Search results for "force"
showing 10 items of 3423 documents
Donor-acceptor substituted polyenes : orientation in mono- and multilayers
1992
Large molecules containing different chemical units whose interactions within the molecule result in new macroscopically observable effects, have become increasingly important.The organization of molecules of this type in ordered structures leads to functional molecular materials.Their use in molecular electronics requires that the units exhibit specific electronic properties. Recently, we reported on the intramolecular energy transfer through terminally substituted conjugated polyenes. An intramolecular electron transfer within donor-acceptor substituted polyenes can be achieved by introducing suitable terminal groups.
ChemInform Abstract: Synthesis of 5-Substituted α,β-Butenolides by Iron-Promoted Intramolecular Cyclocarbonylation: Addition of Organometallic Reagen…
2010
Translational and rotational molecular motion in supercooled liquids studied by NMR and forced Rayleigh scattering
1994
It has been shown that translational diffusion coefficients, Dt, in the supercooled van der Waals liquids, orthoterphenyl, phenolphthaleindimethylether, and salol, have a weaker temperature dependence than the shear viscosity, η, at T ≲ 1.2Tg and can be described by Dt ∼ η−χ with χ < 1 whereas Dr ∼ η−1 applies for the mean rotational diffusion coefficients, Dr, down to the glass transition temperature, Tg. This apparent decoupling of translational and rotational motion has been discussed in relation with possible anomalous short time diffusion, spatial heterogeneity, and cooperative molecular motions close to Tg.
Metallophilic interactions in stacked dinuclear rhodium 2,2'-biimidazole carbonyl complexes
2012
Non-covalent metallophilic interactions were studied by investigating the stacking of two neutral rhodium complexes [Rh2I(R2bim)Cl2(CO)4] (R = Et, ethyl or Pr, propyl) in the solid state. Both dinuclear complexes formed infinite arrays of square planar d8 rhodium centres with intramolecular Rh⋯Rh distances of 3.1781(5) A (R = Et) and 3.1469(3) A (R = Pr) and the intermolecular Rh⋯Rh distances of 3.4345(6) A (R = Et) and 3.4403(3) A (R = Pr) between the adjacent molecules. The crystalline solids were stable and did not contain any solvent of crystallization. The effect of the metallophilic interactions on the absorption properties were studied using TD-DFT methods. The computational results …
Hydrogen-Bonding Effects in Calix[4]arene Capsules
2000
The synthesis and spectroscopic characterization of self-assembling calix[4]arene based capsules 1a.1a and 1b.1b are described. These compounds feature four urea substituents at the upper rims and four secondary amide fragments at the lower rims that can participate in inter- and intramolecular hydrogen bonding in apolar solution. Communication between the calixarene rims in 1a, b influences the self-assembled cavity's size and shape. Specifically. dimerization results in a perfect cone conformation of the calixarene skeleton in 1a, b and stabilizes a seam of intramolecular amide C=O...H-N hydrogen bonds at the lower rim. This seam is cycloenantiomeric, with either clockwise or counterclock…
ChemInform Abstract: Synthesis of Pyrrolidin-2-ones and of Staurosporine Aglycon (K-252c) by Intermolecular Michael Reaction.
2010
Indolo[2,3-a]pyrrolo[3,4-c]carbazoles were isolated from nature, e.g., from low plants, especially fungi, as structurally rare natural substances. Responsible for naming and also the most important representative of this type is staurosporine (1), isolated from Streptomyces staurosporeus, and its aglycon (2), also known as staurosporinone or K-252c. 3,4-Disubstituted pyrrolidin-2-ones, a group of compounds with many interesting biological properties are related to staurosporinone. The most important property is the inhibition of protein kinase C (PKC), so that this antiproliferative agent can interfere with the cell cycle. The synthetic strategy, developed by us, allows the synthesis of pyr…
The conformational polymorphism and weak interactions in solid state structures of ten new monomeric and dimeric substituted dibenzyldimethylammonium…
2009
In this study, ten new dibenzyldimethyl/ethyl ammonium chloridopalladate(II) compounds with five different cations and two anions have been synthesized and a simple method for a synthesis, in which hydrochloric acid solutions are used, has been described. Furthermore, twelve structures including two polymorphs have been obtained from hydrochloric and methanol/acetonitrile solutions. The anion–cation and cation–cation interactions of the synthesized compounds have been studied mainly by means of single X-ray diffraction in order to study the effects of varying either the anion or the cations in these QA2PdCl4 and QA2Pd2Cl6 salts. The results indicate that the effects of intermolecular cation…
Self-Assembly of the Hexabromorhenate(IV) Anion with Protonated Benzotriazoles: X-ray Structure and Magnetic Properties
2014
Two novel ReIV compounds of formulas [HBTA]2[ReIVBr6] (1) and [HMEBTA]2[ReIVBr6] (2) [BTA = 1H-benzotriazole and MEBTA = 1-(methoxymethyl)-1H-benzotriazole] have been synthesized and magneto-structurally characterized. 1 and 2 crystallize in the triclinic system with space group P1̅. In both compounds, the rhenium ion is six-coordinate, bonded to six bromo ligands in a regular octahedral geometry. Short ReIV–Br···Br–ReIV contacts, π–π stacking, and H-bonding interactions occur in the crystal lattice of both 1 and 2, generating novel supramolecular structures based on the ReIV. The different dispositions of the cations and the intermolecular Br···Br contacts in 1 and 2 play an important stru…
ChemInform Abstract: Base-Dependent Stereodivergent Intramolecular Aza-Michael Reaction: Asymmetric Synthesis of 1,3-Disubstituted Isoindolines.
2014
For the reaction of the compounds (I) the careful choice of the base allows the exclusive formation of either cis or trans diastereoisomer with the exception of the trihalogenates (Ie) and (If), which afford the cis-products regardless of the base used.