Tag: Organic Chemistry

Synthesis of 6,13-pentacene-incorporated [10]cycloparaphenylene

Presenter(s): Cyrus Waters − Biochemistry

Faculty Mentor(s): Ramesh Jasti, Brittany White

Poster 20

Research Area: Organic Chemistry

Funding: SAACS Summer Research Award

Cycloparaphenylenes (CPPs) have size-dependent optoelectronic properties: the HOMO/LUMO gap size increases as benzene subunits are added. This capacity to tune the band gap makes CPPs attractive for use in organic electronic devices. Similarly, pentacene shows promise as a component of photovoltaic cells because of its uniquely high capacity for singlet fission (SF), whereby one high-energy incident photon is harnessed to yield two lower-energy triplets. In devices sensitized to SF, two electrons can be pushed per photon, bypassing the Shockley-Queisser efficiency limit and doubling the photocurrent from specific wavelengths of absorbed light relative to traditional, silicon-based photovoltaics. Pentacene-incorporated CPPs combine the two structures in a fully-conjugated system, potentially allowing the size of the CPP to control the energy of light at which the pentacene undergoes SF. Here, the synthesis of 6,13-pentacene-incorporated [10]cycloparaphenylene was attempted. Suzuki coupling of selectively-linked curved precursors yielded a strained macrocyclic intermediate. Attempts at reductive aromatization of the macrocycle have successfully aromatized the CPP backbone but have failed to aromatize the pentacene unit, instead yielding either the insufficiently reduced diol or its overly reduced dihydrogen analogue.

Synthesis of 7,14-Diarylfluoreno[3,2-b]fluorenes

Presenter(s): Tristan Mistkawi − Biochemistry

Faculty Mentor(s): Josh Barker, Michael Haley

Poster 74

Research Area: Organic Chemistry (Natural/Physical Science)

Funding: UROP Mini-grant

The Haley group is interested in a class of organic molecules, known as the indenofluorene (IF) scaffold, for potential use as organic semiconductors (OSCs) in electronic devices. IFs show great promise as OSCs because of their ability to easily and reversibly accept electrons. Similarly to the well-known class of acene OSCs, we are interested in studying the effect of extending IF scaffold -conjugation to discover trends in electronic properties. While other researchers in the literature have studied compounds with similar properties, no one has performed a rational, systematic study. This work requires exploring the synthesis of several 7,14-diarylfluoreno[3,2-b]fluorenes (FFs) to compare to structurally related molecules in the IF scaffold. Along with affecting the optoelectronic properties of FFs, substituting different aryl groups at specific positions on the molecule is important for crystal engineering, which will help improve our understanding of this novel scaffold. Many derivatives have not been explored yet, and studying solid-state packing interactions may improve device performance and influence our ability to implement these compounds as organic semiconductors.

Synthesis of Alkyne Substituted Cycloparaphenylenes for Conjugated Polymers

Presenter(s): William Edgell − Biochemistry

Faculty Mentor(s): Ramesh Jasti

Poster 69

Research Area: Organic Synthetic Chemistry

Funding: Undergraduate Research Opportunities Program (UROP)

Conjugated polymers possess excellent conductive properties that could facilitate the construction of light weight flexible electronics. This potential application makes an efficient route to conjugated polymers synthetically desirable. The current barrier to large-scale synthesis of these molecules is an inversely proportional relationship between solubility and conductivity. The sought-after conductivity is due to charge transfer across a conjugated π system within the polymer. This affords the polymers with electronic properties atypical of organic molecules. Unfortunately, intermolecular stacking of these π systems leads to poor solubility. Cycloparaphenylenes(CPPs) offer a solution for this conflict between solubility and charge transfer. CPPs are large hoops of strained benzene rings which possess a conjugated π system without a clear avenue for π stacking. A CPP polymer would form a sort of molecular necklace; with large bulky hoops hanging off the polymer backbone, the potential polymers would not stack well with each other, thus reducing chance of aggregation. Utilization of the CPPs as monomers for polymer synthesis could produce a polymer chain with the ideal electrical properties without diminishing the solubility. To this end, this research project focuses on the synthesis of the CPP monomers to be used for the polymer reaction. Creating this highly strained hoop requires a series of reactions to form a string of benzene rings that will be coupled to a single alkyne functionalized benzene. Previous work shows challenges in the route that yields the eight ring CPP. Current work has yielded successful synthesis of functionalized six ring cycloparaphenylene.