Crystallographic Mirror Plane Research Articles

Isostructural Crystals of Bis(Guanidinium) Trioxofluoro-Phosphate/Phosphite in the Ratio 1/0, 0.716/0.284, 0.501/0.499, 0.268/0.732, 0/1—Crystal Structures, Vibrational Spectra and Second Harmonic Generation

The title structures of bis(guanidinium) trioxofluorophosphate, bis(guanidinium) trioxofluorophosphate-phosphite (0.716/0.284), bis(guanidinium) trioxofluorophosphate-phosphite (0.501/0.499), bis(guanidinium) trioxofluorophosphate-phosphite (0.268/0.732), and bis(guanidinium) phosphite are crystal-chemically isotypic. Their structures correspond to the structure of bis(guanidinium) trioxofluorophosphate which was determined by Prescott, Troyanov, Feist & Kemnitz (Z. Anorg. Allg. Chem. 2002, 628, 1749–1755). The P and O atoms of the substituted trioxofluorophosphate and phosphite anions share the same positions while the P-F and P-Hhydrido are almost parallel and oriented in the same direction. Two symmetry-independent anions and two of three symmetry-independent cations are situated on the crystallographic mirror planes. The ions are interconnected by N-H⋯O hydrogen bonds of moderate strength. The most frequent graph set motif is R22(8), which involves interactions between the primary amine groups and the trioxofluorophosphate or phosphite O atoms. Fluorine, as well as the hydrido hydrogen, avoids inclusion into the hydrogen-bond network. The Hirshfeld surface analysis was also performed for the comparison of intermolecular interactions in the title structures of bis(guanidinium trioxofluorophosphate and bis(guanidinium) phosphite. The title crystals were also characterized by vibrational spectroscopy methods (FTIR and Raman) and the second harmonic generation (SHG). The relative SHG efficiency considerably decreases from bis(guanidinium) trioxofluorophosphate to bis(guanidinium) phosphite for the fundamental 1064 nm laser line.

Crystal structure of 4,5-dimethyl-1,3-dioxol-2-one.

The planar title compound 4,5-dimethyl-1,3-dioxol-2-one, C5H6O3, 1, crystallizes with its mol-ecular C 2 axis coincident with a crystallographic mirror plane in space group P21/m. In the plane defined by the b axis and an ac face diagonal, anti-parallel linear strands of 1, formed by simple translation, associate to form sheets with close H⋯H and O⋯O inter-molecular contacts. Between the sheets, parallel strands of 1 place the carbonyl O atom near the five-membered ring centroid of a neighboring mol-ecule with close O⋯O and O⋯C contacts.

Tri-methyl-pyrazole: a simple heterocycle reflecting Kitaigorodskii's packing principle.

The five-membered heterocycle 1,3,5-trimethyl-1H-pyrazole, C6H10N2 (1) crystallizes in space group Pnma with all non-hydrogen atoms of the mol-ecule on the crystallographic mirror plane. This arrangement has been recognized as favorable with respect to space filling by Kitaigorodskii and Wilson, pioneers in the field of crystal packing; Pnma represents a particularly rare space group for residues exclusively in a general position. Neighboring mol-ecules in 1 inter-act via non-classical C-H⋯N bonds in the plane and C-H⋯π contacts between adjacent layers. In Pnma, crystallographic inversion relates dipolar mol-ecules located on successive mirror planes and results in their head-to-tail arrangement. The inter-layer distance in the [010] direction is closely related to the van der Waals radii of C and N.

Mirror-plane disorder in a nickel chloride Schiff base complex: a suitable case study for crystallographic instruction

The nickel chloride complex of the Schiff base N2,N2'-propanediylbis(2,3-butanedione-2-imine-3-oxime), namely, chlorido(3,9-dimethylundeca-3,8-diene-2,10-dione 10-oxime 2-oximato-κ4N,N',N'',N''')nickel(II), [NiCl(C11H19N4O2)], at 100 K crystallizes in the orthorhombic space group Cmce. The structure exhibits mirror disorder of the main molecule that is not present in the bromide analogue. The relatively small number of unique reflections in the data set and the disorder imposed by the crystallographic mirror plane present a challenging educational case study.

