Liangbing Gan

Preparation of Open‐Cage Fullerenes and Incorporation of Small Molecules Through Their Orifices

Open-cage fullerenes can act as hosts for small molecules such as water, nitrogen, or hydrogen, forming endohedral fullerenes. Following a brief summary of carbon, nitrogen, and oxygen insertion in the fullerene framework to form homofullerenes, methods of creating a hole in the fullerene surface are surveyed. Techniques of hole enlargement and the insertion of atoms or molecules through the orifice to form endohedral fullerenes are described. Finally, the possibility of subsequent closure of the hole is considered.

Salts of C60(OH)8 Electrodeposited onto a Glassy Carbon Electrode: Surprising Catalytic Performance in the Hydrogen Evolution Reaction

With the energy crisis becoming increasingly serious, hydrogen is proposed as a promising energy carrier substitute to fossil energy. A practical technique to produce hydrogen is the splitting of water by either electrochemical or photochemical methods. Usually, catalysts are widely used to overcome the overpotential for the hydrogen evolution reaction (HER) and to obtain high efficiency. Among the catalysts produced for the HER, Pt, Pd, and Ru show the best performance, but their high cost seriously limits their use. On the other hand, less expensive substitutes using metals such as Ni and Co suffer from corrosion, passivation, and lower catalytic activity. The need for active, stable, and inexpensive electrocatalysts has aroused intensive research interest, resulting in the development of molecular catalysts. Thus far, relatively few molecular catalysts have been studied for the HER in aqueous solutions, and most of catalysts studied consisted of transition metals. Herein, we report a novel molecular catalyst based on carbon: a salt consisting of fullerenol anions electrodeposited onto a glassy carbon electrode (GCE) coated with Nafion in an aqueous solution for the HER. The onset potential was estimated to be 0.11 V (vs. RHE) with low loading and high exchange current density. Polyhydroxylated fullerene (fullerenol) is one of the most studied fullerene derivatives, because of their low biological toxicity and outstanding radical scavenging ability. Various synthetic methods have been reported, but most of them obtained complicated mixtures of fullerenols with different structures, which limited further study of their properties. We have previously reported the preparation of the first isomerically pure multihydroxylated fullerene, C60(OH)8. [6] Its solubility in water is much greater than that of C60 due to the eight hydroxy groups on the carbon cage, which makes it possible to study its electrochemical properties in aqueous solutions; these properties are fundamental for investigating electrocatalysis based on fullerenols. There have been few reports to date about the electrochemical properties of fullerenols in water, therefore, we investigated electrochemical behavior of C60(OH)8 in aqueous solutions. Figure 1 displays a cyclic voltammogram of C60(OH)8 in an aqueous solution of KCl (0.1m). A reduction peak at

Substituent and solvent effects on photoexcited states of functionalized fullerene[60]

Steady-state absorption/fluorescence spectra and time-resolved absorption/fluorescence spectra were measured to investigate the photoexcited states properties of N-methylpyrrolidinofullerenes C60[(C3H6N)R] [R=H (1), p-C6H4CHO (2), p-C6H4NO2 (3), p-C6H4OMe (4), p-C6H4NMe2 (5)]. Functionalization causes bandshifts to longer wavelength for absorption and fluorescence spectra, accompanied by enhancements in the fluorescence quantum yields in nonpolar solvents. The triplet (T) states of these derivatives show very similar properties (quantum yields, molar absorption coefficients and O2 quenching) to C60 whereas T–T absorption bands shift to short wavelength and the lowest triplet energies decrease compared with those of C60. Derivative 5, which has a strong electron-donating group, shows a prominent solvent polarity effect on the fluorescent quantum yield and lifetime, and triplet formation, suggesting that intramolecular charge transfer takes place.

