Synthesis of Open‐Cage Fullerene Derivatives Containing Multiple Hydroxyl and Amino Groups on the Rim of the Orifice^†

Abstract

Comprehensive Summary Most of the known open‐cage fullerene derivatives contain carbonyl and other relatively inert groups on the rim of the orifice. It is difficult to rationally design further reactions and attach other functional groups on to these open‐cage derivatives. In the present work, two molecules of difunctional 1,4‐benzenediamine have been incorporated into the rim of an open‐cage C60 derivative through one amino group leaving the other amino group free for further functionalization. The difunctional 4‐aminophenol reacted analogously to form an open‐cage derivative with a free OH group each on the two phenyl rings. The amino and hydroxyl groups on the phenyl ring above the rim of the orifice showed similar reactivity as aniline and phenol. One of the carbonyl groups on the rim of the orifice could be selectively reduced by NaBH4 and P(OEt)3. The reduction reactions were reversible and the reduced products could be readily converted back to the carbonyl precursor. Thus, this redox process acts as a tool to fine tune the size of the orifice for host‐guest studies.

Selective deletion of one carbon atom from C60 through benzylamine mediated reactions

“…As expected, the hemiaminal derivative 2 was obtained following the same route as the aryl amine reactions. 8 Oxidation of 2 with DIB (diacetyliodobenzene) gave product 3 , which is quite different from the analogous reactions with the aryl amino adducts. 8 Only the two more hindered hydroxyl groups were oxidized.…”

“…8 Oxidation of 2 with DIB (diacetyliodobenzene) gave product 3 , which is quite different from the analogous reactions with the aryl amino adducts. 8 Only the two more hindered hydroxyl groups were oxidized. Compound 3 was not very stable and slowly decomposed into compounds 4 and 5 along with other uncharacterized products upon storage.…”

“…Compound 1 was prepared from C 60 in 3 steps as we have previously reported. 8 The two carbonyl groups in 1 are in close proximity. Aryl amines readily attack the less hindered carbonyl group to form a hemiaminal moiety together with the other carbonyl group.…”

“…Surprisingly, the aryl imino group was very stable and could not be hydrolysed under various conditions such as heating in the presence of hydrochloric acid. 8…”

Open-[60]fullerene–aniline conjugates with near-infrared absorption

“…1). 6 Recently, we reported a dehydrative condensation of a carbonyl group on the [60]fullerene orifice with o - and p -substituted aromatic diamines, which afford NIR-absorbing dyes showing absorption edges at 900 nm (benzonitrile) 7 and 1050 nm (toluene), 8 respectively. In these molecules, the aniline moiety is conjugated with the [60]fullerene skeleton by an imino group.…”