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Your search keyword '"Schiaffino, Luca"' showing total 130 results
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130 results on '"Schiaffino, Luca"'

1. Inherently chiral uranyl-salophen macrocycles: Computer-aided design and resolution

Author

Cort, Antonella Dalla, Mandolini, Luigi, Pasquini, Chiara, and Schiaffino, Luca

Subjects
Transition state (Chemistry) -- Research, Molecular dynamics -- Research, Methyl groups -- Chemical properties, Biological sciences, Chemistry
Abstract

The resulting complexes dissociate upon chromatographic treatment, an alternative approach to the design and synthesis of robust, nonflipping uranyl-sclophen compounds is described. Calculations showed that the chains are those composed of 12 and 13 methylene units.

Published
2005

2. Stereomutations of atropisomers of sterically hindered salophen ligands

Author

Cort, Antonella Dalla, Gasparrini, Francesco, Lunazzi, Lodovico, Mandolini, Luigi, Mazzanti, Andrea, Pasquini, Chiara, Pierini, Marco, Rompietti, Romina, and Schiaffino, Luca

Subjects
Schiff bases -- Chemical properties, Ligand binding (Biochemistry) -- Research, Biological sciences, Chemistry
Abstract

The stereomutations in nonsymmetrical salophen ligands were studied by means of dynamic NMR and HPCL methods. The values compare well with those determined by chromatography on an enantioselective HPLC column at low temperatures, thus confirming that DNMR and DHPLC can be conveniently employed as complementary techniques.

Published
2005

3. Rates and equilibria of the Michael-type addition of benzenethiol to 2-cyclopenten-1-ones

Author

Castelli, Valeria van Axel, Bernardi, Fernando, Cort, Antonella Dalla, Mandolini, Luigi, Rossi, Ivan, and Schiaffino, Luca

Subjects
Chemistry, Organic -- Research, Chloroform -- Research, Solution (Chemistry) -- Research, Catalysis -- Research, Biological sciences, Chemistry
Abstract

Research has been conducted on the triethylamine-catalyzed addition reactions of benzenethiol to 2-cyclopenten-1-one and its derivatives. Results demonstrate that these reactions are reversible in chloroform solutions.

Published
1999

4. 6-azahemiporphycene: a new member of the porphyrinoid family

Author

Mandoj, Federica, Nardis, Sara, Pomarico, Giuseppe, Stefanelli, Manuela, Schiaffino, Luca, Ercolani, Gianfranco, Prodi, Luca, Genovese, Damiano, Zaccheroni, Nelsi, Fronczek, Frank R., Smith, Kevin M., Xiao Xiao, Jing Shen, Kadish, Karl M., and Paolesse, Roberto

Subjects
Hydrogen bonding -- Chemical properties, Hydrogen bonding -- Structure, Methylene chloride -- Chemical properties, Methylene chloride -- Structure, Nuclear magnetic resonance spectroscopy -- Usage, Oxidation-reduction reaction -- Analysis, Porphyrins -- Chemical properties, Porphyrins -- Structure, X-ray crystallography -- Usage, Chemistry
Published
2009

6. The role of attractive van der Waals forces in the catalysis of Michael addition by a phenyl decorated uranyl-salophen complex

Author

Cort, Antonella Dalla, Mandolini, Luigi, and Schiaffino, Luca

Subjects
Uranium dioxide -- Chemical properties, Hydrogen bonding -- Research, Biological sciences, Chemistry
Abstract

A plausible mechanism that has involved concomitant nucleophilic attack at the [beta]-carbon and hydrogen bonding between the [Et.sub.3]N[H.sup.+] countercation and the carbonyl oxygen of the s-cis conformation of the enone reactant is described. The role of the van der Waals interactions with the aromatic side arm of the phenyl-substituted uranyl-salophen compound as a key driving force for catalysis is analyzed.

