Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Saebo, Svein

Committee Member

Sygula, Andrzej

Committee Member

Gwaltney, Steven R.

Committee Member

Zhang, Dongmao

Committee Member

Henry, William P.

Date of Degree

12-14-2013

Document Type

Dissertation - Open Access

Major

Chemistry

Degree Name

Doctor of Philosophy

College

College of Arts and Sciences

Department

Department of Chemistry

Abstract

Theoretical studies of pi-pi interactions on several dimers of curved polycyclic aromatic systems have been carried out. In the first part, dispersion corrected density functional theory methods (DC-DFT) were used to evaluate the basis set superposition errors (BSSE) in dispersion interactions of the corannulene dimer, and the accuracy of the calculations using DC-DFT methods was compared with high level benchmark calculations. In these calculations, Grimme’s B97D DC-DFT method provided reasonably accurate results with the benchmark calculations. In addition, BSSE obtained with the B97D method along with cc-pVQZ basis set was negligible. Furthermore, a series of calculations were carried out to obtain the pi-pi interaction energy and most stable conformation for the sumanene dimer system. In these calculations, Grimme’s B97D method was used. The potential energy minimum of the sumanene dimer was determined as the concave-convex stacked arrangement with one monomer unit rotated to 60°. The binding energy of the dimer was found to be 19.34 kcal/mol with a 3.72 angstrom distance between two monomer units. Dimers of three different heterosumanenes along with the parent sumanene were also studied. In this set of calculations, two different concave-convex dimer motifs were chosen, eclipsed and staggered (60° rotated). For all the heterosumanenes, as well as the parent sumanene, the staggered conformation is the most stable geometry. The parent sumanene had the highest binding energy. The –NH substituted sumanene produced the second highest binding energy, while the –O analog was the weakest bonded dimer. Finally, dispersion calculations were carried out for the planar aromatic compound of triphenylene. The pi-system of the dimer was distorted by rotating one monomer unit around the principle axis and parallel displacing one monomer unit relative to the other one. Among the rotational dimers, the 39° rotated dimer was the minimum energy conformation. Interaction energy of that dimer was 14.42 kcal/mol with 3.40 angstrom separation between monomers at the B97D/cc-pVQZ level. The parallel displaced minimum energy dimer has a binding energy about 1.0 kcal/mol smaller than the rotational minimum energy geometry.

URI

https://hdl.handle.net/11668/18702

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