Abstract:
Pyrroles, thiophenes and furans represent building blocks conjugated poly(heterocycles)
which, as organic conductors are potential materials for various applications. Oxidation of βsubstituted
pyrroles, thiophenes and furans constitutes an important first step in the process of
electroplymerization. Key electrochemical parameters such as function coefficient (Fn),
atomic charge distribution, ionization potential (IP) and bandgap and salvation energy are
most important properties regarding monomers and their radical cations. These properties
are studied as a function of electron withdrawing and electron donating substituent of pyrrole,
thiophene and furan ring and studied as a function of solvent polarity. Evaluation of
electrical, structural and thermodynamic properties the monomers and their corresponding
radical cations are studied as an effect on various electrochemical parameters using density
functional theory (DFT) and B3LYP methods with 6-31G(d, p) and 6-31++G(d, p) basis set in
solution phase using Polarized Continuum Model (PCM) method. The theoretical calculation
indicates electron-withdrawing solvents increase the IP while electron-donating groups
decrease the value and hence contributing for easer oxidation step. It was also observed that
dipole moment, Fn, atomic charge distribution and bandgap follows generally the order
pyrroles > furans > thiophenes. Besides, the results showed that charge distribution decrease
with polarity of solvent and in the case of electron donating group whereas solvent polarity on
Fn have no significant effect. On the other hand, bandgap of monomers are greater than their
radical cations indicating the stability of the monomers. Generally, the DFT calculation demonstrates that efficiency of polymerization is affected with the nature of substituent and
solvent polarity.
