Ring-strain release in neutral and dicationic 7,8,17,18-tetrabromo-5,10,15,20-tetraphenylporphyrin: crystal structures of C44H26Br4N4and C44H28Br4N42+·2ClO4−·3CH2Cl2

Two porphyrin complexes were studied to determine the effects of protonation on ring deformation within the porphyrin. The porphyrin 7,8,17,18-tetrabromo-5,10,15,20-tetraphenylporphyrin, C44H26Br4N4, was selected because the neutral species is readily doubly protonated to yield a dication, which was crystallized here with perchlorate counter-ions as a dichloromethane trisolvate, C44H28Br4N42+·2ClO4−·3CH2Cl2. The centrosymmetric neutral species is observed to have a mild `ruffling' of the pyrrole rings and is essentially planar throughout; intramolecular N—H...N hydrogen bonds occur. In contrast, the dication exhibits considerable deformation, with the pyrrole rings oriented well out of the plane of the porphyrin, resulting in a `saddle' conformation of the ring. The charged species forms N—H...O hydrogen bonds to the perchlorate anions, which lie above and below the plane of the porphyrin ring. Distortions to the planarity of the pyrrole rings in both cases are very minor. The characterization of the neutral species represents a low-temperature redetermination of the previous room-temperature analyses [Zouet al.(1995).Acta Cryst.C51, 760–761; Rayatiet al.(2008).Polyhedron, pp. 2285–2290], which showed disorder and physically unrealistic displacement parameters.

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4-(Piperidin-1-yl)pyridinium hexafluorophosphate at 150 K

Acta Crystallographica Section C Crystal Structure Communications ◽

10.1107/s0108270103019358 ◽

2003 ◽

Vol 59 (11) ◽

pp. o622-o624 ◽

Cited By ~ 1

Author(s):

Bruce D. James ◽

Siti Mutrofin ◽

Brian W. Skelton ◽

Allan H. White

Keyword(s):

Hydrogen Bonds ◽

Structural Characterization ◽

Title Compound ◽

Ion Pairs ◽

Piperidine Ring ◽

Torsion Angles ◽

Compound C ◽

Counter Ions

Structural characterization of the title compound, C10H15N2 +·PF6 −, shows it to be ionic, with the pyridine rather than the piperidine N atom being protonated and forming hydrogen bonds to the counter-ions, resulting in two independent ion pairs. A number of unusual features are noted, in particular the remarkably close inter-ring hydrogen contacts [1.97 (3)–2.00 (3) Å] and the considerable differences in the pair of cations, in respect of the torsion angles within the piperidine ring involving the bonds to either side of the N atom.

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Crystal structure of 8-hydroxyquinoline: a new monoclinic polymorph

Acta Crystallographica Section E Structure Reports Online ◽

10.1107/s1600536814016110 ◽

2014 ◽

Vol 70 (9) ◽

pp. o924-o925 ◽

Cited By ~ 10

Author(s):

Raúl Castañeda ◽

Sofia A. Antal ◽

Sergiu Draguta ◽

Tatiana V. Timofeeva ◽

Victor N. Khrustalev

Keyword(s):

Molecular Structure ◽

Crystal Structure ◽

Hydrogen Bonds ◽

Room Temperature ◽

Three Dimensional ◽

Solvent Mixture ◽

Acta Cryst ◽

Space Group ◽

Compound C ◽

Centrosymmetric Dimers

In an attempt to grow 8-hydroxyquinoline–acetaminophen co-crystals from equimolar amounts of conformers in a chloroform–ethanol solvent mixture at room temperature, the title compound, C9H7NO, was obtained. The molecule is planar, with the hydroxy H atom forming an intramolecular O—H...N hydrogen bond. In the crystal, molecules form centrosymmetric dimersviatwo O—H...N hydrogen bonds. Thus, the hydroxy H atoms are involved in bifurcated O—H...N hydrogen bonds, leading to the formation of a central planar four-membered N2H2ring. The dimers are bound by intermolecular π–π stacking [the shortest C...C distance is 3.2997 (17) Å] and C—H...π interactions into a three-dimensional framework. The crystal grown represents a new monoclinic polymorph in the space groupP21/n. The molecular structure of the present monoclinic polymorph is very similar to that of the orthorhombic polymorph (space groupFdd2) studied previously [Roychowdhuryet al.(1978).Acta Cryst.B34, 1047–1048; Banerjee & Saha (1986).Acta Cryst.C42, 1408–1411]. The structures of the two polymorphs are distinguished by the different geometries of the hydrogen-bonded dimers, which in the crystal of the orthorhombic polymorph possess twofold axis symmetry, with the central N2H2ring adopting a butterfly conformation.

