Synthesis, characterization and thermal properties of small R2R′2N+X−-type quaternary ammonium halides

2005

Twenty-one R {sub 2} R {sup '} {sub 2}N{sup +} X {sup -} -type (R=methyl or ethyl, R {sup '}=alkyl, X=Br or I) quaternary ammonium (QA) halides have been prepared by using a novel one-pot synthetic route in which a formamide (dimethyl-, diethylformamide, etc.) is treated with alkyl halide in the presence of sodium or potassium carbonate. The formation of QA halides was verified with {sup 1}H-NMR, {sup 13}C-NMR, MS and elemental analysis. The crystal structures of four QA halides (two bromide and two iodide) were determined using X-ray single crystal diffraction, and the powder diffraction method was used to study the structural similarities between the single crystal and microcrystalline bu…

Self-assembling resorcinarene capsules: solid and gas phase studies on encapsulation of small alkyl ammonium cations

2002

The self-assembling process of unsubstituted resorcinarenes (1, 2 and 3) to dimeric capsules encapsulating small tetra-alkyl ammonium cations 4–7 has been studied in solid and gaseous states by X-ray crystallographic and mass spectrometric methods. Hydrogen bonding and cation-π interaction as well as the proper encapsulation in the empty cavity of the capsule appear to be the most important interactions in the capsule formation process. Competitive mass spectrometric studies clearly indicated preference of the tetramethyl ammonium cation (4) over tetraethyl ammonium cation (6) and especially tetrabutyl ammonium cation (7). The crystal structures of altogether eight dimeric capsules of resor…

Crystal structures of O-acetylated 2-acylamino-2-deoxy-d-galactose derivatives

2003

The X-ray structures of 1,3,4,6-tetra-O-acetyl-2-deoxy-alpha-D-galactopyranoside derivatives with four different 2-(acylamino) substituents have been determined with Mo K(alpha) radiation at 123 K. The structure of the 2-acetylamino derivative and of its acyl-homologs with a 2-(propanoylamino)-, 2-(butanoylamino)-, and 2-(2-methyl-propanoylamino)-group crystallized in the monoclinic space group C2. The pyranose unit of all compounds has the usual 4C(1) shape. The different orientations of the 6-O-acetyl-groups are discussed. Conformations of the acylamino-group are compared to those found in the crystal structure of N-acetyl-alpha-D-galactosamine.

Encapsulation of diquats by resorcinarenes: a novel staggered anion–solvent mediated hydrogen bonded capsule

2002

Crystallisation studies of ethyl resorcinarene with diquats 2b and 3a (1,4-dimethyl-1,4-diazoniabicyclo[2.2.2]octane dibromide and 1,4-diazoniabicyclo[2.2.2]octane dichloride, respectively) resulted in hydrogen bonded molecular capsules in which the cations are encapsulated in between the cavities of two resorcinarene molecules and anions are located in the middle of the lower rim ethyl chains.

Solvent Exchange in Thermally Stable Resorcinarene Nanotubes

2006

The assembly of C-methyl resorcinarene into a tubular supramolecular solid-state structure, its thermal stability, and its hosting properties are reported. Careful control of the crystallisation conditions of C-methyl resorcinarene and 1,4-dimethyl-1,4-diazoniabicyclo[2.2.2]octane (1,4-dimethyl DABCO) dibromide leads to a formation of two crystallographically different, but structurally very similar, solid-state nanotube structures. These structures undergo a remarkable variety of supramolecular interactions, which lead to the formation of 0.5 nm diameter nonpolar tubes through the crystal lattice. The formation of these tubes is templated by suitably sized small alcohols, namely, n-propano…

Noncovalentπ⋅⋅⋅π-Stacked Exo-Functional Nanotubes: Subtle Control of Resorcinarene Self-Assembly

2004

Structurally diverse second-generation [2.2]paracyclophane ketimines with planar and central chirality: syntheses, structural determination, and eval…

2005

A set of 20 novel [2.2]paracyclophane ketimines with planar and central chirality has been synthesized from enantiomerically pure and racemic 5-acyl-4-hydroxy[2.2]paracyclophane and alpha-branched chiral amines. Their X-ray structures were determined to elucidate the three-dimensional structures and the absolute configuration. The ketimines were used as catalysts in the asymmetric 1,2-addition reactions of diethylzinc with substituted benzaldehydes to furnish chiral alcohols in up to 95 % ee.

A versatile metathesis reaction for the formation of labile bonds between group 13 and group 15 atoms.

2003

C-Methyl resorcin[4]arene packing motifs with alkyl ammonium salts: From molecular capsules to channels and tubes

2005

A variety of packing motifs of C-methyl resorcinarene were obtained when complexed with small alkyl ammonium salts of different size and shape. Using bromide and chloride salts of the small quaternary alkyl ammonium cations, tetramethyl ammonium and dimethyldiethyl ammonium, leads to a grid-like packing of solvent mediated dimeric capsules while the use of salts of larger diquaternary cations bearing a 1,4-diazabicyclo[2.2.2]octane (DABCO) scaffold produces solvent/anion mediated chains and channels or tubular structures. The connecting interactions between resorcinarenes in each structure are hydrogen bonding and/or π⋯π interactions.

Eine vielseitige Metathesereaktion zur Knüpfung labiler Bindungen zwischen Gruppe-13- und Gruppe-15-Elementen

2003

Weak interactions between resorcinarenes and diquaternary alkyl ammonium cations

2005

The interactions of resorcin[4]arenes 1 with alkyl ammonium cations bearing a 1,4-diazabicyclo[2.2.2]octane (DABCO) scaffold (32+, 42+ and 52+) were analyzed in the solid state by X-ray crystallography, in solution by 1H NMR spectroscopy, and in the gas phase by ESI-TOF mass spectrometry. The results are complemented with AM1 calculations and compared to previous reports on complexation studies of resorcinarenes with quaternary alkyl ammonium cations. The NMR titration results indicate that there are hardly any differences in the binding of the quaternary tetramethyl ammonium cation 2+ and the diquaternary N,N’-dimethyl DABCO dication 42+. The large N,N’-dibenzyl DABCO dication 52+ has two …