Molecular and supramolecular engineering

The design of molecules, supermolecules and materials presenting NLO activity involves molecular and supramolecular engineering. At the molecular level, a high polarizability, leading to large quadratic ft and cubic y hyperpolarizability coeffi-... 

Fig. 1.10 A curricular structure discussed during the Touchstones of Modem Polymer Processing workshop, where a novel discipline called Molecular and Supramolecular Engineering and Science, becomes the initial, common core of macromolecular, chemical molecular, and Biomacromolecular engineering.

J. Roncali, P. Frere, P. Blanchard, R. de Bettignies, M. Turbiez, S. Roquet, P. Leriche and Y. Nicolas, Molecular and supramolecular engineering of jr-conjugated systems for photovoltaic conversion. Thin Solid Films, 511-512, 567-575 (2006). 

Strong intermolecular interactions between active SCO mononuclear building blocks stem from the presence of efficient hydrogen-bonding networks or 7i-7i stacking interactions and have led to abrupt spin transitions [1], sometimes with associated hysteresis [2-4]. Despite the important efforts made by crystal engineers in establishing reliable connections between molecular and supramolecular structures on the basis of intermolecular interactions, the control of such forces is, however, difficult and becomes even more complicated when uncoordinated counter-ions and/or solvent molecules are present in the crystal lattice. 

Sharma CVK, Panneerselvam K, Shimoni L, Katz H, Carrell HL, Desiraju GR (1994) 3-(3 ,5 -Dinitrophenyl)-4-(2 ,5 -dimethoxyphenyl)cyclobutane-l,2-dicarboxylic acid engineered topochemical synthesis and molecular and supramolecular properties. Chem Mater 6 1282-1292... 

By varying the relative site occupancies of G and G2, inclusion compounds with different properties would result. Some progress in this direction has been achieved [30,31] and Desiraju [32], in an article entitled Matching of molecular and supramolecular symmetry. An exercise in crystal engineering , has indicated the direction of future progress. 

Crystal engineering involves the understanding of intermolecular interactions in the context of crystal packing and the utilization of such understanding in the design of new solids with desired physical and chemical properties.1 A major aim of crystal engineering is to establish reliable connections between molecular and supramolecular structure on the basis of intermolecular forces.2... 

Simon, J., and Pierre Bassoul. Design of Molecular Materials Supramolecular Engineering. New York Wiley, 2000. 

The crystal structures of six 3,6-diaryl-l,2,4,5-tetrazines have been determined and their molecular packing has been compared to the supramolecular architecture observed in related carboxylic acid dimers. In the tetrazines, covalent N-N bonds are considered to replace the intermolecular O-H- - -O hydrogen bonds of the carboxylic acids. In the system investigated, the covalent six-membered ring of the tetrazine was an appropriate replacement for the carboxylic acid synthon. This apparent interplay between molecular and supramolecular units may have applications in the crystal engineering of new materials (Figure 1) <2003HCA1205>. 

Recently, many scientists and engineers have looked for methods to control the sizes of QDs and make possible the formation of ordered lateral two-dimensional superlattices or vertical superlattices for heterojunction thin films. One approach is the top-down method, molecular beam epitaxy nanolithographic technology, which has been developed with the development of microelectronics and processing techniques for traditional inorganic semiconductors. This technique of nanoscale manipulation can reach only the upper limits of sizes defined by nanostructure physics, and has successfully manipulated artificial atoms and molecules [10-12). Bottom-up method is based on molecular and supramolecular assembly techniques that have been proposed by chemists in recent years. With this method, it is possible to prepare monodispersed defect-free nanocrystal QDs 1-10 nm in size and to control easily QDs coupling to form nanocrystal molecules, even quantum dot superlattices in two or three dimensions. 

Irrespective of the gel and stimuli nature, a molecular mechanochemical engine implies a receptor, usually located at the level of the functional groups, and a functional part, at the molecular and supramolecular level. Figure 4.10. 

GENETIC ENGINEERING OF MOLECULAR AND SUPRAMOLECULAR STRUCTURE IN POLYMERS... 

J. Simon and P. Bassoul, Design of molecular materials supramolecular engineering, Wiley-VCH, Weinheim, 2000. 

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