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Crystal structure of 2-bromobenzoic acid at 120 K: a redetermination

Acta Crystallographica Section E Structure Reports Online ◽

10.1107/s160053681402087x ◽

2014 ◽

Vol 70 (10) ◽

pp. o1139-o1140 ◽

Cited By ~ 1

Author(s):

Kornelia Kowalska ◽

Damian Trzybiński ◽

Artur Sikorski

Keyword(s):

Crystal Structure ◽

Hydrogen Bonds ◽

Room Temperature ◽

Three Dimensional ◽

Interplanar Distance ◽

Geometrical Parameters ◽

Framework Structure ◽

Acta Cryst ◽

Compound C ◽

Centroid Distance

The crystal structure of the title compound, C7H5BrO2, was originally studied using photographic data at room temperature with Cu Kα radiation [Ferguson & Sim (1962).Acta Cryst.15, 346–350]. The present study was undertaken at 120 K with a CCD diffractometer using Cu Kα radiation, and resulted in improved geometrical parameters. In the molecule, the carboxy group is inclined to the benzene ring by 18.7 (2)° and there is a close intramolecular Br...O contact of 3.009 (3) Å. In the crystal, molecules are linked by pairs of O—H...O hydrogen bonds, forming inversion dimers with the classicalR22(8) ring motif for carboxylic acids. Neighbouring dimers are linked by weak C—H...O hydrogen bonds, forming tapes propagating in [1-10]. Adjacent tapes interact by slipped parallel π–π interactions [inter-centroid distance = 3.991 (2), interplanar distance = 3.509 (2) Å, slippage = 1.900 Å] to form columns approximately along theb-axis direction. Neighbouring columns interact dispersively, forming a three-dimensional framework structure.

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4-(3-Chlorophenyl)-1-(3-chloropropyl)piperazin-1-ium chloride redetermined at 100 K

IUCrData ◽

10.1107/s2414314616001681 ◽

2016 ◽

Vol 1 (2) ◽

Cited By ~ 7

Author(s):

Muzzaffar Ahmad Bhat ◽

Sanjay K. Srivastava ◽

Pooja Sharma ◽

Ambika Chopra ◽

Ray J. Butcher

Keyword(s):

Crystal Structure ◽

Hydrogen Bonds ◽

Room Temperature ◽

Ion Pairs ◽

Three Dimensional ◽

Chair Conformation ◽

Temperature Data ◽

Acta Cryst ◽

Piperazine Ring ◽

Dimensional Network

The crystal structure of the title salt, C13H19Cl2N2+·Cl−, has been reported previously [Homrighausen & Krause Bauer (2002).Acta Cryst.E58, o1395–o1396] based on room-temperature data, where it was found to contain a disordered chloropropyl group. We now present the structure at 100 K in which the chloropropyl group is ordered. The piperazine ring adopts a chair conformation with the exocyclic N—C bonds in equatorial orientations. The dihedral angle between the piperazine ring (all atoms) and the benzene ring is 28.47 (5)°. The chloropropyl group has an extended conformation [N—C—C—C = −177.25 (8) ° and C—C—C—Cl = 174.23 (7)°]. In the crystal, charge-assisted N—H...Cl hydrogen bonds link the cation and anion into ion pairs. Numerous weak C—H...Cl interactions link the ion pairs into a three-dimensional network. Short Cl...Cl contacts [3.2419 (4) Å] are also observed.

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Crystal structure of bis(2-amino-5-chloropyridinium) tetrachloridocobaltate(II)

Acta Crystallographica Section E Crystallographic Communications ◽

10.1107/s2056989015007707 ◽

2015 ◽

Vol 71 (5) ◽

pp. 555-557 ◽

Cited By ~ 3

Author(s):

Marwa Mghandef ◽

Habib Boughzala

Keyword(s):

Crystal Structure ◽

Aqueous Solution ◽

Hydrogen Bonds ◽

Dihedral Angle ◽

Room Temperature ◽

Asymmetric Unit ◽

Slow Evaporation ◽

Acta Cryst

The title salt, (C5H6ClN2)2[CoCl4], was synthesized by slow evaporation of an aqueous solution at room temperature. The asymmetric unit consists of two essentially planar (C5H6ClN2)+cations [maximum deviations = 0.010 (3) and 0.014 (3) Å] that are nearly perpendicular to each other [dihedral angle = 84.12 (7)°]. They are bonded through N—H...Cl hydrogen bonds to distorted [CoCl4]2−tetrahedra, leading to the formation of undulating layers parallel to (100). The structure is isotypic with the Zn analogue [Kefiet. al(2011).Acta Cryst.E67, m355–m356.]

