Pseudo-inversion Centre Research Articles

Moxifloxacinium chloride monohydrate

The title compound {systematic name: 7-[(1S,6S)-8-aza-2-azonia­bicyclo­[4.3.0]non-8-yl]-1-cyclo­propyl-6-fluoro-8-meth­oxy-4-oxo-1,4-dihydro­quinoline-3-carb­oxy­lic acid chloride monohydrate}, C21H25FN3O4 +·Cl−·H2O, crystallizes with two moxi­floxa­cinium cations, two chloride ions and two uncoordinated water mol­ecules in the unit cell. The crystal structure has a pseudo-inversion center except for the chloride ions. In both moxi­floxa­cinium cations, the quinoline rings are approximately planar, the maximum atomic deviations being 0.107 (3) and 0.118 (3) Å. The piperidine rings adopt a chair conformation while the pyrrolidine rings display a half-chair conformation. In the crystal, the carboxyl groups, the protonated piperidyl groups, the uncoordinated water mol­ecule and chloride anions participate in O—H⋯O, O—H⋯Cl and N—H⋯Cl hydrogen bonding; weak inter­molecular C—H⋯O and C—H⋯Cl hydrogen bonding is also present in the crystal structure.

2-Hydroxy-2,3,5,10,11,11a-hexahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepine-5,11-dione

The seven-membered ring of the title compound, C12H12N2O3, which is fused with the phenyl­ene ring, adopts a boat-shaped conformation (with the methine C atom as the prow and the phenyl­ene C atoms as the stern); the H atom on the methine linkage exists in an axial position. The five-membered ring that is fused with the seven-membered ring adopts an envelope conformation (with the C atom bearing the hy­droxy substituent representing the flap) [the deviation from the plane defined by the other four atoms is 0.200 (7) Å in one mol­ecule and 0.627 (5) Å in the other]. The two independent mol­ecules are disposed about a pseudo center of inversion and are connected by a pair of N—H⋯O hydrogen bonds. Adjacent dimers are linked by a pair of O—H⋯O hydrogen bonds, generating a chain running along the b axis.

Tetraaquabis(2,6-diamine-7H-purine-κN9)cobalt(II) benzene-1,2,4,5-tetracarboxylate tetrahydrate

The title compound, [Co(C(5)H(7)N(6))(2)(H(2)O)(4)](C(10)H(2)O(8))·4H(2)O, is an ionic structure comprising a [Co(Hdap)(2)(H(2)O)(4)](4+) cation (dap is 2,6-diaminopurine) in a general position, two benzene-1,2,4,5-tetracarboxylate (btc(4-)) anions straddling two different inversion centres and four solvent water molecules. The structure presents a remarkable degree of pseudosymmetry, with the Co(II) cation lying almost exactly on a noncrystallographic pseudo-inversion centre. The overall spatial arrangement can be described in terms of cationic and anionic chains running along the [111] direction and linked into a three-dimensional network by a very complex hydrogen-bonding scheme in which all the available N-H and O-H groups take part.

3-{2-[(3-Phenylquinoxalin-2-yl)oxy]ethyl}-1,3-oxazolidin-2-one

The asymmetric unit of the title compound, C19H17N3O3, consists of two independent mol­ecules that are disposed about a pseudo-centre of inversion. The plane of the phenyl substituent is twisted by 38.1 (1)° [43.6 (1)° in the second mol­ecule] out of the plane of the quinoxaline ring system. The five-membered ring of the substituent at the 2-position adopts an envelope conformation; the 5-CH2 atom representing the flap lies out of the plane defined by the other four atoms [deviation 0.264 (7) Å in the first mol­ecule and 0.291 (6) Å in the second]. The dihedral angle between the five-membered ring and the 4-phenyl ring is 84.9 (1)° while that between the five-membered ring and the 5-phenyl ring is 65.6 (1)°.

