A faux hawk fullerene with PCBM-like properties

Area of Science:

• Fullerenes chemistry
• Organic synthesis
• Materials science

Background:

• Fullerenes are carbon allotropes with unique electronic and structural properties.
• Functionalization of fullerenes is crucial for tuning their properties for specific applications.
• Perfluorinated organic compounds offer distinct reactivity and stability.

Purpose of the Study:

• To synthesize and characterize novel fullerene derivatives with perfluorinated substituents.
• To investigate the reactivity and thermal stability of these new compounds.
• To evaluate their potential in organic electronic applications.

Main Methods:

• Reaction of C60 with C6F5CF2I and SnH(n-Bu)3 to yield fullerene derivatives.
• Isolation and characterization using HPLC and NMR spectroscopy.
• Thermal stability studies in oDCB and PhCN/C6D6.
• DFT calculations to elucidate reaction mechanisms.
• Gas-phase electron affinity determination via low-temperature PES.
• Electrochemical measurements (cyclic voltammetry).
• Time-resolved microwave conductivity studies in P3HT blends.
• Single-crystal X-ray diffraction analysis.

Main Results:

• Two new fullerene derivatives, 1,9-C60(CF2C6F5)H (1) and 1,9-C60(cyclo-CF2(2-C6F4)) (2), were synthesized with yields up to 35% for compound 1.
• Compound 1 can be thermally converted to compound 2.
• DFT calculations suggest intramolecular S_NAr annulation of a fullerene-cage carbanion intermediate leads to compound 2.
• Compound 2 exhibits a higher gas-phase electron affinity (2.805 eV) than C60 and PCBM.
• Compound 2 shows comparable charge-carrier mobility in P3HT blends to PCBM.
• Single-crystal X-ray diffraction reveals a higher number of nearest-neighbor interactions for compound 2 compared to PCBM.
• Compound 2 demonstrates significantly greater thermal stability than PCBM.

Conclusions:

• The synthesis of novel perfluorinated fullerene derivatives was achieved.
• The facile conversion of compound 1 to 2 via an S_NAr mechanism highlights unique fullerene carbanion reactivity.
• Compound 2 possesses promising electronic and thermal properties for organic photovoltaic applications.
• The structural packing of compound 2 in crystals influences its intermolecular interactions and stability.