Investigating the Thermal Stability of Organic Thin-Film Transistors and Phototransistors Based on [1]-Benzothieno-[3,2-b]-[1]-benzothiophene Dimeric Derivatives

A Review on the Synthetic Methods towards Benzothienobenzothiophenes

Benzothienobenzothiophenes (BTBTs) are a class of heteroacenes for which two distinct isomers have been identified depending on the locations of the fused benzothiophene motifs. Benzothienobenzothiophenes represent a class of heteroacenes demonstrating remarkable electronic properties that make them prominent in the realm of organic semiconductors. The structure of BTBTs, incorporating two sulfur atoms, contributes to their unique electronic characteristics, including narrow bandgaps and effective charge transport pathways. These compounds have gained attention for their high charge carrier mobility, making them desirable candidates for application in organic field-effect transistors (OFETs) and other electronic devices. Researchers have explored various synthetic strategies to design and tailor the properties of BTBT derivatives, leading to advancements in the development of high-performance organic semiconductors. Various synthetic techniques for benzothienobenzothiophenes have been reported in the literature including multistep synthesis, tandem transformations, electrochemical synthesis, and annulations. This review investigates the generality of each synthetic methodology by highlighting its benefits and drawbacks, and it analyses all synthetic approaches described for the creation of the two isomers. For the advantage of the readers, we have delved upon every mechanism of the reactions that are known. Finally, we have also summarized the synthetic methodologies that are used for making benzothienobenzothiophene analogues for material applications.

Modular synthesis of unsymmetrical [1]benzothieno[3,2-b][1]benzothiophene molecular semiconductors for organic transistors

A modular approach to underexplored, unsymmetrical [1]benzothieno[3,2-b][1]benzothiophene (BTBT) scaffolds delivers a library of BTBT materials from readily available coupling partners by combining a transition-metal free Pummerer CH-CH-type cross-coupling and a Newman-Kwart reaction. This effective approach to unsymmetrical BTBT materials has allowed their properties to be studied. In particular, tuning the functional groups on the BTBT scaffold allows the solid-state assembly and molecular orbital energy levels to be modulated. Investigation of the charge transport properties of BTBT-containing small-molecule:polymer blends revealed the importance of molecular ordering during phase segregation and matching the highest occupied molecular orbital energy level with that of the semiconducting polymer binder, polyindacenodithiophene-benzothiadiazole (PIDTBT). The hole mobilities extracted from transistors fabricated using blends of PIDTBT with phenyl or methoxy functionalized unsymmetrical BTBTs were double those measured for devices fabricated using pristine PIDTBT. This study underscores the value of the synthetic methodology in providing a platform from which to study structure-property relationships in an underrepresented family of unsymmetrical BTBT molecular semiconductors.

Catalyst-controlled switchable [4 + 1], [4 + 3] and [3 + 2] domino reactions of azadienes and MBH carbonates: diverse synthesis of benzothiophene fused derivatives

Catalyst-controlled switchable domino reactions between azadienes bearing a benzothiophene moiety and isatin-derived MBH carbonates were developed. The [4 + 1] annulation was triggered in the presence of DABCO, giving a variety of benzothiophene fused pyrrole derivatives, while the [4 + 3] annulation occurred when changing the catalyst to DMAP. Furthermore, the [3 + 2] annulation mode was observed with the use of catalytic Ph₂PMe. Additionally, the synthetic utility of these domino reactions was demonstrated by gram-scale experiments and simple transformations of the products. To the best of our knowledge, catalyst-controlled synthesis of benzothiophene fused or spiro derivatives has rarely been reported.