Synthesis of radio-metallofullerenols

Water-soluble fullerene derivatives have been investigated to date mostly within the framework of biological and medical applications. For example, C60 derivatives have been applied as HIV inhibitors, radical scavenging capabilities and anti-cancer. The C60 fullerenols, C60(OH)n, have been synthesized and have shown excellent water solubility. Kitazawa and co-workers also reported a more efficient reaction to obtain C60(OH)n, using NaOH aq and tetrabutylammonium hydroxide as a phase transfer catalyst. Water-soluble endohedral metallofullerene derivatives are particularly interesting because of their possible applications to radiotracers and magnetic resonance imaging (MRI) contrast agents. We investigate to trace the synthesis process of metallofullalnols using radioactivity, and obtain the effective process of radio-metallofullerenols. Carbon soot containing Sm endohedoral metallofullerenes was produced by the dc arc discharge method. The resulting soot was extracted with o-dichlorobenzene by reflux for 5 h. The obtained crude was irradiated for 30 min in the JRR4, After irradiation, crude was dissolved by toluene and filtrated by 0.2 μm pore size filter. The separation of the Sm doped C82 including 153Sm tracer from the crude was achieved by HPLC method which is a HPLC process on the Buckyprep column. We obtained fraction containing of three kinds of Sm doped C82. Details of the syntheses of endohedral metallofullerenols have been reported elsewhere. Briefly, toluene solutions of isolated Sm doped C82 including 153Sm with C60 were vigorously vibrated with saturation KOH aq containing few drops of TBAH (10 % in water) as catalyst at room temperature. The reaction times were changed from l minute to 8 hours. The reaction mixture was filtrated by 0.2 μm filter. The residue was rinsed with methanol to ensure the removal of the catalyst and KOH. The rinsed residue was dissolved in water for 7 hours. The resultant brown- solution was the passed down a Sephadex G25 size-exclusion gel chromatography column using distilled water as the eluent. All products of reaction process were traced 103.2 keV γ-emission of l53Sm by HPGe detector. The recovery yield of 153Sm doped C82(OH)x at 8 hours reaction time was 82 % before the size-exclusion gel chromatography and was 56 % after that. 153Sm adsorbed 26% and eluted Sm ion using 1M HCl aq in column. To investigate the distribution of 153Sm in the extraction system for synthesis of hydrophilic 153Sm doped C82(OH)x. The amount of the 153Sm in KOH aqueous and toluene phases as a function of reaction time. The 153Sm radioactivity in the toluene phase decreased with increasing reaction time and has been 3 % at 5 minutes, and that in the KOH aqueous phase increased up to 1 hour and fixed 10 % to 8 hours. We did the attempt to obtain radio-metallofullerenols by another method. In first step, Sm doped C82(OH)x was synthesized and isolated from Sm doped C82 without radioactivity. In second step, Sm doped C82(OH)x with C60(OH) performed neutron irradiation in the reactor. In yield in another method, a result that was eight times higher was obtained compared with it in the first method.