Investigation of the Conductivity Properties of Pyrrole with the Attachment of Electron-Donating Groups (–NH2) and (–Cl) as Substituents

The rapid advancements in science and technology have created the need for the production of new materials with distinct physical and chemical properties, ease of production, and a wide range of applications. Conductive polymers can be used to modify conductivity properties. One method for achieving this modification is by adding different substituents to the monomer. For this purpose, the HOMO-LUMO gap was measured by substituting electron-donating groups (–NH2 and –Cl) in place of the methyl groups in the phenyl groups of 1-(4-methylphenyl)pyrrole and 3-(4-methylphenyl)pyrrole. The interactions when the substituted phenyl group was attached at the nitrogen position or the carbon position were calculated using the Gaussian16 software package. The configurations obtained were optimized by increasing the chain length from n=1 to n=5. Additionally, the topological properties of the interactions were compared based on electron densities. It was observed that electron-donating groups increased the HOMO energy and decreased the LUMO energy, thereby reducing the band gap and enhancing conductivity. The fact that electron densities are in the opposite direction to conductivity shows that AIM theory is a preferable and reliable method for determining conductivity. The incorporation of –Cl and –NH₂ substituents leads to significant changes in the IR spectral properties. Subsequent polymerization results in changes in band intensity and broadening, with small but noticeable frequency and intensity shifts observed between the 1 and 3 isomeric forms.