Molecular Arrangement Control of [1]Benzothieno[3,2-b][1]benzothiophene (BTBT) via Charge-Assisted Hydrogen Bond

Organic semiconductors have pi-conjugation in the constituent molecules and exhibit optical and electrical properties. Since these properties are significantly affected by the overlap of pi-orbitals between adjacent molecules, not only their molecular structures but also their molecular arrangement has been well known as critical; however, control of the molecular arrangement without modifying the electronic character of the constituent molecule has been difficult. In the current work, we report organic salts composed of disulfonic acid with a moiety of a representative organic semiconductor molecule, [1]benzothieno[3,2-b]-[1]benzothiophene (BTBT), as a functional component, and different types of alkylamines as an arrangement-controlling component via charge-assisted hydrogen bonds. We successfully controlled the molecular arrangement of BTBT moiety by changing alkylamines, without changing the structure of disulfonic acid with the BTBT functional moiety. Depending on the bulkiness of alkylamines, the molecular arrangement of these organic salts changed from an edge-to-face herringbone-type arrangement, where CH/pi interactions were dominant similar to the common crystal structure of BTBT, to a novel one-dimensional (1D) slipped parallel-type arrangement for BTBT, without changing the molecular structure of disulfonic acid. In addition, we revealed that the dimensionality of the electronic state and properties of the organic salts also changed according to the molecular arrangement of BTBT moiety.