Mobius Twist Localization

Posted May 7th, 2010 at 3:04 pm.

Ashley Donovan

Mentor: Dr. Michelle Francl

Theoretical chemists have long been intrigued by molecules frequently dubbed as ‘topologically interesting.’ A molecule of particular interest is the ‘Mobiusene,’ seen in Fig. 1. In 1964, E. Heilbronner suggested that a large [4n]annulene might be reformed to mimic the structure of a Mobius strip, a one-sided, non-orientable structure; perhaps not surprisingly, despite Heilbronner’s belief that this amendment to the structure might in fact be stabilizing, the synthesis of these molecules has proved to be extremely challenging. It was reported in 2003 that a molecule of this sort had been successfully synthesized, but what invariably remains is a question that has aroused the interest of chemists and mathematicians alike: why is the twist in the Mobius band localized?

Figure 1
[n]Mobiusene

It is hoped that, with extensive investigation into the physical properties of these molecules through computational chemistry techniques and advanced mathematics (including, but not limited to, topology and differential geometry), a chemically useful answer can be used to obtain the twist localization. A computational program called Gaussian 03 will be employed, first in order to build molecular models that can be tested via quantum mechanical methods to check for energetic minima, and second to modify these minima to see whether ‘extending’ the twist lowers the energy and thus stabilizes the molecule. Other properties of the Mobiusenes that will be probed include aromaticity around the twist and determining whether a linear versus alternating benzene pattern is more conducive to a stable compound:

linear

linear

versus

alternating
alternating

While the synthesis of this molecule is not the goal, it is believed that results obtained from this summer’s research will help in understanding how to most effectively synthesize this compound; in fact, molecules of potential synthetic interest include the [n]phenacenes studied and synthesized in Dr. Frank Mallory’s laboratory. Although the research approach to be taken this summer is more theoretical in nature, it is believed that Mobiusenes could be applied in the ongoing development of biochemical, medicinal, and nanochemical technologies.

Filed under: 2005,Donovan, Ashley,Francl, Dr. Michelle by Ann Dixon

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