Enantioselective Photochemical Rearrangements of Spirooxindole Epoxides Catalyzed by a Chiral Bifunctional Xanthone

2015 ◽  
Vol 68 (11) ◽  
pp. 1682 ◽  
Author(s):  
Mark M. Maturi ◽  
Alexander Pöthig ◽  
Thorsten Bach
Keyword(s):  
Hydrogen Bonding ◽  
The Other ◽  
Photochemical Rearrangement ◽  
Photochemical Rearrangements

The title compounds were shown to undergo an enantioselective photochemical rearrangement to 3-acylindolin-2-ones (16–33 % ee). A xanthone, which is tethered via an anellated oxazole to a chiral 1,5,7-trimethyl-3-azabicyclo[3.3.1]nonan-2-one scaffold, efficiently catalyzed this reaction at λ 366 nm, presumably by triplet sensitization. The observed enantioselectivity can be explained by hydrogen bonding of the oxindole substrate and the putative 1,3-diradical intermediate to the lactam part of the catalyst. Although one substrate enantiomer is processed with minor preference over the other, it was shown that the reaction is not stereospecific. Rather, the main reason for the observed selectivity is the enantioselective migration step.

The effect of cation concentration on the nitrogen splitting constant of nitroxide free radicals

1990 ◽  
Vol 55 (10) ◽  
pp. 2377-2380
Author(s):  
Hamza A. Hussain
Keyword(s):  
Hydrogen Peroxide ◽  
Hydrogen Bonding ◽  
Free Radicals ◽  
Esr Spectroscopy ◽  
The Other ◽  
Tetraethylammonium Bromide ◽  
Splitting Constant ◽  
The One ◽  
Positively Charged ◽  
Two Equilibria

Nitroxide free radicals prepared from diethylamine, piperidine and pyrrolidine by oxidation with hydrogen peroxide were studied by ESR spectroscopy. The changes in the 14N splitting constant (aN) caused by the addition of KBr or tetraethylammonium bromide were measured in dependence on the concentration of the ions. For diethylamine nitroxide and piperidine nitroxide, the results are discussed in terms of two equilibria: the one, involving the anion, is associated with a gain or loss of hydrogen bonds to the nitroxide oxygen atom, the other is associated with the formation of solvent shared units involving the cation, which results in changes in the hydrogen bonding strenght. The large increase in the aN value in the case of pyrrolidine nitroxide is explained in terms of an interaction from one side of the positively charged N atom; the increase in aN in the case of diethylamine and piperidine nitroxides is explained in terms of interactions with both sides of the positively charged N atom.

scholarly journals Two New Polyiodides in the 4,4´-Bipyridinium Diiodide/Iodine System

2012 ◽  
Vol 67 (1) ◽  
pp. 5-10
Author(s):  
Guido J. Reiss ◽  
Martin van Megen
Keyword(s):  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Complex I ◽  
The Other ◽  
Cyclic Dimer ◽  
Water Molecules ◽  
Spectroscopic Methods ◽  
Halogen Bonds ◽  
One Dimensional ◽  
Hydroiodic Acid

The reaction of bipyridine with hydroiodic acid in the presence of iodine gave two new polyiodide-containing salts best described as 4,4´-bipyridinium bis(triiodide), C10H10N2[I3]2, 1, and bis(4,4´-bipyridinium) diiodide bis(triiodide) tris(diiodine) solvate dihydrate, (C10H10N2)2I2[I3]2 · 3 I2 ·2H2O, 2. Both compounds have been structurally characterized by crystallographic and spectroscopic methods (Raman and IR). Compound 1 is composed of I3 − anions forming one-dimensional polymers connected by interionic halogen bonds. These chains run along [101] with one crystallographically independent triiodide anion aligned and the other triiodide anion perpendicular to the chain direction. There are no classical hydrogen bonds present in 1. The structure of 2 consists of a complex I144− anion, 4,4´-bipyridinium dications and hydrogen-bonded water molecules in the ratio of 1 : 2 : 2. The I144− polyiodide anion is best described as an adduct of two iodide and two triiodide anions and three diiodine molecules. Two 4,4´-bipyridinium cations and two water molecules form a cyclic dimer through N-H· · ·O hydrogen bonds. Only weak hydrogen bonding is found between these cyclic dimers and the polyiodide anions.

