Conformational Analysis of a Furan, Thiophene Alternating Π System

Cline, Laura (2016) Conformational Analysis of a Furan, Thiophene Alternating Π System. Undergraduate thesis, under the direction of Gregory Tschumper from Chemistry & Biochemistry, University of Mississippi, College of Liberal Arts.

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Abstract

Organic materials with conjugated π-electron networks are increasingly being studied as an alternative to inorganic semiconductors. In order to effectively transport charge as a semiconductor, the organic materials should maintain a planar conformation, exhibit π conjugation, and be rigid to rotational interconversion. Both furan and thiophene systems have been investigated as potential organic semiconductors but difficulties with solubility, synthesis, and effectiveness hampered these efforts. A novel furan-thiophene hybrid system that exhibits promising semiconducting properties is examined here. Full geometry optimizations and corresponding harmonic vibrational frequency computations were run on a diverse set of potential furan and thiophene oligomer structures using the GAUSSIAN09 software package. Scans of the potential energy surface were also computed in order to determine the rigidity of the system. All computations were done at the B3LYP/6-31G(d,p) level of theory. Overall, it was determined that the hybrid systems consisting of alternating furan and thiophene rings stemming from a central benzothiadiazole (BTD) ring have promising structural properties. The most promising structures were ones with low relative energies, high rotational barriers, and planar conformations. The lowest energy structures are those in which the furan rings are directly connected to the central BTD ring and adopt an anti polarity to the furan O atom away from the S atom in BTD. As subsequent rings are added to the system, the rotational barrier is largely unchanged, with little preference to the conformation of these additional rings.

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