in the space groupP2₁2₁2 with cell dimensionsa=11.890(3),b=12.057(1),c=18.528(4). Both these conformations are uncommon for cyclodipeptides containing a proline residue. The tyrosyl side chains of these conformers are folded towards the diketopiperazine (DKP) ring. The DKP ring adopts a flattened chair conformation in contrast to the typical boat conformation generally observed for DKP rings. The conformation of the pyrrolidine ring can be described as a pseudo C₂ symmetrical twist. One intermolecular hydrogen bond was observed for each of the two conformations of cyclo(Tyr-Pro). The hydrogen of the hydroxyl group of the tyrosyl residue is hydrogen bonded to the oxygen of the carbonyl group of the diketopiperazine ring, i.e., the carbonyl group originating from the tyrosyl residue. NMR spectroscopic studies indicated a different conformation for cyclo(Tyr-Pro) in solution similar to the generally observed conformation of cyclodipeptides, i.e., extended aromatic side chain and boat conformation for the DKP ring.     

Structure and conformation of the tripeptide: N-t-Boc-Prolyl-Phenylalanyl-Proline (Boc-Pro-Phe-Pro)

The structure and conformation of the tripeptide N-t-Boc-Prolyl-Phenylalanyl-Proline (Boc-Pro-Phe-Pro) (C₂₄H₃₃N₃O₆) have been investigated with X-ray crystallographic and spectroscopic methods. Two conformations of Boc-Pro-Phe-Pro crystallized in the space groupP2₁2₁2₁ with cell dimensionsa=11.912(1),b=14.256(1),c=30.402(3). The conformation of the backbone, the orientation of the aromatic side chain and the puckering modes for the pyrrolidine rings of these conformers differ significantly. The peptide bonds exist in the generally preferredtrans conformation being slightly non-planar. These two conformations reflect-helix- and collagen-type prolines. The crystal structures of both the conformers are stabilized by two, although different intermolecular hydrogen bonds. An intermolecular bond between the carbonyl oxygen of the carboxy terminal (³Pro) and the amide proton (²Phe) is observed for both the conformers. The second intermolecular hydrogen bond for conformer 1 is between the hydrogen of the carboxy terminal (³Pro) and the carbonyl oxygen of the N-t-Boc protecting group in contrast to the second hydrogen bond between the carbonyl oxygen of the (²Phe) residue and the hydrogen of the carboxy terminal (³Pro) for conformer 2. NMR spectroscopic studies indicated the presence of stereo-conformations due to thecis andtrans amide bonds similar to other proline-containing peptides.     

Crystal structure and conformation of N-(t-butoxycarbonyl)-L-isoleucyl-L-alanine benzylester

C₂₂N₂O₅H₃₂,M _r =404.5, monoclinic,C2,a=21.781(5),b=5.065(1),c=22.333(4)Å,=112.81(2)°,V=2271.1(9)ų,D _calc=1.148 g cm³, (CuK )=1.5418 Å,=5.89 cm^–1,F(000)=848, room temperature,R=0.058 for 2178 unique reflections [I2.5(I)]. The peptide linkage is in thetrans conformation. The molecule adopts the-sheet structure. The crystal structure is stabilized by a three-dimensional network of N-HO and C-HO hydrogen bonds.DCB Contribution No. 813.     

Structures of Bis(1-ethylbenzimidazol-2-yl)alkyl Copper(II) Dichlorides: An Unusual Cocrystallization

Abstract  Two structures containing pseudo-tetrahedral Cu(II)N₂Cl₂ coordination complexes are reported. The first molecular structure (A) of the compound, 1,1′bis(1-ethylbenzimidazol-2-yl)propane copper(II) dichloride (triEtBBIM)Cu(II)Cl₂, 1, is reported. The complex crystallized in the triclinic space group P-1 with a = 8.616(3) ?, b = 9.302(3) ?, c = 14.314(4) ?, α = 85.613(6)°, β = 85.170(6)°, γ = 66.117(6)° and V = 1044.1(5) ?³ with Z = 2. The second structure (B) contains 1 and (3,3′bis(1-ethylbenzimidazol-2-yl)pentane) copper(II) dichloride (tetEtBBIM)Cu(II)Cl₂, 2, both of which, cocrystallize in an equal molar ratio with a nitromethane solvate molecule. The complex crystallized in the monoclinic space group P2₁/c with a = 18.876(4) ?, b = 14.975(3) ?, c = 18.344(4) ?, β = 116.75(3)°, and V = 4630.3(16) ?³ with Z = 4. The cocrystallization of such discrete complexes has been coined a chemical Janus. Graphical Abstract  The title complexes contain pseudo-tetrahedral Cu(II)N₂Cl₂ coordination. One of the structures is the result of an unusual cocrystallization, in which two different discrete Cu(II) molecules cocrystallize in an equimolar ratio with a nitromethane solvate molecule.      

