“…The doubly, triply, and quadruply charged hydrogenated fullerenes were efficiently detected [13]. This ability to undergo multiple ionization under routine EI conditions more closely resembles the features observed for pure fullerenes [13,14]. The formation of dications has been established for fluorofullerenes [15], while any efficient multiple ionization of organic ligand bearing fullerenes has not been reported [13].…”
mentioning
confidence: 58%
“…Previous experimental data on fullerene ionization has established that multiple ionization of C 60 is readily achievable by EI or collision-induced ionization [9 -12]. The doubly, triply, and quadruply charged hydrogenated fullerenes were efficiently detected [13]. This ability to undergo multiple ionization under routine EI conditions more closely resembles the features observed for pure fullerenes [13,14].…”
Mass spectra of the methylated [60]fullerenes were obtained by EI mass spectrometry using "desorption" or "in-beam" technique. The mass spectra of the methylated fullerenes, C 60 Me n , have the molecular ion peak M ϩ indicating that the product is stable under the MS (EI) conditions. The appearance of an intense peak at m/z 360 was assigned to the formation of fullerene dication C 60 ϩϩ . The remaining peaks were assigned to successive loss of methyl groups from molecular monocation and dication. A lkylation involves reaction of fullerene anions with positive alkyl groups. This leads to different addition patterns, which vary also according to the alkylation technique. These compounds are exceptionally soluble fullerenes, and promise to be useful cross-linking additives, for which the parent fullerenes are too insoluble.Their relative simplicity aids structural characterization, and many of them form suitable crystals for X-ray structure determination [1,2]. Although the small size of the methyl group and the reasonable stability of the methylfullerenes toward electron impact (EI) mass spectrometry made the reaction suitable for elucidating mechanistic features of fullerene additions, the polymethylation was a disincentive to further work [3]. The availability of high-pressure liquid chromatography (HPLC) columns dedicated to fullerene separation has enabled progress to be made.The methylated fullerenes were prepared in our previous works by different methods [1-4]: (1) reaction of fullerene with lithium followed by MeI, (2) reduction of fullerene with sodium n-propylthiolate followed by quenching with MeI, (3) reduction of fullerene by Al-Ni alloy and aqueous NaOH-dimethyl sulfoxide followed by quenching with MeI, and (4) methylation by nucleophilic substitution of halogenated fullerene C 60 Cl 6 . The resulting methylated fullerenes differ according to the method used, indicating different addition pathways: Separation of methylated fullerenes was performed with HPLC using a Cosmosil Buckyprep column with either heptane, toluene, toluene/heptane, or cyclohexane/toluene mixtures, with UV detection at 285 nm and a flow rate of 4 mL/min.Mass spectra were obtained using a VG Autospec (Sussex University, UK) mass spectrometer using 70-eV EI ionization. The samples were introduced into the mass spectrometer using the direct insertion probe with desorption CI (chemical ionization) tip operated at a temperature between 50 and 500°C. The samples were coated on a surface and inserted directly inside an ion source, as close to the ionization area as possible, by means of an extended direct insertion probe. The Љin-beamЉ technique gives a better chance of observing molecular ions in the mass spectra at the lower temperature and small sample size [5].
