Abstract
Direct nucleophilic addition of -OH groups on the C(60) skeleton in the basic hydrolysis of ethyl ester of T(h)-symmetric fullerenehexamalonic acid (T(h)-FHMA), leading to the formation of a hybrid with features of T(h)-FHMA and fullerenol, has been observed as an important side reaction. The hydroxylation takes place at considerably milder conditions as those usually used in the synthesis of C(60) fullerenols. UV/Vis and IR spectroscopy were successfully used as a fast monitoring tool which might be of help also in other investigations where additions on C(60) skeleton of molecules with distinct absorption spectra take place.
Highlights
Since the discovery of fullerenes many attempts have been made to synthesize per se structurally attractive fullerene-based compounds and compounds that could be applied for technological[1] or biological[2] purposes
The most troublesome is the final step of the synthesis where, during the hydrolysis of Th-symmetric fullerenehexamalonic acid (Th-FHMA) ester into its salt, partial decarboxylation as a side reaction was observed.[9]
During our previous preparations of Th-FHMA we have already observed that bright yellow color of Th-C66(COOEt)[12] slightly changed into a bit more brownish color after hydrolysis with NaOMe
Summary
Since the discovery of fullerenes many attempts have been made to synthesize per se structurally attractive fullerene-based compounds and compounds that could be applied for technological[1] or biological[2] purposes. In a recent decade scientists discovered other nanostructured materials besides fullerene, there are still some areas where perfectly spherical cage of C60 offers possibilities that can be hardly superseded by other molecules One of such topics is investigation of properties of solutions of highly charged particles where salts of Th-symmetric fullerenehexamalonic acids (ThC66(COOH)[12], in further text denoted as Th-FHMA ) are almost ideal model compounds.[3,4,5,6] It is that C60’s spherical shape significantly facilitates calculation of electrostatic field around the functionalized molecule;[7,8], in numerous cases rigidity of its skeleton is important as well as exactly defined number of ionizable functional groups in the molecule.[5] The synthesis of welldefined Th-FHMA sample, is accompanied with serious difficulties. There exist other water-soluble fullerene compounds but they are either less water-soluble or cannot be prepared pure enough to be utilized in studies where working with well-defined samples is of utmost importance Among the latter compounds one has to certainly mention polyhydroxylated fullerenes, denoted more popularly as fullerenols or fullerols. Hydrolysis of ethyl ester of Th-FHMA (1) producing Th-FHMA (2) and a hybrid (3) between Th-FHMA and fullerenol
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