Structure and conformation of 6-nitro-2,4-bis(dichloromethyl)-1,3-benzdioxin

6-Nitro-2,4-bis(dichloromethyl)-1,3-benzdioxin is monoclinic,P2₁/c, witha=8.514(1),b=22.187(3),c=7.931(1) Å,=117.96(1)°,Z=4. The structure was solved, from data collected with MoK radiation on an Enraf-Nonius CAD4 diffractometer, by direct methods and refined by full-matrix least squares using 2170 unique reflections to give a finalR factor of 0.032. The heterocyclic ring in the title compound has an envelope conformation with thecis-dichloromethyl groups in pseudoequatorial positions. The average C-C(HCl₂) distance is 1.516(4) Å. A comparison is given with the structure of the analogous compound 6-nitro-2,4-bis(trichloromethyl)-1,3-benzdioxin (Irving, A., and Irving, H. M. N. H. (1986)J. Crystallogr. Spectrosc. Res. 16, 703) which also containscis-halogenoalkyl groups but in which the –CCl₃ group at the 4-position occupies a pseudoaxial position.     

Unusual alignment during wet coating of oligo(phenylene vinylene)s thin films

Were formed anisotropic thin films of oligo(p-phenylene vinylene) dye on the surface of rubbed nylon during rod-coating from chloroform and chlorobenzene solutions. The order parameter and alignment direction of films depend on the solvent type and the temperature. On coating from chloroform solution molecules in the dye film align perpendicular and parallel to rubbing direction at temperatures below 40?°C and above 60?°C, correspondingly. Homogeneously oriented anisotropic films with a dichroic ratio of more than 25 were obtained.     

The conformation of pentaazamacrocyclics. I. Crystal structures of nickel (II) and copper (II) complexes of 1,4,7,11,14-pentaazacycloheptadecane

The crystal structures of [Ni(17-aneN₅)H₂O]Br₂·3H₂O (17-aneN₅=1,4,7,11,14-pentaazacycloheptadecane) and of [Cu(17-aneN₅)]CuBr₄ are reported. Diffraction data using MoK radiation were measured with a CAD-4 diffractometer and the structures refined by full-matrix least squares. The nickel compound has regular octahedral coordination with coordinated water completing the octahedron. The copper is approximately square-pyramidal with an apical Cu-N bond of 2.29(4) Å, compared to a mean bond length of 2.06(2) Å in the basal plane. As a result, the folding of the 17-membered macrocyclic rings is completely different in the two compounds.     

A twist boat: Structure and conformation oftrans-2,4,6-tris(trichloromethyl)-1,3,5-trithian

Trans-2,4,6-tris(trichloromethyl)-1,3,5-trithian, (CCl₃·CHS)₃, has been prepared free from persistent impurification bycis-trans-2,4,6-tris(trichloromethyl)-1,3,5-oxadithian and its conformation determined by single crystal x-ray crystallography. The title compound is orthorhombic,Pbca, a=10.479(10),b=27.957(14),c=11.093(3) Å,V=3250 ų,Z=8. The structure was solved by direct methods, from data collected at room temperature on an Enraf-Nonius CAD4 diffractometer, and refined by full-matrix least squares to a finalR value at 0.074 using 1186 reflections. The molecule exhibits a twist boat conformation with the –CCl₃ groups occupying pseudoequatorial positions. The torsion angles in the trithian ring are successively 29(1), –79(1), 41(1), 41(1), –84(1), 39(1)°. Average values are: S-C 1.82(2), C(ring)-C(Cl₃) 1.56(4), C-Cl 1.76(2) Å, S-C-S 112.7(2)°. The C-S-C angles are 97.4(7), 101.4(7), 97.3(7)°.     

