Self-Assembly Properties of Semiconducting Donor–Acceptor–Donor Bithienyl Derivatives of Tetrazine and Thiadiazole—Effect of the Electron Accepting Central Ring

Abstract

Scanning tunneling microscopy was used to study the effect of the electron-accepting unit and the alkyl substituent's position on the type and extent of 2D supramolecular organization of penta-ring donor-acceptor-donor (DAD) semiconductors, consisting of either tetrazine or thiadiazole central acceptor ring symmetrically attached to two bithienyl groups. Microscopic observations of monomolecular layers on HOPG of four alkyl derivatives of the studied adsorbates indicate significant differences in their 2D organizations. Ordered monolayers of thiadiazole derivatives are relatively loose and, independent of the position of alkyl substituents, characterized by large intermolecular separation of acceptor units in the adjacent molecules located in the face-to-face configuration. The 2D supramolecular architecture in both derivatives of thiadiazole is very sensitive to the alkyl substituent's position. Significantly different behavior is observed for derivatives of tetrazine (which is a stronger electron acceptor). Stronger intermolecular DA interactions in these adsorbates generate an intermolecular shift in the monolayer, which is a dominant factor determining the 2D structural organization. As a consequence of this molecular arrangement, tetrazine groups (A segments) face thiophene rings (D segments) of the neighboring molecules. Monolayers of tetrazine derivatives are therefore much more densely packed and characterized by similar π-stacking of molecules independently of the position of alkyl substituents. Moreover, a comparative study of 3D supramolecular organization, deduced from the X-ray diffraction patterns, is also presented clearly confirming the polymorphism of the studied adsorbates.

Synthesis of new, highly luminescent bis(2,2’-bithiophen-5-yl) substituted 1,3,4-oxadiazole, 1,3,4-thiadiazole and 1,2,4-triazole

“…One of the possible ways of the preparation of low molecular mass semiconductors, showing higher than oligothiophene IP values, is to synthesize molecules in which a central electron accepting group separates two bi-, ter- or quaterthiophene units. Such compounds containing thiadiazole [10–15], oxadiazole [14–17] or tetrazine units [13,18–20] have been reported. Moreover, luminescence properties of these derivatives are superior to those of the corresponding penta-ring oligothiophenes.…”

Nanostructured Donor–Acceptor Self Assembly with Improved Photoconductivity

“…[1][2][3][4][5][6][7][8] Well-defined and reproducible nanoscale assemblies of donor-acceptor semiconducting materials are crucial for several devices in the optoelectronic applications. [1][2][3][4] From the perspective of device applications, it is highly desirable to translate the self-assembly of small molecules to processable polymers, which is a non-trivial task.…”

Supramolecular organization of bi- and terthiophene disubstituted diketopyrrolopyrrole, donor–acceptor–donor semiconducting derivatives

“…In the same time inter-row spacing increases because the alkyl substituents in b position of the terminal thiophene ring tend to preferentially locate between the conjugated cores of the neighboring molecules in the row. Such an effect has recently been found for another type of DAD compounds, namely alkylthiophene-disubstituted tetrazines [31].…”

“…Self-assembly of solution processable semiconducting molecules is usually governed by interactions between their conjugated cores and interdigitation of the solubilizing alkyl (or alkoxy) substituents [22][23][24][25][26][27][28][29][30][31][32][33][34][35]. From this point of view, the compounds described here constitute an interesting, albeit complex case in which the formation of the 2D supramolecular organization is governed by several factors associated with the molecule topology.…”