The structures of 1:1 and 1:2 adducts of phosphane-tricarbo-nitrile with 1,4-di-aza-bicyclo[2.2.2]octa-ne.

In the structures of 1:1 and 1:2 adducts of phosphanetricarbo-nitrile (C3N3P) with 1,4-di-aza-bicyclo-[2.2.2]octane (C6H12N2), the 1:1 adduct crystallizes in the ortho-rhom-bic space group, Pbcm, with four formula units in the unit cell (Z' = 0.5). The P(CN)3 unit lies on a crystallographic mirror plane while the C6H12N2 unit lies on a crystallographic twofold axis passing through one of the C-C bonds. The P(CN)3 moiety has close to C 3v symmetry and is stabilized by forming adducts with two symmetry-related C6H12N2 units. The phospho-rus atom is in a five-coordinate environment. As a result of the symmetry, the two trans angles are equal so τ5 = 0.00 and thus the geometrical description could be considered to be square pyramidal. However, the electronic geometry is distorted octa-hedral with the lone pair on the phospho-rous occupying the sixth position. As would be expected from VSEPR considerations, the repulsion of the lone-pair electrons with the equatorial bonding electrons means that the trans angles for the latter are considerably reduced from 180° to 162.01 (4)°, so the best description of the overall geometry for phospho-rus is distorted square pyramidal. The 1:2 adduct crystallizes in the monoclinic space group, P21/m with two formula units in the asymmetric unit (i.e. Z' = 1/2). The P(CN)3 moiety lies on a mirror plane and one of the two C6H12N2 (dabco) mol-ecules also lies on a mirror plane. The symmetry of the P(CN)3 unit is close to C 3v. There are three P⋯N inter-actions and consequently the mol-ecular geometry of the phospho-rus atom is distorted octa-hedral. This must mean that the lone pair of electrons on the phospho-rus atom is not sterically active. For the 1:1 adduct, there are weak associations between the phospho-rus atom and one of the terminal nitro-gen atoms from the C≡ N moiety, forming chains in the a-axis direction. In addition there are weak C-H⋯N inter-actions between a terminal nitro-gen atoms from the C≡N moiety and the C6H12N2 mol-ecules, which form sheets perpendicular to the a axis.

Comparison of the crystal structures of the low- and high-temperature forms of bis-[4-(di-methyl-amino)-pyridine]-dithio-cyanato-cobalt(II).

Single crystals of the high-temperature form I of [Co(NCS)2(DMAP)2] (DMAP = 4-di-methyl-amino-pyridine, C7H10N2) were obtained accidentally by the reaction of Co(NCS)2 with DMAP at slightly elevated temperatures under kinetic control. This modification crystallizes in the monoclinic space group P21/m and is isotypic with the corresponding Zn compound. The asymmetric unit consists of one crystallographically independent Co cation and two crystallographically independent thio-cyanate anions that are located on a crystallographic mirror plane and one DMAP ligand (general position). In its crystal structure the discrete complexes are linked by C-H⋯S hydrogen bonds into a three-dimensional network. For comparison, the crystal structure of the known low-temperature form II, which is already thermodynamically stable at room temperature, was redetermined at the same temperature. In this polymorph the complexes are connected by C-H⋯S and C-H⋯N hydrogen bonds into a three-dimensional network. At 100 K the density of the high-temperature form I (ρ = 1.462 g cm-3) is higher than that of the low-temperature form II (ρ = 1.457 g cm-3), which is in contrast to the values determined by XRPD at room temperature. Therefore, these two forms represent an exception to the Kitaigorodskii density rule, for which extensive inter-molecular hydrogen bonding in form II might be responsible.

Lithium dipotassium citrate monohydrate, LiK2C6H5O7(H2O).