(3R,4S)-3,4-Isopropylidenedioxy-3,4-dihydro-2H-pyrrole 1-oxide

The title compound C7H11NO3 was prepared by intra­molecular nucleophilic displacement of 2,3-O-iso-propyl­idene-d-erythronolactol. There are two mol­ecules in the asymmetric unit, which are related by a pseudo-inversion centre. The crystal structure determination confirms unequivocally the configuration of the chiral centres as 3S,4R. In the crystal structure, inter­molecular C—H⋯O inter­actions link the mol­ecules (into infinite zigzag chains along the a axis.

Bis(tetraethylammonium) bis(dimethylformamide)tetrakis(μ-N,2-dioxidobenzene-1-carboximidato)pentacopper(II)

The title compound, (C8H20N)2[Cu5(C7H4NO3)4(C3H7NO)2], abbreviated as (TEA)2[CuII(12-MCCuII N(shi)-4](DMF)2 [where TEA is tetra­ethyl­ammonium, shi3− is salicyl­hydroximate (or N,2-dioxidobenzene-1-carboximidate) and DMF is N,N-dimethyl­formamide], contains five CuII ions. Four of the CuII ions are members of a metallacrown ring (MC), while the fifth CuII is bound in a central cavity. Two of the ring CuII ions are five-coordinate with distorted square-pyramidal geometry. The coordination sphere is composed of two shi3− ligands and one DMF mol­ecule. The other two ring CuII ions and the central CuII ion are four-coordinate with square-planar geometry. The coordination spheres of these ions are only composed of shi3− ligands. The charge of the [CuII(12-MCCuII N(shi)-4]2− unit is balanced by two uncoordinated TEA+ countercations. The structure shows severe static disorder with the metallacrown, the tetra­ethyl­ammonium cations and the DMF solvent mol­ecule all disordered over each of two mutually exclusive sites, with occupancy rates for the major moieties of 0.6215 (6) for the metallacrown, 0.759 (3) for the tetra­ethyl­ammonium ion and 0.537 (6) for the DMF mol­ecules. The metallacrown unit is located on a crystallographic inversion center and disordered about a non-crystallographic twofold axis. The DMF mol­ecule and the tetra­ethyl­ammonium ion are disordered about a non-crystallographic twofold axis and pseudo-inversion center, respectively.

Dimethyl 2,2′-({2,2′-methylenebis[6-(2H-benzotriazol-2-yl)-4-(2,4,4-trimethylpentan-2-yl)-2,1-phenylene]}dioxy)diacetate

The asymmetric unit of the title compound, C47H58N6O6, comprises three independent mol­ecules, in one of which one tert-butyl group is disordered in a 1:1 ratio. The mol­ecule is a di(ar­yl)methane having two aliphatic and one N-heterocyclic substituent in each aryl ring. For the mol­ecule having the disordered tert-butyl group, the aryl rings make an angle of 115.3 (2)° at the methyl­ene carbon; one aryl ring is aligned at 42.0 (1)° with respect to the N-heterocyclic substituent and the other at 48.7 (1)° with respect to its substituent. The two ordered mol­ecules are disposed about a pseudo center of inversion. The pairs of twist angles in these two mol­ecules differ [52.7 (1) and 61.7 (1)°, and 29.1 (1) and 58.5 (1)°].

Near achiral metal–organic frameworks from conformationally flexible homochiral ligands resulted by the preferential formation of pseudo-inversion center in asymmetric unit

A near identical MOF from the reaction between a homochiral ligand and LaIII ion to that from racemic ligand was obtained due to the preferential formation of the pseudo-centrosymmetric arrangement in asymmetric units.

(1R,4S)-7,8-Dichloro-1,2,3,4-tetrahydro-1,11,11-trimethyl-1,4-methanophenazine

The title compound, C16H16Cl2N2, was synthesized by the condensation reaction between 4,5-dichloro-o-phenyl­ene­diamine and (1R)-(-)-camphorquinone in boiling acetic acid. The two crystallographically independent mol­ecules in the unit cell are related by a pseudo-inversion center.

