Direct observation of magnetic ordering in the (CH3NH2)K3C60 fulleride

The zero-field muon-spin-relaxation (ZF-micro(+)SR) technique provides direct observation of the development of antiferromagnetic long range order in the hyperexpanded methylaminated fulleride salt, (CH(3)NH(2))K(3)C(60) below T(N) approximately 10 K-coherent ordering of the electronic magnetic moments leads to a local field of approximately 25 G at the muon site at 1.2 K.     

Crystal and molecular structures of complex between ammonium iodide monohydrate and the cis-syn-cis isomer of dicyclohexano-18-crown-6

The structure of the [(DCH-6A ? NH₄)(H₂O)I]₂ complex obtained by the reaction between the cis-syn-cisisomer of dicyclohexano-18-crown-6 (DCH-6A) and NH₄I has been determined by X-ray diffraction analysis. The crystals are triclinic, a = 9.314(3) Å, b = 11.951(2) Å, c = 12.040(1) Å, α = 77.36(1)°, β = 81.59(1)°, γ = 80.41(2)°, space group $P\bar 1$ , Z = 2, and the final R factor is 0.044. The structure is built up of the (DCH-6A ? NH₄) + cationic complexes, iodide anions, and water molecules. The ammonium ion forms three hydrogen bonds of the NH?O type [N?O, 2.881(5)–2.890(5) Å] with the oxygen atoms of the crown ether molecule. The organic cations are joined together into centrosymmetric dimers through the system of hydrogen bonds of the NH?OH type. The I^??O distances (where the O atom belongs to the bridging water molecule) fall in the range 3.558(4)–3.610(4) Å.     

Crystal structure of hydrazine 5-amino-1-benzyl-1,2,3-triazole-4-carboxylate hexafluorosilicate trihydrate

Hydrazine 5-amino-1-benzyl-1,2,3-triazole-4-carboxylate hexafluorosilicate trihydrate (I) is synthesized. The crystal structure of the compound synthesized is determined. Crystals I are monoclinic, a = 13.353(1) Å, b = 21.094(2) Å, c = 20.233(2) Å, β = 94.05(3)°, space group P2₁/c, and R = 0.0584 for 16 601 reflections with I > 2σ(I). In the asymmetric part of the unit cell, four organic cations protonated at the terminal hydrazine nitrogen atoms, two hexafluorosilicate anions, and six water molecules are linked into a three-dimensional framework through hydrogen bonds of the N-H?F, N-H?O, and O-H?F types.     

Heterocalixarene Inclusion Chemistry. Structure of a Crystalline Host-Guest Complex Including endo-Calix Ethyl Acetate and exo-Calix Clustering of Water

The X-ray crystal structure of the solvent inclusion compound formed between heterocalix[8]arene 1, ethyl acetate and water (1 : 1 : 4.5) has been studied. The compound crystallized in tetragonal space group I4₁/a, a = b = 21.278(3), c = 31.290(4) Å, V = 14167(4) ų, Z = 8. The host molecule, incorporating benzimidazol-2-one and 2,5-dimethoxy-1,3-phenylene subunits in an alternate cyclic arrangement, forms an almost perfectly closed cavity which encapsulates one solvent ethyl acetate guest molecule. Water molecules being entrapped in the lattice cages in the form of cyclic and linear clusters bind the bulky inclusion complexes via H-bonds in infinite layers. Two symmetry center related benzimidazole-2-one moieties of two hosts from neighbouring layers in the crystal lattice are arranged such that they partially overlap exhibiting stacking interaction.     

Crystal structures of benzo-18-crown-6 complexes with oxonium hexafluorotantalate and oxonium hexafluoroniobate

The crystal structures of [(benzo-18-crown-6) · H₃O]TaF₆ and [(benzo-18-crown-6) · H₃O]NbF₆ complex compounds are determined by X-ray diffraction. It is revealed that the tantalum complex has two polymorphic modifications, namely, the monoclinic (I) and orthorhombic (II) modifications. The unit cell parameters of these compounds are as follows: a = 14.784(2) Å, b = 8.390(4) Å, c = 18.005(6) Å, β = 95.78(2)°, Z = 4, and space group P2₁/n for modification I; and a = 8.456(2) Å, b = 21.967(5) Å, c = 24.122(5) Å, Z = 8, and space group Pbca for modification II. The orthorhombic niobium complex [(benzo-18-crown-6) · H₃O]NbF₆ with the unit cell parameters a = 8.454(1) Å, b = 21.943(3) Å, c = 24.127(4) Å, Z = 8, and space group Pbca (III) is isostructural with tantalum complex II. The oxonium cation in complexes I–III is encapsulated by the crown ether and thus forms one ordinary and two bifurcate hydrogen bonds with the oxygen atoms of the crown ether. This macrocyclic cation is bound to the anions through the C-H ...F contacts (H...F, 2.48–2.58 Å).     

