Sonogashira coupling of diacetyl 5-ethynyl-2'-deoxyuridine with diacetyl 5-iodo-2'-deoxyuridine gave the acylated ethynediyl-linked 2'-deoxyuridine dimer (3b) (63%) that was deprotected with ammonia/methanol to ethynediyl-linked 2'-deoxyuridines (3a) (79%). Reaction of 5-ethynyl-2'-deoxyuridine (1a) with 5-iodo-2'-deoxyuridine gave the furopyrimidine linked to 2'-deoxyuridine (78%). Catalytic oxidative coupling of 1a (O2, CuI, Pd/C, DMF) gave the butadiynediyl-linked 2'-deoxyuridines (4) (84%). Double Sonogashira coupling of 5-iodo-2'-deoxyuridine with 1,4-bis(ethynyl)benzene gave 1,4-phenylenediethyne-bridged 5-ethynyl-2'-deoxyuridines (5, 83%). Cu-catalyzed cycloisomerization of dimers 4 and 5 gave their furopyrimidine derivatives. One electron addition to 1a, 3a and 4 gave the anion radical whose ESR spectra showed the unpaired electron largely localized at C6 of one uracil ring (17 G doublet) at 77 K. For the ethynediyl- and butadiynyl-linked uridines 3a and 4 the ESR spectra of their one electron oxidized species at 77 K showed that the unpaired electron is delocalized over both rings. Thus structures 3a and 4 provide an efficient electronic link for hole conduction between the uracil rings. However, for the excess electron, an activation barrier prevents coupling to both rings. These dimeric structures could provide a gate that could separate hole transfer from electron transport between strands in DNA systems. In the crystal structure of acylated dimer 3b the bases were found in the anti position to each other across the ethynyl link. Similar anti conformation was preserved in the derived furopyrimidine–deoxyuridine dinucleoside.
Alkynes; Electron delocalization; ESR; Deoxyuridine; Furopyrimidine; Nucleosides; Synthesis
[Bis(trimethylsilyl)amino](tert-butylimino)thiophosphorane reacts in benzene with isopropyl alcohol via 1,2-addition of an iPrO–H bond across the P=N bond, resulting in the title compound, C13H35N2OPSSi2. In the molecule, the P atom possesses a distorted tetrahedral environment involving two N atoms from (Me3Si)2N– and tBuNH– groups, one O atom from an iPrO group and one S atom, therefore the molecule has a stereocenter on the P atom but crystal symmetry leads to a racemate. In the crystal, a pair of enantiomers form a centrosymmetric dimer via a pair of N—H⋯S hydrogen bonds.
crystal structure; (trimethylsilyl)amino; phosphinothioate; N—H⋯S hydrogen bonding
In the crystal structure of the title salt, C7H12N2
−, the nitrate ions are located in the vicinity of the protonated amine groups, accepting strong N—H⋯O hydrogen bonds. Each ammonium group is involved in a total of three such interactions with neighbouring nitrate ions, generating a three-dimensional network. In addition, there are π–π interactions between the aromatic rings of centrosymmetrically related diammonium moieties, with a centroid–centroid distance of 3.682 (1) Å.
The title compound, C26H23F3N4O, crystallizes with two symmetry-independent molecules in the asymmetric unit, denoted A and B, which differ mainly in the rotation of the methoxyphenyl ring. The –CF3 group of molecule B is disordered by rotation, with the F atoms split over two sets of sites; the occupancy factor for the major component is 0.853 (4). The dihedral angles between the pyrimidine ring and the attached phenyl, methoxyphenyl and trifluoromethylphenyl rings are 8.1 (2), 37.5 (2) and 70.7 (2)°, respectively, in molecule A, and 9.3 (2), 5.3 (2) and 79.7 (2)° in molecule B. An intramolecular N—H⋯N hydrogen bond occurs in each molecule. In the crystal, two crystallographically independent molecules associate into a dimer via a pair of N—H⋯N hydrogen bonds, with a resulting R
2(12) ring motif and π–π stacking interactions [centroid–centroid distance = 3.517 (4) Å] between the pyrimidine rings. For the A molecules, there are intermolecular C—H⋯O hydrogen bonds between an aryl C atom of methoxyphenyl ring and a methoxy O atom of an adjacent molecule. A similar interaction is lacking in the B molecules.
