A polar/ [pi] model of interactions explains face-to-face stacked quinoid rings : a case study of the crystal of potassium hydrogen chloranilate dihydrate

International audienceThe nature of interactions between face-to-face staggered stacked quinoid rings with pi-systems, observed with a short inter-ring centroid. centroid distance, is analyzed by experimental and theoretical methods. Charge density studies based on X-ray diffraction and DFT calculations, complemented by impedance spectroscopy, were employed to define the electronic and structural characteristics of the quinoid rings responsible for their interactions within the crystal packing. The crystal packing is mainly stabilized by strong electrostatic interactions between the K+ cation and the hydrogen chloranilate anion. The proximity and orientation of the stacked quinoid rings in parallel glide-plane arrangement are partly governed by the non-covalent interactions within the dimer. The estimated contribution of dispersion energy to the stacking of the rings about 10 kcal mol(-1), as calculated by DFT methods, is comparable to medium-strong hydrogen bonding. The electronic structure of 3,6-dichloro-2,5-dihydroxyquinone monoanion exhibits alternating electron-rich and electron-poor regions. The calculated electrostatic energy shows variations with the relative orientation of rings within dimers reaching ca. 10-15 kcal mol(-1). Thus, the nature of interactions between pi-systems of quinoid rings can be described by a polar/pi model where electrostatic complementarity plays a determinant role in pi-stacking orientation. These interactions have great potential in crystal engineering and may be employed in the design of functional materials

Crystal structure of isobutylammonium hydrogen oxalate hemihydrate

In the title hydrated molecular salt, C4H12N+·C2HO4−·0.5H2O, the O atom of the water molecule lies on a crystallographic twofold axis. The dihedral angle between the CO2 and CO2H planes of the anion is 18.47 (8)°. In the crystal, the anions are connected to each other by strong near-linear O—H...O hydrogen bonds. The water molecules are located between the chains of anions and isobutylamine cations; their O atoms participate as donors and acceptors, respectively, in O—H...O and N—H...O hydrogen bonds, which form channels (dimensions = 4.615 and 3.387 Å) arranged parallel to [010]

Allylammonium hydrogen oxalate hemihydrate

In the title hydrated molecular salt, C3H8N+·C2HO4−·0.5H2O, the water O atom lies on a crystallographic twofold axis. The C=C—C—N torsion angle in the cation is 2.8 (3)° and the dihedral angle between the CO2 and CO2H planes in the anion is 1.0 (4)°. In the crystal, the hydrogen oxalate ions are linked by O—H...O hydrogen bonds, generating [010] chains. The allylammonium cations bond to the chains through N—H...O and N—H...(O,O) hydrogen bonds. The water molecule accepts two N—H...O hydrogen bonds and makes two O—H...O hydrogen bonds. Together, the hydrogen bonds generate (100) sheets

Crystal structure of allylammonium hydrogen succinate at 100 K

The asymmetric unit of the title compound, C2H8N+·C4H5O4−, consists of two allylammonium cations and two hydrogen succinate anions (Z′ = 2). One of the cations has a near-perfect syn-periplanar (cis) conformation with an N—C—C—C torsion angle of 0.4 (3)°, while the other is characterized by a gauche conformation and a torsion angle of 102.5 (3)°. Regarding the anions, three out of four carboxilic groups are twisted with respect to the central C–CH2–CH2–C group [dihedral angles = 24.4 (2), 31.2 (2) and 40.4 (2)°], the remaining one being instead almost coplanar, with a dihedral angle of 4.0 (2)°. In the crystal, there are two very short, near linear O—H...O hydrogen bonds between anions, with the H atoms shifted notably from the donor O towards the O...O midpoint. These O—H...O hydrogen bonds form helical chains along the [011] which are further linked to each other through N—H...O hydrogen bonds (involving all the available NH groups), forming layers lying parallel to (100)

Naphthalene-2,6-diyl bis(4-methylbenzenesulfonate)

The complete molecule of the title compound, C24H20O6S2, is generated by a crystallographic inversion centre at the middle of the naphthalene ring system. The dihedral angle between the naphthalene ring system and the pendant benzene ring is 10.23 (6)° and the C—S—O—C torsion angle is −172.05 (10)°. In the crystal, weak C—H...O interactions link the molecules into (10\overline{1}) sheets

N,N-Dicyclohexylnitramine

Molecules of the title compound, C12H22N2O2, are composed of an nitramine group substituted by two cyclohexane rings. The cyclohexane rings have chair conformations, with the exocyclic C—N bonds in axial orientations. In the crystal, C—H...O hydrogen bonds connect the molecules into C(6) [-101] zigzag chains

Acetylhydroxamic acid

There is one independent molecule in the asymmetric unit of the title compound (alternatively named N-hydroxyacetamide), C2H5NO2. It crystallizes in the noncentrosymmetric space group P43. The structure is an anhydrous form of acetylhydroxamic acid with typical geometry that corresponds well with the hydrated structure described by Bracher & Small [Acta Cryst. (1970), B26, 1705–1709]. In the crystal, N—H...O and O—H...O hydrogen bonds connect the molecules into chains in the c-axis direction

N,N′-Bis(pyridin-2-yl)octanediamide

The complete molecule of the title compound, C18H22N4O2, is generated by crystallographic inversion symmetry. In the crystal, N—H...N hydrogen bonds connect the molecules into [010] chains, which feature R22(8) loops. The packing is consolidated by C—H...O interactions

N-(Pyrazin-2-yl)adamantane-1-carboxamide

Molecules of the title compound, C15H19N3O, are composed of an adamantine unit and a pyrazine ring connected to each other through an amide bond. The H—N—C=O moiety is close to planar [C—N—C—O and C—N—C—C torsion angles of 4.7 (2) and −173.8 (1)°, respectively]. The N3—C5 bond has partial double-bond character [1.370 (1) Å]. The geometries of the pyrazine ring and the adamantane substituent are normal and in good agreement with closely related structures. In the crystal, molecules are connected by N—H...O hydrogen bonds, forming zigzag chains in the [001] direction and are arranged in a herringbone fashion

2-Methyl-N-(pyrazin-2-yl)propanamide–1,2,4,5-tetrafluoro-3,6-diiodobenzene (2/1)

In the title compound, C8H11N3O·0.5C6F4I2, molecules of iPr-substituted pyrazine are co-crystallized with 1,4-diiodo-2,3,5,6-tetrafluorobenzene. The complete molecule of 1,4-diiodo-2,3,5,6-tetrafluorobenzene is generated by an inversion centre at the middle of the aromatic ring. Both molecules have normal geometry and the iPr acylamine group is disordered over two sets of sites with an occupancy ratio of 0.51:0.49. In the crystal, the components are linked by I...N halogen bonds [2.830 (2) Å] and C—H...F interactions are observed