Crystal structure and solid-state31P CP-MAS NMR spectrum of the bis(trifluoroacetato) (triphenylphosphine)mercury(II) dimer [Hg(CF3CO2)2PPh3]2

The title compound belongs to the monoclinic space groupP2₁/c,a=20.29(1),b=12.644(8),c=18.25(1), Å,=95.76(5)°. The unit cell contains two dimeric [Hg(CF₃CO₂)₂PPh₃]₂ molecules in which each Hg atom forms strong primary bonds to a PPh₃ molecule and an oxygen of a monodentate trifluoroacetate ligand. These two Hg atoms are bridged by two extra trifluoroacetate ligands, one providing a single oxygen to a Hg-O-Hg bridge, the other including both carboxylate oxygens in a Hg-O-C-O-Hg bridging moiety. This unusual type of bridging makes the two halves of the molecule symmetry independent, leading to distinct signals at 31.5 and 29.9 ppm for the phosphines in the³¹P CP-MAS NMR spectrum of the solid complex.     

Studies of systemic acylanilide fungicides: Part V. Crystal structure and molecular conformation ofDL-methylN-(2,6-dimethylphenyl)-N-(2-phenylacetyl) alaninate

The crystal structure of the title compound (C₂₀H₂₃NO₃) was determined by three-dimensionalx-ray analysis from diffractometer data. Crystal data are: monoclinic,C2/c,a=22.425(18) Å,b=11.201(5) Å,c=15.388(16) Å,=108.95(7)°,Z=8,D _x=1.182 g·cm^–3, (MoK)=0.075 mm^–1. FinalR=0.083 for 1148 observed reflexions. The 2,6-dimethylphenyl ring is almost perpendicular to the amidic plane of the molecule (dihedral angle of 92.5°) whereas the phenyl group of the phenylacetyl moiety is inclined at 65.4° with respect to the plane through the central part of the molecule. The distance between the two carbonyl oxygens is 3.095 Å, i.e., within the hitherto observed range of 3.028–3.100 Å for related systemic acylanilide fungicides.     

Studies of systemic acylanilide fungicides. Part I. Crystal structure and molecular conformation ofdl-methyl-N-(2,6-dimethylphenyl)-N-(2-methoxyacetyl) alaninate

The crystal structure of metalaxyl (C₁₅H₂₁NO₄) was determined by three-dimensional X-ray analysis from diffractometer data. The crystals are monoclinic,P2₁/c,a=7.851(3) Å,b=13.119(10) Å,c=15.107(7) Å,=101.71(6)°,Z=4,D _x=1.218 g cm^–3, (MoKa)=0.095 mm^–1. FinalR=0.079 for 1203 observed reflections. The dimethylphenyl ring is almost perpendicular to the amidic plane of the molecule.     

Studies of systemic acylanilide fungicides. Part II. Crystal structure and molecular conformation ofdl-methylN-(2,6-dimethylphenyl)-N-(2-furoyl)alaninate

A crystalline modification of the title compound (C₁₇H₁₉NO₄) was determined by three-dimensional X-ray analysis from diffractometer data. Crystal data: monoclinic,Cc,a=15.997(12) Å,b=7.929(7) Å,c=14.664(11) Å,=118.70(5)°,Z=4;D_x=1.227 Mg m^–3,(MoK)=0.094 mm^–1. FinalR=0.068 for 852 observed reflections. The dimethylphenyl ring is strongly twisted (94.9°) with respect to the amidic plane of the molecule, which almost coincides with the furan ring (6.9°).     

Structure and conformation of 6,8-dinitro-2,4-bis(trichloromethyl)-1,3-benzdioxin: X-ray crystallographic determination

6,8-dinitro-2,4-bis(trichloromethyl)-1,3-benzdioxin is monoclinic,P2₁/c,Z=4,a=12.348(2),b=11.575(3),c=12.183(4) Å,=107.48(2)°. The structure was solved by direct methods, from data collected at room temperature on an Enraf-Nonius CAD4 diffractometer, and refined by least-squares to a finalR value of 0.032 using 2192 reflections. The heterocyclic ring is an envelope structure, the dihedral angle between the plane of the aromatic ring and that containing five of the atoms of the heterocycle being 4.98(6)°. One -CCl₃ group is pseudoequatorial while the (Ar-C)CCl₃ group is pseudoaxial. C-C_eq 1.526(3) Å; C-C_ax 1.537(3) Å; C-C(C_ax)-O 112.4(2)°; C(C_ax)-O-C(C_eq) 115.2(2)°.     

