Controlling Interlocked Molecular Machines Through Coordination Chemistry

Date of Award


Publication Type

Doctoral Thesis

Degree Name



Chemistry and Biochemistry


Chemistry, Inorganic.


Loeb, Stephen (Chemistry and Biochemistry)




This thesis presents the design, synthesis and characterization of the [2]pseudorotaxanes and [2]rotaxanes for the purpose of designing a range of new interlocked molecular machines utilizing a 2,2':6'2"-terpyridine based thread and 24- crown-8 macrocycle as beads. Chapter 1 introduces the concepts of interpenetrated and interlocked compounds like pseudorotaxanes, rotaxanes, catenanes and also defines the molecular machines with representative examples of existing systems found throughout the literature. Chapter 2 presents a designing of metal coordination controlled molecular switch in which a chelating group has been incoorporated into the cationic dipyridyl ethane thread. In this chapter, pseudorotaxanes containing a tridentate terpyridine (terpy) group are designed in order to prove that the threading and unthreading of [2]pseudorotaxanes can be manipulated by controlling the coordination geometry of the terpy group attached to the thread. Chapter 3 presents a designing of another metal coordination controlled molecular machine named a mechanical flip-switch, using an unsymmetrical thread and unsymmetrical crown ether. The chapter provides the evidence that an unsymmetrical [2]rotaxane can exist in two distinct co-conformations and the relative ratio of these two co-conformations can be controlled by changing the coordination environment. Room temperature NMR method is established for the analysis. Chapter 4 describes the introduction of strong electrostatic ion-ion interactions to a coordination controlled flip-switch. This chapter provides the evidence that adding sulfonate group to the crown ether can significantly increase the Ka of the [2]pseudorotaxane, formed using positively charged 2,2':6'2"-terpyridine based thread and a negatively charged 24-crown-8ether beads containing one sulfonate (SO3-) functionalities. [2] rotaxane with long chain ester groups was synthesized by modifying the bulky stopper groups. The bulky diester end groups were substituted with alkyl chains with six units in order to increase the solubility of rotaxanes in non-polar solvents.

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