ISSN:
0020-7608
Keywords:
bithiophene
;
internal rotation
;
DFT calculations
;
MP2 calculations
;
Fourier-fitted torsional potentials
;
Chemistry
;
Theoretical, Physical and Computational Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The internal rotation of 2,2′-bithiophene was investigated within the density functional theory (DFT) approach. Fully optimized DFT torsional potentials are compared with Møller-Plesset (MP2) results which predict a fourfold potential with s-cis- and s-trans-gauche minima. DFT calculations fail in describing the energetics of the internal rotation because they favor planar vs. perpendicular conformers. Gradient-corrected functionals provide torsional potentials where the gauche minima have almost vanished and the s-cis↔s-trans interconversion barriers are twice as high as the barriers obtained at the MP2 level. The use of local functionals augments the shortcomings of the DFT approach. The gauche minima completely disappear and the rotational barriers are now about three times higher than the MP2 barriers. As an efficient computational approach, we suggest having geometries optimized at the DFT level and conformational energies evaluated via single-point MP2 calculations. The fitting of MP2//DFT energies to truncated Fourier expansions allows one to predict the torsional angles and the relative energies of the critical points of the rotational potential with an accuracy similar to that afforded by MP2 calculations including full geometry optimization. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 70: 303-312, 1998
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