The crystal structure of dilithium potassium citrate monohydrate, Li+·2K+·C6H5O7 3-·H2O or LiK2C6H5O7·H2O, has been solved by direct methods and refined against laboratory X-ray powder diffraction data, and optimized using density functional techniques. The complete citrate trianion is generated by a crystallographic mirror plane, with two C and three O atoms lying on the reflecting plane, and chelates to three different K cations. The KO8 and LiO4 coordination polyhedra share edges and corners to form layers lying parallel to the ac plane. An intra-molecular O-H⋯O hydrogen bond occurs between the hydroxyl group and the central carboxyl-ate group of the citrate anion as well as a charge-assisted inter-molecular O-H⋯O link between the water mol-ecule and the terminal carboxyl-ate group. There is also a weak C-H⋯O hydrogen bond.

Two 3D supramolecular isomeric Zn(II)-MOFs as photocatalysts for photodegradation of methyl violet dye

Two new Zn(II) metal-organic-frameworks displaying supramolecular isomerism have been synthesized using 1,3-bis(2-methylimidazolyl)propane (bmp) and 1,3,5-benzenetricarboxylic acid (H3BTC). The isomer [NH2(CH3)2][Zn2O(bmp)(BTC)] (1) adopt 2-fold interpenetrating framework topology defined by bey-type of interpenetration while another isomer [NH2(CH3)2][Zn2O(bmp)(BTC)].1.5DMF (2) adopt 2-fold interpenetrating framework topology defined by CdSO4-type of interpenetration. The difference in topologies of two MOFs can be ascribed to the flexibility of 1,3-bis(2-methylimidazolyl)propane ligand; because of which 2 lies on a crystallographic mirror plane. Both MOFs display efficient photocatalytic properties for the photodegradation of model aromatic dye methyl violet (MV). The photocatalytic mechanism in both the MOFs have been explained by using density of states calculations. Moreover, chromatography-mass spectrometry (LC-MS) has been performed to further validate the potential photodegradation mechanism of MV.

Atomically Precise Insights into Metal–Metal Bonds Using Comparable Endo-Units of Sc 2 and Sc 2 C 2

The precise identification of metal–metal bonds is critical to fully understanding the nature of metal–metal bonding but remains a fundamental challenge. Herein, we show the essence of Sc–Sc bonds ...

Crystal structure of pyridinium tetra-iso-thio-cyanato-dipyridine-chromium(III) pyridine monosolvate.

In the crystal structure of the title compound, (C5H6N)[Cr(NCS)4(C5H5N)2]·C5H5N, the CrIII ions are octa-hedrally coordinated by four N-bonding thio-cyanate anions and two pyridine ligands into discrete negatively charged complexes, with the CrIII ion, as well as the two pyridine ligands, located on crystallographic mirror planes. The mean planes of the two pyridine ligands are rotated with respect to each other by 90°. Charge balance is achieved by one protonated pyridine mol-ecule that is hydrogen bonded to one additional pyridine solvent mol-ecule, with both located on crystallographic mirror planes and again rotated by exactly 90°. The pyridinium H atom was refined as disordered between both pyridine N atoms in a 70:30 ratio, leading to a linear N-H⋯N hydrogen bond. In the crystal, discrete complexes are linked by weak C-H⋯S hydrogen bonds into chains that are connected by additional C-H⋯S hydrogen bonding via the pyridinium cations and solvent mol-ecules into layers and finally into a three-dimensional network.

Investigation of nitro-nitrito photoisomerization: crystal structures of trans-bis-(acetyl-acetonato-O,O')(pyridine/4-methyl-pyridine/3-hy-droxy-pridine)nitro-cobalt(III).

