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Title page for ETD etd-01112017-115010


Type of Document Dissertation
Author Engerer, Laura Kathryn
Author's Email Address Laura.Engerer@gmail.com
URN etd-01112017-115010
Title Investigations of non-covalent bonding: synthesis-aided calculations
Degree PhD
Department Chemistry
Advisory Committee
Advisor Name Title
Timothy P. Hanusa, Ph.D. Committee Chair
Charles M. Lukehart, Ph.D Committee Member
D. Greg Walker, Ph.D. Committee Member
David W. Wright , Ph.D. Committee Member
Keywords
  • manganese(II)
  • cation-π
  • computational
  • dispersion-corrected functionals
Date of Defense 2016-12-12
Availability unrestricted
Abstract
This work describes three separate projects, for which Density Functional Theory (DFT)

computations provide a unifying theme. The DFT approach gives a theoretically sound way to

model the chemical and physical properties of a system based its electron density. Although the

exact functional has been proven to exist, its form is not completely known and so all calculations

are completed with various approximations, which sometimes seriously affect the results.

Conventional functionals, for example, fail to account for dispersion corrections adequately, and

consequently dispersion-corrected functionals were used extensively in this work.

Cation-π interactions involve the largely noncovalent attraction of a cation with a ligand's p-

electrons, which are often those of an arene or a heteroarene. These interactions incorporate

electrostatic, inductive, and charge transfer effects, and in some cases, dispersion forces. Factors

that could affect the strength of cation-p interactions were examined with the use of a simple

geometric model. A chief finding was that the relationship between the strength of the

interaction and the number of π-bonds involved is not linear. Asymmetric cation-π interactions

(i.e., those in which the cations are not in line with the centers of π-electron density) were also

examined; despite their relative weakness compared to more symmetric arrangements, they can

contribute considerably to the total bonding energy in molecules.

The σ- and π-bonding in high-spin manganese(II) allyls was examined with the aid of DFT

methods. Comparisons were made to structurally similar magnesium allyls, as neither of these

similarly-sized cations (Mn2+/Mg2+) provide ligand field stability to their compounds.

The structure and bonding of group 2 and 14 metallocenes were studied with dispersion-

corrected functionals. Metallocene compounds of calcium, strontium, and barium commonly

display non-linear Cp-M-Cp (Cp = cyclopentadienyl) angles. Of the various explanations for this

phenomenon, dispersion interactions between the cyclopentadienyl rings are among the most

difficult to model computationally. Presently available DFT methods are not able to provide

unambiguous evidence for the source(s) of the non-linear structures.

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