The title compound, [Na(C12H8N2O8P)], consists of one Na+ cation and one bis(p-nitrophenyl)phosphate anion with a considerable distortion of the phosphate tetrahedron due to the presence of two P—O ester bonds. The anion bridges five Na+ cations whereby each cation is chelated by the nitro O atoms of one anion and bonded via a nitro O atom and phosphate O atoms to four other anions. This bridging arrangement leads to the formation of double layers parallel to (001). Adjacent layers are linked through weak C—H⋯O hydrogen bonds.
The title compound, C13H8INO, was prepared by a condensation reaction of 4-nitrobenzene with phenylacetonitrile in NaOH–ethanol solution. There are two independent molecules in the asymmetric unit, in which the dihedral angles between the benzene ring and the benzoisoxazole unit are 4.2 (3) and 4.1 (3)°. The crystal packing is governed by C—H⋯N, C—I⋯π and C—I⋯O interactions.
The asymmetric unit of the title compound, C17H15NO4, contains two independent molecules with similar geometric parameters. In both molecules, the conformation of the cyclohexene ring is half-chair, while the pyrrolidinone ring adopts an envelope conformation with the γ-carbon atom of the α-pyrrolidinone ring as the flap. In the crystal, O—H⋯O hydrogen bonds between the carboxylic and carbonyl groups link alternate independent molecules into chains propagating in the b-axis direction. The crystal packing also features weak C—H⋯π interactions.
In the title compound, C24H18Cl4N4, the pyrimidine ring makes dihedral angles of 19.1 (2), 4.1 (2) and 67.5 (2)°, respectively, with phenyl and two benzene rings, and the molecular conformation is stabilized by an intramolecular N—H⋯N hydrogen bond closing a six-membered ring with an S(6) motif. In the crystal, a pair of intermolecular N—H⋯N hydrogen bonds connect two molecules, forming inversion dimers with R
2(12) motifs. C—H⋯π interactions links the dimers into a chain running along the a-axis direction. There are also π–π stacking interactions [centroid–centroid distance = 3.666 (4) Å] between the benzene rings of adjacent chains.
In the title compound, C25H23FN4, the pyrimidine ring makes dihedral angles of 11.3 (2), 24.5 (2) and 70.1 (2)° with the phenyl and two benzene rings, and the molecular conformation is stabilized by an intramolecular N—H⋯N hydrogen bond with an S(6) ring motif. In the crystal, a pair of weak C—H⋯F hydrogen bonds link two molecules into an inversion dimer with an R
2(16) motif. In the dimer, there is also an intermolecular π–π stacking interaction [centroid–centroid distance = 3.708 (4) Å] between the fluorinated benzene rings. The dimers are further linked by a C—H⋯π interaction, so forming a column along the c axis.
The title salt, (C12H12N4O2)[ReCl6], consists of 2,2′-[(1E,2E)-1,2-bis(hydroxyimino)ethane-1,2-diyl]dipyridinium cations and [ReCl6]2− anions which are both located on inversion centres. Each cation consists of a glyoxime moiety attached to two protonated pyridine rings in ortho positions. In the crystal, E,E isomers of the cation are observed which differ in the spatial arrangement of the pyridine rings. These rings are positionally disordered over two positions with site-occupancy factors of 0.786 (7) and 0.214 (7). The geometry of the cation is compared with that of a recently reported dipyridylglyoxime with the same configuration. The cations and anions are involved in a network of intermolecular O—H⋯Cl, N—H⋯Cl and C—H⋯Cl hydrogen bonds.
The asymmetric unit of the title compound, C26H25FN4O, consists of two symmetry-independent molecules, denoted A and B. The conformation of each molecule is mainly determined by an intramolecular N—H⋯N hydrogen bond, which closes a six-membered ring. The dihedral angles between the pyrimidine ring and the phenyl, fluorophenyl and ethoxyphenyl rings are 15.4 (2), 28.4 (2) and 77.5 (2)°, respectively, in molecule A, and 15.9 (2), 2.7 (2) and 61.8 (2)° in molecule B. Intermolecular N—H⋯N hydrogen bonds and π–π stacking interactions between pyrimidine rings [centroid–centroid distance = 3.692 (4) Å] connect molecules A and B into dimers and C—H⋯O hydrogen bonds link the dimers into zigzag chains along . The (4-ethoxyanilino)methyl group of the B molecule is disordered over two sets of sites, the occupancy factor for the major component being 0.900 (2).
