Close Packing in Trans Conformers Promotes the Formation\nof Supramolecular Structures with C<sub>1</sub> Symmetry

Assemblies with C<sub>1</sub> symmetry\nexhibit important applications\nin many fields such as enantioselective catalysis. However, their\nformation is challenging due to their large entropic disadvantage,\nand molecular information on their formation dynamics is limited because\nof the lack of effective characterization techniques. Here, using\nachiral amphiphilic molecules such as N-oleoyl ethanolamide (OEA)\nand its analogues as modeling assembly units, we demonstrated that\nthe sss polarization signals, generated by femtosecond sum frequency\ngeneration vibrational spectroscopy (SFG-VS), provide a powerful tool\nto monitor the formation dynamics of the C<sub>1</sub> symmetric supramolecular\nstructures at the interfaces. The trans conformation of the assembly\nunits can provide strong π–π interactions and thus\nproduce enough enthalpy to drive the formation of C<sub>1</sub> symmetric\nsupramolecular structures. However, the cis conformation impedes the\nassembly of C<sub>1</sub> symmetric structures and cannot generate\nsss and chiral polarization SFG signals. These findings may aid in\nrationally constructing ordered and functional superstructures and\nunderstanding the mechanism of chirality formation.