Board‐like Fused‐Thiophene Liquid Crystals and their Benzene Analogs: Facile Synthesis, Self‐Assembly, p‐Type Semiconductivity, and Photoluminescence

Abstract

Fused-thiophene discotic liquid crystals were designed and easily synthesized by Suzukic oupling and FeCl 3 oxidized tandemc yclodehydrogenation reactions, including homo-andcross-coupling reactions. The resultingh exagonal and rectangular columnar mesomorphic supramolecular structures formed werec haracterized by polarizing optical microscopy,d ifferential scanning calorimetry,a nd smallangle X-ray scattering. The charge carrier transport proper-ties in the mesophases of two of the synthesized fused-thiophene discogensw ere measured by transient photocurrent time-of-flight (TOF) technique, revealing fast hole transport values in the range of 10 À3 to 10 À2 cm 2 V À1 s À1 ,t hus demonstratingp otentiala pplications in electronic devices.T he luminescent sanidic mesogens, with different extended p-conjugated systems, also emitb lue, green, or red light,w ith absolute photoluminescent quantum yields as high as 18 %.

Nonlinear Nonacenes with a Dithienothiophene Substructure: Multifunctional Compounds that Act as Columnar Mesogens, Luminophores, π Gelators, and p‐Type Semiconductors

“…D1 exhibits a narrow columnar mesophase range both on the heating and cooling run, while both D2 ‐ 3 exhibit a monotropic behavior (thermodynamically stable during the cooling run only). The occurrence of a mesophase for these tetra‐aryl‐DTT derivatives, even though monotropic, is quite remarkable as compared to the tetra‐aryl‐thienothiophene and thiophene derivatives recently reported, which did not display any mesophase . The mesophase stabilization might just be attributed to the larger coplanar thiophene‐fused core, which as a result enhances face‐to‐face stacking into supramolecular columnar structures, and possibly supported by additional S…S intermolecular interactions, reminiscent from the crystalline packing .…”

“…The crowding of chains near stacked mesogens is hence locally released ( q ch,ell ), explaining conversely that the q ch,cyl ratio does not deviate at all from unity. In addition, the minimum overall space requirement of the chains near the stacked units is below the available area, which is against the formation of tilted columns and thus a further area increase, on the contrary reported for structurally close compounds …”

“…However, due to their poor solubility in most common organic solvents, 1 H NMR spectra recorded for the sanidic molecules were of rather poor quality ( Figures S7-9 in the Supporting Information). The simpler signature of the aromatic part displaying 3 [54] benzothieno-benzothiophene (BTBT) [53] and di(benzo)-dithieno-thiophene (DTT) derivatives (R = À C n H 2n + 1 ). clear singlets (compared to the rather complicated signature of compounds D, with the free rotating side aryls) were in agreement with the extension of the conjugated system of M and higher molecular symmetry, and sufficient to attest unambiguously on the formation of the cyclodehydrogenated structures.…”

“…The occurrence of a mesophase for these tetra-aryl-DTT derivatives, even though monotropic, is quite remarkable as compared to the tetra-aryl-thienothiophene and thiophene derivatives recently reported, which did not display any mesophase. [53,54] The mesophase stabilization might just be 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 attributed to the larger coplanar thiophene-fused core, which as a result enhances face-to-face stacking into supramolecular columnar structures, and possibly supported by additional S…S intermolecular interactions, reminiscent from the crystalline packing. [57] D1-3 also exhibited an erratic solid state behavior with the formation of metastable solid crystalline phases on heating ( Figure S14 in the Supporting Information), likely attributed to the freely-rotating dialkyl-aryl side groups.…”

“… Molecular structures of mesogenic di(benzo)‐thiophene (DT), benzothieno‐benzothiophene (BTBT) and di(benzo)‐dithieno‐thiophene (DTT) derivatives (R=−C n H 2 n +1 ).…”