A tetranuclear carbonyl fluoro rhenium(I) cluster, [Re(CO)3F]4,4H2O

1981 ◽  
Vol 34 (4) ◽  
pp. 737 ◽  
Author(s):  
E Horn ◽  
MR Snow
Keyword(s):  
Hydrogen Bonding ◽  
Title Compound ◽  
The Other ◽  
Water Molecules ◽  
Molecular Symmetry ◽  
Group 14 ◽  
Full Matrix ◽  
Abstraction Reaction ◽  
R Value ◽  
Silver Fluoride

The title compound has been prepared from Re(CO)5Br by a bromide-abstraction reaction with silver fluoride. It completes the series of known halide clusters of the type [Re(CO)3X]4 (where X = halide). The crystals are tetragonal, space group 14, with a 11.716(5), c 8.988(3) �, and Z 2. The structure was refined by full-matrix least-squares to an R value of 0.027 for 1380 observed reflections. The molecules are cubane-type clusters of Re(CO)3 groups at one set of corners interpenetrated with fluorine atoms at the other set. The clusters exhibit the molecular symmetry 43m. Each of the fluorine atoms is involved in μ3 type bridging with the rhenium atoms at an average bonding distance of 2.200(5) �. The clusters are held together by hydrogen bonding of fluoride to water molecules.

Polymorphs of phenazine hexacyanoferrate(II) hydrate: supramolecular isomerism in a 2D hydrogen-bonded network

2021 ◽  
Vol 77 (2) ◽  
pp. 211-218
Author(s):  
Ivica Cvrtila ◽  
Vladimir Stilinović
Keyword(s):  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Crystal Structures ◽  
The Other ◽  
Two Dimensional ◽  
Structural Motifs ◽  
Supramolecular Isomerism ◽  
Other Hand ◽  
Π Stacking ◽  
Hydrogen Bonded

The crystal structures of two polymorphs of a phenazine hexacyanoferrate(II) salt/cocrystal, with the formula (Hphen)3[H2Fe(CN)6][H3Fe(CN)6]·2(phen)·2H2O, are reported. The polymorphs are comprised of (Hphen)2[H2Fe(CN)6] trimers and (Hphen)[(phen)2(H2O)2][H3Fe(CN)6] hexamers connected into two-dimensional (2D) hydrogen-bonded networks through strong hydrogen bonds between the [H2Fe(CN)6]2− and [H3Fe(CN)6]− anions. The layers are further connected by hydrogen bonds, as well as through π–π stacking of phenazine moieties. Aside from the identical 2D hydrogen-bonded networks, the two polymorphs share phenazine stacks comprising both protonated and neutral phenazine molecules. On the other hand, the polymorphs differ in the conformation, placement and orientation of the hydrogen-bonded trimers and hexamers within the hydrogen-bonded networks, which leads to different packing of the hydrogen-bonded layers, as well as to different hydrogen bonding between the layers. Thus, aside from an exceptional number of symmetry-independent units (nine in total), these two polymorphs show how robust structural motifs, such as charge-assisted hydrogen bonding or π-stacking, allow for different arrangements of the supramolecular units, resulting in polymorphism.

scholarly journals Crystal structure of tetraaqua(5,5′-dimethyl-2,2′-bipyridyl-κ2N,N′)iron(II) sulfate

2014 ◽  
Vol 70 (12) ◽  
pp. 544-546 ◽  
Author(s):  
Yamine Belamri ◽  
Fatima Setifi ◽  
Bojana M. Francuski ◽  
Sladjana B. Novaković ◽  
Setifi Zouaoui
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Coordination Bond ◽  
Octahedral Geometry ◽  
The Other ◽  
Distorted Octahedral Geometry ◽  
Cationic Complex ◽  
Centroid Distance ◽  
Distorted Octahedral ◽  
Coordination Bonds

In the title compound, [Fe(C12H12N2)(H2O)4]SO4, the central FeIIion is coordinated by two N atoms from the 5,5′-dimethyl-2,2′-bipyridine ligand and four water O atoms in a distorted octahedral geometry. The Fe—O coordination bond lengths vary from 2.080 (3) to 2.110 (3) Å, while the two Fe—N coordination bonds have practically identical lengths [2.175 (3) and 2.177 (3) Å]. The chelating N—Fe—N angle of 75.6 (1)° shows the largest deviation from an ideal octahedral geometry; the other coordination angles deviate from ideal values by 0.1 (1) to 9.1 (1)°. O—H...O hydrogen bonding between the four aqua ligands of the cationic complex and four O-atom acceptors of the anion leads to the formation of layers parallel to theabplane. Neighbouring layers further interact by means of C—H...O and π–π interactions involving the laterally positioned bipyridine rings. The perpendicular distance between π–π interacting rings is 3.365 (2) Å, with a centroid–centroid distance of 3.702 (3) Å.

