Two pi-conjugated oligomer models which only differ from the methoxy groups on the phenyl ring, 1,4-bis(2-thienyl) benzene and 1,4-dimethoxy-2,5-bis(2-thienyl) benzene, have been considered to investigate the intramolecular non-covalent sulfur-oxygen interactions. For this purpose, we used far-infrared measurements coupled to density functional theory based calculations. We found that the most sensitive modes to the sulfur-oxygen interactions are located around 300 cm (1) and they are assigned to in-plane shear of thiophene rings coupled to the methoxy groups. (C) 2012 Elsevier B. V. All rights reserved.