COLL 432 |
| Jeffrey I. Zink1, Payam Minoofar2, Raquel Harnandez1, B. Dunn1, and J Fraser Stoddart3. (1) Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive East, Room 2505 MSB, Los Angeles, CA 90095-1569, (2) Department of Chemistry, UCLA, 405 Hilgard Ave, Los Angeles, CA 91403, (3) Department of Chemistry and Biochemistry, California NanoSystems Institute, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095-1569 |
| Functional mesostructured films are synthesized by incorporating appropriate molecules designed to carry out the desired function. A dip-coating method that allows one or more molecules to be deliberately placed in specified spatially separated regions of mesostructured silicate materials in a one step synthesis has recently been developed. The mesostructured thin films contain three distinct regions: the silica framework, the organic non-polar region in the hydrophobic interior of the micelle, and the ionic interface between the charged surfactant head groups and the silica pore surface. Three strategies, succinctly termed "philicity" (or like dissolves like), “bonding”, and “bifunctionality”, have been developed for incorporating molecules and directing them to any one of the regions. Deliberate simultaneous placement of two different molecules in two different regions has also been demonstrated. Such placement and the maintenance of long range order requires a delicate balance among film preparation methodology, design of the molecules to be incorporated in specific regions, and concentrations of all of the species. Energy or electron transfer properties are designed by choosing pairs of molecules (one a donor and the other an appropriate acceptor) that are spatially separated in the regions of the films. Detailed studies of energy transfer use a chelated lanthanide as the donor and a rhodamine derivative as the acceptor. Electron transfer is studied using a trisbipyridylruthenium derivative as the electron donor and a substituted viologen as the acceptor A functioning nano-machine in the form of a supramolecular nanovalve that opens and closes the orifices to a nanocontainer made out of mesoporous silica and releases a small number of molecules on demand will also be discussed. The nanovalve, which is used to open and close the mesopores, is a pseudorotaxane composed of two components – a long thread containing a 1,5-dioxnaphthalene donor unit, which is attached to the solid support, and the moving part, the tetracationic cyclophane acceptor/receptor, cyclobis(paraquat-p-phenylene), which controls access to the interior of the nanopore. This nanovalve is a supramolecular machine consisting of a solid framework with moving parts capable of doing useful work. |
|
Symposium in Memory of Arthur W. Adamson
2:00 PM-5:40 PM, Wednesday, March 31, 2004 Marriott -- Orange County 4, Oral
Division of Colloid and Surface Chemistry |