Pseudo-inversion Centre Research Articles

Tetraethylammonium tricarbonylchlorido(isoquinoline-1-carboxylato-κ2 N,O)technetate(I)

The asymmetric unit of the title compound, (C8H20N)[Tc(C10H6NO2)Cl(CO)3], consists of two crystallographically independent technetium complexes related via a pseudo-inversion centre and two tetra­ethyl­ammonium cations. The Tc atoms have slightly distorted octa­hedral coordination geometries, and they are linked with the cations by inter­molecular C—H⋯O and C—H⋯Cl hydrogen-bonding contacts, forming two-dimensional columns, which lie approximately parallel to (001) in the crystal structure. The isochinolate (isoquinoline-1-carboxyl­ate) ligands link the columns by partial π–π stacking [centroid–centroid distance 4.3733 (11) Å], forming a three-dimensional network structure.

6-[(E)-3,7-Dimethylocta-2,6-dienyl]-5,7-dihydroxy-8-(2-methylbutanoyl)-4-phenyl-2H-chromen-2-one fromMesua kunstleriKing (Kosterm)

The title compound, C30H34O5, crystallizes with two symmetry-independent mol­ecules in the asymmetric unit. In the crystal structure, the two independent mol­ecules are disposed about a pseudo-center of inversion. An intra­molecular O—H⋯O hydrogen bond is observed in each independent mol­ecule. The crystal structure is stabilized by C—H⋯O hydrogen bonds.

Diethyl 2,5-bis[(E)-2-furylmethyleneamino]thiophene-3,4-dicarboxylate

The title compound, C20H18N2O6S, crystallizes as two independent mol­ecules that are disposed about a pseudo-inversion center (1/2, 1/4, 1/8). The mean planes of the two terminal furyl rings are twisted with respect to the central thio­phene ring by 7.33 (4) and 21.74 (5)° in one mol­ecule, and by 6.91 (4) and 39.80 (6)° in the other.

1-[3-(1H-Indol-2-yl)-2-furyl]ethanone

En route to furostifoline, we synthesized the title compound, C14H11NO2, as a yellow crystalline material, with two independent mol­ecules in the asymmetric unit, related by a pseudo-centre of inversion; they have an approximately planar conformation, and similar bond lengths and angles. An intra­molecular N—H⋯O hydrogen bond was observed for each mol­ecule, as well as several inter­molecular C—H⋯O inter­actions, linking the two mol­ecules together into dimers. The dimers themselves are linked to neighbouring dimers by C—H⋯O and C—H⋯π inter­actions.

Synthesis, Crystal Structure, and Characterization (Vibrational and Solid-State 31P MAS NMR Spectroscopy) of the High-Temperature Modification of Calcium catena-Polyphosphate(V)

The metastable high-temperature modification of calcium catena-polyphosphate, α-Ca(PO3)2, was obtained by quenching the recrystallized sample from a temperature shortly below the melting point. The novel crystal structure [Cc, Z = 16, a = 13.6835(14) A, b = 19.981(2) A, c = 6.7535(7) A, β = 94.514(2)°, V = 1840.7(3) A3, 4929 structure factors, 326 parameters, R[F2 > 2σ(F2)] = 0.0561] was determined from a combined X-ray diffraction and solid-state 31P NMR study. The unit cell features a pseudoinversion center. The structure contains 4 Ca, 8 P, and 24 O atoms in the asymmetric unit and is composed of two different kinds of polyphosphate chains, with one helical chain running with a periodicity P of 12 parallel to [101], whereas the second chain is corrugated and directed parallel to [001] with a periodicity P of 4. 31P chemical shift parameters were determined for all eight phosphorus positions, and peaks were assigned to the two different polyphosphate chains. α-(CaPO3)2 was further characterized by IR an...

Diaquabis(3-hydroxybenzoato-κO)bis(1,10-phenanthroline-κ2 N,N′)barium(II)

The two independent molecules of the title compound, [Ba(C7H5O3)2(C12H8N2)2(H2O)2], are disposed about a pseudo-inversion centre. The Ba atom is eight-coordinate in a square-antiprismatic geometry in both molecules.

Hydrogen-bonding motifs in 4-carboxyphenylammonium nitrate and perchlorate monohydrate, and in bis(4-carboxyphenylammonium) sulfate

In the title compounds, C7H8NO2+.NO3-, (I), C7H8NO2+.ClO4-.H2O, (II), and 2C7H8NO2+.SO4(2-), (III), the carboxyl planes of the 4-carboxyphenylammonium cations are twisted from the aromatic plane. A homonuclear C(8) hydrogen-bonding motif of 4-carboxyphenylammonium cations is observed in both (I) and (II), leading to ;head-to-tail' layers. The cations in (III) form carboxyl group dimers, making a graph-set motif of R2(2)(8). In all the structures, anions connect the cationic layers and an infinite chain running along the c axis is observed, having the C2(2)(6) graph-set motif. Interestingly, in (II), the anions are connected through weak hydrogen bonds involving the water molecules, leading to a graph-set motif of R4(4)(12). Alternate hydrophobic and hydrophilic layers are observed in all three compounds as a result of the column-like arrangement of the aromatic rings of the cations and the anions. Furthermore, in (I), head-to-tail N-H...O interactions and interactions linking the cations and anions form an R6(4)(16) hydrogen-bonding motif, resulting in a pseudo-inversion centre at (1/2, 1/2, 0).

