(Invited) The Varying Packing Behaviors of Tb@C82 (I, II) Isomers in Their Cocrystals with Ni(OEP)

Abstract

Carbon soot containing terbium endohedral fullerenes was prepared by vaporizing a graphite rod doped with Tb4O7 in an electric arc-discharge chamber. After Soxhlet extraction with 1,2,4-trichlorobenzene and rotary evaporation, the obtained residue was ultrasonically dissolved in toluene and then subjected to a three-stage high-pressure liquid chromatographic (HPLC) isolation process to collect the Tb@C82 (I, II) isomers. The molecular structures of Tb@C82 (I, II) are unambiguously characterized as Tb@C 2v(9)-C82 and Tb@C s(6)-C82, respectively, in line with single-crystal X-ray diffraction. Moreover, Tb@C82 (I, II) isomers demonstrated different packing behaviors in their cocrystals with Ni(OEP). Tb@C82 (I) forms 1:1 cocrystal with Ni(OEP), whereas Tb@C82 (II) forms 2:2 cocrystal with Ni(OEP). Tb@C s(6)-C82 forms a centrosymmetric dimer in 2[Tb@C s(6)-C82]∙2[Ni(OEP)]∙2(C6H6)∙(CS2), and the two C s(6)-C82 cages are connected by a new C-C bond with a bond length of 1.618(4) Å. Density functional theory calculations show that the dominant unpaired spin exists on a particular C atom of Tb@C s(6)-C82, leading to regionally selective dimerization.