Search results for "Mole"
showing 10 items of 35882 documents
6-Methyluracil: a redetermination of polymorph (II)
2019
6-Methyluracil, C5H6N2O2, exists in two crystalline phases: form (I), monoclinic, space group P21/c [Reck et al. (1988). Acta Cryst. A44, 417–421] and form (II), monoclinic, space group C2/c [Leonidov et al. (1993). Russ. J. Phys. Chem. 67, 2220–2223]. The structure of polymorph (II) has been redetermined providing a significant increase in the precision of the derived geometric parameters. In the crystal, molecules form ribbons approximately running parallel to the c-axis direction through N—H...O hydrogen bonds. The radical differences observed between the crystal packing of the two polymorphs may be responsible in form (II) for an increase in the contribution of the polar canonical forms…
New supramolecular fluorescent NDI-gels as bioimaging materials
Hybrid ionogels: adsorbent for the removal of pharmaceutical active compounds from wastewater
Selective Formation of S4- and T-Symmetric Supramolecular Tetrahedral Cages and Helicates in Polar Media Assembled via Cooperative Action of Coordina…
2020
We report on the synthesis and self-assembly study of novel supramolecular monomers encompassing quadruple hydrogen-bonding motifs and metal coordinating 2,2’-bipyridine units. When mixed with metal ions such as Fe2+ or Zn2+, the tetrahedron cage complexes are formed in quantitative yields and full diastereoselectivity, even in highly polar acetonitrile or methanol solvents. The symmetry of the complexes obtained has been shown to depend critically on the flexibility of the ligand. Restriction of the rotation of the hydrogen-bonding unit with respect to the metal coordinating site results in a T-symmetric cage, whereas by introducing flexibility either through a methylene linker or rotating…
The Hexameric Resorcinarene Capsule as a Brønsted Acid Catalyst for the Synthesis of Bis(heteroaryl)methanes in a Nanoconfined Space
2019
Herein, we show that the hexameric resorcinarene capsule C is able to catalyze the formation of bis(heteroaryl)methanes by reaction between pyrroles or indoles and carbonyl compounds (α-ketoesters or aldehydes) in excellent yields and selectivity. Our results suggest that the capsule can play a double catalytic role as a H-bond catalyst, for the initial activation of the carbonyl substrate, and as a Bronsted acid catalyst, for the dehydration of the intermediate alcohol.
Supramolecular Organocatalysis in Water Mediated by Macrocyclic Compounds
2018
In the last decades many efforts have been devoted to design supramolecular organocatalysts able to work in water as the reaction medium. The use of water as solvent provides promising benefits with respect to environmental impact. In this context, macrocyclic compounds played a role of primary importance thanks to their ease of synthesis and their molecular recognition abilities toward the reactants. The aim of this review is to give an overview of the recent advances in the field of supramolecular organocatalysis in water, focusing the attention on calixarene and cyclodextrins derivatives. Calixarenes and cyclodextrins, thanks to their hydrophobic cavities, are able to host selectively th…
Liquid Structure Scenario of the Archetypal Supramolecular Deep Eutectic Solvent: Heptakis(2,6-di-O-methyl)-β-cyclodextrin/levulinic Acid
2023
The concept of supramolecular solvents has been recently introduced, and the extended liquid-state window accessible for mixtures of functionalized cyclodextrins (CDs) with hydrogen bond (HB) donor species, e.g., levulinic acid, led to the debut of supramolecular deep eutectic solvents (SUPRA-DES). These solvents retain CD’s inclusion ability and complement it with enhanced solvation effectiveness due to an extended HB network. However, so far, these promising features were not rationalized in terms of a microscopic description, thus hindering a more complete capitalization. This is the first joint experimental and computational study on the archetypal SUPRA-DES: heptakis- (2,6-di-O-methyl)…
Inorganic Anion-Mediated Supramolecular Entities of 4-Amino-3,5-Bis(4-Pyridyl)-1,2,4-Triazole Salts Assisted by the Interplay of Noncovalent Interact…
2023
The development of new families of synthetic molecular systems projecting neutral, bi-, or multi-H-bonding donor units is significant to acquire the desired selectivity within the fascinating area of anion recognition. Here, we illustrate the reaction between a neutral 4-amino-3,5-bis(4-pyridyl)-1,2,4-triazole ligand (L) with acidic solutions containing either chloride, bromide, nitrate, phosphate, iodide, sulfate, hexafluorosilicate, fluoride, tetrafluoroborate or perchlorate anions, yielding 16 new anion-mediated supramolecular entities, H2LCl2 (1), H2LBr2 (2), H2L(NO3)2 (3), HL(H2PO4) (4), H2L(H2PO4)2 (5), [H2L]2I4 (6), H2L(NO3)2 (7), H2L(SO4)·H2O (8), H2LSiF6 (9), H2LSiF6·2H2O (10), H2L…
Influencing the self‐sorting behavior of [2.2]paracyclophane based ligands by introducing isostructural binding motifs
2020
Two isostructural ligands with either nitrile ( L nit ) or isonitrile ( L iso ) moieties directly connected to a [2.2]paracyclophane backbone with pseudo‐meta substitution pattern have been synthesized. The ligand itself ( L nit ) or its precursors ( L iso ) were resolved via HPLC on a chiral stationary phase and the absolute configuration of the isolated enantiomers was assigned by XRD analysis and/or by comparison of quantum‐chemical simulated and experimental ECD‐spectra. Surprisingly, the resulting metallosupramolecular aggregates formed in solution upon coordination of [(dppp)Pd(OTf) 2 ] differ in their composition: whereas L nit forms dinuclear complexes L iso exclusively forms trinuc…
Self-assembly of M4L4 tetrahedral cages incorporating pendant P=S and P=Se functionalised ligands
2019
Herein, the synthesis of metal–organic tetrahedral cages featuring flexible thio- and selenophosphate-based ligands is described. The cages were prepared by sub-component self-assembly of A=P(OC6H4NH2-4)3 (A = S, Se) or S=P(SC6H4NH2-4)3,2-pyridinecarboxaldehyde, and either Fe[BF4]2 or Co[BF4]2. Preliminary host–guest studies into the ability of the pendant PQS and PQSe groups to interact with suitable substrates will be discussed. peerReviewed