Putrescinium Sulfate: A Low Temperature Study of Disordered, Non-Symmetric Molecule in a Special Position

The structure of butane-1,4-diaminium sulfate, C4H14N2 2+ × SO4 2− is, in both room temperature and 100 (1) K, an example of the centro–non-centrosymmetric ambiguity in the crystal structure determination. It is possible to solve and successfully refine this structure in Pnma and Pna2 1 space groups, with slightly better results obtained for the centrosymmetric group. In both models the cation is disordered over two positions, the ordered terminal nitrogen atoms are connected with two disordered aliphatic chains that cross each other in the middle of the central C–C bond, at the pseudo-inversion center—although the cation itself is not symmetrical—in case of the centrosymmetric model. In this model, the anion is also situated in the special position, on the mirror plane. The conformations of two alternative forms of the cation are not fully extended, as it is often the case for simple salts of linear α,ω-diamines, but trans-gauche-gauche. Each of amine groups displays the same N–H···O hydrogen bonding patterns, with two single and one bifurcated hydrogen bonds. These hydrogen bonds connect the ionic species into rings and further into alternating waved layers. The room-temperature structure of this salt has been reported recently (van Blerk and Kruger J Chem Crystallogr 38:175–179, (2008)), the present analysis adds the low temperature data, and–what is more important—the different description of the disorder, the refined positions of N–H hydrogen atoms and the discussion of centro- non-centro ambiguity. Crystal data: crystal system: orthorhombic, a = 9.9722 (4) A, b = 9.4675 (4) A, c = 8.6532 (4) A, space group: Pnma, V = 816.96 (6) A3, Z = 4. The cation is disordered over two positions, the ordered terminal nitrogen atoms are connected with two disordered aliphatic chains that cross each other in the middle of the central C–C bond, at the pseudo-inversion center—although the cation itself is not symmetrical—in case of the centrosymmetric model.

Benzene-1,3,5-triyl triacetate

The asymmetric unit of the title compound, C12H12O6, contains two essentially identical mol­ecules related by a pseudo-inversion centre. The three acet­oxy groups in each mol­ecule are essentially planar and are tilted, in a regular propeller-style arrangement, with their normals oriented between 56.72 (12) and 76.35 (9)° from the normal to the mean plane of the central C6 ring; in each mol­ecule the three carbonyl O atoms are on the same side of the C6 ring, with the Cring—O—C—Me bonds in a trans conformation. The principal inter­molecular contacts appear to be C—H⋯π-ring inter­actions; each C6 ring has such a contact to both faces of the ring; in addition, each mol­ecule has two inter­molecular C—H⋯O contacts with H⋯O distances less than 2.55 Å.

1D, 2D, and 3D Metal−Organic Frameworks Based on Bis(imidazole) Ligands and Polycarboxylates: Syntheses, Structures, and Photoluminescent Properties

Ten new coordination polymers constructed from two structurally related ligands, 1,1′-(1,5-pentanedidyl)bis(imidazole) (biim-5) and 2,2′-bis(1H-imidazolyl)ether (BIE), have been synthesized: [Co(L1)(biim-5)] (1), [Co(L2)(biim-5)]·H2O (2), [Co(L3)(biim-5)] (3), [Co(L4)(biim-5)]·4H2O (4), [Co(L5)0.5(biim-5)] (5), [Co2(L6)(BIE)2]·1.5H2O (6), [Zn2(L6)(BIE)2]·2.5H2O (7), [Cd(L6)0.5(BIE)(H2O)]·H2O (8), [Zn2(L7)(BIE)2]·H2O (9) and [Cd(L8)0.5(BIE)(H2O)] (10), where H2L1 = 1,2-benzenedicarboxylic acid, H2L2 = 1,3-benzenedicarboxylic acid, H2L3 = 5-OH-1,3-benzenedicarboxylic acid, H2L4 = DL-camphoric acid, H4L5 = 1,2,3,4-butanetetracarboxylic acid, H4L6 = 4,4′-oxidiphthalic acid, H4L7 = 4,4′-(hexafluoroisopropylidene)diphthalic acid, and H4L8 = 1,2,3,4-benzenetetracarboxylic acid. Compounds 1 and 4 display the same 2D layer structures with 63-hcb nets, but in 4 the water tetramers extend the layers to a 3D supramolecular framework by intermolecular hydrogen bonds. Compound 2 is an uncommon example of 2D double layers with the Schläfli symbol of (42·63·8). 3 shows a 2D sql net with large open windows, while 5 exhibits a rare 3,4-connected (83)2(85·10) topology. The crystal structures of 6 and 7 are close to being isostructural with a scarce (32·62·72)(32·4·62·7)2 topology. 8 contains two kinds of chiral layers, one left-handed and the other right-handed, with a unique topological type of (52·64)(53·62·7)2. Compound 9, related by a pseudocenter of inversion, possesses a 3D porous framework with a (3,4)-connected (4·102)2(42·104)-dmd-net. 10 shows a 1D chain structure. The structural and topological differences of these ten compounds indicate that the polycarboxylate ligands play important roles in producing novel frameworks and topologies of the coordination complexes. The infrared spectra and thermogravimetric and luminescent properties were also investigated for the compounds.

