Fused-pentagon C70Cl26 obtained via chlorination-promoted Stone-Wales cage transformations of C70

Ultrahigh Capacity from Complexation-Enabled Aluminum-Ion Batteries with C70 as the Cathode

Restricted by the available energy storage modes, currently rechargeable aluminum-ion batteries (RABs) can only provide a very limited experimental capacity, regardless of the very high gravimetric capacity of Al (2980 mAh g-1 ). Here, a novel complexation mechanism is reported for energy storage in RABs by utilizing 0D fullerene C70 as the cathode. This mechanism enables remarkable discharge voltage (≈1.65 V) and especially a record-high reversible specific capacity (750 mAh g-1 at 200 mA g-1 ) of RABs. By means of in situ Raman monitoring, mass spectrometry, and density functional theory (DFT) calculations, it is found that this elevated capacity is attributed to the direct complexation of one C70 molecule with 23.5 (super)halogen moieties (superhalogen AlCl4 and/or halogen Cl) in average, forming (super)halogenated C70 ·(AlCl4 )m Cln-m complexes. Upon discharging, decomplexation of C70 ·(AlCl4 )m Cln-m releases AlCl4 - /Cl- ions while preserving the intact fullerene cage. This work provides a new route to realize high-capacity and long-life batteries following the complexation mechanism.

Chlorination-Promoted Skeletal Transformations in Isolated-Pentagon Rule (IPR) Isomers of Fullerene C86 to Non-IPR Chloro- and Trifluoromethyl Derivatives

Fullerene C86 contains two isomers obeying the Isolated-Pentagon Rule (IPR), CS-C86(16) and C2-C86(17). Both isomers undergo unprecedented skeletal transformations at high-temperature (400 °C) chlorination with SbCl5. One-step Stone-Wales rearrangement (SWR) in C86(17) results in the pentagon-fused #63614C86 cage found in the structure of #63614C86Cl24. CF3 derivatives with the same cage, two isomers of #63614C86(CF3)18 and #63614C86(CF3)18O2, were obtained by high-temperature trifluoromethylation of the chlorination products with CF3I, followed by HPLC separation. The skeletal transformation of C86(16) proceeds via two SWRs under the formation of a #63624C86 cage with one fused-pentagon pair found in the structure of #63624C86(CF3)18. The addition patterns in skeletally transformed molecules are discussed in detail, disclosing the influence of the pentagon fusions, isolated C=C bonds, and benzenoid rings on the stability of the molecules with non-IPR C86 cages. The chlorination-promoted SWRs in C86 isomers have been observed for the first time, which contribute a lot to the understanding of skeletal transformations in fullerenes.

Structural Chemistry of Pentagon-Fused C82 Fullerene Derivatives #39173C82(CF3)14,16,18 and #39173C82Cl28

High-temperature chlorination of the most stable Isolated-Pentagon-Rule (IPR) isomer of fullerene C₈₂, C₂-C₈₂(3), invariably produces non-IPR ^#39173C₈₂Cl₂₈, containing one pentagon-pentagon fusion in the carbon cage. High-temperature trifluoromethylation of ^#39173C₈₂Cl₂₈ followed by HPLC separation resulted in the isolation and structure elucidation of eight ^#39173C₈₂(CF₃)_n (n = 14, 16, 18) compounds. Structural chemistry of ^#39173C₈₂(CF₃)_14,16,18 and ^#39173C₈₂Cl₂₈ is characterized by the variation of the addition patterns in the region of a pentagon-pentagon fusion. The regiochemistry of CF₃ addition in the remaining cage region is similar to that of the known IPR C₈₂(3)(CF₃)_n compounds. Theoretical calculations revealed that ^#39173C₈₂(CF₃)_n possess lower thermodynamic stability than isomeric IPR derivatives.

Crippling the C70 fullerene: non-classical C68Cl26(OH)2 and C68Cl25(OH)3 with three heptagons and only fused pentagons via chlorination-promoted skeletal transformations

High-temperature (440 °C) chlorination of C₇₀ with SbCl₅ promotes Stone-Wales transformations and loss of the C₂ fragment, which results in a non-classical C₆₈Cl₂₈ partially hydrolyzed to C₆₈Cl₂₆(OH)₂ and C₆₈Cl₂₅(OH)₃. X-ray diffraction reveals an unprecedented C₆₈ cage with three heptagons and 15 pentagons arranged in fused pairs and triples. The shortest possible transformation pathways include one C₂ loss step and four Stone-Wales transformation steps.

Fused-Pentagon C70Cl6 and C70Cl8 Obtained via Chlorination-Promoted Skeletal Transformation of IPR C70

The isolated-pentagon-rule (IPR) D_5h-C₇₀ fullerene is least susceptible to skeletal transformations in comparison with higher fullerenes and even C₆₀. A cage transformation in IPR C₇₀ via a one-step Stone-Wales rearrangement was accomplished by high-temperature (440 °C) ampule chlorination with SbCl₅. Subsequent dechlorination at 450 °C, followed by high-performance liquid chromatography separation, allowed the isolation of non-IPR C₇₀Cl₆ and C₇₀Cl₈. X-ray diffraction study revealed the presence of an unprecedented C₇₀ carbon cage, possessing two pairs of fused pentagons and the chlorination patterns located on one cage hemisphere. A high energetic and thermal stability of both non-IPR chlorides was also confirmed by theoretical calculations of formation energies. Pathways of skeletal transformations of IPR C₇₀ in comparison with those in C₆₀ are discussed.