The title compound, C17H14N3O2
−, is an aroylhydrazone-based material consisting of a 4-(hydrazinecarbonyl)pyridinium cation and a nitrate anion. In the cation, the dihedral angle between the benzene ring and the naphthalene ring system is 2.20 (7)°. In the cation, the configuration about the C=N bond is E. There is an intramolecular O—H⋯N hydrogen bond in the cation, and the supramolecular structure is stabilized by intermolecular N—H⋯O hydrogen bonds and weak C—H⋯O contacts between the cation and the nitrate anion.
The conformation of the title molecule, C25H23FN4O, is mainly determined by an intramolecular N—H⋯N hydrogen bond closing a six-membered ring and the dihedral angles between the pyrimidine ring and the three benzene rings which are 12.8 (2), 12.0 (2) and 86.1 (2)°. An intramolecular N—H⋯F interaction also occurs. The crystal stucture is stabilized by weak C—H⋯O and C—H⋯π interactions. An intermolecular N—H⋯N interaction is also observed.
Comparison of the crystal structures of two pentadehydropeptides containing ΔPhe residues, namely (Z,Z)-N-(tert-butoxycarbonyl)glycyl-α,β-phenylalanylglycyl-α,β-phenylalanylglycine (or Boc0–Gly1–ΔZPhe2–Gly3–ΔZPhe4–Gly5–OH) methanol solvate, C29H33N5O8·CH4O, (I), and (E,E)-N-(tert-butoxycarbonyl)glycyl-α,β-phenylalanylglycyl-α,β-phenylalanylglycine (or Boc0–Gly1–ΔEPhe2–Gly3–ΔEPhe4–Gly5–OH), C29H33N5O8, (II), indicates that the ΔZPhe residue is a more effective inducer of folded structures than the ΔEPhe residue. The values of the torsion angles ϕ and ψ show the presence of two type-III′ β-turns at the ΔZPhe residues and one type-II β-turn at the ΔEPhe residue. All amino acids are linked trans to each other in both peptides. β-Turns present in the peptides are stabilized by intramolecular 4→1 hydrogen bonds. Molecules in both structures form two-dimensional hydrogen-bond networks parallel to the (100) plane.
There are two structurally similar but crystallographically independent molecules (A and B) in the asymmetric unit of the title compound, C21H22N2O2, which are linked via two O—H⋯O hydrogen bonds. An intramolecular O—H⋯O hydrogen bond also occurs in each molecule. In the crystal, the A and B molecules are further linked through C—H⋯O interactions. The benzene ring is twisted at an angle of 69.9 (1) and 83.4 (1)° relative to the 1,4-dihydroquinoline skeleton in molecules A and B, respectively. Adjacent 1,4-dihydroquinoline units of molecules A are parallel, while molecules A and B are oriented at an angle of 32.8 (1)°.
In the crystal structure of the title compound, C13H8O4, the inversely oriented molecules form inversion dimers through pairs of O—H⋯O hydrogen-bonding interactions. An intramolecular O—H⋯O hydrogen bond occurs. In the packing of the molecules, the nearly planar 2-(furan-2-yl)-4H-chromene units [dihedral angle between the chromene and furan rings = 3.8 (1)°] are either parallel or inclined at an angle of 80.7 (1)°.
In the title salt, [ReO2(C5H5N)4]I3, the cation and anion are both located on centres of symmetry. The ReV atom adopts a trans-ReO2N4 octahedral coordination and short intramolecular C—H⋯O contacts occur within the cation. In the crystal, the cations form layers perpendicular to  and a weak C—H⋯O interaction links the cations.
The title compound, (C4H12NO3)[ReO4], contains two cations and two anions in the asymmetric unit, related by a non-crystallographic centre of symmetry. The crystal structure is stabilized by an extensive hydrogen-bonding network with the formation of puckered layers perpendicular to . In the tris(hydroxymethyl)ammonium cations, intramolecular O—H⋯O hydrogen bonds are present with the formation of an S
1(6) graph-set motif. The crystal structure is further consolidated by N—H⋯O hydrogen bonds.
