Redetermination of 2,2'-bithiophene

Abstract

The structure of 2,2'-bithiophene, C8H652, has been redetermined at low temperature (173 K) with a good degree of accuracy. The molecules are planar and although the transoid form predominates, there is some disorder.

Polymorphism in Oligothiophenes with an Even Number of Thiophene Subunits

“…A direct consequence of this packing difference is that the tilt angle of the long axis of the molecule with re- [a] U eq is defined as one third of the trace of the orthogonalized U ij tensor. spect to the normal to the plane of highest density is higher in the Z = 2 form than in the Z = 4 one; this angle is 30.5 in 2T, [5,6] 31.5 in the 4T single crystal (this work), and 33 in 6T/HT, [12] against 24.5 in polycrystalline 4T [9] and 23.5 in 6T. [10] The change in the packing mode also induces a slight change in the density.…”

“…Focusing on the unsubstituted oligothiophenes, the crystal structure of bithiophene (2T) was first reported in 1968 [4] and redetermined more recently. [5,6] One of the most interesting points concerning the crystal structure of unsubstituted oligothiophenes is the appearance of polymorphism. If we exclude terthiophene, [7] which has a complex structure that comprises two independent sublattices, and the earliest report on 6T, [8] which was based on a limited number of X-ray reflections, the structures of unsubstituted nTs can be distributed among two classes.…”

Phase transition equilibrium of terthiophene isomers

“…As shown by X-ray analysis [38], there is some degree of degeneracy in the sulphur atoms in 3,3 0 -bithiophene that was not observed in the 2,2 0 -bithiophene isomer [39]. Eight identical positions in 3,3 0 -bithiophene can be visualized in the obtained X- ray structure which indicates that the S atoms can be indistinctly positioned in the lattice.…”

Interchain Interactions in Organic π-Conjugated Materials: Impact on Electronic Structure, Optical Response, and Charge Transport

“…[131] In the latter work, the absorption band lying 0.3±0.4 eV above the low Davydov component (that we assign to the high-Davydov component) has been attributed to the signature of CT excited states; our quantum-chemical calculations, however, locate the lowest CT excited state~0.2 eV above the high Davydov component; this is consistent with the electroabsorption spectra of crystalline thin films of 6T at 4 K, indicating that the CT state is very close to the high Davydov feature. [132] We have also estimated the Davydov splitting in the 2T, [133] 4T, 6T, and 8T single crystals; these all possess very similar lattice parameters within the bc layers. The main difference among the oligomers is then related to the increase with chain size of the extent of the exciton wavefunction in the lowest excited state.…”