Search results for " Force"
showing 10 items of 2250 documents
Sublimable Single Ion Magnets Based on Lanthanoid Quinolinate Complexes: The Role of Intermolecular Interactions on Their Thermal Stability
2018
We report the design, preparation, and characterization of two families of thermally robust coordination complexes based on lanthanoid quinolinate compounds: [Ln(5,7-Br2q)4]− and [Ln(5,7-ClIq)4]−, where q = 8-hydroquinolinate anion and Ln = DyIII, TbIII, ErIII, and HoIII. The sodium salt of [Dy(5,7-Br2q)4]− decomposes upon sublimation, whereas the sodium salt of [Dy(5,7- ClIq)4]−, which displays subtly different crystalline interactions, is sublimable under gentle conditions. The resulting film presents low roughness with high coverage, and the molecular integrity of the coordination complex is verified through AFM, MALDI-TOF, FT-IR, and microanalysis. Crucially, the single-molecule magnet …
Polymeric alloys: Model materials for the understanding of the statistical thermodynamics of mixtures
1997
Polymeric materials find industrial applications that are comparable to those of metals and ceramics.1 In addition to the great variability via the synthesis of various monomers and the choice of the degree of polymerization (N), alloying of polymers finds increasing attention for combining favorable materials properties.1,2 But polymeric (binary) alloys (A,B) of flexible polymers with chain lengths NA, NB are also most interesting for testing theoretical concepts: changing NA, NB one controls the entropy of mixing, keeping intermolecular forces invariant. Variation of these control parameters thus allows stringent tests of the theories on miscibility, unmixing etc. Furthermore, the large s…
Role of C–H···Au and Aurophilic Supramolecular Interactions in Gold–Thione Complexes
2014
The role of noncovalent gold–hydrogen and aurophilic interactions in the formation of extended molecular systems of gold complexes was studied. Three new gold compounds with a heterocyclic thione ligand N-methylbenzothiazole-2-thione (mbtt), namely, [AuCl(mbtt)] (1), [AuBr(mbtt)] (2), and [Au(mbtt)2][AuI2]1–n[I3]n (3), were synthesized and characterized. The halide ligand had a considerable effect on the complex structures and thus to noncovalent contacts. Intermolecular C–H···Au and aurophilic Au···Au contacts were the dominant noncovalent interactions in structures 1–3 determining the supramolecular arrays of the gold complexes. In 1 and 2, unusual intermolecular C–H···Au gold–hydrogen co…
Synthesis of β-d-mannosides from β-d-glucosides via an intramolecular Sn2 reaction at C-2
1992
Abstract The selective synthesis of β- d -mannosides was achieved by first synthesizing β- d -glucosides that carry a N -phenylcarbamoyl protecting group at O-3. These derivatives were transformed into the corresponding β- d -mannosides by intramolecular nucleophilic substitution with inversion of configuration at C-2, the O -triflyl group being the leaving group. Subsequent intramolecular attack of the neighboring carbamoyl group resulted in the formation of the 2,3-carbonate of the desired β d -mannoside.
Intermolecular hydrogen bonding H···Cl in crystal structure of palladium(II)-bis(diaminocarbene) complex
2018
Abstract The reaction of bis(isocyanide)palladium complex cis-[PdCl2(CNXyl)2] (Xyl=2,6-Me2C6H3) with excess of 4,5-dichlorobenzene-1,2-amine in a C2H4Cl2/MeOH mixture affords monocationic bis(diaminocarbene) complex cis-[PdClC{(NHXyl)=NHC6H2Cl2 NH2}{C(NHXyl)=NHC6H2Cl2NH2}]Cl (3) in moderate yield (42%). Complex 3 exists in the solid phase in the H-bonded dimeric associate of two single charged organometallic cations and two chloride anions according to X-ray diffraction data. The Hirshfeld surface analysis for the X-ray structure of 3 reveals that the crystal packing is determined primarily by intermolecular contacts H–Cl, H–H, and H–C. The intermolecular hydrogen bonds N–H···Cl and C–H···C…
Micropatterning of neurons using organic substrates in culture
1997
Abstract In this study, we have used spatially defined surfaces of organic thin films to micropattern the outgrowth of central nervous system neurons in culture. Glass substrates were first chemically modified with synthetic peptides derived from an extra-cellular matrix protein laminin to couple a functionality that promotes a neuron-substrate interaction. The modification procedure was verified using X-ray photoelectron spectroscopy. The functionality of the modified glass surfaces was examined by growing neurons dissociated from mammalian central nervous tissues in culture. Spatially defined surfaces of the peptide were then fabricated by selectively attaching the peptide to coplanar sur…
Photosensitive polyurethanes for optical record
2011
The method of synthesis of photosensitive polyurethanes polymers on glycerine, toluenediisocyanate and Disperse Red 1 base has been described. Two types of polymers with different amount of Disperse Red 1 fragments in macromolecules were compared. Films of the polymers were obtained from solutions in organic solvents on glass substrate. The dry film thickness was in the range of 3,5 - 4.5 μm. The transmission spectrums of the films were studied. Possibility of formation of side product in the process of synthesis was observed. The photobirefringence measurements of polymers films were performed. Surface relief grating (SRG) formation was observed during polarization holographic recording pr…
Graphene related magnetic materials: micromechanical exfoliation of 2D layered magnets based on bimetallic anilate complexes with inserted [FeIII(aca…
2015
The syntheses, structures and magnetic properties of the coordination compounds of formula [FeIII(acac2-trien)][MnIICrIII(Cl2 An)3]·(CH3CN)2 (1), [FeIII(acac2-trien)][MnIICrIII(Br2An)3]·(CH3CN)2 (2) and [GaIII(acac2-trien)][MnIICrIII(Br2An)3]·(CH3CN)2 (3) are reported. They exhibit a 2D anionic network formed by Mn(II) and Cr(III) ions linked through anilate ligands, while the [FeIII(acac2-trien)]+ or [GaIII(acac2-trien)]+ charge-compensating cations are placed inside the hexagonal channels of the 2D network, instead of being inserted in the interlamellar spacing. Thus, these crystals are formed by hybrid layers assembled through van der Waals interactions. The magnetic properties indicate …
Structure Formation of Polymeric Building Blocks: Complex Polymer Architectures
2013
This chapter describes macromolecules with a complex structure, their defined aggregation in solution, their adsorption to surfaces, and their possible aggregation on surfaces. The term “complex structure” implies that the macromolecules show different, distinct structural elements or building blocks on a supra-atomic length scale. Key to understanding the complex structure of macromolecules, their aggregation, and adsorption to surfaces are intra- and intermolecular interactions such as van der Waals, electrostatic, π–π interactions, and hydrogen bonds.
Photoconductivity of Poly(Arylenevinylene)S and Poly(Hetarylenevinylene)S
1994
Abstract The intramolecular condensation of aromatic Schiff bases leads under strong alkaline conditions to the poly(arylenevinylene)s and poly(hetarylenevi-nylene)s A - H. Due to the extreme stereoselectivity the resulting products are rigid, (E)-configurated polymers. The broad band gap of the unsubstituted intrinsic insulators is decreased by alkoxy substituents. Investigations of the photoconductivity and the photoreactivity, as well as of the AC-conductivity of some undoped, doped and quaternized systems are performed.