Organic–Inorganic Azafullerene‐Gold C 59 N‐Au Nanohybrid: Synthesis, Characterization, and Properties

Azafullerene (C 59 N) was functionalized using a Mannich‐type reaction and then subsequently condensed with lipoic acid to yield dithiolane‐modified C 59 N. In the following step, the extended dithiolane moiety from the C 59 N core was utilized to decorate the azafullerene sphere with gold nanoparticles (Au NPs). The latter were initially stabilized with dodecanothiol (DT ⋅ Au) and then integrated on azafullerene through a ligand exchange reaction with the dithiolane‐functionalized C 59 N to produce the C 59 N/DT ⋅ Au nanohybrid. The nanohybrid was fully characterized by spectroscopy and microscopy, revealing the formation of spherical nanoparticles with a diameter in the range of 2–5 nm, as imaged by HR‐TEM. In the electronic absorption spectrum of C 59 N/DT ⋅ Au nanohybrid, the characteristic surface plasmon band (SPB) of Au NPs was observed, however, it was redshifted compared with that of DT ⋅ Au. The redshift of the SPB is indicative of closer interparticle proximity of Au NPs, in accordance with the formation of aggregated NPs as observed by TEM, in C 59 N/DT ⋅ Au nanohybrid. Excited‐state interactions in C 59 N/DT ⋅ Au were probed by photoluminescence assays. It was found that the weak emission of C 59 N at 819 nm was blueshifted by 14 nm in C 59 N/DT ⋅ Au, but was stronger in intensity, thus suggesting energy transfer to C 59 N, within the organic–inorganic C 59 N/DT ⋅ Au nanohybrid. Finally, with the aid of pump–probe measurements and transient absorption spectroscopy, the formation of the singlet excited state of C 59 N was identified.