An X-ray study of a 12-crown-4 host-guest complex. Crystal structure of the 4∶6 complex between 12-crown-4 and aminosulfuric acid

The title compound was prepared by treating a methanolic solution of 12-crown-4 with an aqueous solution of aminosulfuric acid. The crystal for X-ray analysis was obtained by recrystallization from acetone. The compound [(12-crown-4)₄·[NH₃SO₃)₆] (1) is monoclinic, space groupP2₁/a,a=21.900(8),b=15.499(5),c=18.079(5) Å, =67.85(2)°. Refinement led to a final conventionalR value of 0.0788 for 3280 reflections. Supplementary Data relating to this publication have been deposited with British Library as Supplementary Publication No. 82160 (22 pages) and include: the list ofF _obs,F _calc; tables of bond distances, bond angles and selected least square planes, as well as a figure of 12-crown-4 in C₄-conformation.     

Crystal structure analysis of the carbon tetrabromide clathrate of hexakis(phenylseleno)benzene

The 12 inclusion compound of hexakis(phenylseleno)benzene (1) with CBr₄ is trigonal, space groupR , witha=14.474(3),c=21.487(4) Å, and three host and six guest molecules in a unit cell referred to hexagonal axes. A true clathrate structure is found and in each closed cage there are two carbon tetrabromide guest molecules, orientated such that a C–Br bond of each is colinear with thec-axis of the crystal. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82002. To obtain copies, see page ii of this issue.     

Asymmetric Synthesis of Octahydrobenzofuran Core Structure with Three Contiguous Stereogenic Centers and Development of the Absolute Configurations

Cyclization of enantiopure (S/R)-1 with halogen-reagent-constructed enantiopure octahydrobenzofuran core structure with contiguous three stereogenic centers of both enantiomers (SRR and RSS). The absolute configurations of all compounds have been established from x-ray analysis of the single crystal of (3aS,7aR,7R)-3. The chiral initiation in diastereoselective mode of 5-exo ring closure across C?C bond of pendant cyclohexene moiety has been proposed.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Reaction of trimethylaluminum with crown ethers. III. The synthesis and crystal structure of (12-crown-4)bis(trimethylaluminum)

The crown ether 12-crown-4 reacts with trimethylaluminum in toluene to form the complex [AlMe₃]₂[12-crown-4]. Attempts to utilize the remaining two oxygen atoms for coordination to AlMe₃ molecules were unsuccessful. The 21 complex crystallizes in the monoclinic space groupP2₁/n witha=11.342(7),b=12.941(4),c=6.973(6) Å, and =95.48(4)°. Refinement led to a finalR value of 0.047 for 925 observed reflections. The molecule resides on a crystallographic center of inversion, and as required by symmetry, the four oxygen atoms are planar. The Al–O bond is strong as revealed by the bond length of 1.977(3) Å. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82013 (9 pages).     

Comparison of the structures of 1,5-dichloro- and 1,5-dibromonaphthalene-2,6-diol and their co-crystalline compounds with dioxane

The 1,5-dichloro-(1) and 1,5-dibromo-(2) naphthalene-2,6-diols form isostructural lattices incorporating ...O–H...O–H...O–H... hydrogen bonding surrounding 2₁ screw axes. Each phenolic hydroxy group participates in one donor and one acceptor hydrogen bond. When crystallised from dioxane, both compounds form new 1:1 co-crystalline materials whose lattices are closely related but not isostructural. All inter-phenolic hydrogen bonding is now absent with each hydroxy group acting instead as a donor to a dioxane oxygen atom. In consequence, the hydrogen bonded layer structures of pure1 or2 are now replaced by hydrogen bonded chain arrangements. All four crystal structures are analysed and compared in crystal engineering terms through discussion of the various types of other weak intermolecular attractions involved in their lattice constructions. Supplementary Data relating to this article are deposited with the British Library as supplementary publication No. SUP 82202 (19 pages).     

