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

Abstract

Board‐like liquid‐crystalline semiconductors based on the dithieno[3,2‐b;2′,3′‐d]thiophene (DTT) substructure were synthesized and their thermal, self‐assembly, optical, and semiconducting properties investigated. These sanidic compounds, bearing eight peripheral chains, are mesomorphic and spontaneously self‐assemble into columnar hexagonal mesophases (Colhex) over broad temperature ranges, as confirmed by polarized optical microscopy, differential scanning calorimetry, and small‐angle X‐ray scattering. Strong blue photoluminescence with absolute quantum yields up to 33 % were measured. These compounds also form blue‐light emitting gels in various organic solvents. The fibrillar‐like morphology of these gels, reminiscent of the columnar structure, and stabilized by efficient intermolecular interactions, was characterized by scanning electron microscopy. The charge carrier mobility of these π‐extended mesogens was measured by time‐of‐flight transient photocurrent technique in the Colhex mesophase, and showed good hole‐transport performance with charge carrier mobility of 10−3 cm2 V−1 s−1.

Butterfly‐like Shape Liquid Crystals Based Fused‐Thiophene as Unidimensional Ambipolar Organic Semiconductors with High Mobility

“…However, the ketone derivatives BDTDd and CDTOc-e with 8 peripheral alkyls chains showed lower solubility in organic solvents and could only be purified by crystallization in dry hot toluene. All the new precursors and annulated compounds but the poorly soluble diphenanthrene derivatives BDTDd and CDTOc-e were characterized by 1 and Scholl (bonds in blue) reactions: DT, [25] BTBT, [26] DTT, [27] BDT, BDTD and CDTO, this work (R and R' are alkyl chains, C n H 2n + 1 ). 13 C NMR spectroscopy (Figures S17-S30).…”

“…The observation of mesomorphism in these tetraaryl thiophene molecules suggests that the electron-deficient core strongly promotes molecular stacking and columnar mesophases' formation, similarly to some other structurally related systems reported in the literature. [35,36] Recall in particular that the analogous dithienothiophene derivatives DTT, [27] whose S-atom is replaced by the carbonyl group (4 d), exhibits only a monotropic and over a narrower mesophase range (from 67 to 26°C on cooling).…”

“…[24] Structurally related butterfly-like shape molecules specifically made from fused-thiophene aromatics also stack up into columnar mesophases, and were found to exhibit attractive optical properties as well as enhanced electron-conducting properties. [25][26][27] Sulphur-containing heterocyclic aromatics are electron-rich and extended π-orbitals benefit largely to enhanced π-π stacking, and charges hop smoothly among positionally ordered molecules. [28][29][30] Furthermore, rotational freedom and conformational flexibility may lead to lower mesophases' stability and narrower temperature ranges, [25,31] while conformationally fixed π-conjugated scaffolds display in contrast very stable columnar mesophases with high phase transition temperatures, that can act as high temperature organic semiconductors in addition to promote self-assembly in supramolecular organic gels (Figure 1).…”

“…[28][29][30] Furthermore, rotational freedom and conformational flexibility may lead to lower mesophases' stability and narrower temperature ranges, [25,31] while conformationally fixed π-conjugated scaffolds display in contrast very stable columnar mesophases with high phase transition temperatures, that can act as high temperature organic semiconductors in addition to promote self-assembly in supramolecular organic gels (Figure 1). [27] Lately, we have successfully combined both the Suzuki-Miyaura coupling and the Scholl cyclo-dehydrogenation model reactions to synthesize, in few efficient steps, several new mesogens yielding columnar liquid crystalline semiconductors. [25][26][27]31] Our exploration of original molecular systems and the understanding of structure-activity relationships lent us to construct novel butterfly-shaped molecules based on fused-thiophene with different π-extended scaffolds (Figure 1).…”

“…[27] Lately, we have successfully combined both the Suzuki-Miyaura coupling and the Scholl cyclo-dehydrogenation model reactions to synthesize, in few efficient steps, several new mesogens yielding columnar liquid crystalline semiconductors. [25][26][27]31] Our exploration of original molecular systems and the understanding of structure-activity relationships lent us to construct novel butterfly-shaped molecules based on fused-thiophene with different π-extended scaffolds (Figure 1). Chemical design of organic semiconductors is an important research subject, as it can help tuning the materials light absorption and emission, their stability in ambient condition, and the semiconducting p-or n-type, or both (ambipolar) character.…”