Search results for "bond"

Friction based solid state welding processes

2012

Synthèse et caractérisation de phosphine, borane, amine sur plateforme ferrocène polyfonctionnelle

2016

Ferrocene platforms are useful in coordination chemistry and catalysis thanks to their robustness and versatile functionalization. Ferrocene backbone allows the implantation of several key functional groups in a restricted space, inducing close proximity and potential polyfunctional cooperation (see for instance ferrocenyl polyphosphine chemistry). Ansa ferrocene and ferrocene bearing conformational control inducing groups maximizing the proximity of key groups have been widely reported.The first part of this thesis focuses on the synthesis of new borylated cyclopentadienyl, and their use in formation of borylated metallocenes bearing conformational constraints. NMR analysis and DFT calcula…

Quantum gap and spin-wave excitations in the Kitaev model on a triangular lattice

2017

We study the effects of quantum fluctuations on the dynamical generation of a gap and on the evolution of the spin-wave spectra of a frustrated magnet on a triangular lattice with bond-dependent Ising couplings, analog of the Kitaev honeycomb model. The quantum fluctuations lift the subextensive degeneracy of the classical ground-state manifold by a quantum order-by-disorder mechanism. Nearest-neighbor chains remain decoupled and the surviving discrete degeneracy of the ground state is protected by a hidden model symmetry. We show how the four-spin interaction, emergent from the fluctuations, generates a spin gap shifting the nodal lines of the linear spin-wave spectrum to finite energies.

Bending Carbon Nanoforms for Supramolecular Recognition: A Topological Study on Hemifullerene-Based Aggregates

2018

International audience; Buckybowls have risen as appealing fullerene fragment derivatives. Their intrinsic curvature has been exploited in the generation of host–guest supramolecular assemblies, not only through concave–convex complementarity but also through less-known concave–concave staggered arrangements. Whereas the stabilization of bowl-in-bowl dispositions has been ascribed to efficient π–π forces together with favorable dipole–dipole interactions, a detailed analysis on the forces guiding the formation of the staggered arrangements is missing so far. Herein, we present a thorough theoretical characterization of bowl-in-bowl vs staggered hemifullerene-based homodimers and heterodimer…

Molecular polarizability of fullerenes and endohedral metallofullerenes

2002

The interacting induced dipoles polarization model implemented in our program POLAR is used for the calculation of the molecular dipole µ and tensor quadrupole moments and also the dipole–dipole polarizability . The method is tested with Scn, Cn (fullerene and graphite) and endohedral Scn@Cm clusters. The polarizability is an important quantity for the identification of clusters with different numbers of atoms and even for the separation of isomers. The results for the polarizability are of the same order of magnitude as from reference calculations performed with our version of the program PAPID. The bulk limit for the polarizability is estimated from the Clausius–Mossotti relationship. The…

ChemInform Abstract: Covalently Supported Ionic Liquid Phases: An Advanced Class of Recyclable Catalytic Systems

2016

In this review, the most recent advances in the synthesis and catalytic applications of covalently supported ionic liquid (IL) phases will be discussed. This class of recyclable catalytic materials is based on the covalent attachment of several types of ammonium salts, usually imidazolium, but also thiazolium, triazolium, and pyrrolidinium salts, on the surface of different supports, for example, silica, periodic mesoporous organosilica, polystyrene, magnetic-based materials, carbon nanotubes (NTs), halloysite NTs, polyhedral oligomeric silsesquioxane (POSS), and fullerenes. Moreover, poly(ionic liquid) materials, in which the IL-based structure also acts as a support, will be considered. T…

Interface engineering in efficient vacuum deposited perovskite solar cells

2016

Abstract We studied the effect of the charge transport layers in p-i-n perovskite solar cells using vacuum deposited methylammonium lead iodide thin-film absorbers. While solution-processed perovskite films are frequently deposited directly on PEDOT:PSS leading to good solar cell performances, in some cases even to very good Voc values, we show that in devices employing vacuum deposited MAPbI3 perovskites, the removal of the polyTPD electron blocker substantially reduces the photovoltaic behavior. This is indicative of rather different charge transport properties in the vacuum deposited MAPbI3 perovskites compared to those prepared from solution. On the other hand, we investigated the use o…

Topological effects of a rigid chiral spacer on the electronic interactions in donor-acceptor ensembles

2005

Two triads (donor-spacer-acceptor), etTTF-BN-C 6 0 (6) and ZnP-BN-C 6 0 (7), in which electron donors (i.e., exTTF or ZnP) are covalently linked to C 6 0 through a chiral binaphthyl bridge (BN), have been prepared in a multistep synthetic procedure starting from a highly soluble enantiomerically pure binaphthyl building block (1). Unlike other oligomeric bridges, with hinaphthyl bridges, the conjugation between the donor and the acceptor units is broken and geometric conformational changes are facilitated. Consequently, distances and electronic interactions between the donor and C 6 0 are drastically changed. Both donor-spacer-acceptor (D-s-A) systems (i.e., 6 and 7) exhibit redox processes…

Substrate templating guides the photoinduced reaction of C60on calcite

2014

cited By 7; International audience; A substrate-guided photochemical reaction of C60 fullerenes on calcite, a bulk insulator, investigated by non-contact atomic force microscopy is presented. The success of the covalent linkage is evident from a shortening of the intermolecular distances, which is clearly expressed by the disappearance of the moiré pattern. Furthermore, UV/Vis spectroscopy and mass spectrometry measurements carried out on thick films demonstrate the ability of our setup for initiating the photoinduced reaction. The irradiation of C60 results in well-oriented covalently linked domains. The orientation of these domains is dictated by the lattice dimensions of the underlying c…

The Preparation and Characterization of New Antazoline Salts with Dicarboxylic Acids

2015

New antazoline salts with organic acids (fumaric acid, oxalic acid, and maleic acid) were prepared. The effect of the crystallization solvent and mechanochemical treatment on the crystalline forms of these salts was studied. Two polymorphs of antazoline hydrogen maleate were identified and their relative stability was determined. The molecular structures of antazoline hydrogen oxalate and antazoline hydrogen maleate showed differences in antazoline cation conformation. In crystal structures of all salts both imidazoline nitrogens of antazoline cation are involved in hydrogen bond formation with carboxyl groups of the acid.