Host-guest chemistry. 2. Amine inclusion compounds of 2-[o-(triphenylphosphoranylidenamino)benzyliden]amino-1H-2,3-dihydroindazol-3-one. X-ray structure of its 1∶1∶1 inclusion complex with isopropylamine and water

The crystal and molecular structure is reported for the inclusion compound 2-[o-(triphenylphosphoranylidenamino)benzyliden]amino-1H-2,3-dihydroindazol-3-one/isopropylamine/water3b. The crystal structure consists of discrete dimeric salt-like aggregates joined together by strong N⁺–H...^–O–C hydrogen bonds between pairs of centrosymmetrically-related indazolonate anions and isopropylammonium cations. Six other inclusion compounds have been prepared and characterized by NMR [with propylamine (3a), withtert-butylamine (3c), withsec-butylamine (3d), withtert-pentylamine (3e), with 1-methylbutylamine (3f) and withiso-pentylamine (3g)]. Two different arrangements are found, both with the host being in the anionic form. The guests are either: (i) one protonated amine and one water molecule (3b and3f); or (ii) one protonated amine and the corresponding neutral amine (3a, 3c, 3d, 3e and3g). Supplementary Data relating to this article (structure factors, thermal components, hydrogen parameters and bond distances and angles, and¹³C-NMR shifts) are deposited with the British Library at Boston Spa, Wetherby, West Yorkshire, U.K., as Supplementary Publication No. SUP 82155 (23 pages).For Part 1, see Reference [1].     

A 13-membered crown ether with an azoxy subunit in the macrocycle: Synthesis and X-ray structure

The presented azoxy compound is an example of a new crown ether analogue. It has been synthesized by the reduction of an open chain dinitro compound with stannite under strongly alkaline conditions. A method for the separation of the azo and azoxy compounds formed simultaneously has been proposed. The structures of two crystallographically independent molecules of compound2 have been determined. In spite of the small size of the macroring in compound2, the phenyl residues around the azoxy group have atrans orientation. Supplementary Data relating to this article have been deposited with the British Library as Supplementary Publication No. 82157 (11 pages).     

The improved synthesis and crystal structure of 20-thiocrown-4

An improved synthesis of 20-thiocrown-4 is reported, which exploits the Kellogg method of cesium carbonate in DMF mediated macrocyclization of precondensed synthones which converge at the cycloicosane structure. The crystal structure of 20-thiocrown-4 reveals a rectangular conformation for the free ligand. Each sulfur is in onegauche and oneanti torsion angle. Four carbon positions make up the corners. There are two short sides comprised of –C–C– torsion angle sequencesg ^–ag^– and two long sides (aaa, g ^–ag⁺). The S–C and C–C bond distances average 1.816(2) and 1.523(3) , respectively. Supplementary data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82147 (9 pages)     

The metrological infrastructure for gas analysis

This presentation to the Metrology in Chemistry symposium held in October 2004 in Beijing, describes the metrological infrastructure for gas analysis. The inputs from National Metrology Institutes, industry, standardisation and accreditation bodies, and organisers of proficiency testing schemes are briefly described. Electronic Supplementary Material Supplementary material is available for this article at Presented at the International Symposium on Metrology in Chemistry, 2004 Beijing, China.     

Crystal structures of inclusion complexes of cholic acid with aniline,mono- and difluorinated anilines: Guest information expressed by molecular assembly

The crystal structures of cholic acid (CA), a naturally occurring bile acid, complexed with aniline, and its mono- and difluorinated derivatives were elucidated by X-ray crystallography. Comparison of the structures obtained shows that the molecular assembly pattern and the related structural change of the CA molecule vary among different complexes. These structural changes are the molecular information of the guests. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82197 (27 pages).     

A theoretical study of radical-only and combined radical/carbocationic mechanisms of arachidonic acid cyclooxygenation by prostaglandin H synthase

Prostaglandin H synthase catalyzes the oxygenation of arachidonic acid into the cyclic endoperoxide, prostaglandin G₂ (PGG₂), and the subsequent reduction of PGG₂ to the corresponding alcohol, prostaglandin H₂ (PGH₂), the precursor of all prostaglandins and thromboxanes. Both radical abstraction by a neighboring tyrosyl radical and combined radical/carbocationic models have been proposed to explain the cyclooxygenase part of this reaction. We have used density functional theory calculations to study the mechanism of the formation of the cyclooxygenated product PGG₂. We found an activation free energy for the initial hydrogen abstraction by the tyrosine radical of 15.6 kcal/mol, and of 14.5 kcal/mol for peroxo bridge formation, in remarkable agreement with the experimental value of 15.0 kcal/mol. Subsequent steps of the radical-based mechanism were found to happen with smaller barriers. A combined radical/carbocation mechanism proceeding through a sigmatropic hydrogen shift was ruled out, owing to its much larger activation free energy of 36.5 kcal/mol. Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00214-003-0476-9. Electronic Supplementary MaterialSupplementary material is available in the online version of this article at Electronic Supplementary Material: Supplementary material is available in the online version of this article at     