X-ray crystallographic determination of the structure and conformation of 7-(1-acetoxy-1-methylethyl)-4a-methyl-octahydro-2(3H)-naphthalenone

The crystal structure of 7-(1-acetoxy-1-methylethyl)-4a-methyl-octahydro-2(³H)-naphthalenone, C₁₆H₂₄O₃ has been determined by X-ray diffraction. The crystals are orthorhombic, P2₁2₁2₁,a=5.938(2),b=12.081(4),c=21.607(7) Å,Z=4. The structure was solved by direct methods, and refined to an R value of 0.062 for 1013 nonzero independent amplitudes. Ring A has the C(6) distorted sofa conformation whereas the B ring possesses the slightly deformed chair conformation. The side chain in the C(10) position is oriented in relation to the plane of the B ring.The nomenclature of IUPAC for the name of compound in the title is applied. However, for simplicity reason numbers of atoms in the paper follow Fig. 1.     

Structure and conformation of 6-nitro-2,4-bis(trichloromethyl)-1,3-benzdioxin: X-ray crystallographic determination

6-Nitro-2,4-bis(trichloromethyl)-1,3-benzdioxin is triclinic,P¯1;a=6.604(2),b=7.678(6),c=15.201(4) Å; =91.57(5),=99.39(2), =90.50(5)°;Z=2. The structure was solved by direct methods from data collected at room temperature on an Enraf-Nonius CAD4 diffractometer and refined by least squares to a finalR value of 0.035 using 2092 reflections.The molecule consists of a heterocycle in a distorted screw boat conformation fused to a significantly nonplanar aromatic ring. One-CCl₃ group is pseudoequatorial while the (Ar-C)CCl₃ group is pseudoaxial. The C_Ar-C-O-C side of the ring is much flatter than the C_Ar-C_Ar-O-C side, the distortion being caused by the necessity of the-C_axCl₃ group to bend away from the heterocycle. C-C_eq 1.532(4) Å; C-C_ax 1.550(4) Å; C-C(C_ax)-O 113.0(3)°; C(C_ax)-O-C(C_eq) 115.5(2)°.     

X-ray structure and conformation of some (R,R)-N,N′-tetrasubsubstituted 1,2-diamines

The conformational arrangement of a series of (R,R)-N,N′-tetrasubstituted cyclohexyl-1,2-diamines have been examined by X-ray crystallography.     

Molecular conformation and electronic structure. II: Crystal and molecular structure ofN-(p-bromobenzylidene)-p-bromoaniline

The structure of the title compound C₁₃H₉Br₂N has been determined with MoKα₁ diffractometer data, and refined by full-matrix least squares toR = 0.061 for 888 observed reflections. The crystals are monoclinic: space groupP2₁/a,a = 24.912(13),b = 5.877(1),c = 4.046(1) Å,β = 92.42(3) °Z = 2. The uv absorption spectrum indicates a nonplanar conformation in solution. In the solid, the molecule is disordered about a crystallographic inversion center and is planar to within 0.045 Å.     

Crystal and molecular structures of 2-(p-methylbenzyl)- and 2-(p-chlorobenzyl)-5-(p-bromobenzylidene)cyclopentanone. Influence of chloro and methyl substitution on solid-state reactivity

The crystal structures of the title compounds have been determined as part of an investigation into the factors which may influence the solid-state reactivity of benzylidene cyclopentanones. Thep-methyl derivative, which is photoactive in the crystalline state, in monoclinic:P2₁/c,a=18.381(2),b=11.209(2),c=8.285(2) Å,=94.46(12)°, andz=4. The chloro derivative, which is photostable, is also monoclinic:P2₁/c,a=17.522(4),b=7.906(2),c=11.888(2) Å,=91.19(14)°, andz=4. The structures were solved and developed via the heavy-atom method and refined by least-squares to finalR values of 0.062 and 0.061, respectively, using 1902 and 2356 observed reflections measured using an automatic diffractometer. The conformations of the two molecules in their crystal structures are significantly different and lead to dissimilar packing arrangements, which clearly account for the different photochemical behaviors.