Host-guest complexes [(H4L)(SiF6)2-4H2O] and [(H4L)(GeF6)2 4H2O] (L =meso-5,7,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane)

Synthesis and X-ray structure analysis of host-guest complexes [(H₄L)(SiF₆)₂-4H₂O] (I) and [(H₄L)(GeF₆)₂-4H₂O] (II) are reported (L = meso-5,7,7,12,12,14-hexamethyl-l,4,8,11-tetraazacyclo-tetradecane). The crystals of both compounds are triclinic with close unit cell parameters. I: a = 9.576(3), b= 9.217(3), c= 8.334(2) å, α= 105.66(2), Ω= 83.68(2), α = 105.38(2)? II: a= 9.627(3), b = 9.358(3), c.= 8.497(4) A, a= 106.02(2), Ω = 83.74(2), α= 106.06(2)?. The structural units of the crystals are the (H₄L)⁴⁺ cations, the hexafluorosilicate (or hexafluowgemanate) anions, and the water molecules linked by a system of H bonds. The macrocycle in the complexes has C₁ symmetry. In the inorganic anions, the silicon as well as germanium atom is surrounded by an octahedron of six fluorine atoms.

     

Oxidation of phenylphosphonites with aqueous hydrogen peroxide

An effective route to the oxidation of organic derivatives of trivalent phosphorus with an aqueous solution of hydrogen peroxide was considered. Phenylphosphonites, including those having a hydrolytically unstable phosphorus-nitrogen bond were involved into the oxidation. The identification of oxidation products, the phenylphosphonates, was carried out using the method of ion cyclotron resonance mass spectrometry with Fourier transform combined with electrospray ionization, and by ³¹P and ¹H NMR spectroscopy. The influence of an effective antioxidant of natural origin, quercetin, on the oxidation was demonstrated.     

Crystal structure of p-nitroanilinium hexafluorosilicate

Complex (p-O₂NC₆H₄NH₃)₂SiF₆ (I) is prepared by reacting fluorostlicic acid with p-nitroaniline in methanol and structurally studied using single-crystal X-ray diffraction. In the ionic structure of this complex, SiF ₆ ^2? centrosymmetrical anions (avg. Si-F, 1.671(3) Å) and O₂NC₆H₄NH ₃ ⁺ cations are linked through NH…F interionic H-bonds (N…F 2.823(5)-3.205(7) Å). The thermochemical features of complex I are discussed in light of the structure data.     

(4R)-4-Hydroxy-1-nitroso-l-proline: synthesis, X-ray structure, ab initio and conformational calculations

4-Hydroxy-l-proline, an amino acid, an important component of collagen, was transformed into its N-nitroso-derivative, (4R)-4-hydroxy-1-nitroso-l-proline, 1 by butylnitrite in the acidic medium. The structure is a cyclic hydroxy-N-nitrosoacid with the carboxyl and hydroxyl groups trans to each other. The carboxyl group is in the syn-conformation. In the structure, the neutral molecules are connected via classical intermolecular O-H?O hydrogen bonds involving the hydroxyl and carboxyl groups [O?O=2.6251(14) Å], and form chains along the a-axis direction. The chains are linked into sheets via O-H?O hydrogen bond, [O?O=2.6813(15) Å] with participation of oxygen atom of nitroso group. Ab initio calculations based on density functional theory at the B3LYP/6-311++G(d, p) level of theory were performed to analyze the influence of 4-hydroxy-l-proline (Hyp) nitrosation on the conformation of the synthesized N-nitroso-compound. The geometry optimization of 1 and initial 4-hydroxy-l-proline was carried out in the gas phase and in solution using the polarizable continuum model. The single-point calculation was performed for the crystal structure of 1. The most stable conformer of 1 is observed in an aqueous solution. In this state, the pyrrolidine ring adopts an envelope conformation, which is also maintained in the gas phase. The twisted conformation of the pyrrolidine ring is present in all states of Hyp and in the crystal structure of 1. In 1 the interchange of five-membered ring conformation in solution and in the gas phase in comparison with the crystal is accompanied by an increase of the dipole moment of the molecule, which is maximal in solution.