Process for the synthesis of [6,6]-phenyl-c61butyric acid pentyl ester (pc61bp)

A process for the synthesis of [6,6]-phenyl(C61)butyric acid pentyl ester (PC61BP) of Formula 1, comprising the steps of:

• i) reacting an organic acid ester and a p-toluene sulphonyl hydrazide in the range of 1:1.2 to 1:1.5 by dissolving the compounds in methanol and refluxing with stirring for 4-6 hrs followed by stirring at room temperature in the range of 20-30° C. for a period in the range of 10-12 hr and cooling at 0-10° C. to obtain organic acid ester hydrazone crystals;
• ii) washing the hydrazone crystals as obtained in step (i) with cold methanol to obtain pure organic acid ester hydrazone;
• iii) dissolving the organic acid ester hydrazone as obtained in step (ii) in an organic solvent and cooled to −10 to 10° C., followed by adding alkyl amine and stirring for a period in the range of 1-3 hrs to obtain an organic acid ester hydrazone solution;
• iv) adding a fullerene solution to the organic acid ester hydrazone solution as obtained in step (iii) in the ratio ranging between 1:0.33-1:0.5 and temperature raised to 80-100° C. by continuous stirring for a period in the range of 18-24 hrs followed by precipitating with methanol to obtain a mixture;
• v) centrifuging the mixture as obtained from step (iv) to obtain a solid;
• vi) loading the solid as obtained in step (v) on a silica gel column and purifying it with toluene to obtain unreacted fullerene and monoadduct [5,6]PC61BP;
• vii) refluxing the monoadduct as obtained in step (vi) in o-dichlorobenzene for a period in the range of 5-7 hrs followed by centrifuging to obtain [6,6]-phenyl(C61)butyric acid pentyl ester.