Switchable Open‐Cage Fullerene for Water Encapsulation

Fullerenes have a cavity large enough to encapsulate atoms and molecules. Making a suitable hole in the fullerene cage followed by attaching an easily removable stopper into the orifice can produce a single-molecule-based vial. There are many possible applications for such a vial; for example, it may be used as a carrier for radioactive atoms or small molecules such as tritiated water (T2O) in radiopharmaceuticals for diagnostic or therapeutic studies. Over the past decade, much progress has been made in the area of fullerene cage opening. A number of open-cage fullerenes have been reported, some of which can encapsulate small organic molecules. However, there have been no successful attempts to cover the orifice with a removable blocker. The known open-cage fullerenes are analogous to a round-bottom flask without a stopper. Herein, we report the preparation of the first open-cage fullerene with a stopper that can be attached and removed through a single-step reaction. Water was shown to be effectively trapped by the present compound. We recently reported the preparation of compound 1a and its water-encapsulated complex H2O@1a through a peroxide-mediated cage-opening strategy. Carbonyl groups on the rim of the orifice are quite reactive towards various nucleophiles. Treatment of 1 with triethylphosphite resulted in compound 2 with a phosphate group attached above the orifice (Scheme 1). Under basic conditions, the phosphate can be hydrolyzed to retrieve compound 1. The phosphate formation reaction is more efficient than the hydrolysis process, as the reaction time at room temperature is 10 min for the forward reaction but 2 h for the backward hydrolysis reaction. The formation of the phosphate moiety in compound 2 was unexpected. Analogous reactions of classical organic carbonyl compounds with triethylphosphite usually yield ahydroxy phosphonates (Abramov reaction) with the phosphorus atom connected to the carbonyl carbon atom, whereas the hydrogen atom is connected to the carbonyl oxygen atom. The opposite is observed in the present reaction with compound 1. A possible mechanism is proposed in Scheme 1. Owing to the electron-deficient nature of the fullerene cage and the presence of carbonyl groups in compound 1, single electron transfer is favored in the first step instead of phosphite attack at the carbonyl carbon atom. The so-formed radical ion pair A then forms the zwitterionic intermediate B through formation of an O P bond. Steric hindrance is probably responsible for the regioselectivity. Finally, protonation of the carbon anion and hydrolysis of the phosphonium yields compound 2. Alternatively, intermediate B may be formed through phosphorus attack at the carbonyl carbon atom to form a zwitterion, followed by a Phospha– Brook rearrangement. The structure of compound 2 was determined from spectroscopic data. The number of carbon signals in the C NMR spectrum confirms the Cs symmetry of the structure. There is just one signal for the two hydroxy groups at d = 7.63 and 8.11 ppm for 2a and 2 b, respectively, further supporting the Cs symmetry. The fullerenyl proton appears as a doublet at d = 7.36 (2a) and 7.6 ppm (2b) owing to coupling to the phosphorus atom. In the H NMR spectrum of compound 2a, there is a minor signal at d = 7.64 ppm and a minor doublet at d = 7.37 ppm, corresponding to the OH and fullerenyl proton groups for the water encapsulated compound H2O@2a. Thus, Scheme 1. Addition of a phosphate blocker to the orifice.

Preparation of Azafullerene Derivatives from Fullerene-Mixed Peroxides and Single Crystal X-ray Structures of Azafulleroid and Azafullerene

Azafullerene was prepared by addition of hydroxylamine to a cage-opened fullerendione derivative and subsequent PCl5 induced rearrangement processes. X-ray structures were obtained for the azafullerene and its azafulleroid precursor.

Molecular containers with a dynamic orifice: open-cage fullerenes capable of encapsulating either H2O or H2 under mild conditions

Open-cage fullerene derivatives with an imide moiety above the orifice have been prepared. Rotation of the N–Ar imide bond can tune the orifice to a size large enough to encapsulate H2O at r.t. and also to a size small enough to keep H2 from escaping the cavity rapidly.

