Synthesis and Aggregation Studies of Bingel-Hirsch Monoadducts of Gadofullerene

The monoadducted malonic ester derivative of paramagnetic gadofullerene, Gd@C-82[C(COOCH2CH3)(2)], was synthesized by the Bingel reaction, which Gd@C-82 was reacted with diethyl bromomalonate in the presence of 1,8-diazabicyclo[5.4.0] undec-7-ene. It was isolated and purified by high performance liquid chromatography, and subsequently hydrolyzed to yield water-soluble disodium salt form Gd@C-82[C(COONa)(2)] by the Hirsch reaction. The disodium salt was purified by dialysis. The resulting materials were characterized by various measurements, such as matrix assisted laser desorption ionization time-of-flight mass spectrometry, ultraviolet-visible near-infrared and fourier transform infrared spectroscopy. The aggregation behavior of the newly water-soluble nanoparticles was investigated by scanning electron microscopy and dynamic light scattering analysis. This presented synthetic methodology opens the avenue for the preparation of novel water-soluble malonate derivatives of paramagnetic Gd@C-82, which are expected to be useful species with potential applications in biomedicine.