Search results for "Bas"
showing 10 items of 28787 documents
Smoothed Spherical Truncation based on Fuzzy Membership Functions: Application to the Molecular Encoding.
2019
A novel spherical truncation method, based on fuzzy membership functions, is introduced to truncate interatomic (or interaminoacid) relations according to smoothing values computed from fuzzy membership degrees. In this method, the molecules are circumscribed into a sphere, so that the geometric centers of the molecules are the centers of the spheres. The fuzzy membership degree of each atom (or aminoacid) is computed from its distance with respect to the geometric center of the molecule, by using a fuzzy membership function. So, the smoothing value to be applied in the truncation of a relation (or interaction) is computed by averaging the fuzzy membership degrees of the atoms (or aminoacid…
Monte Carlo Simulations of Au38(SCH3)24 Nanocluster Using Distance-Based Machine Learning Methods
2020
We present an implementation of distance-based machine learning (ML) methods to create a realistic atomistic interaction potential to be used in Monte Carlo simulations of thermal dynamics of thiol...
Switching and redox isomerism in first-row transition metal complexes containing redox active Schiff base ligands.
2014
International audience; The reversible redox isomerisms in first row transition metal complexes of the type ML2 were studied. The six ML2 complexes (M = Mn(III) (), Fe(II) (), Co(III) (), Ni(II) (), Cu(II) () and Zn(II) ()) were synthesized with a redox active Schiff base ligand [2-(3,5-di-tert-butyl-2-hydroxyphenylamino)-4-chlorophenol] (H3L) presenting different oxidation states from -2 to 0 (L(2-), L(-) and L(0)). EPR spectra and magnetic susceptibility measurements indicate the presence of complexes of the type [Mn(III)(L(2-))(L(-))] () with S = 1/2, [Fe(II)(L(-))2] () with S = 2, [Co(III)(L(2-))(L(-))] () with S = 1/2, [Ni(II)(L(-))2] () with S = 1, [Cu(II)(L(-))2] () with S = 1/2 and …
The first example of cofacial bis(dipyrrins)
2016
International audience; Two series of cofacial bis(dipyrrins) were prepared and their photophysical properties as well as their bimolecular fluorescence quenching with C-60 were investigated. DFT and TDDFT computations were also performed as a modeling tool to address the nature of the fluorescence state and the possible inter-chromophore interactions. Clearly, there is no evidence for such interactions and the bimolecular quenching of fluorescence, in comparison with mono-dipyrrins, indicates that C-60-bis(dipyrrin) contacts occur from the outside of the "mouth" of the cofacial structure.
2,4,5-Triaryl imidazole probes for the selective chromo-fluorogenic detection of Cu(II). Prospective use of the Cu(II) complexes for the optical reco…
2019
The sensing behaviour toward metal cations and biothiols of two 2,4,5-triarylimidazole probes (3a and 3b) is tested in acetonitrile and in acetonitrile-water. In acetonitrile the two probes present charge-transfer absorption bands in the 320-350 nm interval. Among all cations tested only Cu(11) is able to induce bathochromic shifts of the absorption band in the two probes, which is reflected in marked colour changes. Colour modulations are ascribed to the formation of 1:1 Cu(II)-probe complexes in which the cation interacts with the imidazole acceptor heterocycle. Besides, the two probes present intense emission bands (at 404 and 437 nm for 3a and 3b respectively) in acetonitrile that are q…
9,10-Phenanthrenedione as Visible-Light Photoredox Catalyst: A Green Methodology for the Functionalization of 3,4-Dihydro-1,4-Benzoxazin-2- Ones thro…
2018
A visible-light photoredox functionalization of 3,4-dihydro-1,4-benzoxazin-2-ones through a Friedel-Crafts reaction with indoles using an inexpensive organophotoredox catalyst is described. The reaction uses a dual catalytic system that is formed by a photocatalyst simple and cheap, 9,10-phenanthrenedione, and a Lewis acid, Zn(OTf)2. 5W white LEDs are used as visible-light source and oxygen from air as a terminal oxidant, obtaining the corresponding products with good yields. The reaction can be extended to other electron-rich arenes. Our methodology represents one of the most valuable and sustainable approach for the functionalization of 3,4-dihydro-1,4-benzoxazin-2-ones, as compared to th…
Elucidating the Influence of the Activation Energy on Reaction Rates by Simulations Based on a Simple Particle Model
2020
An application for visualizing the dynamic properties of an equimolar binary mixture of isotropic reactive particles is presented. By introducing a user selectable choice for the activation energy, the application is useful to demonstrate qualitatively that the reaction rate depends on the above choice and on temperature. The application is based on a 2D realistic dynamic model where atoms move because of their thermal energies and the trajectories are determined by solving numerically Newton’s laws according to a Molecular Dynamics (MD) scheme. Collisions are monitored as time progresses, and every time the collision energy is larger than the selected activation energy, a reactive event oc…
Dual role of silver in a fluorogenic N-squaraine probe based on Ag(i)–π interactions
2021
In the presence of Ag(I), the monoanion of cyano-N-squaraine (I) generates an intense fluorescence turn-on response. Experimental evidence and DFT calculations reveal a sequence of deprotonation-coordination events in which the Ag(I) ions play a dual role as a Lewis acid and coordinating metal. The observed effect is highly selective for Ag(I) compared to other metals.
Hierarchical Beta zeolites as catalysts in a one-pot three-component cascade Prins–Friedel–Crafts reaction
2020
Hierarchical Beta zeolites obtained from concentrated reaction mixtures (H2O/Si = 2.5–7.0) in the presence of CTAB and their conventional and nanosponge analogues were investigated in a one-pot cascade environmentally friendly Prins–Friedel–Crafts reaction of butyraldehyde with 3-buten-1-ol and anisole under mild conditions (60 °C). The highest yields of the desired products with 4-aryltetrahydropyran structure were achieved when using hierarchical zeolites characterised by well-developed mesoporosity (facilitating the formation of bulky intermediates and products) and by an increased fraction of highly accessible (evaluated by TTBPy method) medium-strength Bronsted acid sites. Acid sites w…
Functionalised diimidazolium salts: the anion effect on the catalytic ability
2016
The catalytic ability of some functionalised diimidazolium ionic liquids was tested using the Michael addition of malononitrile to t-chalcone as probe reaction. Diimidazolium salts characterized by the presence of 1-(1-imidazolylmethyl)-3,5-di-[1-(3-octylimidazolylmethyl)]benzene cation and differing in the anion structure were used. Both mono- and dianions were employed and among these some chiral anions generally used as organocatalysts were taken into account. Data collected were analysed both as function of ionic liquids structure and basicity, evaluated using the Hammett basicity function. Although the use of chiral anions did not allow performing a stereochemical control of the reacti…