With this CAREER Award, the Chemical Synthesis Program of the Chemistry Division supports the research of Professor Bradley L. Merner at Auburn University. The main objective of Professor Merner's research is to develop new strategies for the controlled synthesis of carbon nanotubes. At the present, one of the chief problems interfering with the synthesis of carbon nanotubes is our inability to make them in a uniform manner. Modern carbon nanotube syntheses lead to mixtures that complicate correlations between nanotube structure and physical properties. To address this gap, the Merner group is developing the synthetic tools needed to build smaller sections of a carbon nanotube that can then be assembled into larger nanotubes in a systematic way. By controlling the size of the smaller pieces, the size of the larger nanotube can be intentionally controlled. Since carbon nanotubes are made of a series of benzene rings that are stitched together, the synthesis initially targets larger cyclic systems that contain both multiple benzene rings and the functionality needed to bind the them together and build the targeted nanotubes. The lynchpin of this approach is the use of an unstrained benzene surrogate during the construction of the larger rings. Once those rings are assembled, then strained, bent benzene rings are released so they are trapped with in the larger ring structure. The route offers many opportunities to access carbon nanotube building blocks that were previously unavailable. The educational component of the program involves the development of chemical synthesis-teaching modules that are offered to rising junior and senior-level high school students in the Southeast region as part of the Auburn University Summer Science Institute. Underrepresented undergraduate students wishing to pursue graduate-level training in STEM-related fields participate in a chemical synthesis summer research program. Furthermore, in order to expose more undergraduate students to graduate-level research experiences, students enrolled in honors organic chemistry at Auburn University synthesize important starting materials that are used in future synthetic method development by graduate students in Professor Merner's laboratory.

Carbon nanotubes are of great interest in the fields of materials science, engineering and biological sensing. However their use in these areas is hampered by the inability to access carbon nanotubes that are of a defined, homogenous structure. In this research project, Professor Merner and his group are tackling this challenge with new synthetic strategies that imbed the nonplanar benzene rings that comprise carbon nanotubes within functionalized polycyclic building blocks. This is an important step in the construction of uniform carbon nanotubes because if the size and shape of the building blocks can be controlled, then the size and shape of the nanotube assembled from the building blocks can be controlled. In this project, the molecular complexity of the building blocks are increased systematically so that they can better understand the reactivity of strained molecules, possible releases of this strain energy to afford undesired by-products, and the reaction mechanisms by which these processes occur. This information guides the synthesis of the more complex systems eventually culminating in the construction of the carbon nanotubes themselves. The initial strategy being pursued uses a non-cross-coupling-based approach to prepare macrocyclic, functionalized carbon nanotube substructures. These functionalized systems are employed in programmed, late-stage carbon-carbon bond forming reactions to build larger structures. Several annulation strategies to join adjacent arenes are investigated and the reactions afford pi-extended macrocyclic segments that are representative of carbon nanotube sidewall structures. The target structures not only lead to development of new chemical tools for accessing these complex organic molecules, but also provide first-rate training in chemical synthesis to undergraduate and graduate students, and deepen the understanding of chemical reactivity in strained, complex hydrocarbons.

Agency
National Science Foundation (NSF)
Institute
Division of Chemistry (CHE)
Application #
1654691
Program Officer
Jin Cha
Project Start
Project End
Budget Start
2017-05-01
Budget End
2022-04-30
Support Year
Fiscal Year
2016
Total Cost
$699,993
Indirect Cost
Name
Auburn University
Department
Type
DUNS #
City
Auburn
State
AL
Country
United States
Zip Code
36832