The Various Packing Structures of Tb@C 82 (I, II) Isomers in Their Cocrystals with Ni(OEP).

Soot-containing terbium (Tb)-embedded fullerenes were prepared by evaporation of Tb 4 O 7 -doped graphite rods in an electric arc discharge chamber. After 1,2,4-trichlorobenzene extraction of the soot and rotary evaporation of the extract, a solid product was obtained and then dissolved into toluene by ultrasonication. Through a three-stage high-pressure liquid chromatographic (HPLC) process, Tb@C 82 (I, II) isomers were isolated from the toluene solution of fullerenes and metallofullerenes. With the success of the growth of cocrystals of Tb@C 82 (I, II) with Ni(OEP), the molecular structures of Tb@C 82 (I) and Tb@C 82 (II) were confirmed to be Tb@C 2v (9)-C 82 and Tb@C s (6)-C 82 , respectively, based on crystallographic data from X-ray single-crystal diffraction. Moreover, it was found that Tb@C 82 (I, II) isomers demonstrated different packing behaviors in their cocrystals with Ni(OEP). Tb@C 2v (9)-C 82 forms a 1:1 cocrystal with Ni(OEP), in which Tb@ C 2v (9)-C 82 is aligned diagonally between the Ni(OEP) bilayers to form zigzag chains. In sharp contrast, Tb@C s (6)-C 82 forms a 2:2 cocrystal with Ni(OEP), in which Tb@C s (6)-C 82 forms a centrosymmetric dimer that is aligned linearly with Ni(OEP) pairs to form one-dimensional structures in the a-c lattice plane. In addition, the distance of a Ni atom in Ni(OEP) to the C s (6)-C 82 cage is much shorter than that to the C 2v (9)-C 82 one, indicative of a stronger π-π interaction between Ni(OEP) and the C 82 carbon cage in the cocrystal of Tb@C S (6)-C 82 and Ni(OEP). Density functional theory calculations reveal that the regionally selective dimerization of Tb@C S (6)-C 82 is the result of a dominant unpaired spin existing on a particular C atom of the C S (6)-C 82 cage.