Self-Assembly of Alkyl-Substituted Oligothiophenes on MoS2: A Joint Experimental/Theoretical Study

The molecular arrangements of two different alkyl-substituted oligothiophenes, alpha,alpha'-dihexylquaterthiophene (DH4T) and alpha,alpha'-dioctylterthiophene (DOTT), in monolayers on molybdenum disulfide (MoS2) were studied with a joint theoretical/experimental approach. Scanning tunneling microscopy was used both at the liquid/solid interface and in dry conditions to investigate the ordering of the conjugated oligomers in two-dimensional layers. DH4T and DOTT form well-ordered monolayers at large scales with interdigitated packing on MoS2. In addition, DOTT exhibits an arrangement in which a dimer-type stacking of the conjugated backbone with an interlocking of the alkyl side chains is formed. Molecular modeling simulations have been used to provide insights into the microscopic morphology and to assess the stability of the different assemblies of DOTT and DH4T on MoS2.