Search results for "RAM"
showing 10 items of 35643 documents
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
Agent assisted interactive algorithm for computationally demanding multiobjective optimization problems
2015
We generalize the applicability of interactive methods for solving computationally demanding, that is, time-consuming, multiobjective optimization problems. For this purpose we propose a new agent assisted interactive algorithm. It employs a computationally inexpensive surrogate problem and four different agents that intelligently update the surrogate based on the preferences specified by a decision maker. In this way, we decrease the waiting times imposed on the decision maker during the interactive solution process and at the same time decrease the amount of preference information expected from the decision maker. The agent assisted algorithm is not specific to any interactive method or s…
Clinical Behavior of Ceramic, Hybrid and Composite Onlays. A Systematic Review and Meta-Analysis
2020
A systematic review and meta-analysis was performed to analyze the survival of onlay restorations in the posterior region, their clinical behavior according to the material used (ceramic reinforced with lithium disilicate, conventional feldspathic ceramic or reinforced with leucite; hybrid materials and composite), possible complications, and the factors influencing restoration success. The systematic review was based on the preferred reporting items for systematic reviews and meta-analyses (PRISMA) statement, without publication date or language restrictions. An electronic search was made in the PubMed, Scopus, Embase, and Cochrane databases. After discarding duplicate publications and stu…
Rural Renewal Program in the Aspect of Sustainable Development of Rural Areas in the Opinion of Respondents from the Opole Voivodeship
2018
Sustainable development has a complex nature and is represented by economic, social and ecological pillars. Connected with the concept of multifunctionality on the rural areas it translates by diverse economic activities carried out with respect for environmental aspects, with the development of social and cultural functions, and with the attention to ensure good living conditions for the inhabitants. Effective achievement of sustainable development goals needs constant and consistent raising of public awareness, as well as an increase in the public access to information and its participation in the decision-making process. The aim of the paper is to assess, basing on the respondents‘ opini…