The deformability of the thiophene ring: A key to the understanding of the conformational properties of oligo‐ and polythiophenes

Abstract

Oligothiophenes in solution and in the solid state have different conformational properties, as can be concluded from the spectroscopic and theoretical data and X‐ray structure of three di‐ and tetramethyl α‐conjugated quaterthiophenes (see Figure) reported here.

Crystal structure of head-to-head and tail-to-tail β,β′-dibromo-substituted bithiophenes as model compounds for poly(3-bromothiophene)

“…Firstly, the compound displays non-coplanar syn conformation, characterized by a S 1a -C 2a -C 2b -S 1b torsion angle of 59.0(6) 8. A similar, strongly twisted syn orientation between adjacent thienyl rings has previously been observed only for the 3-methly-substituted inner and outer rings of one a-conjugated quaterthiophene derivative, where the corresponding torsion angle is 53.4(1) 8 [19]. Another noteworthy feature of compound 2 is the loss of crystallographic equivalence between the individual thiophene rings, which exhibit only approximate two-fold symmetry; nevertheless, none of the corresponding bond distances and angles differs by more than two estimated standard deviations.…”

The Versatile Thiophene: An Overview of Recent Research on Thiophene‐Based Materials

“…Indeed, even at the current, very rough stage of understanding, the self-assembly and self-organization properties of these materials and their ability to create supramolecular hierarchical structures of many types spontaneously appears impressive. These properties are certainly mostly due to the large atomic polarizability of the sulfur atom that confers the characteristic of plasticity' to the thiophene ring even in the solid state, [107] making it very adaptable to the environment. The low barriers to rotation around the inter-ring carbon±carbon bond [108] make the aromatic backbone highly flexible, and it is the atropoisomerism related to these rotations when they are frozen [109] that allows the formation of chiral structures even in the absence of chiral substituents.…”

Photoluminescence Efficiency of Substituted Quaterthiophene Crystals

“…The samples are ordered for increasing average inter-ring dihedral angle [10], a simple geometrical parameter for estimating the molecular distortion. Details on sample preparation, x-ray characterization and roomtemperature optical characterization of these compounds are reported elsewhere [10][11][12][13].PL efficiency measurements were carried out by using a nitrogen purged integrating sphere, at room temperature, by exciting the samples with an Ar-ion laser #1 #2 #3 #4 #5 #6 θ θ θ θ θ θ =1.8 =17.8 =20.6 =21.1 =35.0 =38.0 0 0 0 0 0 0 FIG. 1.…”