Synthesis and characterization of dis-assemblage rotaxanes with unique blocking groups.

Abstract

By Natalie Scott, Chemistry

Advisor: David Smithrud

Presentation ID: AM_D27

Abstract: Rotaxanes are a new class of molecular machines. Their wheel can slide and pirouette around an axle without falling off due to the presence of blocking groups. Inner components of the machine are able to shift position on the molecule in response to certain stimuli, resulting in a new class of sensors. Recently, dis-assemblage rotaxanes have been constructed and investigated as possible sensors. For example, an external stimulus clips off a blocking group to release the wheel, separating the rotaxane components. These rotaxanes require at least one unique blocking group that is chemically sensitive to a stimuli. One problem with this approach is that the unique blocking group is usually insoluble in an apolar solvent needed to form rotaxanes. My project is to determine whether decreasing the polarity of an axle would increase the yield of rotaxane formation. The unique blocking group is more polar by being smaller than traditional blocking groups. High temperature will be the stimulus to dis-assemble the rotaxane with the wheel slipping over the unique blocking group. Synthesis of the rotaxane requires a multistep approach. 1H NMR analyses were used to assess the structures of intermediate components and final rotaxane.