C64H4:  Production, Isolation, and Structural Characterizations of a Stable Unconventional Fulleride

Unconventional fullerenes are those smaller than C60 or those intermediate between C60 and C70, which are not stable in structure as none of the unconventional fullerene isomers satisfying the “isolated-pentagon-rule” (IPR). Below we report the synthesis of a stable unconventional fullerene derivative C64H4 by introducing methane in the fullerene productions with the normal Krätschmer−Huffman method. We also applied various spectroscopic measurements such as mass spectrometry, 13C NMR, IR, UV−vis absorption spectrometry, etc. to characterize the structural and electronic properties of this molecule, revealing an unprecedented fullerene cage with a triplet of directly fused pentagons in the framework of C64H4. Four hydrogen atoms are added to the carbons at vertexes of fused pentagons to allow the bond angles at these sites close to the sp3 tetrahedral angle, which essentially release the sp2 bond strains on the abutting-pentagon sites of C64. Ab initio calculations were performed to explore the electronic property and simulate the 13C NMR and IR spectra of this fulleride, which reproduced well the experimental results and confirmed the structural assignment of the C64H4.