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Formation and Structural Characterization of [RuCl2(CO)2(SPh2)2], [RuCl2(CO)3(OH2)], and [Ru(OH2)6][RuCl3(CO)3]2 · 2H2O

Zeitschrift für Naturforschung B ◽

10.1515/znb-2003-1005 ◽

2003 ◽

Vol 58 (10) ◽

pp. 959-964 ◽

Cited By ~ 5

Author(s):

Marjaana Taimisto ◽

Raija Oilunkaniemi ◽

Risto S. Laitinen ◽

Markku Ahlgrén

Keyword(s):

Hydrogen Bonding ◽

Hydrogen Bonds ◽

Room Temperature ◽

Three Dimensional ◽

Temperature Reaction ◽

X Ray ◽

X Ray Crystallography ◽

Dimensional Network ◽

Moderate Yield

While the room temperature reaction of [RuCl2(CO)3]2 and Ph2S in tetrahydrofuran in air affords [RuCl2(CO)2(SPh2)2] (1) in moderate yield, that in dichloromethane results in the formation of a mixture of [RuCl2(CO)3(H2O)] (2) and [Ru(H2O)6][RuCl3(CO)3]2·2H2O (3). Very small amounts of 1 are produced only upon prolonged reflux of the reagents. All compounds were characterized by X-ray crystallography. 1 crystallizes as discrete octahedral cis(CO), cis(Cl), trans(Ph2S) complexes, which are joined into stacks by weak H···Cl hydrogen bonds. 2 is also composed of discrete octahedral complexes. Four hydrogen bonds involving aqua and chlorido ligands link two complexes into a dimer. The structure of 3 consists of octahedral hexaaquaruthenium cations and two tricarbonyltrichloridoruthenate anions. The water of crystallization is involved in hydrogen bonding between the cations and anions resulting in the formation of a continuous three-dimensional network.

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Reinvestigation of tricyclic acyclovir: characterization of a `proton-wire' model

Acta Crystallographica Section C Crystal Structure Communications ◽

10.1107/s0108270113021082 ◽

2013 ◽

Vol 69 (9) ◽

pp. 1077-1080 ◽

Cited By ~ 2

Author(s):

Montha Meepripruk ◽

Kenneth J. Haller

Keyword(s):

Crystal Structure ◽

Hydrogen Bonds ◽

Three Dimensional ◽

Gramicidin A ◽

Strong Hydrogen Bond ◽

Water Molecules ◽

Asymmetric Unit ◽

Acta Cryst ◽

Dimensional Network

The crystal structure of a dihydrate of the title compound, 3-[(2-hydroxyethoxy)methyl]-6-methyl-3H-imidazolo[1,2-a]-purin-9(5H)-one, C11H13N5O3·2H2O, has been reinvestigated. The asymmetric unit contains two molecules of tricyclic acyclovir and four molecules of water. The structure consists of a three-dimensional network of strong hydrogen bonds that integrates all of the components. While the crystal structure and the formation of an (H2O)8solvent water molecule cluster through a disordered strong hydrogen bond [O...O = 2.807 (3) Å] between two water molecules across an inversion centre has been described previously [Suwińska, Golankiewicz & Zielenkiewicz (2001).Acta Cryst.C57, 767–769], the disorder was incompletely modelled. In this work, the disorder model is extended and includes disorder of one tricyclic acyclovir hydroxy group across another inversion centre [O...O = 2.644 (4) Å]. The resulting infinite O—H...O hydrogen-bonded water–hydroxy chains, analogous to the `proton wires' found in the membrane protein gramicidin A, are discussed and an unusual disorder model involving infinite concerted chains of O—H...O hydrogen bonds is provided.

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Spectroscopic and Thermoanalytical Characterization of (+)-Fenfluramine Hydrochloride

Applied Spectroscopy ◽

10.1366/0003702963905439 ◽

1996 ◽

Vol 50 (7) ◽

pp. 871-879 ◽

Cited By ~ 2

Author(s):

Vittorio Berbenni ◽

Amedeo Marini ◽

Gianna Bruni ◽

Marcella Bini ◽

Angelo Magnone-Grato ◽

...

