Graduate Program
Chemistry
Degree Name
Master of Science (MS)
Semester of Degree Completion
2013
Thesis Director
Radu F. Semeniuc
Thesis Committee Member
Mark E. McGuire
Thesis Committee Member
Douglas G. Klarup
Thesis Committee Member
Zhiqing Yan
Abstract
The host-guest abilities of macrocyclic compounds made them important players in the field of supramolecular chemistry, especially those studying mechanical bonds. Rotaxanes and catenanes are among the most well-known examples of mechanically interlocked molecules. Our approach in the synthesis of poly-rotaxane systems involves the preparation of pseudorotaxanes with donor capabilities and then use metallic centers to assemble the poly-rotaxane architectures.
A pyridine-based half-rotaxane has been synthesized and the subsequent solution studies revealed a large association constant. 1H-NMR studies show that these interlocked species exhibit a slow exchange on the NMR timescale. Using the single point method and VT-NMR several thermodynamic parameters were calculated. Our studies determined that the association process is enthalpically favorable and entropically disfavorable. Solid state studies were employed to evaluate the ability of the pyridine group in the pseudorotaxane to exhibit metal coordination. These studies determined the orientation of the macrocycle leaves the pyridine nitrogen available for metal coordination.
Metal complexes of this rota-ligand have been also prepared, using rhodium and rhenium metallic centers. Solution studies of the Rh-based [3]rotaxane revealed that the rhodium acetate dimer and rota-ligand assembled, however, there were two species in solution: the [3]Rotaxane and free axle coordinated to the rhodium atoms. Influence of the interlocked structure on absorption properties revealed there is no change in the UV region with the coordination of the half-rotaxane to the rhodium dimer. Solid state studies demonstrated the formation of the [3]rotaxane, by coordination of two half-rotaxanes to the rhodium dimer.
In order to study the effects of the interlocked architecture on emission a rhenium complex was assembled. Absorption studies on the half-rotaxane coordinated to the rhenium metal center had no significant effects on absorption properties, however, there was a slight increase in the absorption intensity. Likewise, there was no significant change in emission properties, however, the addition of the interlocked architecture slightly quenched the fluorescence.
Recommended Citation
Schoonover, Heather Renee, "From Half-Rotaxanes to Poly-Rotaxane Architectures" (2013). Masters Theses. 1156.
https://thekeep.eiu.edu/theses/1156