“…The doubly, triply, and quadruply charged hydrogenated fullerenes were efficiently detected [13]. This ability to undergo multiple ionization under routine EI conditions more closely resembles the features observed for pure fullerenes [13,14]. The formation of dications has been established for fluorofullerenes [15], while any efficient multiple ionization of organic ligand bearing fullerenes has not been reported [13].…”
mentioning
confidence: 58%
“…Previous experimental data on fullerene ionization has established that multiple ionization of C 60 is readily achievable by EI or collision-induced ionization [9 -12]. The doubly, triply, and quadruply charged hydrogenated fullerenes were efficiently detected [13]. This ability to undergo multiple ionization under routine EI conditions more closely resembles the features observed for pure fullerenes [13,14].…”
Mass spectra of the methylated [60]fullerenes were obtained by EI mass spectrometry using "desorption" or "in-beam" technique. The mass spectra of the methylated fullerenes, C 60 Me n , have the molecular ion peak M ϩ indicating that the product is stable under the MS (EI) conditions. The appearance of an intense peak at m/z 360 was assigned to the formation of fullerene dication C 60 ϩϩ . The remaining peaks were assigned to successive loss of methyl groups from molecular monocation and dication. A lkylation involves reaction of fullerene anions with positive alkyl groups. This leads to different addition patterns, which vary also according to the alkylation technique. These compounds are exceptionally soluble fullerenes, and promise to be useful cross-linking additives, for which the parent fullerenes are too insoluble.Their relative simplicity aids structural characterization, and many of them form suitable crystals for X-ray structure determination [1,2]. Although the small size of the methyl group and the reasonable stability of the methylfullerenes toward electron impact (EI) mass spectrometry made the reaction suitable for elucidating mechanistic features of fullerene additions, the polymethylation was a disincentive to further work [3]. The availability of high-pressure liquid chromatography (HPLC) columns dedicated to fullerene separation has enabled progress to be made.The methylated fullerenes were prepared in our previous works by different methods [1-4]: (1) reaction of fullerene with lithium followed by MeI, (2) reduction of fullerene with sodium n-propylthiolate followed by quenching with MeI, (3) reduction of fullerene by Al-Ni alloy and aqueous NaOH-dimethyl sulfoxide followed by quenching with MeI, and (4) methylation by nucleophilic substitution of halogenated fullerene C 60 Cl 6 . The resulting methylated fullerenes differ according to the method used, indicating different addition pathways: Separation of methylated fullerenes was performed with HPLC using a Cosmosil Buckyprep column with either heptane, toluene, toluene/heptane, or cyclohexane/toluene mixtures, with UV detection at 285 nm and a flow rate of 4 mL/min.Mass spectra were obtained using a VG Autospec (Sussex University, UK) mass spectrometer using 70-eV EI ionization. The samples were introduced into the mass spectrometer using the direct insertion probe with desorption CI (chemical ionization) tip operated at a temperature between 50 and 500°C. The samples were coated on a surface and inserted directly inside an ion source, as close to the ionization area as possible, by means of an extended direct insertion probe. The Љin-beamЉ technique gives a better chance of observing molecular ions in the mass spectra at the lower temperature and small sample size [5].
“…Preliminary experiments based on resonant electron capture mass spectrometry have provided indications for the possible existence of the long-lived molecular negative ion of C 60 H 18 •- ; however, the elemental composition of this ion could not be established unambiguously . Following our recent investigations into the fragmentation and ionization dynamics of hydrogenated C 60 , we report here on the unprecedented finding of long-lived, negative molecular ions derived from C 60 H 18 . 1 Negative ion laser desorption/ionization ToF mass spectra of C 60 H 36 (a) and C 60 H 18 (b) recorded at the threshold of the ion formation.…”
Long-lived molecular negative ions are generated from C 60 H 18 following the application of several ionization methods such as laser desorption/ionization, negative ion chemical ionization, and resonant free electron capture. The mass spectrometric observation of stable negative fullerene ions showing such a high degree of hydrogen attainment is unprecedented. The identity of the negative molecular ion is confirmed by highresolution accurate mass measurements. The attachment of monochromatic electrons to C 60 H 18 is studied in the energy range from 0 to 20 eV, and the resulting negative ion effective yield curve is discussed together with the mean lifetime curve of the ion. Negative molecular ions that result from capture of thermal electrons at a molecular temperature of 600 K possess a maximum mean lifetime in the range of 1 ms. From the experimental data the electron affinity of C 60 H 18 is estimated to lie between 1.4 and 1.6 eV, which is in excellent agreement with the results obtained here from semiempirical calculations.
“…[8][9][10][11][12] Although small hydrocarbons could be detected following the thermal treatment of deutero[60]fullerenes, 13 indicating that cage rupture may play a role, there is recent evidence that the C 60 + signal observed in most mass spectra of these compounds is essentially due to a complete thermal removal of all hydrogen atoms from the neutral molecule. 14 The fact that the carbon core can be completely released from the stored hydrogen and thus be regenerated is a rare feature, as hydrocarbons normally degrade via C-C bond rupture.…”
C(60)H(36) has been used as the source of hydrogen for the in situ hydrogenation of (C(59)N)(2), leading to C(59)NH(5) as the main reaction product identified by negative-ion mass spectrometry and providing evidence of the usage of C(60) as a storage device for hydrogen.
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