Structure of [(CH3)2NH2]2CoCl4 at elevated temperatures

1999 ◽  
Vol 55 (5) ◽  
pp. 752-757 ◽  
Author(s):  
Amir H. Mahmoudkhani ◽  
Vratislav Langer
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Phase Transitions ◽  
Physical Properties ◽  
Electric Conductivity ◽  
Title Compound ◽  
Structural Changes ◽  
Elevated Temperatures ◽  
The Other ◽  
Cell Parameters

The crystal structure of the title compound, dimethylammonium tetrachlorocobaltate(II), has been determined at four temperatures between 297 and 366 K, in order to investigate possible phase transitions at 313 and 353 K [Kapustianik, Polovinko & Kaluza et al. (1996). Phys. Status Solidi A, 153, 117–122]. We found that there is no significant change either in the hydrogen-bonding network or in the cell parameters, apart from a linear dilatation with temperature. This study reveals that the anomalous variation in electric conductivity and some of the other physical properties of the compound cannot be explained by structural changes.

scholarly journals Self-Organization of -Crown Ether Derivatives into Double-Columnar Arrays Controlled by Supramolecular Isomers of Hydrogen-Bonded Anionic Biimidazolate Ni Complexes

2012 ◽  
Vol 2012 ◽  
pp. 1-10
Author(s):  
Makoto Tadokoro ◽  
Kyosuke Isoda ◽  
Yasuko Tanaka ◽  
Yuko Kaneko ◽  
Syoko Yamamoto ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Crown Ether ◽  
Building Block ◽  
The Other ◽  
Optical Isomer ◽  
Self Organization ◽  
Optical Isomers ◽  
One Dimensional ◽  
Molecular Building Block ◽  
Hydrogen Bonded

Anionic tris (biimidazolate) nickelate (II) ([Ni(Hbim)3]−), which is a hydrogen-bonding (H-bonding) molecular building block, undergoes self-organization into honeycomb-sheet superstructures connected by complementary intermolecular H-bonds. The crystal obtained from the stacking of these sheets is assembled into channel frameworks, approximately 2 nm wide, that clathrate two cationic K+-crown ether derivatives organised into one-dimensional (1D) double-columnar arrays. In this study, we have shown that all five cationic guest-included crystals form nanochannel structures that clathrate the 1-D double-columnar arrays of one of the four types of K+-crown ether derivatives, one of which induces a polymorph. This is accomplished by adaptably fitting two types of anionic [Ni(Hbim)3]−host arrays. One is a network with H-bonded linkages alternating between the two different optical isomers of the and types with flexible H-bonded [Ni(Hbim)3]−. The other is a network of a racemate with 1-D H-bonded arrays of the same optical isomer for each type. Thus, [Ni(Hbim)3]−can assemble large cations such as K+crown-ether derivatives into double-columnar arrays by highly recognizing flexible H-bonding arrangements with two host networks of and .

More examples of the 15-crown-5...H2O—M—OH2...15-crown-5 motif, M = Al3+, Cr3+ and Pd2+

2010 ◽  
Vol 66 (2) ◽  
pp. 213-221 ◽  
Author(s):  
Maxime A. Siegler ◽  
Jacob H. Prewitt ◽  
Steven P. Kelley ◽  
Sean Parkin ◽  
John P. Selegue ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Water Molecule ◽  
Lattice Water Molecule ◽  
Literature Survey ◽  
The Other ◽  
Water Molecules ◽  
Lattice Water ◽  
Hydrogen Bonding Pattern ◽  
Hydrogen Bonded

