C–H· π Interaction and N·H–O Hydrogen Bonding in the Chair-like p-tert-Butylcalix[8]arene Complex Including Four Pyridine Molecules

Crystal structure analysis shows that the p-tert-butylcalix[8]arene host and its four pyridine guests sit around an inversion center in the P2₁/c crystal lattice. The monoclinic cell parameters and its volume are: a = 19.617(4), b = 9.912(2), c = 25.178(5) , = 101.03(3)°, V =4805.27(17) ³. For Z = 2 and Mw = 1614.18, the calculated density Dcalc = 1.116 g/cm³. A host calixarene molecule includes four pyridine guests in two different ways: by hydrogen bonding and by possible C–H· interaction between the molecules. The hydrogen bonding drives the host macrocycle into a chair-like conformation.     

Miscible blends through hydrogen bonding: effects on polymer properties

Miscible blends through hydrogen bonding have been intensively studied. The effects of a variety of miscible hydrogen bonded polymer blends on properties such as thermal and thermal oxidative stability, moisture sensitivity, modulus and glass transition temperature are discussed. In addition, the preparation of semi-interpenetrating polymer networks (IPNs) and studies of the effect of crosslinking on the miscibility in hydrogen bonded polymer blends are reviewed.     

Crystal Structures of 1,5,9,18,22,26-Hexaaza[11.11]-p-cyclophane Adducts; Two-dimensional Supramolecular Networks

Two newly identified supramolecular structures arise from self-assembly of the macrocyclic 1,5,9,18,22,26- hexaaza[11.11]-p-cyclophane salts with o-nitrophenol (C₂₈H₅₀N₆)⁴⁺·4(C₆H₄NO₂O)⁻ (1) and with HCl (C₂₈H₅₂N₆)⁶⁺·6Cl^-·4H₂O (2). In both cases two-dimensional supramolecular sheets are formed.     

Solid-state binding of dimethyl sulphoxide involving carboxylic host molecules. X-ray crystal structures of four inclusion species

The crystal structures of four dimethyl sulphoxide (DMSO) inclusion compounds with different carboxylic acid hosts,1–4, have been studied by single crystal X-ray analysis. Crystals of thetrans-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylic acid inclusion compound (1a), [1 · DMSO (1: 1)] show monoclinic (P2₁/n) symmetry with the unit cell dimensionsa = 11.522(4),b = 18.658(2),c = 8.709(1) Å and = 98.92(2)°. The clathrate of the 9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylic acid (2a), [2 · DMSO (1: 2)] is triclinic (P) with the cell dimensionsa = 15.043(7),b =9.657(4),c = 8.118(7) Å, = 101.81(5), = 96.05(4) and = 100.04(4)°. Triclinic (P) symmetry is shown also by the inclusion compound of 9,10-dihydro-9,10-ethanoanthracene-11-monocarboxylic acid (3a) [3 · DMSO (1:1)] with the cell dimensionsa=6.3132(1),b=7.9846(2),c=17.5314(4) Å, = 96.46(2), = 87.08(2) and = 106.02(2)°. The 9,9-bianthryl-2-monocarboxylic acid clathrate (4a) [4 · DMSO (1:1)] is monoclinic (P2₁/n) and the cell dimensions area = 19.625(18),b = 8.817(1),c = 14.076(8) Å and = 97.92(6)°. In all these structures, the hosts show the same basic recognition pattern for the DMSO guest, involving a strong O-H ... O bond from the COON to the S=O group, and a possible C-H ... O type interaction between the carbonyl O atom of the host and a CH₃ group of the guest. The crystals consist of discrete host-guest aggregates which are mainly held together by weak intermolecular interactions of the Van der Waals' type. The stoichiometries of the aggregates are, however, different.     

Synthesis and Crystal Structure of Tetraimidazolium Dinicotinatooctamolybdate

1INTRODUCTIONPolyoxometallates(POM)areofgreatinterestnotonlyfortheirstructuralvarietybutalsotheirunexpectedproperties[1,2].Theseinorganicanionshavebeenwidelyinvestigatedasdiversascatalysis,biology,medicine,magnetochemistryandmaterialscience[3～7].Thestudiesonthecoordinatedpoly-oxometallateswithorganicligandsmighthelptounderstandtherolesofpolyoxometallatesoncatalysis.Todate,aseriesofoctamolybdateswhichcanbedescribedas[Mo8O26X2]2n－4(nisthenormalchargeofthecoordinatedbaseX)havebeenreport…     

Crystalline Inclusion Compounds Derived from Derivatives of Mandelic Acid. Host Synthesis, Inclusion Formation, and X-Ray Structures of a Free Host Compound and of DMSO Inclusion Complexes in Both Racemic and Optically Resolved Forms

New chiral host compounds based on mandelic acid derivatives having methyl (6a, b and 8a, b) or bromo substituents (7a, b) attached to the phenyl ring of mandelic acid and involving additional aromatic groups were synthesized. The inclusion properties of both the racemic and the optically resolved host species are reported, including solvent co-crystallization as well as chiroselective and vapour sorptive inclusion. The structures of the free racemic host compound 6b and of the DMSO inclusion compounds of optically resolved and racemic 8 (8a and 8b, respectively) have been determined by X-ray analysis. Enantiomeric pairs of molecules in 6b form centro-symmetric dimers by mutual hydrogen bonding of one hydroxyl group while the other is involved in O-–H ... interactions. The guest molecules in the DMSO complexes of 8a and 8b are bound via hydrogen bonds to two host molecules related by translation along crystallographic axes. Parallels to previous hosts of this type are drawn.     

Comparison of side-on and end-on coordination of E2 ligands in complexes [W(CO)5E2] (E=N,P, As,Sb, Bi,Si-, Ge-, Sn-, Pb-)

Complexes of W(CO)(5) with neutral diatomic pnictogen ligands N(2), P(2), As(2), Sb(2), and Bi(2) and anionic Group 14 ligands Si(2) (2-), Ge(2) (2-), Sn(2) (2-), and Pb(2) (2-) coordinated in both side-on and end-on fashion have been optimized by using density functional theory at the BP86 level with valence sets of TZP quality. The calculated bond energies have been used to compare the preferential binding modes of each respective ligand. The results were interpreted by analyzing the nature of the interaction between the ligands and the metal fragment using an energy partitioning method. This yields quantitative information regarding the strength of covalent and electrostatic interactions between the metal and ligand, as well as the contributions by orbitals of different symmetry to the covalent bonding. Results show that all the ligands studied bind preferentially in a side-on coordination mode, with the exception of N(2), which prefers to coordinate in an end-on mode. The preference of the heavier homologues P(2)-Bi(2) for binding in a side-on mode over the end-on mode in the neutral complexes [(CO)(5)WE(2)] comes mainly from the much stronger electrostatic attraction in the former species. The energy difference between the side-on and end-on isomers of the negatively charged complexes with the ligands Si(2) (2-), Ge(2) (2-), Sn(2) (2-), and Pb(2) (2-) is much less and it cannot be ascribed to a particular bonding component.     

Intrinsic infrared absorption for carbon–fluorine bonding in fluorinated nanodiamond

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Unusual ion pairs and their relationship to acid ionization

Osmotic and activity coefficients, determined from isopiestic measurements, are presented for aqueous solutions of eight tetramethylguanidinium salts. It is proposed that both hydronium and tetramethylguanidinium ions are capable of forming stable ion pairs with many anions by means of bridged hydrogens forming six-membered rings and that these ion pairs are stable in rather dilute aqueous solutions.