Two-Dimensional Supramolecular Organization in Oligomers of Dialkylterthiophenes—Effect of the Alkyl Substituent Position

Abstract

Strictly monodispersed fractions of two types of regioisomers of increasing molecular mass, namely, oligomers of 3,3′′-dioctyl-2,2′:5′,2′′-terthiophene (3,3′′DOTT) and 4,4′′-dioctyl-2,2′:5′,2′′-terthiophene (4,4′′DOTT) (nmers, n ) 2-5) were studied by STM with the goal to establish the effect of the type of regioregularity on the 2D supramolecular organization of these compounds on HOPG. Both regioisomers show strikingly different supramolecular organizations. In the 4,4′′DOTT series, a two-dimensional arrangement is found for short oligomers (2-mers and 3-mers). With increasing oligomer length (4-mers and 5-mers), this two-dimensional structure evolves toward a more one-dimensional one characterized by randomly oriented rows of parallelaligned molecules. This evolution arises from the interdigitation of the terminal and the side alkyl groups in two perpendicular directions. In the 3,3′′DOTT series, independent of the oligomer length, a two-dimensional organization is observed. Because of a significantly shorter distance between the two alkyl substituents in the mer, only one type of interdigitation takes place for this regioisomer in the direction perpendicular to the molecule's long axis.

Self-assembly of tetraalkoxydinaphthophenazines in monolayers on HOPG by scanning tunneling microscopy

“…In addition to strictly defined conditions of thermodynamical nature such as their reduction and oxidation potentials [7,8], the organic semiconductors suitable for the applications in highly performing devices should meet several requirements concerning their capability of forming ordered supramolecular structures in thin films and monolayers, possibly via self-assembly [9][10][11][12][13][14][15][16][17]. Thus self-assembly of conjugated molecules is one of the crucial factors which influence or even determine the electrical transport properties in organic semiconductors.…”

“…It is therefore a question of fundamental importance to determine the influence of the number, length and position of these substituents on the spontaneous organization of molecules. STM techniques have been frequently used for such investigations in monolayers of organic molecules of very different chemical natures, for example alkyl (alkoxy) derivatives of: benzoic acids [18], thiophene [15,16,[19][20][21][22], annulene [23,24], fluorenone [25,26], stilbene [27], and others [28][29][30][31].…”

Solvent Choice and Kinetic Isotope Effects (KIEs) Dramatically Alter Regioselectivity in the Directed ortho Metalation (DoM) of 1,5‐Dichloro‐2,4‐dimethoxybenzene

“…Meanwhile, one of the thiophene rings adopts a cis conformation with respect to its neighbor, so that the octyl chains of each molecule can rotate to the same side to interdigitate with those from the adjacent rows, thereby determining the interlamellae distance. The QTA molecules packed back‐to‐back in the same lamellae may interact through weak electrostatic interactions37, 38 between the sulfur atoms. The unit cell parameters are a =(1.9±0.1) nm, b =(2.6±0.1) nm, and α =(119±3)°.…”

Adlayer structures of thiophene and pyrrole derivatives on Au(1 1 1) probed by scanning tunneling microscopy

“…The introduction of substituents into the 3 or 4 position of thiophene/pyrrole can not only bring some novel properties to individual molecules, but also affect the process and structure of electrochemical polymerization of monomers [25,29]. Alkyl chain is an important functional group to stabilize and modulate the molecular assembly [36,37]. The different alkane substituted monomers are chosen here as a model system to understand the effect of chemical composition on the adsorption behavior.…”