Published
2008

7. Enantiomerization of chiral uranyl-salophen complexes via unprecedented ligand hemilability: toward configurationally stable derivatives

Author

Ciogli, Alessia, Cort, Antonella Dalla, Gasparrini, Francesco, Lunazzi, Lodovico, Mandolini, Luigi, Mazzanti, Andrea, Pasquini, Chiara, Pierini, Marco, Schiaffino, Luca, and Mihan, Francesco Yafteh

Subjects
Enantiomers -- Research, Chirality -- Research, Biological sciences, Chemistry
Abstract

The synthesis of a new chiralmacrocyclic uranyl-salophen derivative and the analysis of its configuration stability carried out by dynamic chiral HPLC are described. The studies have shown that the new structural motif has imparted a higher configurational stability, thus raising the half-life for the enantiomerization to more than 2 months at room temperature.

Published
2008

8. A kinetic study of the conjugate addition of benzenethiol to cyclic enones catalyzed by a nonsymmetrical uranyl-salophen complex

Author

van Axel Castelli, Valeria, Cort, Antonella Dalla, Mandolini, Luigi, Pinto, Valentina, and Schiaffino, Luca

Subjects
Benzene -- Chemical properties, Chemical reaction, Rate of -- Analysis, Biological sciences, Chemistry
Abstract

The [Et.sub.3]N-assisted addition of benzenethiol to enones in chloroform catalyzed with high turnover efficiency by the phenyl-substituted uranyl-salophen compound is described.

Published
2007

10. Molecular recognition of carbonyl compounds by uranyl-salophen based neutral receptors driven by Van der Waals forces

Author

van Axel castelli, V., van Axel Castelli, Valeria, Dalla Cort, Antonella, Mandolini, Luigi, Pinto, Valentina, Reinhoudt, David, Ribaudo, Fabrizio, Sanna, Cecilia, Schiaffino, Luca, and Ruel, Bianca H.M.

Subjects
chemistry.chemical_classification, Chloroform, Stereochemistry, Chemistry, IR-37947, Van der Waals strain, Neutral molecule recognition, General Chemistry, enone guests, ketone guests, neutral molecule recognition, uranyl-salophen, van der waals forces, symbols.namesake, chemistry.chemical_compound, Crystallography, Molecular recognition, symbols, Non-covalent interactions, Phenyl group, van der Waals forces, Titration, van der Waals force, Ketone guests, METIS-206206, Molecular tweezers, Enone guests, Uranyl-salophen
Abstract

The complexation of the salophen-uranyl metallocleft 2 and of its half-cleft analogue 3 with enones and other carbonyl compounds was assessed in chloroform by UV-Vis titration and, occasionally, by FT-IR measurements. Complexes with receptors 2 and 3 are in all cases more stable than those with the control unsubstituted uranyl-salophen 1 , showing that in addition to the primary binding force provided by coordination of the carbonyl oxygen to the uranium, a significant driving force for complexation, typically in the range of 2-3 kcal/mol, results from van der Waals interactions of the guest with the aromatic walls. Replacement of the phenyl group in 3 with larger aromatic residues to give 4 and 5 , led to enhanced complex stabilities, due to more extended contact surfaces between host and guest.

Published
2002

13. Catalysis of the Addition of Benzenethiol to 2-Cyclohexen-1-ones by Uranyl-Salophen Complexes: A Catalytic Metallocleft with High Substrate Specificity

Author

van Axel castelli, V., van Axel Castelli, Valeria, Dalla Cort, Antonella, Mandolini, Luigi, Reinhoudt, David, and Schiaffino, Luca

Subjects
IR-11666, Base (chemistry), Kinetics, Binding, Competitive, Catalysis, Substrate Specificity, chemistry.chemical_compound, Phenols, Organometallic Compounds, Organic chemistry, Sulfhydryl Compounds, Binding site, METIS-106277, chemistry.chemical_classification, Chloroform, Binding Sites, Cyclohexanones, Antinematodal Agents, Organic Chemistry, Titrimetry, Substrate (chemistry), General Chemistry, Combinatorial chemistry, Salicylates, Enzymes, Michael additions, chemistry, Product inhibition, Enzyme mimetics, supramolecular metallocatalysts, Uranium, Enone
Abstract

