Since the discovery of the conducting properties of polymers in 1977  large attention has been paid to the use of π-conjugated systems. as alternative to inorganic semiconductors, for advantages that include low cost manufacture, simple processing, and mechanical flexibility . The high polarizability of the S atom in the rings stabilizes the conjugated chain conferring excellent charge transport properties which are of fundamental importance for applications in organic and molecular electronics. Due to this importance, an extensive comprehension of the electronic structure of short oligomeric systems is essential to correctly interpret and exploit the mechanisms underlying their potential device applications.
In a previous work  we characterized the gas phase electronic structure of thiophene (T), 2,2'-bithiophene (2T) and 2,2′:5′,2′′-terthiophene (3T), which represent the monomer the dimer and the trimer of polythiophene, respectively. We employed a series of characterization techniques – both experimental and theoretical - at the K-edge of carbon to shed light on the electronic structure of these compounds. The computation allowed to assign unambiguously the experimental features and to point out the strong electronic effects related to the aromatic stabilization, as well as the inductive and relaxation effects generated by the presence of the S atom. In this work we probe directly the sulphur atom in the same systems, by combining Near-Edge X-ray-Absorption Fine-Structure (NEXAFS) and X-ray Photoemission Spectroscopy (XPS) at the L2,3-edges of sulphur with Time Dependent density functional theory (TD-DFT) calculations. The joint experimental and theoretical approach used here shows its ability in providing insight into the properties of short-chain oligothiophenes.
 H. Shirakawa, E. J. Louis, A. G. MacDiarmid, C. K. Chiang, A. J. Heeger, J. Chem. Soc., Chem. Commun. (1977) 578; C.K. Chiang, C. R. Fincher, Y. W. Park, A. J. Heeger, H. Shirakawa, E. J. Louis, S. C. Gau, A. G. MacDiarmid, Phys. Rev. Lett. 39 (1977) 1098.
 Conjugated Polymeric Materials: Opportunities in Electronics, Opto- electronics, and Molecular Electronics, NATO AS1 Series E, edited by J. L. Brédas and R. R. Chance (Kluwer, Dordrecht, The Netherlands, 1990), Vol. 182.
 C. Grazioli, O. Baseggio, M. Stener, G. Fronzoni, M. de Simone, M. Coreno, A. Guarnaccio, A. Santagata, and M. D’Auria, J. Chem. Phys. 146, 054303 (2017)