Conformational analysis of 2,2 '-bithiophene: a H-1 liquid crystal NMR study using the C-13 satellite spectra

Concistré, M., De Lorenzo, L., De Luca, G., Longeri, M., Pileio, G. and Raos, G. (2005) Conformational analysis of 2,2 '-bithiophene: a H-1 liquid crystal NMR study using the C-13 satellite spectra. Journal of Physical Chemistry A, 109 (44), 9953-9963. (doi:10.1021/jp054003f).

Abstract

We have obtained a very large data set of spectral parameters from the analysis of ¹H NMR and ¹³C satellite spectra of 2,2′-bithiophene dissolved in anisotropic, partially orienting mesophases. In particular, this parameter set includes 33 dipolar couplings, which are directly related to the interatomic distances, the dihedral angle φ between the two thiophenic rings, and the anisotropic solute - solvent interaction potential. This allows an exhaustive investigation of the conformational equilibrium of 2,2′-bithiophene in a liquidlike phase. Comparison with the predictions of high-level theoretical calculations for the isolated molecule provides evidence of a strong flattening as well as the sharpening effect of the medium on the conformer population. The approximations needed to apply vibrational corrections to flexible molecules are discussed in detail and some general conclusions concerning their effect on structure and conformational equilibria are proposed.

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Contributors

Author: M. Concistré

Author: G. Pileio

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