Graduate Program

Chemistry

Degree Name

Master of Science (MS)

Semester of Degree Completion

Summer 2021

Thesis Director

Radu F. Semeniuc

Thesis Committee Member

Gopal R. Periyannan

Thesis Committee Member

Zhiqing Yan

Thesis Committee Member

Michael W. Beck

Abstract

Mechanically interlocked molecules (MIMs) are arranged with mechanical bonds. These molecules cannot be separated without breaking the required covalent bonds. There are different kinds of MIMs, such as rotaxanes, catenanes, suitanes, borromean rings, and molecular knots. These MIMs are stabilized by non-covalent interactions such as hydrogen bonds, π-π stacking, and ion-dipole interactions. Dialkylammonium ions, bis(pyridinium)ethane dications, viologen species, and naphthalene diimide π-deficient groups are typical examples of recognition motifs for crown ethers.

In the research described here, we synthesized a new axle, based on a combination of benzobis(imidazolium) (BBI) and viologen species. The axle contains two recognition sites: one is at BBI salt and the second one is at the viologen part. These axles form pseudorotaxanes with the bis-1,5(dinaphtho)-38-crown-10 (15DN38C10) and dibenzo-24-crown-8 (DB24C8). We named this species “two station starburst pseudorotaxanes”. When the axle forms pseudorotaxanes with 15DN38C10, and the crown is positioned on the BBI moiety it is referred as starburst [24]pseudorotaxanes, where the first number 2 represents total number of components (one axle + one ring), and the second number 4 (as subscript) represents the number of the arms protruding from the center of the crown.

According to 1H-NMR studies, the pseudorotaxanes display a rapid exchange on the NMR timescale. We performed NMR titrations in acetone-d6 at 293 K, to calculate the association constant Ka.

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