Abstract
Water-soluble malonate multiadducts of paramagnetic gadolinium endohedral metallofullerene, Gd@C82[C(COOH)2]6 and Gd@C82[C(COOH)2]8, were synthesized by Bingel-Hirsch reaction. Gd@C82 was firstly reacted with diethyl bromomalonate in the presence of alkali metal hydride to produce malonic ester multiadducted derivatives, Gd@C82[C(COOCH2CH3)2]x (x = 3-8), by Bingel reaction. They were isolated and purified to obtain Gd@C82[C(COOCH2CH3)2]6 and Gd@C82[C(COOCH2CH3)2]8 by silica-gel column chromatography with a gradient elution method, which were subsequently hydrolyzed to yield water-soluble Gd@C82[C(COOH)2]6 and Gd@C82[C(COOH)2]8 by Hirsch reaction. The structures of the derivatives were characterized by Fourier transform infrared spectrometry and matrix assisted laser desorption ionization time-of-flight mass spectrometry. The longitudinal relaxivities of Gd@C82[C(COOH)2]8 and Gd@C82[C(COOH)2]6, in buffer solution, were found to be 18.20 and 11.08 mM(-1) s(-1) at concentration range between 0.001-0.025 mM Gd, and to be 12.71 and 6.73 mM(-1) s(-1) between 0.050-0.200 mM Gd, respectively. The results showed that the measured relaxivities for malonate derivatives of Gd@C82 were dependent on the concentration of these solutions and the number of hydrophilic carboxyl groups appended on the surface of the Gd@C82 cage.
Published Version
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