Effects of Perfluorination on Thiophene and Pyrrole Oligomers

Abstract

The effect of perfluorination on thiophene and pyrrole oligomers in neutral, cationic, and anionic states was investigated with density functional theory at the (TD)B3P86-30%/6-31G* level. For the title compounds fluorination leads to planarization. For pyrroles a band gap reduction of 0.58 eV results, as unsubstituted pyrroles are nonplanar and disordered in the solid state. For thiophene the band gap is slightly increased as long thiophene oligomers are almost planar. Ionization energies and electron affinities increase upon fluorination by 0.65 and 0.60 eV for polythiophene and by 0.45 and 0.90 eV for polypyrrole. Conduction band widths increase by 0.5 for polythiophene and by 0.7 eV for polypyrrole. Spectra of charged (doped) forms are almost identical to those of the parent systems. Like parent systems, fluorinated oligomers with chain lengths of more than six rings develop a third UV absorption that increases in strength and decreases in energy upon chain length increase.

Ab-initio study of interaction of some atmospheric gases (SO2, NH3, H2O, CO, CH4 and CO2) with polypyrrole (3PPy) gas sensor: DFT calculations

“…Today many studies focused on the polymeric sensors [7]. Based on our finding poly (3,4- extensively studied as biosensor and gas sensors [7].Theoretical studies on conducting polymers are mainly limited to the study of electronic and structural properties of doped/undoped polymers [8,9].…”

Spectral and electronic properties of π-conjugated oligomers and polymers of Poly (o-chloroaniline-co-o-toluidine) calculated with density functional theory

“…Taking the optimized geometric structures the I.R, Raman, I.E, E.A, HOMO, LUMO and band gap calculations were performed with same level of theory at ground state, while UV-vis spectra were simulated with TD-SCF using B3LYP/6-31+G (d,p). The oligomers properties such as IP, EA, HOMO, LUMO, and band gap and band width were extrapolated for polymeric study through second-degree polynomial fit equation [19]. For better correlation of computed value with the experimental one, a scaling factor of 0.9613 was multiplied to the calculated frequencies [20,21].…”

A Benchmark Study on the Properties of Unsubstituted and Some Substituted Polypyrroles

“…The oligomers were extrapolated to polymer through second-degree polynomial fit equation [24]. The band gap (or the π−π* lowest electron transition) is estimated as the difference between the HOMO and LUMO orbital energies.…”