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
- dispersion-corrected functionals
Date of Defense 2016-12-12 Availability unrestricted AbstractThis 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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