Observation of Both Thermal First-Order and Photochemical Zero-Order Kinetics in the Rearrangement of [6,5] Open Fulleroids to [6,6] Closed Fullerenes

Abstract

A series of [6,5] open fulleroids with radical stabilizing groups on the methano bridge were synthesized and their rearrangements to the more stable [6,6] closed fullerenes studied. These [6,5] open fulleroids all rearrange both by a zero-order photochemical process and by a higher energy unimolecular pathway involving disrotatory closure to the [6,5] closed fullerene, which subsequently rearranges to the [6,6] closed fullerene via a biradical-like intermediate.

Open-Cage Fullerenes: Synthesis, Structure, and Molecular Encapsulation

“…4 However, generally these derivatives are thermally unstable and are known to isomerize to the corresponding [6,6] closed methanofullerenes under various conditions. 4,29,30 In contrast, bis(fulleroid) 7 is thermally more stable than the corresponding bis(methano)fullerene 8, 28 and such isomerization never took place. 24 …”

Preparation and Characterization of Sulfonyl‐Azafulleroid and Sulfonylaziridino‐Fullerene Derivatives

“…The solution of the product mixture was reduced to 10 mL and flash chromatography on silica gel 40 (toluene/cyclohexane, 1:2) gave 19 mg (6%) of 5c (3rd fraction) and 28 mg (9%) of 4c (4th fraction). 2 signals, C-3Ј), 135.13 (C-6Ј), 129.97 (C-5Ј, C-7Ј), 128.98 (C-4Ј, C-8Ј), 22.04 (C-9Ј)…”

Cycloadditions

“…The ease of thermal isomerization from diaryl-, arylalkyl and dialkyl-fulleroids to the corresponding methanofullerene decreases in that order. It appears that these rearrangements involve a biradical intermediate that achieves a major part of its radical stabilization from the fullerene ring [115]. Several studies report zero-order kinetics, which are inconsistent with this mechanism.…”

“…The addition of other diazo compounds, for example substituted diphenyldiazomethanes [110] or alkyl diazoacetates [129], also leads to mixtures of different isomers [2,115]. Four different isomers A-D (R = R′) obtained from single additions of symmetric diazo compounds are principally possible (Figure 4.5).…”