5-[(Cyclohexylamino)methylene]-2,2-dimethyl-1,3-dioxane-4,6-dione

In the title enaminone, C13H19N1O4, the Meldrum's acid group has a distorted boat conformation. The two independent mol­ecules of the asymmetric unit are dimerized about a pseudo inversion center through two inter­molecular N—H⋯O hydrogen bonds, with N⋯O distances of 3.049 (4) and 3.093 (4) A. The dimers are stacked along the [010] direction.

2-(1,3-Benzothiazol-2-yloxy)-N-(4-fluorophenyl)-N-isopropylacetamide

The asymmetric unit of the title compound, C18H17FN2O2S, contains two independent mol­ecules related by a pseudo-inversion centre. The mol­ecular packing is stabilized by C—H⋯O and C—H⋯π inter­actions.

Charge ordering state ofβ″−(ET)3(HSO4)2andβ″−(ET)3(ClO4)2by temperature-dependent infrared and Raman spectroscopy

We present the temperature-dependent infrared and Raman spectra of ${\ensuremath{\beta}}^{\ensuremath{''}}\text{\ensuremath{-}}{(\mathrm{ET})}_{3}{X}_{2}$ ($X=\mathrm{H}\mathrm{S}{\mathrm{O}}_{4}$ and $\mathrm{Cl}{\mathrm{O}}_{4}$; $\mathrm{ET}=\mathrm{bis}$-ethylenedithio-tetrathiafulvalene) compounds which undergo a metal-insulator transition. The infrared-active ${v}_{27}$ mode discontinuously split into two bands at the metal-insulator transition temperature of $127\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ in the $X=\mathrm{H}\mathrm{S}{\mathrm{O}}_{4}$ salt, whereas, the corresponding mode continuously changed across the metal-insulator transition temperature of $\ensuremath{\sim}170\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ in the $X=\mathrm{Cl}{\mathrm{O}}_{4}$ salt. In both compounds, the charge-sensitive ${v}_{27}$ mode split into two in the insulating phase. This drastic spectral change indicates that the metal-insulator transition originated in the charge ordering. Employing the frequencies of the split ${v}_{27}$ bands, the site charges are estimated to be $+{0.3}_{4}$ and $+{0.8}_{1}$ for $X=\mathrm{H}\mathrm{S}{\mathrm{O}}_{4}$ and $+{0.3}_{6}$ and $+{0.8}_{1}$ for $X=\mathrm{Cl}{\mathrm{O}}_{4}$. We also estimated the site charges using the Raman-active ${v}_{2}$ mode and obtained consistent results. Examining the selection rule of the ${v}_{3}$ mode, we reached the conclusion that the unit cell with space group $P1$ has a pseudoinversion center in the charge-ordered phase. Based on the symmetry, we propose a charge-ordering pattern for the $X=\mathrm{H}\mathrm{S}{\mathrm{O}}_{4}$ and $X=\mathrm{Cl}{\mathrm{O}}_{4}$ salts, which is quite different from that of the $X=\mathrm{Re}{\mathrm{O}}_{4}$ salt reported previously. We qualitatively discuss the differences in the charge-ordering pattern considering the anisotropic intersite Coulomb interaction.

Proton-bifurcated C—H...(O,O) hydrogen bonds in 2,3-dichloro-6-nitrobenzylaminium chloride

In the crystal structure of the title salt, C7H7Cl2N2O2+.Cl-, the chloride anions participate in extensive hydrogen bonding with the aminium cations and indirectly link the molecules through multiple N+-H...Cl- salt bridges. There are two independent molecules in the asymmetric unit, related by a pseudo-inversion center. The direct intermolecular coupling is established by C-H...O, C-H...Cl and C-Cl...Cl(-) interactions. A rare three-center (donor bifurcated) C-H...(O,O) hydrogen bond is observed between the methylene and nitro groups, with a side-on intramolecular component of closed-ring type and a head-on intermolecular component.

Tetraaquabis(3,5-dihydroxybenzoato-κO)nickel(II) trihydrate

The covalently bonded monodentate carboxyl­ate groups in the title compound, [Ni(C7H5O4)2(H2O)4]·3H2O, are trans to each other; the octa­hedrally coordinated Ni atom lies on a pseudo-center of inversion that relates the carboxyl­ate groups to each other as well as two coordinated water mol­ecules to the other two. Extensive hydrogen bonding leads to the formation of a three-dimensional network.

