Mutual Monomer Orientation To Bias the Supramolecular Polymerization of [6]Helicenes and the Resulting Circularly Polarized Light and Spin Filtering Properties

We report on the synthesis and self-assembly of 2,15- and4,13-disubstituted carbo[6]helicenes1and2bearing 3,4,5-tridodecylox-ybenzamide groups. The self-assembly of these [6]helicenes is stronglyinfluenced by the substitution pattern in the helicene core that affects themutual orientation of the monomeric units in the aggregated form. Thus,the 2,15-substituted derivative1undergoes an isodesmic supramolecularpolymerization forming globular nanoparticles that maintain circularlypolarized light (CPL) withglumvalues as high as 2x10-2. Unlikecarbo[6]helicene1, the 4,13-substituted derivative2follows a cooperativemechanism generating helical one-dimensionalfibers. As a result of thishelical organization, [6]helicene2exhibits a unique modification in its ECDspectral pattern showing sign inversion at low energy, accompanied by asign change of the CPL withglumvalues of 1.2x10-3, thus unveiling anexample of CPL inversion upon supramolecular polymerization. Thesehelical supramolecular structures with high chiroptical activity, when deposited on conductive surfaces, revealed highly efficientelectron-spinfiltering abilities, with electron spin polarizations up to 80% for1and 60% for2, as measured by magnetic conductingatomic force microscopy

Automated summary

This study reports on the synthesis and self-assembly of 2,15- and 4,13-disubstituted carbo[6]helicenes bearing 3,4,5-tridodecylox-ybenzamide groups. The self-assembly of these helicenes is influenced by the substitution pattern in the helicene core, resulting in different supramolecular structures. The helical supramolecular structures exhibit efficient electron-spin filtering abilities when deposited on conductive surfaces.