Comparison between the photophysical properties of pyrazolo- and isoxazolo[60]fullerenes with dual donors (Ferrocene, Aniline and Alkoxyphenyl)

Two series of new pyrazolo- and isoxazolo[60]fullerenes covalently linked to vinylenephenylene bearing ferrocene, dibutylaniline or dodecyloxyphenyl electron-donor groups attached in the periphery have been synthesized. The photophysical properties of these newly synthesized dual-donor-C₆₀ derivatives have been investigated and compared by applying time-resolved fluorescence and nanosecond transient techniques in both polar and nonpolar solvents. Charge separation via the excited singlet state of C₆₀ is more efficient in the pyrazolo-C₆₀ triads than in the isoxazolo-C₆₀ triads. It was found that the pyrazoline ring mediates charge separation as a result of the stronger electron-donating character of the nitrogen atom of the pyrazoline ring compared with the oxygen atom of the isoxazoline ring.