The crystal structure of the syn-proximal-5,11,17,23-tetra-tert-butyl-25,26-bis[(2-pyridylmethyl)oxy]-27,28-dihydroxy-calix[4]arene ethanol 1 : 1 Inclusion Complex

The crystal structure of the title compound (1 · C₂H₅OH) has been determined by single-crystal X-ray analysis and refined to anR-value of 0.074 for 2732 observed reflections [I > 2.0(I)]. Crystals are triclinic, space group P , witha = 13.6150(18),b = 13.7195(11),c = 16.5497(16) Å, = 73.132(7), = 66.165(9), = 65.580(8)° andZ = 2. Calix[4]arene (1) adopts a relatively open distorted cone conformation in the solid state, with two pendantsyn-proximal O-CH₂-Py groups. The major conformation determining features in (1 · C₂H₅OH) are the presence of (a) an intramolecular O-H...O hydrogen bond between adjacent proximal phenolic oxygens, O...O 2.719(7) Å and (b) an intramolecular O-H...N hydrogen bond between a phenolic oxygen and a proximal pyridinyl nitrogen, O...N 2.810(8) Å. The intramolecular hydrogen bonding and the interplanar angles of 65.1(3) and 50.7(3)° between opposite aromatic rings facilitate the inclusion of an ethanol molecule within the calixarene cup.Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82141 (26 pages).     

Host: Guest chemistry of diaza-18-crown-6: Selective precipitation from mixtures of oligohydroxy phenols and the structures of five host: Guest complexes

Diaza-18-crown-6 (1,4,10,13-tetraoxa-7,16-diaza-cyclo-octadecane) selectively precipitates as a 1,4-dihydroxybenzene-complex from a mixture of isomeric phenols and as a 2,6-dihydroxynapthalene-complex from mixtures of isomeric diols. These selective precipitations are discussed in terms of structure and solubility of the host-guest complexes and phenol acidity. The crystal structures of diaza-18-crown-6 with guestsp-nitrophenol (2: 1), 2,4-dinitroaniline (2: 1), 5,5-diethylbarbituric acid (2: 1), salicylaldoxime (2: 1) and 1,4-dihydroxybut-2-yne (1: 1) are reported. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82065 (74 pages).     

Crystal and molecular structures of binuclear caesium complexes with 1,3-calix[4]-bis-crown-6 and 1,3-calix[4]-bis-benzo-crown-6

The crystal structures of two binuclear complexes between caesium and 1,3-calix[4]-bis-crowns have been determined. Cs₂ Bis-benzoC6(NO₃)₂. 3CHCl₃ (1) in whichBis-benzoC6 is 1,3-calix[4]-bis-benzo-crown-6, crystallizes in the orthorhombic system: space groupPca2 ₁ a=19.513(10),b=15.382(5),c=23.708(9) Å,V=7116(5) ų,Z=4. Refinement led to a final conventionalR value of 0.065 for 2321 reflections. The structure of (1) is analogous to those already reported withBis-C6, (in whichBis-C6 is, 1,3-calix[4]-bis-crown-6) and NO ₃ ^– as a counter-ion. Cs₂ Bis-C6(NCS)₂ (2) crystallizes in the monoclinic system: space, groupC2 a=36.57(2),b=11.47(1),c=13.65(1) Å, =109.03(5)°.,V=5415(6) ų,Z=4. Refinement led to a final conventionalR value of 0.063 for 2227 reflections. Compound (2) is made of dimers bridged by a disordered NCS^– ion. The crown ether chain conformations are discussed. Supplementary data relating to this article (atomic coordinates, anisotropic displacement parameters, bond distances and angles and observed and calculated structure factors) are deposited with the British Library as Supplementary Publication No. SUP 82199 (52 pages).     

Calixarenes: Structure of an acetonitrile inclusion complex and some transition metal rimmed derivatives

The hostt-butylcalix[4]arene,1a, forms a 11 inclusion compound with acetonitrile as guest. The inclusion compound has been isolated and characterised by X-ray analysis of a twinned crystal at 123 K. The acetonitrile guest lies on a crystallographic four-fold symmetry axis passing through the centre of the bowl of1a which adopts a regular cone conformation. A known tetradentate and a new tridentate phosphinitocalix[4]arene derivative,2a and2c respectively, have been synthesized from1a and Ph₂Cl. Both2a and2c show a strong ability to coordinate with late transition metals and new complexes of gold(I), palladium(II) and platinum(II) are reported. Supplementary Data relating to this paper have been deposited with the British Library as Supplementary Publication No. SUP 92171 (5 pp.)This paper is dedicated to the commemorative issue on the 50th anniversary of calixarenes.     

