Molecular architectonics and electronics

ORGN 347

J. Fraser Stoddart, stoddart@chem.ucla.edu1, Amar Flood, aflood@indiana.edu2, William R. Dichtel, wdichtel@chem.ucla.edu1, Ken C-F. Leung, cfleung@chem.ucla.edu1, Ognjen S. Miljanic, miljanic@chem.ucla.edu1, Sourav Saha1, Ivan Aprahamian1, Taichi Ikeda, ikeda@chem.ucla.edu1, and Soo-Young Kim1. (1) California NanoSystems Institute and Department of Chemistry and Biochemistry, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095-1569, (2) Department of Chemistry, Indiana University, Bloomington, IN 47405
We will report on the kinetics and thermodynamics associated with the electrochemically driven molecular mechanical switching of the bistable [2]rotaxanes A and B in solution, polymer electrolyte gels and molecular-switch tunnel junctions (MSTJs). For all the rotaxanes, an electron-deficient cyclobis(paraquat-p-phenylene) (CBPQT4+) ring component encircles one of two recognition sites within a dumbbell component. The [2]rotaxanes contain tetrathiafulvalene (TTF) / monopyrrolotetrathiafulvalene (MPTTF) / bispyrrolotetrathiafulvalene (BPTTF) and 1,5-dioxynaphthalene (DNP) recognition units. Oxidation of the TTF (MPTTF or BPTTF) unit is accompanied by movement of the CBPQT4+ ring to the DNP site. Reduction back to TTF is followed by relaxation to the equilibrium distribution of translational isomers. The relaxation kinetics are strongly environmentally dependent, yet consistent with a single switching mechanism. The ground-state equilibrium properties of the bistable [2]rotaxanes A and B were reflective of molecular structure in all environments. These results provide direct evidence for the control by molecular structure of the electronic properties exhibited by the MSTJs. Moreover, the switchable, bistable [2]rotaxane C containing a rigid and linear backbone was constructed. This new rigid bistable [2]rotaxane will enhance the superstructural integrity in the cross-bar device as well as switching in self-assembling monolayers. The redox-switching process of the bistable [2]rotaxane will be discussed. This accurate switching process gives rise to two different electron-conducting environments when the molecules are sandwiched between two electrodes thus permitting them to function as molecular memory. Finally, we have also developed a highly convergent approach to the synthesis of electrochemically switchable mechanically interlocked molecules. The Cu(I)-catalyzed 1,3-cycloaddition of organic azides and alkynes (click chemistry) has been utilized to efficiently prepare [2], [3], and [4]rotaxanes and catenanes, many of which were synthetically inaccessible before the development of this methodology. New methods of incorporating interlocked molecules and polymeric materials into molecular electronic devices using click chemistry will also be discussed.

 

Organic Approaches to Nanotechnology
8:00 AM-12:00 PM, Tuesday, 12 September 2006 Moscone Center -- Room 135, Oral

Division of Organic Chemistry

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