The reaction cavities of the nitro groups in the title compounds, trans-bis-(acetyl-acetonato-κ2 O,O')(nitro)(pyridine-κN)cobalt(III), [Co(C5H7O2)2(NO2)(C5H5N)], (I), trans-bis-(acetyl-acetonato-κ2 O,O')(4-methyl-pyridine-κN)(nitro)cobalt(III), [Co(C5H7O2)2(NO2)(C6H7N)], (II), and trans-bis-(acetyl-acetonato-κ2 O,O')(3-hy-droxy-pyridine-κN)(nitro)cobalt(III) monohydrate, [Co(C5H7O2)2(NO2)(C5H5NO)]·H2O, (III), have been investigated to reveal that bifurcated inter-molecular C(py)-H⋯O,O contacts in (III) are unfeasible for the nitro-nitrito photochemical linkage isomerization process. In each structure, the pyridine ring and the Co atom lie on a crystallographic mirror plane; in (I) and (II) the nitro group lies in the same plane, whereas in (III), which crystallizes as a monohydrate, the nitro group is disordered over three orientations in a 0.672 (16):0.164 (8):0.164 (8) ratio; the water mol-ecule of crystallization is statistically disordered over two sites adjacent to the mirror plane. In the crystals of (I) and (II), the mol-ecules are linked into [100] chains by C-H⋯O hydrogen bonds, whereas the extended structure of (III) features (010) layers linked by O-H⋯O and C-H⋯O hydrogen bonds. Compounds (I) and (II) were refined as inversion twins.

5-Bromo-1-(4-bromophenyl)isatin

In the title compound [systematic name: 5-bromo-1-(4-bromophenyl)-2,3-dihydro-1H-indole-2,3-dione], C14H7Br2NO2, all of the atoms except the C—H groups in the bromobenzene ring lie on a (010) crystallographic mirror plane, with the benzene ring completed by reflection. The dihedral angle between the ring systems is constrained to be 90° by symmetry. In the crystal, molecules are linked by weak C—H...Br interactions in the [001] direction and paired very weak C—H...O interactions to the same acceptor in the [100] direction, generating (010) sheets. Possible extremely weak π–π stacking occurs between the layers.

1-(2-Amino-4,5-dimethylphenyl)ethanone

The molecule of the title compound, C10H13NO, also referred to as 2-amino-4,5-dimethylacetophenone, lies on a crystallographic mirror plane with four molecules in the orthorhombic unit cell and features an intramolecular N—H...O hydrogen bond. In the crystal, the molecules are linked by N—H...O hydrogen bonds, forming ribbons along theaaxis that pack to form sheets lying in the (010) plane.

3,5-Dibromobenzonitrile

Molecules of the title compound (I), C7H3Br2N, lie on a crystallographic mirror plane that bisects the benzene ring and the cyano group. In the crystal, no C[triple-bond]N...Br or Br...Br short contacts are observed. Head-to-tail C(7) chains form based on weak hydrogen bonding between the the para H atom and the cyano N atom. Although molecules of (I) pack differently than 3,5-difluorobenzonitrile, both compounds have similarly distorted benzene rings. For (I), the endocyclic bond angles are 121.16 (16)° and 117.78 (16)° about the ipso and para C atoms, respectively.

Crystal structures of 2,4,6-tri-iodo-benzo-nitrile and 2,4,6-tri-iodo-phenyl isocyanide.

The title crystals, C7H2I3N, are isomorphous. Both mol-ecules lie across two crystallographic mirror planes and a twofold axis. The principal supra-molecular inter-action is centric R22(10) CN/NC⋯I short contacts involving both ortho I atoms, with two contacts bis-ecting each cyano and iso-cyano group. These form ribbons along [010] and give rise to a planar sheet structure parallel to (100). All pairs of adjacent sheets have centric stacking, a mode not previously reported for sheets of this type. This study completes the series of homo-2,4,6-trihalobenzo-nitriles, in which I atoms give the strongest CN⋯X and NC⋯X inter-actions (X = F, Cl, Br, I).

Crystal structures of 2,6-di-bromo-4-methyl-benzo-nitrile and 2,6-di-bromo-4-methyl-phenyl isocyanide.

In the title crystals, C8H5Br2N, which are isomorphous, the steric bulk of the methyl group causes neighboring mol-ecules to become mutually inclined. This prevents the formation of planar or nearly planar sheets, which were observed in the tri-chloro and tri-bromo analogs. Instead of CN/NC⋯Br contacts, tetra-meric Br⋯Br contacts are observed. These contacts form tetra-gonally puckered sheets parallel to (001). The CN/NC and methyl groups are grouped at the peaks and troughs. Both mol-ecules lie across crystallographic mirror planes; thus, the methyl H atoms are disordered over two sets of sites with equal occupancy. The title nitrile is a redetermination. The refinement converged at R[F2 > 2σ(F2)] = 0.020, whereas the original determination [Gleason & Britton, (1976 ▸). Cryst. Struct. Commun.5, 229-232] had R = 0.112.

