Search results for "Molecule"
showing 10 items of 5162 documents
Defect-Free Chemical Functionalization of Magnetic Monolayers Based on Coordination Polymers
2018
<p>Chemical functionalization has demonstrated to be a powerful approach to tailor the physical and chemical properties of two-dimensional (2D) materials, to increase their processability and</p> <p>stability, to add new functionalities and, even, to create new 2D materials. However, this post synthetic method – which involves the anchoring of molecules on the surface of an exfoliated 2D crystal – inevitably leads to defective materials, which lack long-range structural order. If defect-free functionalized monolayers are required, a radically new approach needs to be developed. Here we present a pre-synthetic method based on coordination chemistry that affords the isolatio…
Critical micellization density: A small-angle-scattering structural study of the monomer-aggregate transition of block copolymers in supercriticalCO2
2000
In this paper we report a small-angle neutron-scattering investigation of micelle formation by the fluorocarbon-hydrocarbon block copolymer, polyvinyl acetate-b-poly (1,1,2,2-tetrahydroperfluoro-octyl acrylate) in supercritical CO{sub 2} (scCO{sub 2}) at 313 K. At high pressure the copolymer is in a monomeric state with a random coil structure, while at low pressure the polymer forms spherical aggregates stable in a wide range of thermodynamic conditions. By profiling pressure, a sharp monomer-micelle transition is obtained due to the tuning of the solvating ability of scCO{sub 2}. We confirm the previous finding that this aggregate-monomer transition is driven by the gradual penetration of…
Cycloaddition of benzothiete and electron-deficient nitriles
1991
The o-quinoid 8π electron system 2, generated by thermal ring opening of benzothiete (1), enters regio-specific [8π + 2π] cycloaddition reactions with electron-deficient nitriles 3a-d, yielding the 4H-1,3-benzothiazines 4a-d. A competitive dimerization of 1 leads to 1,5-dibenzo[b,f]dithiocin (5). Depending on the nitrile further competitive or subsequent reactions (2 + 3b 7b, 2 + 3d 4d 8d) can occur. The cycloadducts 10e and 11e gained from 3e anticipate a primary cleavage of 3e to methylisothiocyanate 9e which reacts at the CN double bond as well as at the CS double bond.
Structure and properties of pharmacologically active polymers
1975
Although the concept of using pharmacologically active macromolecular compounds as drugs is still regarded with much skepticism for both theoretical and practical reasons, interest in this field has grown in recent years because of the opportunity to take advantage of the specific properties of polymeric materials. For low molecular weight drugs, changes in structure often lead to a loss of specific activity. On the other hand, the properties of macromolecular drugs depend on the structure of the polymer used and this can be varied over a wide range by the incorporation of comonomer units, by the application of polymer-analogous reactions, or by related structural changes. A new model is pr…
Phthalocyanine-based hybrid materials for chemosensing
2013
In the present review, we show how the chemical variability of phthalocyanines allowed to synthesize a broad range of hybrid materials. The combination of phthalocyanines or related derivatives with polymers or carbonaceous materials led to efficient chemical sensors. It is shown how the incorporation of macrocyclic molecules in hybrid materials highly modifies the structural and morphological characteristics of the materials. Rugosity, specific surface and porosity being key parameters in the analyte-sensing material interactions, these modifications highly improve the performance of chemical sensors. This is the reason why they are particularly promising materials for the development of …
Mechanismus und Reaktionswege der Xanthenylierung an ambidenten nukleophilen Arzneistoffen
1986
Am Beispiel der ambidenten nukleophilen Arzneistoffe 4-Aminobenzolsulfonamid (3), Indometacin (7) und Phenylbutazon (10) werden Aralkylierungen mit dem SN1-aktiven Reagens Xanthydrol (1) vorgestellt. Mechanism and Reaction Path of the Xanthenylation of Ambident Nucleophilic Drugs The aralkylation of ambident nucleophilic drugs, e.g. 4-aminobenzenesulfonamide (3), indometacine (7) and phenylbutazone (10), with SN1-active xanthydrol (1) is described.
A new access to 2′-amino-substituted vinylindoles as donor-activated heterocyclic dienes and their first diels-alder reactions
1992
Abstract Reactions of the 3-acylindoles 5, 10 , and 15 with α-amino-α′-diphenylphosphinoyl-substituted carbanions gave rise to the 2′-amino-substituted 3− and 2-vinylindoles 7, 12 , and 17 by way of the isolable carbinols 6 , 11 , and 16 . The heterocyclic dienes 7 , 12 , and 17 readily underwent Diels-Alder reactions with N -phenylmaleimide.
<title>Optically induced switching of dicyclohexylamino substituted azobenzene derivatives in thin ordered films</title>
2005
During the last years, there has been an increasing interest in the photoinduced switching effects. Among the objects of concern azobenzene derivatives, isomerizing under UV and visible light, occupy a prominent position. To understand the photoresponse of these materials in the condensed phase, their spectroscopic and electrical properties are studied. It is shown that the photoresponse depends on the orientation of the molecules and their packing. A number of novel azobenzene derivatives containing a N,N-dicyclohexyl sulfonamide moiety is synthesized. The derivatives differ in the length of alkyl chains between the azobenzene moiety and SH or COOH groups. The morphology and the photoinduc…
Structure elucidation of benzopyran-2-ol in solution and in solid state following the reduction of coumarin by DIBAL-H
2001
Lactols are compounds of increasing interest in the synthesis of active pharmaceutical derivatives. Nevertheless, the product obtained by the reduction of the carbonyl group of coumarin has been described only twice, and without definition of its precise chemical structure. Since these studies, doubts have been raised about the existence of a monomeric or dimeric form. Our study has led us to conclude definitely that the single dimeric form exists and to precisely define the spectral properties of the two diastereoisomers.
ChemInform Abstract: Studies on Bicyclo[3.3.1]nonanes for Synthesis of Cyclooctenes.
2010
This paper describes a full conformational and stereochemical study of bicylo[3.3.1]nonanes, obtained from the reaction between cinnamaldehyde and 1-morpholine 1-cyclohexene. NMR data and stereochemistry were unequivocally established and assigned by two-dimensional experiments and single-crystal X-ray analysis. The crystal structure of a minor compound, 4, is reported. Cyclooctenes, which are present in natural products with biological activities, were synthesized from the bicyclononanes via the Wharton fragmentation.