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Topic Name: Integrative Chemistry and Soft Supramolecular Chemistry

Category: Chemical

Research persons: Renal Backov

Location: Research Center Paul Pascal (C.R.P.P.), France

Details

The concepts and practices in chemistry are evolving.In 1977, Jacques Livage * invents sweet chemistry that aims to synthesize materials drawing on the capabilities of living organisms to produce glass from silicates in solution at room temperature.Jean-Marie Lehn, Nobel Prize for Chemistry in 1987, formalizes the concepts of supramolecular chemistry, whose objective is to use molecular bricks, which once mixed solution, come together to give buildings nanometric.In the current chemistry, which aims to develop at different scales architectures increasingly complex, emerges the concept of integrative chemistry, developed especially by the Center Renal Backov Paul Pascal Research (CNRS Unité own Bordeaux) [1 ].

At the moment, we asked the chemist to develop systems of varied shapes and types, with functions that we should be able to control. They should also be able to control the size and morphology of these systems, at different scales.The achievement of such complex architectures involves transverse mode synthesis, combining skills using different areas of chemistry: Chemistry soft, supramolecular, physical chemistry of biological systems and complex fluids etc.We can consider the chemical as a mixture integrative and changing concepts of 'soft chemistry "and" supramolecular chemistry. " The synthesis, performed at room temperature (based on the chemistry sweet), will help to interact systems organic, inorganic and biological connecting the complex structures of soft matter, ** without destruction of organic matter particularly sensitive to elevations temperature.By self connections via low (principle of supramolecular chemistry), the organic matter will organize and impose its morphology entities inorganic growth. It is the coupling between organic matter and complex fluids which, for example, may serve as a footprint in the inorganic material (titanium dioxide, silica, etc.), that is to give its final form: tape , foam, fiber, ball .... The ability to vary the imprint organic and flexible ways of organizing at different scales can literally cut the material and imagine an infinite number of morphologies, as shown in the figure below underneath.

This new integrative concept of chemistry is, in some ways, an extension strategies inspired synthesis [2]. Moreover, Life Sciences, "integrative physiology" and "integrative biology ***" are now recognized and affirmed disciplines, which should not take too long for chemistry Integrative.In the United States, the National Science Foundation (NSF) has incorporated this discipline within its chemical division as the "Chemistry Integrative Activities."

Figure: Examples of complex architectures obtained by integrative Chemistry. A foam titanium dioxide (TiO2) two polygonal cell foam TiO2 three spherical cell foam TiO2 fibrillar four-sided foam TiO2 walled ribbons in five of macro Material silica mineralization obtained by an emulsion concentrate macro six polymeric material obtained by emulsion polymerization of a concentrated where nanoparticles Silica 7 nucleated were condensed under laminar shear flow August Fiber macroscopic vanadium oxide (V2O5) obtained by extrusion nine shells of silica obtained by emulsion diluted 10 Nanocoques Multiwall silica obtained by using a lamellar phase lyotrope trimethylbenzene inflated by 11 three-dimensional colloidal crystal failing tape obtained via optical technique Langmuir (thin films) 12 Silica condensed under shear flow lamino-turbulent 13 balls mono size polymers obtained with a tool millifluidique 14 Mésopores materials porosity hierarchical hybrid organic macroporous 15 phospholipid vesicles multi-lamellaires introducing nanoparticles of gold within the space called .

* Member of the Academy of Sciences since 2001.
** All structures ranging from thermodynamic systems metastable (foams, emulsions, etc.). Molecular systems whose organization is intermediate between that of liquid and solid materials.

*** The integrative biology concerns the description integrated multiple phenomena occurring in various levels of organizations structural and functional relationships of living beings.

Note for Supramolecular chemistry

Supramolecular chemistry refers to the area of chemistry that focuses on the noncovalent bonding interactions of molecules. While traditional chemistry focuses on the covalent bond, supramolecular chemistry examines the weaker and reversible noncovalent interactions between molecules. These forces include hydrogen bonding, metal coordination, hydrophobic forces, van der Waals forces, pi-pi interactions and electrostatic effects. Important concepts that have been demonstrated by supramolecular chemistry include molecular self-assembly, folding, molecular recognition, host-guest chemistry, mechanically-interlocked molecular architectures, and dynamic covalent chemistry. The study of non-covalent interactions is crucial to understanding many biological processes from cell structure to vision that rely on these forces for structure and function. Biological systems are often the inspiration for supramolecular research.

History
The existence of intermolecular forces was first postulated by Johannes Diderik van der Waals in 1873. However, it is with nobel lauriate Hermann Emil Fischer that supramolecular chemistry has its philosophical roots. In 1890, Fischer suggested that enzyme-substrate interactions take the form of a "lock and key", pre-empting the the concepts of molecular recognition and host-guest chemistry. In the early twentieth century noncovalent bonds were understood in gradually more detail, with the hydrogen bond being described by Latimer and Rodebush in 1920.

The use of these principles led to an increasing understanding of protein structure and other biological processes. For instance, the important breakthrough that allowed the elucidation of the double helical structure of DNA occurred when it was realized that there are two separate strands of nucleotides connected through hydrogen bonds. The use of noncovalent bonds is essential to replication because they allow the strands to be separated and used to template new double stranded DNA. Concomitantly, chemists began to recognize and study synthetic structures based on noncovalent interactions, such as micelles and microemulsions.

Eventually, chemists were able to take these concepts and apply them to synthetic systems. The breakthrough came in the 1960s with the synthesis of the crown ethers by Charles J. Pedersen. Following this work, other researchers such as Donald J. Cram, Jean-Marie Lehn and Fritz Vogtle became active in synthesizing shape- and ion-selective receptors, and throughout the 1980s research in the area gathered a rapid pace with concepts such as mechanically-interlocked molecular architectures emerging.

The importance of supramolecular chemistry was established by the 1987 Nobel Prize for Chemistry which was awarded to Donald J. Cram, Jean-Marie Lehn, and Charles J. Pedersen in recognition of their work in this area. The development of selective "host-guest" complexes in particular, in which a host molecule recognizes and selectively binds a certain guest, was cited as an important contribution.

In the 1990s, supramolecular chemistry became even more sophisticated, with researchers such as James Fraser Stoddart developing molecular machinery and highly complex self-assembled structures, and Itamar Willner developing sensors and methods of electronic and biological interfacing. During this period, electrochemical and photochemical motifs became integrated into supramolecular systems in order to increase functionality, research into synthetic self-replicating system began, and work on molecular information processing devices began. The emerging science of nanotechnology also had a strong influence on the subject, with building blocks such as fullerenes, nanoparticles, and dendrimers becoming involved in synthetic systems.

References

[1] R. Backov, Soft Matter, 2006, 2, 452. Backov, Soft Matter, 2006, 2, 452.
[2] a) C. Sanchez, H. Sanchez, H. Arribart, M.M. Arribart, M.M. Giraud-Guille Nature Materials, 2005, 4, 277.

B) S. Mann, S.L. Mann, S.L. Burkett, S. Burkett, S. A. Davis, C. Davis, C. E. Fowler, N.H. Fowler, N.H. Mendelson, S.D. Mendelson, S.D. Sims, D Walsh, N.T. Sims, D Walsh, N.T. Whilton, Chem. Whilton, Chem. Mater. 1997, 9, 2300. Mater. 1997, 9, 2300.

Contact
Renal Backov

Research Center Paul Pascal (C.R.P.P.), CNRS UPR - 8641, Pessac
Tel: 05 56 84 56 30 Tel: 05 56 84 56 30
Email: backov@crpp-bordeaux.cnrs.fr