Keyword(s):

Hydrogen Bonds ◽

Thermal Effects ◽

Room Temperature ◽

Structural Rearrangement ◽

Sample Treatment ◽

Crystallographic Form ◽

Β Phase ◽

Α Phase ◽

Pure Enantiomer

We have analyzed the vibrational, structural, and thermal properties of a pure enantiomer of fenfluramine. At room temperature the samples, as-received or ground, are in the α-phase, in which hydrogen bonds are formed among adjacent molecules. Evidence of these H bonds is no longer found in samples which have been annealed above a critical temperature. Grain size, sample treatment, or defects influence the temperature range where the H bonds break down; this phenomenon is accompanied by thermal effects such as endothermic peaks or anomalies of heat capacity, and followed by a slow structural rearrangement into a γ-phase. No evidence of hydrogen bonds is found in the water recrystallized fenfluramine, which maintains up to the melting temperature a crystallographic form (β-form) distinct from both α - and γ-phases. It is suggested that “folded” and “extended” fenfluramine molecules are characteristic of the α- and β-phase, respectively.

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Characterization of intergranular cuprous oxide in polycrystalline YBa2Cu3O7-x

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100106466 ◽

1988 ◽

Vol 46 ◽

pp. 880-881

Author(s):

Bradley L. Thiel ◽

Chan Han R. P. ◽

Kurosky L. C. Hutter ◽

I. A. Aksay ◽

Mehmet Sarikaya

Keyword(s):

Grain Boundary ◽

Cuprous Oxide ◽

Room Temperature ◽

Boundary Phase ◽

Spectroscopic Techniques ◽

Transition Width ◽

Practical Applications ◽

Thin Foils ◽

Superconducting Oxides

The identification of extraneous phases is important in understanding of high Tc superconducting oxides. The spectroscopic techniques commonly used in determining the origin of superconductivity (such as RAMAN, XPS, AES, and EXAFS) are surface-sensitive. Hence a grain boundary phase several nanometers thick could produce irrelevant spectroscopic results and cause erroneous conclusions. The intergranular phases present a major technological consideration for practical applications. In this communication we report the identification of a Cu2O grain boundary phase which forms during the sintering of YBa2Cu3O7-x (1:2:3 compound).Samples are prepared using a mixture of Y2O3. CuO, and BaO2 powders dispersed in ethanol for complete mixing. The pellets pressed at 20,000 psi are heated to 950°C at a rate of 5°C per min, held for 1 hr, and cooled at 1°C per min to room temperature. The samples show a Tc of 91K with a transition width of 2K. In order to prevent damage, a low temperature stage is used in milling to prepare thin foils which are then observed, using a liquid nitrogen holder, in a Philips 430T at 300 kV.

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Intrinsic doping limit and defect-assisted luminescence in Cs4PbBr6

10.26434/chemrxiv.7629467.v3 ◽

2019 ◽

Author(s):

Young-Kwang Jung ◽

Joaquin Calbo ◽

Ji-Sang Park ◽

Lucy D. Wahlley ◽

Sunghyun Kim ◽

...

Keyword(s):

First Principles ◽

Room Temperature ◽

Stokes Shift ◽

Green Luminescence ◽

Counter Ions ◽

Self Consistent ◽

Deep Ultraviolet ◽

Halide Perovskite ◽

Related Compounds ◽

Level Analysis

Cs4PbBr6 is a member of the halide perovskite family that is built from isolated (zero-dimensional) PbBr64- octahedra with Cs+ counter ions. The material exhibits anomalous optoelectronic properties: optical absorption and weak emission in the deep ultraviolet (310 - 375 nm) with efficient luminescence in the green region (~ 540 nm). Several hypotheses have been proposed to explain the giant Stokes shift including: (i) phase impurities; (ii) self-trapped exciton; (iii) defect emission. We explore, using first-principles theory and self-consistent Fermi level analysis, the unusual defect chemistry and physics of Cs4PbBr6. We find a heavily compensated system where the room-temperature carrier concentrations (< 109 cm-3) are more than one million times lower than the defect concentrations. We show that the low-energy Br-on-Cs antisite results in the formation of a polybromide (Br3) species that can exist in a range of charge states. We further demonstrate from excited-state calculations that tribromide moieties are photoresponsive and can contribute to the observed green luminescence. Photoactivity of polyhalide molecules is expected to be present in other halide perovskite-related compounds where they can influence light absorption and emission.

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