An experimental and quantum mechanical study on electrochemical properties of N-substituted pyrroles

In this study, successful electropolymerization of a series of N-substituted monomers are reported for the first time at the same reaction conditions in a comparative sense. The electronic properties from quantum mechanical calculations (DFT B3LYP/6-31+G*) and electrochemical properties from the experiment are surveyed. The linear relationship between the inverse chain length and HOMO and HOMO-LUMO energy values of 1-Phenyl-1H-pyrrole allowed us to calculate the ionization energy and the band gap as 3.35 and 2.81 eV, respectively. The linear correlation between the Hammett parameters and the calculated HOMO energies with high regression coefficient has demonstrated the electronic effects of substituents to be important on redox behavior. The correlations between the experimental electrochemical data produced in this study and the calculated molecular orbital energies have shown a relationship between the reversibility of the process and the molecular orbital energy levels, which are in turn related to the nature of substitution. (c) 2008 Elsevier B.V. All rights reserved.