ORGN 186 |
Mecanochemistry of molecular shuttles based on tetrathiafulvalene units and 1,5-dioxynaphthalene ring systems
| Seogshin Kang, Scott Vignon, Brian Northrop, Hsian Rong Tseng, and J Fraser Stoddart. Department of Chemistry and Biochemistry, California NanoSystems Institute, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095 |
| Kinetic and thermodynamic data for shuttling in a series of degenerate [2]rotaxanes are presented. The [2]rotaxanes contain either two tetrathiafulvalene (TTF) units or two 1,5-dioxynaphthalene (DNP) ring systems along their dumbbell component as the recognition sites for a cyclobis(paraquat-p-phenylene) (CBPQT4+) macrocycle. The recognition sites are linked with one of three different spacers in order to investigate the effect of the spacers on the rate of the shuttling process. Dynamic 1H NMR spectroscopy shows that the barrier (ΔG≠) for shuttling between two DNP ring systems (15 kcal/mol) is 3 kcal/mol lower than the barrier in the case of two TTF units (18 kcal/mol). The effect of the spacer is not observed in the ΔG≠ value, but in the enthalpic and entropic activation parameters. This thermodynamic data will be compared to force measurements obtained utilizing force spectroscopy for deslipping of the CBPQT4+ macrocycle along the dumbbell component of a non-degenerate [2]rotaxane bearing TTF and DNP unit. 
|
| |
|
Asymmetric Reactions and Syntheses, Metal-Mediated Reactions, Materials, Molecular Recognition
8:00 PM-10:00 PM, Sunday, August 22, 2004 Pennsylvania Convention Center -- Hall D, Poster
Sci-Mix
8:00 PM-10:00 PM, Monday, August 23, 2004 Pennsylvania Convention Center -- Hall D, Sci-Mix
Division of Organic Chemistry
The 228th ACS National Meeting, in Philadelphia, PA, August 22-26, 2004
|