Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Sygula, Andrzej

Committee Member

Zhang, Dongmao

Committee Member

Henry, William P.

Committee Member

Mead, Keith T.

Committee Member

Foster, Stephen C.

Date of Degree

5-11-2013

Original embargo terms

MSU Only Indefinitely

Document Type

Dissertation - Campus Access Only

Major

Chemistry

Degree Name

Doctor of Philosophy

College

College of Arts and Sciences

Department

Department of Chemistry

Abstract

The study of polycyclic aromatic hydrocarbons (PAHs) with curved surfaces, also known as buckybowls or fullerene fragments, represent an area which is under intense investigation by organic chemists and material scientists. This dissertation describes research that contributes to this field. The availability of multi-gram quantities of the smallest buckybowl, corannulene, has led to the synthesis of several larger systems with buckybowl subunits. Cyclotrimerization of corannulyne using palladium(0) as the catalyst is described. The resulting product, C60H24, is a highly nonplanar hydrocarbon with very interesting conformational dynamics. The X-ray crystallography of the cyclotrimer confirms the “twist” conformation with C1 symmetry. The cyclotrimer also shows three distinct corannulene bowls with very different inversion barriers as confirmed by both experiment and calculations. The bowl to bowl inversion of the corannulene bowl with the lowest inversion barrier results in pseudorotation of the cyclotrimer, which gives rise to a symmetrized 1H NMR spectrum exhibiting 12 distinct proton signals. 1H NMR line shape analysis gives an estimation of the inversion barrier at 8.5 – 8.6 kcal/mol. The tetrameric hydrocarbon C80H32 was synthesized through the Diels-Alder reaction of the cyclotrimer and 1,2-didehydrocorannulene. The six membered rings adjacent to the central ring in the cyclotrimer are activated enough to react with another corannulyne. The tetramer exhibits different conformational and optical absorption properties when compared to the cyclotrimer. The tetramer (C80H32), which is highly nonplanar and sterically congested, represents the largest fully characterized oligomer of corannulyne reported to date. This is also the first reported example of a cycloaddition reaction in which a corannulene subunit acts as a diene. A tripodal molecular receptor (C87H54O6) with three corannulene pincers and a cyclotriveratrylene tether was synthesized. The molecular receptor was evaluated by 1H NMR titration in toluene-d8 for its ability to bind fullerenes. The experiment demonstrates the formation of 1:1 inclusion complexes of the molecular receptor with fullerenes and provides the association constants of 1500 plus or minus 50 and 1180 plus or minus 30 M-1 for C60 and C70, respectively.

URI

https://hdl.handle.net/11668/20619

Comments

molecular clips||fullerene complexes||cyclotrimerization||corannulene

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