Self-assembly and nonlinear optical properties of N-substituted fulleropyrrolidine bearing adamantane

Abstract

Bearing a highly symmetric and rigid structure, fullerene C₆₀ is a fascinating building block in supramolecular chemistry. The fact that the C₆₀ moiety can be chemically modified brings a wide range of possibilities in fine tuning the self-assembled structures. Herein, we report the synthesis of an N-substituted fulleropyrrolidine bearing adamantane (Ad), where the Ad unit was anchored onto the C₆₀ moiety through a one-step reaction. Self-assembly of the Ad-C₆₀ hybrid was investigated via a modified liquid–liquid interfacial precipitation (LLIP) method. Superstructures with rich morphologies were obtained, including spheres, hexagons, cubes, flowers and stacked flakes. Self-assemblies from xylene systems were selected as examples for deeper investigation. The internal organization was probed by powder X-ray diffraction, which confirms the formation of a monoclinic and orthorhombic lattice. Measurements on nonlinear optical performance revealed reverse saturable absorption, with the maximum nonlinear absorption coefficient (β) reaching 4.82 × 10⁻⁸ cm W⁻¹ for the solvated crystals obtained using m-xylene as a good solvent. The photoluminescence of the Ad-C₆₀ hybrid, both in solution and in the crystalline form, was also discussed with close comparison to two of its monosubstituted counterparts obtained by [1+2] cycloaddition and Prato reactions, respectively. This work provides insight into the structure–property relationship of the C₆₀-based superstructures, and strengthens the charming feature of C₆₀ in both supramolecular chemistry and materials science.