Photoinduced Electron-Transfer Reactions of [60]Fullerene with Triethylamine

Abstract

Fullerene molecules undergo efficient photochemical reactions with tertiary amines to form complex mixtures of addition products. The separation and identification of several monoadducts from photochemical reactions of C60 with triethylamine under different experimental conditions are reported. According to molecular spectroscopic results, the photoaddition of triethylamine to C60 is initiated via photoinduced electron transfer between the excited singlet C60 and the amine, similar to photochemical reactions of conventional aromatic molecules with tertiary amines. However, the reaction products with fullerene are completely different. Mechanistic implications of the results are discussed.

Unexpected Reactions of [60]Fullerene Involving Tertiary Amines and Insight into the Reaction Mechanisms

“…To our surprise, product 3, obtained from our thermal aerobic reaction between C 60 and Et 3 N, possesses the same structure as that obtained from the anaerobic photochemical reaction between C 60 and Et 3 N, whilst neither adduct I nor adduct II, the products of air-saturated photochemical reactions between C 60 and Et 3 N, [9] could be isolated from our thermal reaction. The thermal reaction, however, is far superior to the photochemical reaction, for which the reaction mixture had to be deoxygenated and from which adduct 3 was obtained in about a 10 % yield based on reacted C 60 .…”

“…The spectral data of adduct 3 were fully consistent with those reported previously. [9] Adducts 2 a-c and 3 each possessed a common CH 3 CH moiety, which might conceivably have originated from Et 3 N. We suspected that acetaldehyde might have been generated from the fragmentation/oxidization of Et 3 N in ODCB at reflux and might then have participated in a subsequent reaction under our employed conditions. To substantiate our assumption, other aldehydes (RCHO) were added to the reaction mixture of C 60 and Et 3 N to see if products in which the CH 3 CH group in adduct 3 had been replaced with the RCH moiety could be obtained.…”

“…The thermal reaction, however, is far superior to the photochemical reaction, for which the reaction mixture had to be deoxygenated and from which adduct 3 was obtained in about a 10 % yield based on reacted C 60 . [9] In the reactions shown in Scheme 1, adducts 2 a-c could be envisioned as the products of reactions of C 60 with amino acids and acetaldehyde. [4] Nevertheless, no acetaldehyde had been added to the reaction mixtures.…”

“…[12c, 13] Primary, secondary and tertiary amines can react with C 60 to form amine cation radicals and C 60 À C anion radical. [6,9,14] In most cases the electron transfer between an amine and C 60 has been initiated photochemical- Scheme 6. Synthesis of adduct 9 by the reaction of C 60 with 1 a and (CD 3 CD 2 ) 3 N.…”

“…www.chemeurj.org ly, [6,9] but there is evidence that amines can transfer single electrons to C 60 without photoirradiation. [14] Thus, under our high-temperature conditions, a tertiary amine may transfer an electron to C 60 even in the dark (step i in Scheme 7).…”