We report on the synthesis and self-assembly of 2,15- and 4,13-disubstituted carbo[6]­helicenes 1 and 2 bearing 3,4,5-tridodecyloxybenzamide groups. The self-assembly of these [6]­helicenes is strongly influenced by the substitution pattern in the helicene core that affects the mutual orientation of the monomeric units in the aggregated form. Thus, the 2,15-substituted derivative 1 undergoes an isodesmic supramolecular polymerization forming globular nanoparticles that maintain circularly polarized light (CPL) with g lum values as high as 2 × 10–2. Unlike carbo[6]­helicene 1, the 4,13-substituted derivative 2 follows a cooperative mechanism generating helical one-dimensional fibers. As a result of this helical organization, [6]­helicene 2 exhibits a unique modification in its ECD spectral pattern showing sign inversion at low energy, accompanied by a sign change of the CPL with g lum values of 1.2 × 10–3, thus unveiling an example of CPL inversion upon supramolecular polymerization. These helical supramolecular structures with high chiroptical activity, when deposited on conductive surfaces, revealed highly efficient electron-spin filtering abilities, with electron spin polarizations up to 80% for 1 and 60% for 2, as measured by magnetic conducting atomic force microscopy.

International audienceIn this article the Wells-Dawson polyoxometalate K6[P2W18O62] is grown as an interfacial layer between indium tin oxide and bulk heterojunction of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). The structure of the POM layers depends on the thickness and shows a highly anisotropic surface organization. The films have been characterized by atomic force microscopy and X-ray photoelectron spectroscopy (XPS) to gain insight into their macroscopic organization and better understand their electronic properties. Then, they were put at the anodic interface of a P3HT : PCBM organic solar cell and characterized on an optical bench. The photovoltaic efficiency is discussed in terms of the benefit of the polyoxometalate at the anodic interface of an organic photovoltaic cell