Quantum Systems in Physics, Chemistry, and Biology by Alia Tadjer Rossen Pavlov Jean Maruani Erkki J. Brändas & Gerardo Delgado-Barrio

Author:Alia Tadjer, Rossen Pavlov, Jean Maruani, Erkki J. Brändas & Gerardo Delgado-Barrio
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

The energy difference between the TS at θ = 90° and anticlinal minimum ΔE4, kcal/mol

Stabilisation energy ΔE2 anticlinal versus synclinal, kcal/mol

Details of the calculations (functionals and basis sets) and references

3.46

0.58

Extended Hückel MO approach [40]

7.14

0

SCF localised orbitals method [41]

4.2

1.3

HF/STO-3G [43]

5 ± 2

0.88

HF/STO-3G, STO-3G* [33]

4.68

0.33

Extended-Hückel MO [44]

The conformational properties of bithiophene for the prediction of helical conformations of polythiophene in neutral and doped state in solution have been studied by Cui and Kertesz [44] using semiempirical modified neglect of diatomic overlap (MNDO) method and Extended-Hückel MO approach. It was observed that the first method fails in predicting the planar structures, and therefore cannot be used for characterization of the inter-ring rotation, whereas the second one gives the rotational barrier of 4.68 kcal/mol, which is in line with experimental findings [16].

Later on the relatively large magnitude of the rotational barrier obtained experimentally has been argued and associated with a possible deformation of the bithiophene geometry in a liquid crystal medium. It was also debated that the methods mentioned in Table 2 overestimate heights and positions of the peaks on the potential energy surface. Nevertheless taken together, these early papers provided the necessary groundwork, giving the first basic blueprint for further theoretical characterization of the internal rotation in bithiophene.

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