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

Abstract

The X‐ray structures of 4,4′‐dibromo‐2,2′‐bithiophene 1, 3,3′‐dibromo‐2,2′‐bithiophene 2 and 3,3′,5,5′‐tetrabromo‐2,2′‐bi‐thiophene 3 are rweported. The tail‐to‐tail dimer 1 is found in an anti planar conformation whereas a large distortion is present in the two head‐to‐head bithiophenes 2 and 3. These bromo derivatives are model compounds for structural studies on poly(3‐bromothiophene).

Molecular Packing and Photoluminescence Efficiency in Odd-Membered Oligothiophene S,S-Dioxides

“…Furthermore, in all the compounds, one of the two hexyl chains is affected by conformational disorder involving mainly its fifth C atom which was found to be distributed over at least two sites. There is good agreement between corresponding bond distances and angles, and their values compare well with those previously observed in many oligothiophenes. , In all the compounds, the central thienyl- S , S -dioxide ring shows the lengthening of C−S (mean value 1.773(7) Å) and C3−C4 (mean value 1.480(9) Å) bonds, both ∼0.004 Å longer than the corresponding distances in inner thiophene rings . A parallel shortening of C2−C3 and C4−C5 bonds (mean value 1.356(8) Å) was also observed.…”

“…To our knowledge, this is the first case of syn orientation between unsubstituted thiophene rings with full or major site occupancy in oligothienyls of known structure. Previously, such a conformation was observed only in molecules affected by rotational disorder for the less populated conformer (never exceeding 20−25%). 5b,d …”

Nonradiative Relaxation in Thiophene-S,S-dioxide Derivatives: The Role of the Environment

“…Quite surprisingly TSOs show lower emission efficiency for isolated molecules in solution than in the solid phase, , where instead intermolecular decay channels are usually expected to decrease the emission efficiency. , However, the origin of the strongly different emission properties of TSOs in the two different phases/environments is not completely understood, as the molecular functionalization affects both the intramolecular properties , and the intermolecular interactions. ,, The effects of the solvent and, more generally, of the external environment on the molecular relaxation processes in TSOs are thus still unclear.…”

Synthesis and X-ray single-crystal structure study of 5,5′-bis(silyl)-functionalized 3,3′-dibromo-2,2′-dithiophenes

“…1. The two thiophene subunits show a gauche conformation with a torsion angle of about 72 • between them, compared with the 68 • observed for 3,3 -dibromodithiophene reported by Antolini et al 7 The distortion of the π -conjugation is evident in the very long C(4)-C(5) bond of 1.463(2)Å bridging the two thiophene subunits and the significantly distinct single and double bonds of the thiophenes (see Table 2). However, an extension of the π -conjugation throughout the silicon centers in 3 can be anticipated in the slightly elongated C(1)-Si(1) and C(8)-Si(2) bonds of 1.888(2)Å and 1.885(2)Å respectively and the relatively long C(1)-C(2) and C(7)-C(8) bonds of 1.374(2)Å and 1.378(2)Å respectively.…”

“…The other bond lengths (see Table 2) are similar to compound 3 and the related dithiophenes. 7,8 The packing diagram of 5 (Fig. 3) shows the dominating effect of the tert-butyl groups of the silyl substituents building up layers in an undulating herringbone-type structure, which is also observed for a variety of optoelectronic materials.…”