Nematic phase nuclear magnetic resonance investigations of rotational isomerism. Part IV. Conformational study on the rotamers of 3,3′-bithienyl

The 220 MHz n.m.r. spectrum of partially oriented 3,3′-bithienyl has been obtained and interpreted. A number of models have been tested in order to determine the molecular conformation in solution on the basis of the observed dipolar couplings. It has been shown that the molecule does not exist as a single species but as an equilibrium between two rotational conformers. The two rotamers are not planar (the twisting angle being ca. 22°) and the SS-trans-like rotamer is the more abundant (ca. 66%). The results agree with previous electron diffraction studies in the gas phase.