2-(Methoxycarbonyl)anilinium chloride monohydrate

The asymmetric unit of the title compound, C8H10NO2+·Cl−·H2O, contains two crystallographically independent 2-(methoxy­carbon­yl)anilinium cations related by a pseudo-inversion centre, two chloride ions and two water mol­ecules. A three-dimensional network structure is formed via N—H⋯O, N—H⋯Cl and O—H⋯Cl hydrogen bonds, and π–π stacking inter­actions.

Pargyline hydrochloride, a monoamine oxidase inhibitor: an orthorhombic form

In the crystal structure of the title compound, N-benzyl-N-methyl­prop-2-yn-1-aminium chloride, C11H14N+·Cl−, the asymmetric unit contains two independent enantiomeric cations with a pseudo-inversion center between them. In both mol­ecules, the protonation occurs at the N atom, and the side chains are extended in a direction roughly perpendicular to the benzene rings. The mol­ecules are arranged head-to-head and tail-to-tail, producing hydro­philic and hydro­phobic regions. In addition to the ordinary N—H⋯Cl hydrogen bonds, numerous weak non-standard hydrogen bonds of the type C—H⋯Cl also contribute to the crystal packing.

Bis(nitrato-κ2O,O′)(1,4,7,10,13-pentaoxacyclopentadecane)calcium(II)

The crystal structure of the title compound, [Ca(NO3)2(C10H20O5)], at 120 K contains discrete mol­ecules with nine-coordinate Ca atoms. There are two mol­ecules in the asymmetric unit, related by a pseudo-inversion centre. The crown bonds through five O atoms [Ca—O = 2.464 (2)–2.567 (2) A] and the nitrates are bidentate [Ca—O = 2.444 (2)–2.588 (2) A]. The structure is a polymorph of a previously reported room-temperature form.

D-Phenylglycinium nitrate

In the title compound, C8H10NO2+·NO3−, there are two crystallographically independent cations and two anions, the pairs being related by a pseudo-inversion centre at approx­imately (0, {1 \over 4}, {1 \over 4}). The phenyl­glycinium cations and nitrate anions are linked to each other through strong N—H⋯O and O—H⋯O hydrogen bonds, forming a three-dimensional complex network.

Mixed-Valence States of 1′,1″′-Bis(2-phenylbutyl)-1,1″-biferrocenium(1+) Triiodides: Effects of the Cation Symmetry and Counter Anion on the Electron-Transfer Rate

Abstract The effects of cation symmetry and packing on the mixed-valence state of binuclear ferrocene derivatives are discussed by using chiral isomers and the racemic modification of 1′,1″′-bis(2-phenylbutyl)-1,1″-biferrocenium(1+) triiodide. Although the three chiral isomers showed trapped-valence states at 78 K, only the (R,S) isomer showed a perfect detrapped-valence state at room temperature in the three isomers. The racemic modification consisted of the (R,R) and the (S,S) isomers showed a perfect detrapped-valence state at room temperature. This shows that the packing effect overcomes the effect of cation asymmetry. The electron-transfer rate for each pentaiodide salt was faster than that of the corresponding triiodide salt. A comparison between the (S,S) triiodide and the (S,S) pentaiodide salts reveals an important packing effect. The polymeric pentaiodide skeleton forced the (S,S) cation to have pseudo-inversion center.

The origin of a flat band

The origin of a “flat band” as defined in the “flat band–steep band” model for superconductivity has been studied. A “local inversion center” is derived mathematically as the necessary and sufficient condition for an occurrence of a “flat band” at an arbitrary k → point. From the k → -dependent part of E( k → j) , a “pseudo-inversion center” is demonstrated to be a sufficient condition based on the Patterson symmetry. The chemical bonding origin of a “flat band” is also studied analytically with a tight-binding approach.

L-Phenylalanine fumaric acid

In the title adduct, C9H11NO2·C4H4O4, the amino acid mol­ecules exist as zwitterions and the fumaric acid mol­ecules exist in the unionized state, a feature uncommon in similar crystal structures. The asymmetric unit is composed of two mol­ecules of each species. The fumaric acid mol­ecules are related to each other through a pseudo-inversion centre and are essentially planar. The phenyl­alanine and fumaric acid mol­ecules form hydrogen-bonded double layers, linked together by hydrogen bonds and extending along [001]. These double layers are flanked, on either side, by the hydro­phobic side chains of phenyl­alanine, leading to alternating hydro­philic and hydro­phobic zones.

2-Naphthalenol

In the solid state, the non-centrosymmetric structure of the title compound, C10H8O, is stabilized both by van der Waals interactions and by O—H⋯O intermolecular hydrogen bonds. These hydrogen bonds link every mol­ecule with two neighbouring non-equivalent mol­ecules, forming chains. The asymmetric unit contains two mol­ecules, which are related to each other by a pseudo-inversion centre.