Dynamic Borromean ring networks

ORGN 783

Claire R. Yates, cryates@chem.ucla.edu, California NanoSystems Institute and Department of Chemistry and Biochemistry, University of California Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095, Diego Benitez, diego@chem.ucla.edu, Department of Chemistry and Biochemistry, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095-1569, and J Fraser Stoddart, stoddart@chem.ucla.edu, Department of Chemistry and Biochemistry, University of California Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095-1569.
The molecular construction of the Borromean Ring (BR) topology has been achieved successfully from 18 individual components under dynamic control that characterizes not only the noncovalent, but also the coordinative and covalent bonds formed in the molecules. This dynamic covalent chemistry (DCC) assembly process is dependent on the ability of the system to control the placement of 12 organic ligands around six transition metal (zinc) ions in near quantitative yields. This molecular BR topology provides a unique symmetrical, nanoscale three-dimensional scaffold onto which unique features can be embedded at will. In this sense, the BRs could serve as building blocks for the formation of mesoporous coordination polymers. The significance of this research is to introduce a further level of sophistication structure-wise into the metal containing BRs via the construction (Box) of a dynamic network of BRs. Two synthetic approaches are being explored in order to afford the desired networks – A) divergent synthesis employing olefin metathesis – this approach takes advantage of the wide applicability and reasonable selectivity of ruthenium-catalyzed olefin metathesis, we envisaged that it can be used to attach olefinic substrates in a pre-assembly fashion to the molecular BRs. Once the hexasubstituted Borromeates have been formed, Acyclic Diene Metathesis Polymerization (ADMET) is employed to afford a reversible, dynamic BR network; and B) convergent synthesis in which the building blocks of the BRs are altered strategically. In this context, the tridentate pyridine diimine precursor is synthetically adapted to incorporate four sites for imine bond formation (cf. two in the original BR synthesis). This subtle alteration also facilitates the testing of the limits of the tried-and-tested, all-in-one synthetic approach in an attempt to synthesize the next generation BR frameworks that depend upon the reliable DCC protocol.

 

Total Synthesis, Materials, Molecular Recognition, Process R&D, and Physical Organic Chemistry
8:00 PM-10:00 PM, Wednesday, 13 September 2006 Moscone Center -- Hall D, Poster

Division of Organic Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006