Five structures of co-crystals grown from aqueous solutions equimolar in 15-crown-5 (or 15C5) and [M(H2O)6](NO3) n , M = Al3+, Cr3+ and Pd2+, are reported. The hydrogen-bonding patterns in all are similar: metal complexes including the fragment trans-H2O—M—OH2 alternate with 15C5 molecules, to which they are hydrogen bonded, to form stacks. A literature survey shows that this hydrogen-bonding pattern is very common. In each of the two polymorphs of the compound [Al(H2O)6](NO3)3·15C5·4H2O there are two independent cations; one forms hydrogen bonds directly to the 15C5 molecules adjacent in the stack, while the other cation is hydrogen-bonded to two water molecules that act as spacers in the stack. These stacks are then crosslinked by hydrogen bonds formed by the three nitrate counterions and the three lattice water molecules. The hydrogen-bonded stacks in [Cr(H2O)5(NO3)](NO3)2·1.5(15C5)·H2O are discrete rather than infinite; each unit contains two Cr3+ complex cations and three 15C5 molecules. These units are again crosslinked by the uncoordinated nitrate ions and a lattice water molecule. In [Pd(H2O)2(NO3)2]·15C5 the infinite stacks are electrically neutral and are not crosslinked. In [Pd(H2O)2(NO3)2]·2(15C5)·2H2O·2HNO3 a discrete, uncharged unit containing one Pd complex and two 15C5 molecules is `capped off' at either end by a lattice water molecule and an included nitric acid molecule. In all five structures the infinite stacks or discrete units form an array that is at least approximately hexagonal.

The crystal chemistry of duftite, PbCuAsO4(OH) and the β-duftite problem

1998 ◽  
Vol 62 (1) ◽  
pp. 121-130 ◽  
Author(s):  
Kharisun ◽  
Max R. Taylor ◽  
D. J. M Bevan ◽  
Allan Pring
Keyword(s):  
Hydrogen Bonding ◽  
Crystal Chemistry ◽  
Three Dimensional ◽  
The Other ◽  
Orthorhombic Space Group ◽  
Teller Distortion ◽  
Modulated Structure ◽  
Dimensional Network ◽  
Jahn Teller ◽  
Jahn Teller Distortion

AbstractDuftite, PbCu(AsO4)(OH) is orthorhombic, space group P212121 with a = 7.768(1), b = 9. 211(1), c = 5.999(1) Å, Z = 4; the structure has been refined to R = 4.6% and Rw = 6.5% using 640 observed reflections [F> 2σ(F)]. The structure consists of chains of edge-sharing CuO6 ‘octahedra’, parallel to c; which are linked via AsO4 tetrahedra and Pb atoms in distorted square antiprismatic co-ordination to form a three dimensional network. The CuO6 ‘octahedra’ show Jahn-Teller distortion with the elongation running approximately along <627>. The hydrogen bonding network in the structure was characterized using bond valence calculations. ‘β-duftite’ is an intermediate in the duftite-conichalcite series, which has a modulated structure based on the intergrowth of the two structures in domains of approximately 50 Å. The origin of the modulation is thought to be associated with displacements in the oxygen lattice and is related to the orientation of the Jahn-Teller distortion of CuO6 ‘octahedra’. Approximately half of the strips show an elongation parallel to <627> while the other strips are elongated parallel to [010]. This ordering results in an increase in the b cell repeat compared to duftite and conichalcite.

scholarly journals Poly[tetrakis(μ-1,1,1,3,3,3-hexafluoropropan-2-olato)iron(II)dipotassium]

2014 ◽  
Vol 70 (2) ◽  
pp. m32-m33 ◽  
Author(s):  
Andrew P. Purdy ◽  
Ray J. Butcher
Keyword(s):  
Hydrogen Bonding ◽  
Title Compound ◽  
Three Dimensional ◽  
The Other ◽  
Tetrahedral Coordination ◽  
Compound K ◽  
Coordination Environment ◽  
Weak Hydrogen Bonding ◽  
Alternating Chain ◽  
Distorted Tetrahedral Coordination

The title compound, [K2Fe{OCH(CF3)2}4]n, was formed from the reaction of potassium hexafluoroisopropoxide with iron(II) chloride in toluene. The FeIIatom has a highly distorted tetrahedral coordination environment. All four of the non-equivalent hexafluoroisopropoxy O atoms link the FeIIatoms to one of the K+atoms in an alternating chain of Fe—O—K—O fused four-membered rings, with K—Fe distances of 3.715 (2) and 3.717 (2) Å. This K+atom is also bridged to eight of the F atoms. The other K+atom is bonded to only two of the O atoms, but has seven short K...F contacts, one of which links the chains into a three-dimensional arrangement. Weak hydrogen bonding between the lone H atoms on the hexafluoroisopropoxy groups and F atoms is also present. The crystal studied was refined as an inversion twin.

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