Synthesis and structures of nitromethane complexes of furanotribenzo-21-crown-7 and dibenzo-21-crown-7

Single crystal X-ray diffraction analyses of two nitromethane complexes of furanotribenzo-21-crown-7 (1 and2) and the nitromethane complex of dibenzo-2l-crown-7 (3) are reported. The two nitromethane complexes1 and2 are polymorphic in that the macrocyclic ring adopts the dentist's chair conformation in both structures, with a single nitromethane molecule coordinating to either the lower, concave (1) or upper, convex (2) face of the crown ether. Complex3 adopts an entirely different conformation with a coplanar arrangement of the crown ether oxygen atoms binding a single nitromethane molecule. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. 82209 (31 pages).The U.S. Government right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged.     

Preparation and structural properties of macrocyclic phosphonamides. Structural characterization of a potassium complex

A novel class of organophosphorus macrocycles containing one phosphonamide or one thiophosphonamide group was obtained by condensation of bis(dimethylamino)methyl-phosphine with the appropriate oligoether-bisprimary amine, followed by the oxidation of the P(III) species. The structures of two macrocyclic phosphonamide ligands (3 and4) which differ in the length of the oligoether chain, and that of the potassium thiocyanate complex of4, were studied by Xray diffraction. The crystals of3 and4 containe two crystallographically independent molecules. A cavity appears in the centre of each uncomplexed molecule, but the oxygen atoms of the longer oligoether chain are better oriented towards the centre of this cavity. An important rearrangement of the molecular conformation of4 occurs upon complexation as shown in the crystal structure analysis of the complex4· KSCN. The phosphoryl O atom of one molecule binds to the metal ion of another complexed molecule, leading to the self assembly of4· KSCN complexes. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP. 82161 (27 pages).Research fellow (1986–1989), Université J. Fourier, Grenoble (France)     

Neutral solvent/crown ether interactions, 4. Crystallization and low temperature (−150°C) structural characterization of 18-crown-6 · 2(CH3CN)

The crystal structure of 18-crown-6 · 2(CH₃CN) has been determined via data collection at –150°C. The structure consists of two crown molecules each hydrogen bonded to two acetonitrile moieties in the asymmetric unit, each residing around a center of inversion. The crown ethers display their fullD _3d symmetry; methyl ... O contacts range from 3.189(8) to 3.598(8) Å. There are no close contacts indicative of any interaction between the crown/2(CH₃CN) units. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82056 (14 pages).For Part 3, see reference [1]     

Structural and Electronic Characterization of Antioxidants from Marine Organisms

Density functional theory was employed to investigate the molecular properties of new systems that serve as antioxidants in the marine environment. The B3LYP/6-311++G** protocol was used for all computations. Investigation, performed in gas phase and in solvent, was devoted mainly to the determination of the O–H bond dissociation enthalpies and the ionization potentials of examined compounds, since these quantities represent the most important parameters on which the biological activity can be rationalized. The results, interpreted in terms of conjugation and delocalization effects acting on molecules and all their possible radicals, showed that between the studied systems the hydroquinone derivatives have the greatest potentiality as antioxidants.Electronic Supplementary Material Supplementary material is available in the online version of this article at     

A Simple and Eco-Compatible One-Pot Synthesis of New Symmetrical Dithiocarbamate Podands and Their Dynamic NMR Studies

Abstract

A simple and eco-compatible synthesis of podands as 4_a-i is performed using amines (3_a-c ), CS₂, and dichlordiamides (DCDs) (2_{a, c} ) in the absence of a catalyst in water. Three reacting DCDs (2_a-c ) were obtained in the reaction of aromatic diamines (1_{a, c} ) with chloroacetyl chloride. Dynamic NMR spectroscopic data of three series of podands (4_a-c , 4_d-f , and 4_g-i ) are discussed and their free energies of activations are calculated (ΔG ^≠ _c s) at coalescence temperatures. The ΔG ^≠ _c of these podands were attributed to conformational isomerization in the range of 14.7–17 kcal/mol due to rotation and resonance effects about the thioamide C?N bond.

[Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfer, and Silicon and the Related Elements for the following free supplemental files: Additional figures.]