Study of the electronic structure of short chain oligothiophenes

TL;DR

This study combines experimental NEXAFS and XPS spectroscopy with DFT calculations to analyze the electronic structure of short-chain oligothiophenes, revealing how their spectral features evolve with chain length and identifying carbon site contributions.

Contribution

It provides a detailed correlation between experimental spectra and theoretical calculations for short-chain oligothiophenes, highlighting spectral evolution and site-specific electronic characteristics.

Findings

Spectral features stabilize as chain length increases.

Experimental peaks are assigned to specific carbon sites.

The study offers insights into the electronic effects of sulfur and aromaticity.

Abstract

The electronic structure of short-chain thiophenes (thiophene, 2,2'-bithiophene and 2,2':5',2'-terthiophene) in the gas phase has been investigated by combining the outcomes of Near-Edge X-ray-Absorption Fine-Structure (NEXAFS) and X-ray Photoemission Spectroscopy (XPS) at the C K-edge with those of density functional theory (DFT) calculations. The calculated NEXAFS spectra provide a comprehensive description of the main experimental features and allow their attribution. The evolution of the C1s NEXAFS spectral features is analyzed as a function of the number of thiophene rings; a tendency to a stabilization for increasing chain length is found. The computation of the binding energy allows to assign the experimental XPS peaks to the different carbon sites on the basis of both the inductive effects generated by the presence of the S atom as well as of the differential aromaticity effects.