The base induced addition of benzenethiol to 2-cyclohexen-1-one and its 4, 4-, 5, 5- and 6,6-dimethyl derivatives is catalysed by a salophen-uranyl based metallocleft 2 in chloroform solution with high turnover efficiency and low product inhibition. Analysis of rate data coupled with equilibrium measurements for complexation of the catalyst with the enone reactants and addition products shows that the catalytic mechanism involves the three main steps typical of single-substrate enzymatic processes, namely substrate binding and recognition, transformation of the bound substrate, and release of the reaction product. Unlike the reference salophen-uranyl 1, catalyst 2 is endowed with a structured binding site responsible for a high degree of substrate specificity among the investigated enones, due to recognition of their shape and size.

Published
2000

15. Spectroscopic, Morphological, and Mechanistic Investigation of the Solvent-Promoted Aggregation of Porphyrins Modified in meso-Positions by Glucosylated Steroids

Author

Zelenka, Karel, primary, Trnka, Tomáš, additional, Tišlerová, Iva, additional, Monti, Donato, additional, Cinti, Stefano, additional, Naitana, Mario Luigi, additional, Schiaffino, Luca, additional, Venanzi, Mariano, additional, Laguzzi, Giuseppe, additional, Luvidi, Loredana, additional, Mancini, Giovanna, additional, Nováková, Zdena, additional, Šimák, Ondřej, additional, Wimmer, Zdeněk, additional, and Drašar, Pavel, additional

Published
2011
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28. Enantiomerization of Chiral Uranyl−Salophen Complexes via Unprecedented Ligand Hemilability: Toward Configurationally Stable Derivatives

Author

Ciogli, Alessia, primary, Dalla Cort, Antonella, additional, Gasparrini, Francesco, additional, Lunazzi, Lodovico, additional, Mandolini, Luigi, additional, Mazzanti, Andrea, additional, Pasquini, Chiara, additional, Pierini, Marco, additional, Schiaffino, Luca, additional, and Mihan, Francesco Yafteh, additional

Published
2008
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49. New Insight into the Mechanism of the Conjugate Addition of Benzenethiol to Cyclic and Acyclic Enones and of the Corresponding Uranyl−Salophen-Catalysed Version

Author

Castelli, Valeria van Axel, Cort, Antonella Dalla, Mandolini, Luigi, Reinhoudt, David N., and Schiaffino, Luca

Abstract

A thorough kinetic investigation of the triethylamine-catalysed addition of benzenethiol to 2-cyclopenten-1-one in chloroform shows that the highest energy transition state is a complex of thiol, enone, and base in a 1:1:1 ratio, but whether formation or disruption of the enolate−triethylammonium ion-pair intermediate is rate-limiting is uncertain. Intervention of a second thiol molecule in the assembly of the transition-state complex is ruled out, at least at thiol concentrations not exceeding 0.1−0.2 M. Thiol addition is accelerated significantly by uranyl−salophen complex 1 and its diphenyl derivative 2. The complicated kinetics are described to high precision by means of ad hoc integrated rate equations in which associations to the metal catalyst of the enone reactant and addition product are taken into account. The kinetics are consistent with a four-body transition-state complex, whose formation results from the reaction of a (weak) thiol−base complex with a (strong) enone−uranyl−salophen complex. Open-chain and cyclic enones react at similar rates and respond to the presence of metal catalyst in much the same way. The relative catalytic efficiencies of ethyldimethylamine, triethylamine, and quinuclidine are determined essentially by differences in base strength, rather than steric bulk, in both the presence and absence of a metal complex. Only with the use of the relatively bulky Hünig’s base is an adverse steric influence apparent, which is particularly severe in the reaction catalysed by the sterically demanding 2. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Published
2003
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50. “Inherent chirality” and curvature

Author

Cort, Antonella Dalla, Mandolini, Luigi, Pasquini, Chiara, and Schiaffino, Luca

Abstract

“Inherent chirality” in molecules like calix[4]arenes, fullerenes, and uranyl-salophen complexes can be related to the presence of curvature. This observation serves as a basis for the introduction of a new chirality descriptor.

Published
2004

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