The role of H-bonds in the solid state organization of [1]benzothieno[3,2-b][1]benzothiophene (BTBT) structures: bis(hydroxy-hexyl)-BTBT, as a functional derivative offering efficient air stable organic field effect transistors (OFETs)

Abstract

The study of a [1]Benzothieno [3,2-b][1]benzothiophene (BTBT) derivative decorated with hexyl chains functionalized with hydroxyl end groups is reported. A rapid and inexpensive functionalization of the BTBT in position 2 and 7 has been developed. This compound is able to self-organize into a lamellar structure through σ-π stacking and van der Waals interactions but also through hydrogen bonding interactions. The hydrogen-bonded network controls the interlamellar region in terms of organization and stability. Liquid-crystal phase and structural changes observed by DSC have been characterized using an original approach combining FTIR and powder XRD measurements as a function of temperature. Thermally evaporated diol based OFETs exhibited good mobilities up to 0.17 cm².V-1.s-1 measured under inert atmosphere but also in ambient air. The diol derivative is considered as a very promising platform for the design of new functionalized BTBT.

A positive to negative uniaxial thermal expansion crossover in an organic benzothienobenzothiophene structure

“…The synthesis of the diol BTBT-C4OH was adapted from the synthetic pathway that we described for BTBT-C6OH (Roche et al, 2016). In a first step, the BTBT core was functionalized by a Friedel-Crafts acylation at the positions 2 and 7 to afford BTBT-CO(CH 2 ) 3 Br.…”

“…BTBT derivatives with alkyl chains at the 2 and 7 positions have been reported (Izawa et al, 2008) but also more with bulky fragments (Iino et al, 2015;Schweicher et al, 2015). Roche et al (2016) described the symmetric functionalization of the BTBT core by a hydroxyhexyl chain, thereby offering relatively strong tethering attachments between individual molecules. Thermally evaporated thin film organic field-effect transistors (OFET) based on this diol derivative gave excellent mobilities of 0.17 cm 2 V À1 s À1 at room temperature.…”

“…BTBT-C4OH, 6 , 6 0 -([1]benzothieno [3,2-b][1]benzothiophene-2,7-diyl)bis(butan-1-ol), is a short-chain member of the BTBT-CnOH family of symmetrically functionalizedconjugated BTBT systems, of which especially long-chain members present excellent semiconducting properties for OFET applications (Dautel et al, 2020). The X-ray structure of the n = 6 member, BTBT-C6OH, has been published (Roche et al, 2016) and was shown to display, in addition to its good mobility characteristics, colossal negative uniaxial thermal expansion along the monoclinic b axis, one of the largest negative expansivities in organic compounds observed until now (van der Lee et al, 2018). The compound was also shown to have an isosymmetric phase transition near 210 K. The negative thermal expansion in BTBT-C6OH is related to a compensation mechanism caused by steric hindrance between adjacent molecules and enhanced by moderate anharmonicity in the low-temperature mother phase and strong anharmonicity in the mixed high-temperature phase.…”

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

“…[22][23][24][25][26] The design of novel π-conjugated polycyclic cores is therefore the key to improve the performances of liquid-crystalline (LC) semiconductors. In the last decade, LCs based on fused-thiophene subunits have been flourishing, and organic mesogenic derivatives of oligothiophenes, [27][28][29][30][31][32] thienothiophenes (TT), [33,34] dithienothiophenes (DTT), [35][36][37][38][39][40] benzothiophenes (BT), [41][42][43][44] benzotrithiophenes (BTT), [45,46] benzothieno [3,2-b]benzothiophene (BTBT), [47][48][49][50][51][52] materials have been amply reported. Such compounds exhibit high charge mobility with usual rates up to about 10 cm 2 V À 1 s À 1 for a rod-like mesogen [52] and nearly 0.2 cm 2 V À 1 s À 1 for a discotic mesogen, [45] in their highly ordered crystalline phases, directly obtained after annealing from their mesomorphic temperatures and slowly cooled down.…”

Experimental and theoretical evidence of a supercritical-like transition in an organic semiconductor presenting colossal uniaxial negative thermal expansion

“… 24 – 26 In this context, some of us recently reported thermally evaporated BHH-BTBT based OFETs exhibiting a high mobility of up to 0.17 cm 2 V –1 s –1 measured under an inert atmosphere but also in ambient air. 27 The crystal packing features, morphology and charge transport in organic semiconductors are intimately related, 28 so in order to obtain a deeper understanding of the exceptional NTE in BHH-BTBT we have carried out dynamic ab initio density functional theory (DFT) molecular calculations. Thermal expansion was shown to be the main factor responsible for thermal bandwidth narrowing in organic semiconductors such as pentacene (with a slight negative thermal expansion) and rubrene.…”