The absence of ‘globe-trotting’ hydrogen on the surfaces of aminated fullerenes: 3-D hydrogen bonding between aminated fullerenes and water revealed

Abstract

Unusual temperature dependencies in the 1H NMR spectra of aminated fullerenes, previously attributed to 'globe-trotting' hydrogen, are in fact due to temperature and dilution dependent hydrogen bonding interactions with water.Soon after c 6 0 became available in macroscopic quantities,l addition of R(R')N and H elements across a double bond of several groups worked to functionalize this novel form of C ~O , as one might expect upon the collapse of a [C,]*carbon. Among the more interesting finds, Wudl et al.[R(R')NH]*+ radical ion pair followed by (or subsequent to) discovered2 that C60 reacts readily and repeatedly with proton transfer.3 Wudl etal. also reported2 formation of a primary and secondary amines yielding aminated fullerene morpholine adduct of c60, 1, to which they assigned the derivatives. Suggesting an electron transfer mechanism, it was structure C60H6[N(CH2CH*)20]6,2b,c and claimed2b that the reported2 that each amination reaction is characterized by the methine hydrogens readily 'globe-trot' about the aminated

Photoaddition of N‐Substituted Piperazines to C60: An Efficient Approach to the Synthesis of Water‐Soluble Fullerene Derivatives

“…[22] However, no obvious evidence was obtained for the presence of hydrogen atoms attached to the carbon cage in the fullerene derivatives formed. [23] In contrast, a number of reports indicated unambiguous formation of aminofullerene derivatives C 60 A C H T U N G T R E N N U N G (NR 2 ) n under the same conditions. [24,25] Moreover, conduction of these reactions in air under irradiation by visible light resulted in increased product yields and decreased reaction times in comparison with the syntheses under an argon atmosphere whilst heating at reflux.…”

Reactions between aliphatic amines and [60]fullerene: a review

“…This dynamic behavior, however, was later shown to be due to temperature and dilution dependent hydrogen bonding interactions between amine moieties on the fullerene surface and residual water, not globe-trotting hydrogen. Thus, Miller et al demonstrated [8] that the NMR signals attributed to globe-trotting hydrogens could be completely removed upon the addition of 3 Å molecular sieves and returned again upon spiking samples with additional water. Moreover, dilution dependencies ruled out an intramolecular process.…”

“…Thus, products from the morpholine reaction precipitate from neat morpholine solution after approximately six additions [2,7] while smaller amines like n-propylamine add a dozen times without precipitation. Aqueous solutions of dimethylamine have been utilized to add approximately 10 equivalents of dimethylamine under biphasic conditions (H 2 O/CHCl 3 ) without precipitation of product [8]. Unless oxygen is rigorously excluded, it will be incorporated into the product structures (vide infra).…”

Structural Analysis of Novel [60]Fullerene Bisadduct Regioisomers by DFT Calculation

“…less, it is notable that such a thermodynamically unstable isomer 3a can be the major isomeric product if the kinetic control plays a significant role in the reaction process. This selectivity clearly excludes the rearrangement or trotting of the addends on the C 60 cage surface (9), which may result in the formation of more thermodynamically favorable regioisomers, under the present reaction conditions.…”