A novel oxygen-bridged unsymmetrical dimer composed of C60 cages with 1,2- and 1,4-configurations is obtained. The dimer is interesting due to the existence of only one regioisomer, unique regioselectivity, presence of organo functionalities, and exhibition of stepwise reductions via the alternative sequential electron transfer to the 1,4- and 1,2-C60 cages.

Novel C60 derivatives of a singly bonded dimer and a 1,4-adduct bearing a sulfonic acid functionality have been prepared via the electroreductive transformation of a [60]fullerosultone. It has been shown that the reaction of the in situ formed dianion with benzyl bromide is initiated by a ring-opening of the [60]fullerosultone via the C60–O bond cleavage upon receiving one electron. The [60]fullerosultone dianion is electrooxidized at 0.40 V to afford the singly bonded dimer species, which can be further electrooxidized at 1.30 V to restore the starting material [60]fullerosultone. The reaction mechanism is studied with the cyclic voltammetry and vis–NIR spectroscopy.

The reactions of C702– with organic halides result in several isomeric products. However, the structures of the isomers have not been identified unambiguously and the reactions still remain elusive even though the first report of the reaction appeared more than ten years ago. Herein, the reactions of C702– with ArCH2Br (Ar = Ph, o-, m-, and p-BrC6H4) are revisited. Two types of isomeric para-adducts of 2,5- and 7,23-(ArCH2)2C70 are obtained and characterized with the X-ray single-crystal diffractions, HRMS, 1H and 13C NMR, and UV–vis spectroscopies. An unusual singlet resonance instead of the typical AB quartet resonance is shown for the C2 diastereotopic methylene protons in 1H NMR spectrum of 2,5-(PhCH2)2C70 recorded at ambient temperature. The unexpected magnetic equivalence is studied with the variable-temperature (VT) NMR and density functional theory (DFT) calculations. The results show that the greater local curvature in the C70 polar region is likely responsible for the unusual magnetic equivalence exhibited by the C2 diastereotopic methylene protons of 2,5-(PhCH2)2C70, indicating that under certain cases, it is improbable to elucidate the spectral data of fullerene derivatives with a less symmetrical carbon cage in analogy with those of the C60 derivatives.

Multiadditions of heteroaddends to C60 are achieved via the oxazolination reaction of 1,4-(PhCH2)2C60 with OH– and PhCN, which exhibit a unique regioselectivity regarding the addition sites of the heteroatoms.

Reactions of C60 with oxygen nucleophiles of HO– and CH3O– are revisited in PhCN in the presence of PhCH2Br. Different from previous results that such reactions lead to the formation of complex mixtures, well-structured C60 oxazolines are obtained when HO– is involved, while di- and tetraadducts with methoxy and benzyl addends are obtained when CH3O– is engaged. The reactions are followed by in situ vis–near-IR spectroscopy, which reveals further information for the reactions.

Oxazolination of C70 has been achieved via the aerobic oxidation of C702– in the presence of PhCN. Only one C70 oxazoline regioisomer (1) is obtained, indicating that the oxazolination of C702– occurs with an unusual regioselectivity. Further benzylation of 12– with benzyl bromide leads to the formation of the first cis-1 C70 derivative with respect to the apical pentagon (2), as shown by the X-ray single-crystal structure and various spectral characterizations. The structure of the obtained C70 oxazoline (1) is resolved with H/D labeling benzylation and HMBC (heteronuclear multiple bond coherence) NMR on the basis of the structure of 2. The result shows that for compound 1, the O atom is selectively bonded to the C1, while the N atom is bonded to the C2 of C70. The exhibited regioselectivity for the orientation of oxazolino group on C70 is further rationalized with computational calculations, and a reaction mechanism for the oxazolination of C702– is proposed.

Benzyl(hydro)[70]fullerene regioisomers with the addends in both the equatorial and polar regions of C70 have been prepared via the reaction of dianionic C70 with benzyl bromide and H2O. HRMS, UV-vis, 1H, 13C, HMQC (heteronuclear multiple quantum coherence) and HMBC (heteronuclear multiple bond coherence) NMR characterisations have shown that the addition in the equatorial region of C70 affords a new (PhCH2)HC70 regioisomer with para-positioned addends across a six-membered ring, which is different from the “polar” regioisomers where the addends have an ortho-addition pattern. 1H NMR characterisations have shown a much stronger shielding effect for the addends in the equatorial region with respect to the counterparts in the polar region of C70, while cyclic voltammetry study has shown a surprising positive shift for the first reduction potential of the equatorial regioisomer with respect to those of the polar regioisomer and pristine C70, suggesting that the equatorial region of C70 is rather electropositive than electronegative. D2O experiment has shown a significant difference of the deuterated product distribution between the equatorial and polar regioisomers, which can be justified by the different acidity of the (PhCH2)HC70 regioisomers. Computational calculations have been carried out to rationalize the formation of the C70HR regioisomers.

C60 derivatives have shown enhanced fluorescent emissions with respect to C60 due to the lowering of molecular symmetry and have demonstrated promising potentials as novel organoelectronic materials for application in light-emitting diodes. Previous work has indicated that the fluorescent properties of functionalized C60 are mainly affected by the addition patterns, rather than the nature of addends. However, no report on the fluorescence of C60cis-1 bisadducts, one of the most favorable types of C60 bisadducts, has appeared up to date. Herein, the fluorescent properties of two structurally related C60cis-1 bisadducts of fullerooxazolines, 1 and 2, are examined at room temperature. It shows that a significant difference exists for the fluorescent spectra of 1 and 2, where 1 displays a rather strong unusual blue-shifted emission band, even though the two compounds have the same addition pattern. Monoadducts bearing individual addends of 1 and 2, along with 1a and 1b, which have one PhCD2– positioned either next to the C60–N or C60–O bond, are also examined in order to gain a better understanding of such difference. The results indicate that the unusual blue-shifted emissions for 1 are likely to originate from the vibrational interactions of the addends, suggesting that the fluorescent emissions of C60 derivatives can be tuned not only by the addition patterns, but also by the nature of the adducts. Density functional theory and time-dependent density functional theory calculations are performed to rationalize the experimental observations.

