Etude de Diradicaux singulets hétérocycliques

Diradicals are reputed to be very unstable. For instance, the cyclobutanediyl which is an archetypal organic diradical has been stabilized only in matrixes at low temperature.This study is concerned with the design of singlet diradicals based on phosphorus and boron.In the first chapter, we will show in a bibliographic introduction how the use of heteroelements allowed the isolation of the first localized singlet diradical indefinitely stable at room temperature with a skeleton based on boron and phosphorus.In a second chapter, we will study the influence of the substituents beared by the atoms of boron and phosphorus. After a study of different models already known, we will describe the synthesis of an unsymmetrical model on boron. We will see that this model displayed an unexpected behaviour.In a third chapter, we will study the catenation of diradicals. We will examine different models already synthesized in our group and we will see how the study on the influence of the substituents helped us to understand the phenomena observed with tetraradicals. We will also see the synthesis of new models of tetraradicals.Finally, in the fourth chapter, we will focus on the reactivity of diradicals. We will see that diradicals feature a radical-type reactivity especially when it comes to initiating polymerizations. Then, we will study the electrophilic 1,3 additions of Brönsted acids on diradicals.This last study was carried out by a combination of experimental and computational methods in collaboration with Dr. Laurent Maron of the “Laboratoire de physique quantique”.Les diradicaux sont des espèces réputées extrêmement instables. A titre d'exemple, le cyclobutanediyle qui est l'archétype de ce genre d'espèce en série carbonée n'a, en effet, pu être isolé que dans des matrices à basse température. Cet exposé sera consacré aux diradicaux singulets constitués d'atomes de bore et de phosphore. Nous montrerons dans une introduction bibliographique comment l'utilisation de ces hétéroéléments a permis l'isolation du premier diradical localisé singulet stable basé sur un squelette formé uniquement des hétéroéléments bore et phosphore. Dans un deuxième chapitre, nous nous intéresserons à l'influence des substituants portés par les atomes de bore et de phosphore. Après une étude des différents modèles déjà caractérisés, nous décrirons la synthèse d'un modèle dissymétrique au niveau des atomes de bore. Nous verrons que ce composé dissymétrique a un comportement inattendu. Dans un troisième chapitre, nous étudierons la caténation des diradicaux. Nous examinerons les modèles qui ont déjà été synthétisés et nous verrons comment l'étude de l'influence des substituants nous permet de mieux comprendre les phénomènes observés avec les tétraradicaux. Nous verrons également la synthèse de nouveaux modèles de tétraradicaux. Enfin, dans le quatrième chapitre, nous nous pencherons sur la réactivité des diradicaux. Nous verrons que les diradicaux conservent une certaine réactivité de type radicalaire notamment dans le cadre de la catalyse de polymérisation. Puis, nous étudierons des réactions d'additions 1,3 d'acides de Brönsted sur les diradicaux. Cette dernière étude a donné lieu à une collaboration avec le Dr. Laurent Maron du « Laboratoire de physique quantique » afin de modéliser les systèmes étudiés

Biohybrid block copolymers: towards functional micelles and vesicles.

International audienceThis critical review covers the elaboration of micelles and vesicles made from block copolymers containing peptide or oligonucleotide blocks with a focus on recent developments toward responsive and functional assemblies (166 references)

Ionic-type reactivity of 1,3-dibora-2,4-diphosphoniocyclobutane-1,3-diyls : regio- and stereoselective addition of hydracids

International audienc

Ionic-type reactivity of 1,3-dibora-2,4-diphosphoniocyclobutane-1,3-diyls : regio- and stereoselective addition of hydracids

International audienc

Investigation of the reversibility of the unimer-to-aggregate transition in block copolymers by surface tension-measurements.

International audienceTwo DNA-block copolymers, poly(caprolactone)-DNA and poly(methyl metacrylate)-DNA, were synthesized by conjugation of a short single strand of DNA (12 or 22mer) to a single reactive group at one end of the synthetic polymer. These polymers self-assemble in water, without the need of any cosolvent, forming micelle-like aggregates that were imaged by TEM. The solution behavior of the bioconjugated polymers was investigated by surface tension measurements. In the direction of dilution, the surface tension was measured using a down-scaled Wilhelmy plate method. To proceed in the reverse direction (concentration), we measured the surface tension of a sessile drop during its evaporation. This latter method was firstly validated using ionic and non-ionic surfactants, including polymeric surfactants. It was then applied to investigate the unimer to micelles transition of the DNA-block copolymers. In all cases, a reversible transition was observed demonstrating the existence of a critical micellar concentration, close to 0.01 mmol L(-1) for all the conjugates. The CMC was only slightly influenced by the length of the hydrophilic DNA block

Design of Collective Motions from Synthetic Molecular Switches, Rotors, and Motors

International audiencePrecise control over molecular movement is of fundamental and practical importance in physics, biology, and chemistry. At nanoscale, the peculiar functioning principles and the synthesis of individual molecular actuators and machines has been the subject of intense investigations and debates over the past 60 years. In this review, we focus on the design of collective motions that are achieved by integrating, in space and time, several or many of these individual mechanical units together. In particular, we provide an in-depth look at the intermolecular couplings used to physically connect a number of artificial mechanically active molecular units such as photochromic molecular switches, nanomachines based on mechanical bonds, molecular rotors, and light-powered rotary motors. We highlight the various functioning principles that can lead to their collective motion at various length scales. We also emphasize how their synchronized, or desynchronized, mechanical behavior can lead to emerging functional properties and to their implementation into new active devices and material

Bistable [ c 2] Daisy Chain Rotaxanes as Reversible Muscle-like Actuators in Mechanically Active Gels

International audienceThe implementation of molecular machines in polymer science is of high interest to transfer mechanical motions from nanoscale to macroscale in order to access new kinds of active devices and materials. Toward this objective, thermodynamic and topological aspects need to be explored for reaching efficient systems capable of producing a useful work. In this paper we describe the branched polymerization of pH-sensitive bistable [c2] daisy chain rotaxanes by using copper(I)-catalyzed Huisgen 1,3-dipolar cycloaddition (“click chemistry”). With this cross-linked topology, the corresponding materials in the form of chemical gels can be contracted and expanded over a large variation of volume (∼50%) by changing the protonation state of the system. HR-MAS 1H NMR and neutron scattering experiments reveal that this macroscopic response of the gels results from the synchronized actuation of the mechanical bonds at the molecular level

Self-Assembly of Supramolecular Polymers of N-Centered Triarylamine Trisamides in the Light of Circular Dichroism:Reaching Consensus between Electrons and Nuclei

Contains fulltext : 216193.pdf (Publisher’s version ) (Open Access

DNA-Polymer micelles as nanoparticles with recognition ability

International audienceThe Watson-Crick binding of DNA single strands is a powerful tool for the assembly of nanostructures. Our objective is to develop polymer nanoparticles equipped with DNA strands for surface-patterning applications, taking advantage of the DNA technology, in particular, recognition and reversibility. A hybrid DNA copolymer is synthesized through the conjugation of a ssDNA (22-mer) with a poly(ethylene oxide)-poly(caprolactone) diblock copolymer (PEO-b-PCl). It is shown that, in water, the PEO-b-PCl-ssDNA(22) polymer forms micelles with a PCl hydrophobic core and a hydrophilic corona made of PEO and DNA. The micelles are thoroughly characterized using electron microscopy (TEM and cryoTEM) and small-angle neutron scattering. The binding of these DNA micelles to a surface through DNA recognition is monitored using a quartz crystal microbalance and imaged by atomic force microscopy. The micelles can be released from the surface by a competitive displacement event