Bis{[1-(tert-butoxycarbonyl)pyrrolidin-2-yl]methyl} carbonate

The asymmetric unit of the title compound, C21H36N2O7, consists of two independent half-mol­ecules, the other halves being generated by twofold rotational axes. The two independent half-mol­ecules are related by a pseudo-inversion center. In one, the pyrrolidine ring adopts a twist conformation whereas in the other it is in an envelope conformation. The crystal packing is stabilized by C—H⋯O hydrogen bonds.

N′-[4-(Dimethylamino)benzylidene]acetohydrazide

The title compound, C11H15N3O, crystallizes with two independent mol­ecules per asymmetric unit which differ slightly in their side-chain orientations: the C=N—N—C torsion angle is −176.2 (3)° in one of the mol­ecules and −179.83 (3)° in the other. Each independent mol­ecule adopts a trans configuration with respect to the C=N bond. The two independent mol­ecules are related by a pseudo-inversion center and they exist as a N—H⋯O hydrogen-bonded dimer. The dimers are linked into zigzag chains along [100] by C—H⋯O hydrogen bonds.

Perillartine

The chiral title compound [systematic name: 4-(1-methyl­vinyl)cyclo­hexene-1-carbaldehyde oxime], C10H15NO, crystallizes with two mol­ecules in the asymmetric unit, one of which shows disorder of its propenyl substituent over two sets of sites in a 50:50 ratio. In both mol­ecules, the six-membered carbaldehyde oxime ring adopts an approximate envelope conformation in which the C atom bearing the propenyl substituent represents the flap position. In both mol­ecules, the plane passing through the propenyl substituent is nearly perpendicular to the mean plane of the six-membered ring [dihedral angles = 84.6 (6) and 87.4 (3)°]. In the crystal, the two independent mol­ecules are linked by a pair O—H⋯N hydrogen bonds across a pseudo-inversion centre, generating a dimer. The unit cell of the known racemate of the title compound is similar to the cell found here, but with space group P .

3-Dodecyloxy-2-hydroxy-N,N,N-trimethylpropan-1-aminium bromide

In the title compound, C18H40NO2 +·Br−, the ion pairs formed by the hydrogen-bonded bromide anions and organic cations are arranged into thick layers with the alkyl groups directed to the inside and the trimethyl­aminium groups and the bromide anions situated on the layer surface. The long alkyl chain in the cation adopts an all-trans conformation. In the crystal structure, molecules are connected by intermolecular O—H⋯Br hydrogen bonds, forming ionic pairs that are further connected into an extended chain structure via C—H⋯O hydrogen-bonding interactions. The crystal is chiral but nearly 90% of atoms in the unit cell are related by a pseudo-inversion center. The crystal shows racemic twinning with a 0.33:0.67 domain ratio.

