Structural Motif Modulation in 2D Supramolecular Assemblies of Molecular Dipolar Unit Tethered by Alkylene Spacer

The present work investigates the role of tethered alkylene spacer in the formation of 2D supramolecular assemblies of the gemini amphiphiles (Gn-Cn, n = 2, 4, 6, 8, 10) by scanning tunneling microscopy (STM). All Gn-Cn molecules self-organize into the Type I lamellar structure with close-packed alkyl side chains, whereas Type II lamellar structure with interdigitated alkyl side chains is also observed for Gn-C6 and -C8. Two different dipole–dipole interaction modes, that is, collinear and antiparallel arrangement of Schiff base molecular dipole, are proposed to modulate the formation of two types of lamellar assemblies. The results highlight that the tethered alkyl chain length is far from being a passive part of the self-assembled system and plays a definitive role in the supramolecular engineering at the liquid–solid interface.