Claus D. Weis

Polytryptophane terminated dendritic macromolecules

Abstract The synthesis and characterization of dendritic macromolecules coated with tryptophan moieties are described. A direct relationship between the molecular ellipicity () and the number of surface tryptophans has been demonstrated.

Isocyanate‐Based Dendritic Building Blocks: Combinatorial Tier Construction and Macromolecular‐Property Modification

Used individually or combinatorially, unique isocyanate-based dendritic monomers generate homo- and heterofunctional materials (the sketch shows schematically a molecule with a heterofunctional surface). Tier construction by combinatorial monomer addition offers new avenues to macromolecular architectural design and the control of physical properties.

Molecular Relaxations in Ester-Terminated, Amide-Based Dendrimers

This study utilized Matrix Assisted Laser Desorption/Ionization Time-of- Flight Mass Spectrometry, Thermogravimetric Analysis, Differential Scanning Calo- rimetry, X-Ray Diffraction, and Dielectric Analysis to assess the viscoelastic and structural properties of three generations of tert-butyl and methyl ester, amide-based dendrimers. The effect of generation number and functionality on glass-transition temperatures and corresponding apparent activation energies, obtained via adherence to WLF behavior, were determined. Both were found to increase with increasing generation number and bulkiness of terminal functionalities. WLF constants, C1 and C2, allowed the determination of free volume, and thermal expansion coefficients, respectively. Secondary transitions, conforming to Arrhenius behavior, were also char- acterized and increased in temperature with generation number. The apparent activa- tion energy was greater when the matrix was crystalline. Dielectric relaxation re- sponses were analyzed to yield dielectric strengths of the molecular relaxations which increased with generation number and were comparable for both tert-butyl and methyl esters in the glass-transition region. Electrical properties of the dendrimers were dominated by ionic conductivity in the high temperature region. In order to unmask the glass transition, the data were treated in terms of the electric modulus.

A useful dendritic building block: Di-tert-butyl 4-[(2-tert-butoxycarbonyl)ethyl]-4-isocyanato-1,7-heptanedicarboxylate

Abstract The facile preparation of the title compound, which is a crystalline alkyl isocyanate capable of dendrimerizing (poly)functional materials, is reported. The structure is proven by X-ray analysis and its chemistry is confirmed by its versatile reactivity with diverse molecules.

Interaction of colorformers and coreactants. Part I. First crystal structures of the colorforming species composed of crystal violet lactone and metal

Abstract The first crystalline adducts of a colorformer and coreactants have been synthesized. Crystal Violet Lactone (CVL) reacted with zinc and cadmium iodide, respectively, in acetone solution to form well defined complexes. 13 C NMR, X-ray and crystallographic data have been collected on these complexes. They indicated an ionic structure of [2 CVL·3ZnI 2 - acetone] with a Zn 2 I 3 -moiety rigidly held in place by two encompassing symmetrically situated carboxylate units. A polymeric structure was found for [CVL·3CdI 2 · 1 2 acetone]. The CVL part with its open carboxylate structure is embedded in a carrier matrix built of cadmium and of iodine atoms, forming alternately six- and four-membered rings which are linked with each other in a spiro- arrangement. Intercalated acetone molecules were found to be a prerequisite for the formation of single crystals.

6,6-bis(CARBOXY-2-OXABUTYL)-4,8-DIOXAUNDECANE-I,II-DICARBOXYLIC ACID

(1996). 6,6-bis(CARBOXY-2-OXABUTYL)-4,8-DIOXAUNDECANE-I,II-DICARBOXYLIC ACID. Organic Preparations and Procedures International: Vol. 28, No. 2, pp. 242-244.

Interaction of colorformers and coreactants: Part II. Crystal Structure of a Xanthene type colorformer and cadmium iodide

Abstract A crystalline adduct composed of a xanthene moiety representing the colorformer and cadmium iodide as the coreactant has been synthesized. Single crystals of the composition C 56 H 46 N 2 O 6 Cd 2 I 4 . acetone were obtained as acetone solvate. 13 C-NMR, X-ray and crystallographic data have been collected for this complex. Two xanthene parts are linked via their carboxylate groups to a four-membered ring composed of a Cd 2 I 4 unit. Interatomic distances indicate that the molecule possesses a quinone-like structure, with the phenyl ring bearing the carboxylate group standing nearly at right angles to the xanthene part. Intercalated acetone molecules are a prerequisite for the formation of single crystals.

The crystal structure of 2-amino-5,5′-bis(β-cyanoethyl)-1,2-pyrrolenineN-oxide monohydrate

Abstract2-Amino-5,5′-di(β-cyanoethyl)-1,2-pyrrolenineN-oxide monohydrate, C10H14N4O·H2O, crystallizes from MeCN in space group P212121 witha=7.0007(5),b=8.2998(6),c=20.8418(13) Å,V=1211.0(2) Å3,Z=4. The structure was refined toR=0.034 andRw=0.044 for 2325 observed reflections. The pyrrolenine ring adopts a nearly planar conformation, with maximum deviation from planarity 0.089(2) Å. The N−O distance is 1.345(2) Å. The water molecule bridges two pyrrolenine molecules via hydrogen bonds to theirN-oxide oxygen atoms, and also accepts a hydrogen bond from the NH2 group of another pyrrolenine molecule.