1-(3-Chloro-6-nitro-1H-indazol-1-yl)ethan-1-one

The asymmetric unit of the title compound, C9H6ClN3O3, contains one full molecule in a general position and a half molcule sitting on a crystallographic mirror plane. In the crystal, molecules form stacks extending along theb-axis direction through a combination of offset π–π stacking between indazole units and C—Cl...π(ring) interactions with the six-membered rings of the same units. Elaboration of the C—Cl...π(ring) interactions along thea-axis direction forms slabs of molecules parallel to [001]. The stacks are joined by a combination of C—H...O and C—H...N hydrogen bonds.

The 7-aza-norbornane nucleus of epibatidine: 7-aza-bicyclo-[2.2.1]heptan-7-ium chloride.

7-Aza-bicyclo-[2.2.1]heptane (7-aza-norbornane) is a bridged heterocyclic nucleus found in epibatidine, the alkaloid isolated from the skin of the tropical poison frog Epipedobates tricolor. Since epibatidine is known as one of the most potent acetyl-choline nicotinic receptor agonists, a plethora of literature has been devoted to this alkaloid. However, there are no structural data on the unsubstituted 7-aza-norbornane, the parent bicyclic ring of epibatidine and its derivatives. We herein present the structural characterization of the 7-aza-bicyclo-[2.2.1]heptane parent ring as its hydro-chloride salt, namely 7-aza-bicyclo-[2.2.1]heptan-7-ium chloride, C6H12N+·Cl-. The compete cation is generated by a crystallographic mirror plane with the N atom lying on the mirror, as does the chloride anion. In the crystal, the cations are linked to the anions by N-H⋯Cl hydrogen bonds, which generate [001] chains.

Crystal structures of two bi-cyclo-[5.1.0]octa-nes: potassium trans-bi-cyclo-[5.1.0]octane-4-carboxyl-ate monohydrate and cis-bi-cyclo-[5.1.0]octan-4-yl 4-bromo-benzene-sulfonate.

The crystal structures of the trans-fused compound potassium trans-bi-cyclo-[5.1.0]octane-4-carboxyl-ate monohydrate, K+·C9H13O2-·H2O, (I), and of cis-bi-cyclo-[5.1.0]octan-4-yl 4-bromo-benzene-sulfonate, C14H17BrO3S, (II), have been determined. Compound (I) represents the smallest trans-fused cyclo-propane structure known to date, and features the expected shortening of the bridging C-C bond relative to the other cyclo-propane bond lengths, in contrast to the cis-fused system, (II), where all of the cyclo-propane bond lengths are the same. The bicyclic ring system of (I) is disordered across a crystallographic mirror plane. The geometries of the cis-fused and trans-fused ring systems are compared.

A temperature-dependent phase transformation of (E)-2-[(4-chloro-phen-yl)imino]-ace-naphthylen-1-one.

The crystal structure determination based on 90 K data of the title imine ligand, C18H10ClNO, revealed non-merohedral twinning with three twin domains. In our experience, this is an indication of an ordering phase transition. Consequently, the structure was redetermined with higher temperature data, and a reversible phase transition was discovered. The higher temperature phase is indeed an ordered structure. At the higher temperature, the 4-chloro-phenyl group has rotated by ca 7° into a crystallographic mirror plane. Warming the crystal from 90 K to 250 K changes the space group from triclinic P-1, to monoclinic P21/m. Diverse non-classical inter-actions are present in the crystal packing, and these are described for the phase change reported in this work. The crystal structure of the title imine ligand, measured at 100 K, has been reported on previously [Kovach et al. (2011 ▸). J. Mol. Struct.992, 33-38].