The torsional potentials for inter-ring rotation in 2-(2-thienyl)pyrrole, 2-(2-thienyl) furan, and 2-(2-furyl) pyrrole are systematically studied by highly reliable and accurately convergent ab initio methods. The outcome of the state-of-the-art calculations is used in the investigations on structure and conformational preferences of these systems and aims at further guiding the modeling of polymer folding at conformational defects. A comparison is then made with those results provided by DFT approaches in order to assess the performance of the latter methods along the whole rotational path. Finally, we have assessed other cost effective yet more accurate DFT-based methods by. fine-tuning the energy components entering into the model. (C) 2009 Elsevier B. V. All rights reserved.