Master 2 Internship 2016-2017 at ENS-Lyon (France)
TITLE : Towards Stimuli-Responsive Self-assembled Molecular Materials
SUPERVISOR
Dr. Christophe BUCHER (DR CNRS), christophe.bucher@ens‐lyon.fr Ecole Normale Supérieure de Lyon‐France (http://www.ens‐lyon.eu/ « Supramolecular Chemistry Group » (http://www.ens‐lyon.fr/CHIMIE/recherche/Teams) SCIENTIFIC CONTEXT AND OBJECTIVES
Stimuli‐responsive self‐assembled molecular materials are currently subject to intense research activity.1,2 The ability to control the organization of molecules within molecular materials has indeed emerged in the past decade as a major scientific objective that is mainly motivated by exciting foreseeable applications in areas ranging from electronics and catalysis to medicine. In this field, one key objective is to achieve a control over the organization or over the association/dissociation of molecular tectons (tecton=monomer) within self‐assembled materials using an external stimuli (temperature, light, electrons, chemicals, magnetic field…). H+
Enormous technologic interests are indeed at stake in being able to control and exploit the properties of self‐assembled materials built from monomers held together by reversible and directional interactions. This particular field can lead to applications in various domains as (i) molecular electronics, with the development of molecular wires and devices for data storage, (ii) in analytic science, with materials allowing the controlled binding/release of pollutants or drugs, (iii) in materials science with the development of self‐healing and adaptive supramolecular polymers that could respond to well defined and controlled external stimuli by changes in structure and function. In this context, the aim of this project is to explore a new concept of organic tecton whose self‐assembly and disassembly could be controlled externally, by electron transfer centered on the tectons. The strategy which will be used to allow an electronic control over the assembled and disassembled states of molecular systems or to construct oriented molecular assemblies is based on the formation of soluble coordination polymers or of fully organic supramolecular assemblies that will include redox‐responsive ‐dimerizable bipyridinium‐based hinges3‐6 in their skeleton. Dissociation of the self‐assembled species will be actuated upon changing the redox state of bipyridinium units involved in the tectons from their dicationic state to their radical cation state, the driving force of the disassembling process being the non covalent and fully reversible dimerization occurring between bipyridinium cation radicals.3‐6 This multidisciplinary project is at the interface between organic and supramolecular chemistry. The applicant will ideally have a multidisciplinary background with strong expertise in organic chemistry. REFERENCES
1‐Adaptive soft molecular self‐assemblies. Soft Matter, 2016, 12, 337. http://pubs.rsc.org/en/content/articlelanding/2016/sm/c5sm02397a#!divAbstract 2‐Stimuli‐Responsive Metal−Ligand Assemblies. Chem. Rev. 2015, 115, 7729. http://pubs.acs.org/doi/abs/10.1021/cr500632f 3‐Redox control of rotary motions in ferrocene‐based elemental ball bearings. J. Am. Chem. Soc. 2012, 134, 2653. http://pubs.acs.org/doi/abs/10.1021/ja209766e 4‐Redox Responsive Porphyrin‐based Molecular Tweezers. Chem. Eur. J. 2012 18, 7648. http://onlinelibrary.wiley.com/doi/10.1002/chem.201200842/abstract 5‐ Hydrogen‐Bond Controlled π‐Dimerization in Viologen‐Appended Calixarenes: Revealing a Subtle Balance of Weak Interactions. Org. Lett. 2015, 17, 4058. http://pubs.acs.org/doi/abs/10.1021/acs.orglett.5b01982 6‐Chemically and Electrochemically Triggered Assembly of Viologen Radicals: Towards Multiaddressable Molecular Switches. Chem. Eur. J. 2015, 21, 2090. http://onlinelibrary.wiley.com/doi/10.1002/chem.201405157/abstract