Toxicity of Graphene Quantum Dots in Zebrafish Embryo

OBJECTIVE To evaluate the bio-safety of graphene quantum dots (GQDs), we studied its effects on the embryonic development of zebrafish. METHODS In vivo, biodistribution and the developmental toxicity of GQDs were investigated in embryonic zebrafish at exposure concentrations ranging from 12.5-200 μg/mL for 4-96 h post-fertilization (hpf). The mortality, hatch rate, malformation, heart rate, GQDs uptake, spontaneous movement, and larval behavior were examined. RESULTS The fluorescence of GQDs was mainly localized in the intestines and heart. As the exposure concentration increased, the hatch and heart rate decreased, accompanied by an increase in mortality. Exposure to a high level of GQDs (200 μg/mL) resulted in various embryonic malformations including pericardial edema, vitelline cyst, bent spine, and bent tail. The spontaneous movement significantly decreased after exposure to GQDs at concentrations of 50, 100, and 200 μg/mL. The larval behavior testing (visible light test) showed that the total swimming distance and speed decreased dose-dependently. Embryos exposed to 12.5 μg/mL showed hyperactivity while exposure to higher concentrations (25, 50, 100, and 200 μg/mL) caused remarkable hypoactivity in the light-dark test. CONCLUSION Low concentrations of GQDs were relatively non-toxic. However, GQDs disrupt the progression of embryonic development at concentrations exceeding 50 μg/mL.

Synthesis of an Azahomoazafullerene C59N(NH)R and Gas‐Phase Formation of the Diazafullerene C58N2

and endohedral azafullerenes have been reported. The cage structure of the azafullerene remains fully closed in all these compounds. Skeleton modification of C60 has resulted in many novel fullerene derivatives. The method used by Wudl and coworkers for the first preparation of an azafullerene is based on an open-cage precursor with a ketolactam orifice. Opencage fullerenes with a relatively large orifice can encapsulate various small molecules and noble gases. Endohedral fullerenes containing H2 (H2@C60 ) and H2O (H2O@C60 ) were prepared by “molecular surgery”. Inspired by these results, we investigated the skeleton modification of azafullerenes in an effort to prepare open-cage azafullerene and diazafullerene derivatives. Herein we report the preparation of azahomoazafullerenes C59N(NH)R as potential precursors to the diazafullerene C58N2 and the reaction of one azahomoazafullerene to give an open-cage azafullerene with a ketoimide moiety on the rim of the 15-membered orifice. We previously reported a fullerene-peroxide-mediated method for the preparation of azafullerene derivatives such as 1. To explore the skeleton modification of azafullerenes, we treated 1 with various nucleophiles, including hydroxylamine (Scheme 1). As expected, the bromine atom can be replaced effectively to form compounds 2a–d. Treatment of the hydroxylamine adduct 2d with PCl5 afforded the azahomo

Reactivity of Fullerene Epoxide: Preparation of Fullerene-Fused Thiirane, Tetrahydrothiazolidin-2-one, and 1,3-Dioxolane

The epoxide moiety in the fullerene-mixed peroxide C60(O)(OOtBu)4 1 reacts readily with aryl isocyanates ArNCS (Ar = Ph, Naph) to form both the thiirane derivative C60(S)(OOtBu)4 and fullerene-fused tetrahydrothiazolidin-2-one. The reaction of 1 with trimethylsilyl isothiocyanate TMSNCS yields the isothiocyanate derivative C60(NCS)(OH)(OOtBu)4, the isothiocyanate and hydroxyl moieties of which could be converted to a fullerene-fused tetrahydrothiazolidin-2-one ring with alumina quantitatively. Treating 1 with BF3.Et2O yields the fullerene-fused [1,3,2]-dioxoborolane derivative C60(O2BOH)(OOtBu)4. In the presence of aldehyde or acetone, BF3.Et2O catalyzes the conversion of epoxide to fullerene-fused 1,3-dioxolane derivatives. The products are characterized by spectroscopic data. Two of the compounds are also characterized by single-crystal X-ray analysis.

Microcavity Effect from a Novel Terbium Complex Langmuir-Blodgett Film**

By Yanyi Huang, Anchi Yu, Chun-Hui Huang,*Liangbing Gan, Xinsheng Zhao, Yong Lin, and Bei ZhangThe use of microcavities as optical resonators has re-cently been developed as a potential high-density lightsource for optical communications and color displays. Theelectromagnetic field of microcavities can be enhanced sig-nificantly, and the spontaneous emission of the materials inthe cavity can be modified. The fundamental principle ofthe cavity effect has long been known but novel phenom-ena in microcavities are still attracting scientists’ attention,in terms of both theory and experiments.