Search results for "Supramolecular"
showing 10 items of 830 documents
Studies on supramolecular gel formation using DOSY NMR
2015
Herein, we present the results obtained from our studies on supramolecular self-assembly and molecular mobility of low-molecular-weight gelators (LMWGs) in organic solvents using pulsed field gradient (PFG) diffusion ordered spectroscopy (DOSY) NMR. A series of concentration-dependent DOSY NMR experiments were performed on selected LMWGs to determine the critical gelation concentration (CGC) as well as to understand the behaviour of the gelator molecules in the gel state. In addition, variable-temperature DOSY NMR experiments were performed to determine the gel-to-sol transition. The PFG NMR experiments performed as a function of gradient strength were further analyzed using monoexponential…
Recent advances in steroidal supramolecular gels
2020
During the last decade or two the interest towards small molecules capable of self-assembly leading to gelation has increased intensively. The investigation of these supramolecular gels aims not only at understanding the fundamental processes underlying gel formation but also at development of new materials with a myriad of applications. Steroids are widely-spread natural products with a large and rigid steroidal nucleus combined with derivatizable functional groups leading to an adjustable polarity profile, which makes them attractive building blocks when designing novel low molecular weight gelators. Due to their unique properties, steroid-based supramolecular gels may find use in applica…
Electrochemical synthesis on boron-doped diamond
2012
Abstract Boron-doped diamond (BDD) is a novel and innovative electrode material. In protic media and particular aqueous electrolytes BDD exhibits a large over potential for the evolution of molecular hydrogen and oxygen. The large chemical window allows a variety of electrochemical conversions to be conducted. The anodic process treatment generates oxyl species directly which are known to be extremely reactive. Usually, the electrochemical mineralization of the organic components in the electrolyte occurs. However, with control of the reactivity of these intermediates the use in electroorganic synthesis can be realized. Until today mostly anodic conversions have been studied at BDD. Since h…
Malonic acid: A multi-modal bridging ligand for new architectures and properties on molecule-based magnets
2003
Abstract In this work, we show how the design of one-, two- and three-dimensional materials can strongly benefit from the use of crystal engineering techniques, which can give rise to structures of different shapes, and how these differences can give rise to different properties. We will focus on the networks constructed by assembling malonate ligands and metal centres. The idea of using malonate (dianion of propanedioic acid, H 2 mal) is that they can give rise to different coordination modes with the metal ions bind. Extended magnetic networks of dimensionalities 1 (1D), 2 (2D) and 3 (3D) can be chemically constructed from malonato-bridged metallic complexes. These coordination polymers b…
Naturally occurring polyphenols as building blocks for supramolecular liquid crystals – substitution pattern dominates mesomorphism
2021
A modular supramolecular approach towards hydrogen-bonded liquid crystalline assemblies based on naturally occurring polyphenols is reported. The combination of experimental observations, crystallographic studies and semi-empirical analyses of the assemblies provides insight into the structure–property relationships of these materials. Here a direct correlation of the number of donor OH-groups as well as their orientation with the mesomorphic behavior is reported. We discovered that the number and orientation of the OH-groups have a stronger influence on the mesomorphic behavior of the supramolecular assemblies than the connectivity (e.g. stilbenoid or chalconoid) of the hydrogen bond donor…
The Role of Organic Fluorine in the Supramolecular Assembly of Halogenated β-Hydroxysulphoxides Diastereomers
2006
A series of optically pure γ-halogenated β-hydroxysulphoxides containing two stereogenic centers have been prepared, and the X-ray crystal structures have been determined. The conformational behavior in the solid state and the crystal packing of the different β-hydroxysulphoxide diastereoisomers have been determined. The intermolecular and intramolecular interactions present have been studied in both halogenated and nonhalogenated β-hydroxysulphoxides to establish the influence of the halogen atom in the supramolecular structure. The main intermolecular hydrogen bond OH···OS is always present and produces molecular chains. Self-assembly of these chains includes weak CH···F, C−F···F−C, and C…
Building-block process for the synthesis of new chromium(iii) malonate complexes
2010
We describe the crystal structures of two bimetallic compounds with the malonate and an exo-polydentate N-donor ligand {[Cu(tren)]4[Cr2(mal)4(OH)2]}(ClO4)4·8H2O (3) and [Ni(Htren)2][Cr2(mal)4(OH)2]·8H2O (4) which are prepared from the dinuclear K4[Cr2(mal)4(OH)2]·6H2O precursor (2) [tren = tris(2-aminoethyl)amine and H2mal = malonic acid]. Their crystal packing and supramolecular structures are analyzed in the context of the influence of the dichromium(III) [Cr2(mal)4(OH)2]4− unit, which acts as a building-block. Different supramolecular motifs built up from hydrogen bonds are discussed, and their self-assembly to yield a 3D arrangement is described. The magnetic properties of the compounds…
A Halogen-Bonded Dimeric Resorcinarene Capsule.
2015
Iodine (I2) acts as a bifunctional halogen-bond donor connecting two macrocyclic molecules of the bowl-shaped halogen-bond acceptor, N-cyclohexyl ammonium resorcinarene chloride 1, to form the dimeric capsule [(1,4-dioxane)3@1(2)(I2)2]. The dimeric capsule is constructed solely through halogen bonds and has a single cavity (V=511 Å(3)) large enough to encapsulate three 1,4-dioxane guest molecules.
A dihydrogen arsenate-mediated supramolecular network: crystal structure and magnetic properties of {[(bipy)Cu(μ-H2AsO4)(H2AsO4)]2}n
2002
Treatment of an aqueous suspension of Cu(OH)2 and 2,2′-bipyridine (bipy) with either Na2HAsO4·7H2O (1∶1∶2) or As2O5 (1∶1∶1) yields single crystals of {[(bipy)Cu(μ-H2AsO4)(H2AsO4)]2}n, 1, on standing. The solid-state structure of 1 consists of a three dimensional supramolecular network, supported by a combination of coordination covalent, hydrogen bonding and face-to-face π–π interactions. Variable temperature magnetic susceptibility measurements reveal very weak antiferromagnetic coupling between Cu(II) centres across the dihydrogen arsenate bridges (J = −0.58 cm−1).
Versatile supramolecular self-assembly : Part II. Network formation and magnetic behaviour of copper(ii) malonate anions in ammonium derivatives
2006
Five new metal–organic compounds of formula An[Cu(mal)2(H2O)m] (A being an amine cation and H2mal = malonic acid) have been structurally and magnetically characterized. The crystal structure of these compounds consists of an alternation of malonate-containing copper(II) anionic and amine cationic layers. Depending on the amine cation, the bis(malonate)cuprate(II) units can be connected to other units through carboxylate bridges resulting in anionic networks which exhibit different topologies: monomers (2 and 5), layers (3 and 4) and three-dimensional structures (1). Hydrogen bonding plays an important role in the self-assembling of metal–organic compounds and how the size of the amine catio…