Influence of Fluorination on Energetic Parameters of Silole, Phosphole, Thiophene, Oligomers of Silole and Related Acenes

Abstract

The effects of fluorination on the energetic and thermochemical properties of a series of five-membered rings such as silole, phosphole and thiophene, and oligomers of silole and acenes were evaluated using density functional theory computations. Computed results indicate that substitution by fluorine atoms induces an increase of ionization energy and electron affinity and a decrease of proton affinity and HOMO-LUMO gap. For five-membered rings, fluorination effects are more significant on phosphole and silole as compared to those on thiophene. Changes in energetic properties of the oligomers of silole and acenes follow non-linear curves with increasing monomeric ring numbers. Effects of fluorination on energetic properties of the five-membered rings and oligomers are decreasing in the sequence of P-H > Si-H > C-H bonds. Replacement of H by F atom affects more strongly at Si-H bond than at C-H bond of siloles. Perfluorination of silole oligomers leads to derivatives with large electron affinity (> 4 eV). The anisotropy of induced current density (ACID) plots point out that fluorine replacement largely affects the electron delocalization at the C-C peripheral bonds in oligomers of silole and acenes. The silole unit emerges as a promising five-membered heterocycle to be used to tune up properties of oligomers.