Theoretical study to evaluate polyfuran electrical conductivity and methylamine, methoxy substituent effects

There is a lot of interest from the scientific and technological point of view in the use of furan-based polymer molecules as electroconducting polymers despite some difficulties in their synthesis. In order to shed some light into the factors that affect the electrical conducting properties of furan-based polymers a theoretical study on methylamine and methoxy mono-substituted furan oligomers was performed. The purpose in choosing these substituents is founded on their electro-donning nature, which could have a favorable role on the reactivity of polyfuran molecules and have a direct effect on the band gap (Eg) and ionization potential (IP) facilitating in this way the synthesis of furan-based polymers. In addition the substituents were tested on different ring positions. All molecular geometries were optimized at B3LYP/6-31G(d) level of theory. Energy gaps between HOMO and LUMO orbitals and IPs were obtained from these calculations. IPs, and Egs of the polymers were obtained by extrapolating those of the oligomers to the inverse chain length equal to zero (1/N = 0). The theoretical calculations show that substituted oligomers are stable and have a minor value of Eg and IP in their ground and doubly charged states. It was found that the carbon-carbon bond lengths in the oligomers are distorted in the charged states. This is due to the partial loss of ring aromaticity which forces some bond lengths to shorten or lengthen probably caused by the formation of quinoid-like structures.