Chlorido[(E)-2-hydroxy-6-(isonicotinoylhydrazonomethyl)phenyl]mercury(II) monohydrate

The asymmetric unit of the title compound, [Hg(C13H10N3O2)Cl]·H2O, contains two independent mercury(II) complexes with slightly different conformations, related via a pseudo-inversion centre, and two water mol­ecules. The HgII atoms show a typical linear geometry to a C atom of the benzene ring and to a Cl atom. A benzene C and the azomethine N atom chelate the HgII atoms with weak intra­molecular Hg⋯N bonding distances of 2.735 (3) and 2.739 (3) Å, respectively. The resulting five-membered metallacycles are nearly coplanar with the benzene rings [dihedral angles = 0.9 (1) and 0.7 (1)°], while the pyridine rings make dihedral angles with the benzene units of 58.17 (1) and 56.58 (1)°. In the crystal structure, the HgII complexes are linked by hydr­oxy donor and pyridine acceptor groups into chains along [010]. The water mol­ecules connect the complexes through inter­molecular O—H⋯Ocarbon­yl bonds in the a-axis direction, and the azomethine H atoms donate towards the water O atoms, forming a three-dimensional network of inter­molecular O—H⋯N, O—H⋯O and N—H⋯O hydrogen bonds.

1-[2-(Benzylamino)-4-pyridyl]-2-(4-fluorophenyl)ethane-1,2-dione

The crystal structure of the title compound, C20H15FN2O2, contains two crystallographically independent mol­ecules, which are related by a pseudo-inversion center and linked into dimers via inter­molecular N—H⋯N hydrogen bonds. The 4-fluoro­phenyl ring of mol­ecule A makes dihedral angles of 17.17 (16) and 62.25 (15)°, respectively, with the phenyl and pyridine rings. The 4-fluoro­phenyl ring of mol­ecule B makes dihedral angles of 8.50 (16) and 64.59 (15)°, respectively, with the phenyl and pyridine rings. The dihedral angle between the pyridine ring and the phenyl ring of mol­ecule A [60.97 (15)°] is bigger than in mol­ecule B [59.49 (15)°]. The dihedral angle between the two pyridine rings is 1.37 (14)° and between the two phenyl rings is 3.64 (16)°.

From small structural modifications to adjustment of structurally dependent properties: 1-methyl-3,5-bis[(E)-2-thienylidene]-4-piperidone and 3,5-bis[(E)-5-bromo-2-thienylidene]-1-methyl-4-piperidone.

The molecules of the title compounds, C(16)H(15)NOS(2), (I), and C(16)H(13)Br(2)NOS(2), (II), are E,E-isomers and consist of an extensive conjugated system, which determines their molecular geometries. Compound (I) crystallizes in the monoclinic space group P2(1)/c. It has one thiophene ring disordered over two positions, with a minor component contribution of 0.100 (3). Compound (II) crystallizes in the noncentrosymmetric orthorhombic space group Pca2(1) with two independent molecules in the unit cell. These molecules are related by a noncrystallographic pseudo-inversion center and possess very similar geometries. The crystal packings of (I) and (II) have a topologically common structural motif, viz. stacks along the b axis, in which the molecules are bound by weak C-H...O hydrogen bonds. The noncentrosymmetric packing of (II) is governed by attractive intermolecular Br...Br and Br...N interactions, which are also responsible for the very high density of (II) (1.861 Mg m(-3)).

5,5′-Dimethoxy-2,2′-[2,2-dimethylpropane-1,3-diylbis(nitrilomethylidyne)]diphenol

The asymmetric unit of the title Schiff base compound, C21H26N2O4, consists of four crystallographically independent mol­ecules, viz. A, B, C and D. The A and D, and the B and C mol­ecules are related by a pseudo-inversion centre, and the remaining pairs of mol­ecules differ in the orientations of one of the meth­oxy groups. In each independent mol­ecule, intra­molecular O—H⋯N hydrogen bonds generate two S(6) ring motifs. The dihedral angles between the benzene rings in mol­ecules A, B, C and D are 65.86 (19), 50.41 (19), 68.59 (19) and 50.85 (19)°, respectively. In the crystal structure, mol­ecules are linked by C—H⋯O hydrogen bonds, forming R 2 2(8) dimers. In addition, weak C—H⋯π inter­actions are observed.