Isomerization of an oxazoline cycle from a [6,6]- to [5,6]-junction on the C60 sphere of dianionic [60]fullero-oxazoline (12−) during a 1,4-addition is studied by electrochemistry and a stepwise addition of PhCH2Br and PhCD2Br. Cyclic voltammerty of the in situ generated 12− shows a very unusual positive shift for the anodic peak corresponding to the oxidation of 12−, indicating that the C60 cage of dianionic 1 bears only one unit negative charge due to the heterolytic cleavage of the C60−O bond. Further study with a stepwise addition of PhCH2Br and PhCD2Br, which are used to differentiate the aryl groups added at each step onto dianionic 1, shows explicitly there is an exclusive selectivity of the C−O bond for the ring-opening and ring-closure during the isomerization of the heterocycle. A reaction mechanism is proposed on the basis of the experimental results and computational calculations.

Singly bonded PhCH2C60–C60CH2Ph dimers are generated via controlled-potential bulk electroreduction and electrooxidation of 1,2-(PhCH2)HC60. The reaction mixture was purified by HPLC, and the isolated fraction was characterized with single-crystal X-ray diffractions, 1H and 13NMR, MS, elemental analysis, and cyclic voltammetry. It was shown that the fraction consists of two HPLC-inseparable PhCH2C60–C60CH2Ph regioisomers, which are assigned as the meso and racemic regioisomers. The bulk electrolysis processes for the formation of the dimers were followed by in situ cyclic voltammetry and were further corroborated with an in situ voltammetric titration of 1,2-(PhCH2)HC60 with tetra-n-butylammonium hydroxide (TBAOH), on the basis of which a reaction mechanism is proposed.

Water-soluble supramolecular inclusion complexes of α-, β-, and γ-cyclodextrin-bicapped C60 (CD/C60) have been investigated for their photoinduced DNA cleavage activities, with the aim to assess the potential health risks of this class of compounds and to understand the effect of host cyclodextrins having different cavity dimensions. Factors such as incubation temperature, irradiation time, and concentration of NADH or CDs/C60 supramolecular inclusion complexes have been examined. The results show that α-, β-, and γ-CDs/C60 are all able to cleave double-stranded DNA under visible light irradiation in the presence of NADH. However, a difference in the photoinduced DNA cleavage efficiency is observed, where the cleavage efficiency increases in the order of α-, β-, and γ-CD/C60. The difference is attributed to the different aggregation behavior of the inclusion complexes in aqueous solution, which is correlated to the cavity dimension of the host cyclodextrin molecules.

The formation of fullerooxazoles from C61HPh3− has been examined in benzonitrile (PhCN), m-methoxybenzonitrile (m-OCH3PhCN), m-tolunitrile (m-CH3PhCN), and o-tolunitrile (o-CH3PhCN), where cis-1 bisadducts with Ph-, m-OCH3Ph-, m-CH3Ph-, and o-CH3Ph-substituted cyclic imidate next to the phenylmethano are formed as evidenced by various characterizations. Interestingly, only regioisomers 2a−d with the oxygen atom bonded to C4/C5 and the nitrogen atom bonded to C3/C6 are generated as demonstrated by heteronuclear multiple bond coherence (HMBC) NMR, while the alternative regioisomers 3a−d, which have the oxygen and nitrogen atoms at C3/C6 and C4/C5, respectively, are not formed from the reactions, even though the DFT (density functional theory) calculations have predicted that the energy differences between the two types of regioisomers are very small, with regioisomers 3a−d actually having lower energies than 2a−d. The results are rationalized by the charge distributions of C61HPh3−, where computational calculations have shown that the negative charges on C4 and C5 are greater than those on C3 and C6, indicating that the exhibited site selectivity of heteroatoms is a result of the charge-directed addition process.

Benzyl(hydro)[70]fullerene regioisomers with the addends in both the equatorial and polar regions of C70 have been prepared via the reaction of dianionic C70 with benzyl bromide and H2O. HRMS, UV-vis, 1H, 13C, HMQC (heteronuclear multiple quantum coherence) and HMBC (heteronuclear multiple bond coherence) NMR characterisations have shown that the addition in the equatorial region of C70 affords a new (PhCH2)HC70 regioisomer with para-positioned addends across a six-membered ring, which is different from the “polar” regioisomers where the addends have an ortho-addition pattern. 1H NMR characterisations have shown a much stronger shielding effect for the addends in the equatorial region with respect to the counterparts in the polar region of C70, while cyclic voltammetry study has shown a surprising positive shift for the first reduction potential of the equatorial regioisomer with respect to those of the polar regioisomer and pristine C70, suggesting that the equatorial region of C70 is rather electropositive than electronegative. D2O experiment has shown a significant difference of the deuterated product distribution between the equatorial and polar regioisomers, which can be justified by the different acidity of the (PhCH2)HC70 regioisomers. Computational calculations have been carried out to rationalize the formation of the C70HR regioisomers.

Aerobic oxidations of dianionic C60 were examined in PhCN and PhCH2CN, where dioxygen was activated to O2•– via the single-electron transfer from C602– and underwent oxygenation and dehydrogenation reactions, respectively. Addition of PhCH2Br led to further benzylation for the oxygenated product but not for the dehydrogenated one, suggesting that the initial two negative charges were preserved for the intermediates of the oxygenation reaction but not for those of the dehydrogenation reaction.