In the crystal structure of the title compound, [V2(C22H21N2O2)2O4]·2H2O, oxide-bridged dimers of the complex are linked to water molecules by hydrogen-bonding interactions. The two five-membered chelate rings in the dimeric molecule both adopt twist conformations. Each VV atom is six-coordinated by one oxide group and by two N and one O atom of the tridentate Schiff base ligand, and is bridged by two additional oxide atoms. The metal centre has a distorted octahedral coordination. The monoanionic ligands occupy one equatorial and two axial positions.
The title compound, C10H8N2·C8H10O8, is an example of a system with a short O⋯H⋯N hydrogen bond [O⋯N = 2.565 (3) Å]. The crystal structure comprises a 1:1 adduct between 4,4′-bipyridine and butane-1,2,3,4-tetracarboxylic acid, where both components are centrosymmetric. The component molecules are linked through strong O⋯H⋯N hydrogen bonds, forming chains extending approximately along . The chains are interconnected by O⋯H⋯O hydrogen bonds and weak stacking interactions involving the pyridyl rings of the 4,4′-bipyridine molecules [centroid–centroid distance = 3.73 (2) Å and interplanar distance = 3.35 (1) Å]. The H atom of the short O⋯H⋯N hydrogen bond is disordered over two positions with site occupancy factors of ca 0.6 and 0.4. One methylene group is disordered over two positions; the site occupancy factors are ca 0.9 and 0.1.
The quinuclidinium cation of the title compound, C7H14NO+·Cl−, shows a twist along the C—N pseudo-threefold axis, with N—C—C—C torsion angles of −16.0 (1), −16.9 (1) and −15.6 (1)°. The crystal structure is stabilized by N—H⋯Cl and O—H⋯Cl hydrogen bonds, forming infinite chains along the a and b axes.
The crystal structure of the low-temperature form of the title compound, C4H10NO+·BF4
−, was determined at 80 K. Two reversible phase transitions, at 158/158 and 124/126 K (heating/cooling), were detected by differential scanning calorimetry for this compound, and the sequence of phase transitions was subsequently confirmed by single-crystal X-ray diffraction experiments. The asymmetric unit at 80 K consists of three BF4
− tetrahedral anions and three morpholinium cations (Z′ = 3). Hydrogen-bonded morpholinium cations form chains along the  direction. The BF4
− anions are connected to these chains by N—H⋯F hydrogen bonds. In the crystal structure, two different layers perpendicular to the  direction can be distinguished, which differ in the geometry of the hydrogen bonds between cationic and anionic species.
In the crystal structure of the title compound, [Cd(C15H14NO2)2(C6H7NO)2]n, the Cd atom displays a distorted octahedral geometry, including two pyridine N atoms and two hydroxyl O from four symmetry-related 3-pyridylmethanol (3-pyme) ligands and two carboxylate O atoms from mefenamate [2-(2,3-dimethylanilino)benzoate] anions. The Cd atoms are connected via the bridging 3-pyme ligands into chains, that extend in the a-axis direction. The Cd atom is located on a center of inversion, whereas the 3-pyme ligands and the mefenamate anions occupy general positions.
The crystal structure of the title compound, C21H15N2O4
+·CF3O3S−, is stabilized by C—H⋯O and C—H⋯F hydrogen bonds, by C—F⋯π, N—O⋯π and S—O⋯π interactions, and by O⋯O [2.70 (4) Å] and O⋯F [2.85 (1) or 2.92 (1) Å] contacts; π–π interactions are also present. In the packing of the molecules, acridine units are either parallel or inclined at an angle of 12.5 (1)°. The nitrophenoxycarbonyl unit is disordered over two position; the site occupancy factors are 0.89 and 0.11.
In the title compound, (CH6N3)2[Co(C3H2O4)2(H2O)2], the anions lie on crystallographic centres of inversion. The crystal structure adopts a layered structure, stabilized by an extensive network of N—H⋯O and O—H⋯O hydrogen bonds. One H atom of the guanidinium cation does not participate in any strong hydrogen bonds.