Y.F.Wang

Inter‐carbon‐allotrope architectures consisting of single‐walled carbon nanotubes and fullerenes have been prepared by a very efficient reductive activation/exfoliation synthesis sequence. In their Communication on https://doi.org/10.1002/anie.201902595page 8058 ff., A. Hirsch et al. report the covalent attachment of both empty fullerenes (C₆₀) and endohedral fullerenes (Sc₃N@C₈₀) to the side‐walls of the tubes, based on this hybridization strategy. The new nanomaterials were characterized by TEM.

Peanuts: Room‐temperature mixing of metal ions and W‐shaped bispyridine ligands with polyaromatic panels leads to the quantitative formation of either a peanut‐shaped M₂L₄ capsule or an ML₂ double tube depending on the solvent identity. The capsule incorporates two fullerene molecules within the connected two cavities with a separation of 6.4 Å. The resultant fullerene dimer shows unusual electronic communication.

Abstract

Synthesis of molecular containers capable of incorporating multiple fullerenes remains challenging. Reported here is that room‐temperature mixing of metal ions with W‐shaped bispyridine ligands featuring polyaromatic panels results in the quantitative formation of a peanut‐shaped M₂L₄ capsule. The capsule reversibly converts into two molecules of an ML₂ double tube in response to changes in the solvent. Notably, the capsule allows the incorporation of two fullerene molecules into the connected two spherical cavities at room temperature. The close proximity yet non‐contact of the encapsulated C₆₀ molecules, with a separation of 6.4 Å, was revealed by X‐ray crystallographic analysis. The resultant, unusual fullerene dimer undergoes sequential reduction within the capsule to generate (C₆₀ ^.−)₂, C₆₀ ^.−⋅C₆₀ ²⁻, and (C₆₀ ²⁻)₂ species. Furthermore, temperature‐controlled stepwise incorporation of two C₆₀ molecules into the capsule is demonstrated.

Dumbbell charge transfer: The synthesis of an all‐fullerene electron donor–acceptor conjugate, C₆₀‐Lu₃N@I_h‐C₈₀, is reported. In the dumbbell‐like system, one fullerene moiety acts as the donor (Lu₃N@I_h‐C₈₀) while the other acts as the acceptor (C₆₀). Spin conversion of the charge‐separated singlet state into the corresponding triplet state slows down the charge recombination by one order of magnitude.

Abstract

The synthesis and characterization of a covalent all‐fullerene C₆₀‐Lu₃N@I_h‐C₈₀ electron donor–acceptor conjugate has been realized by sequential 1,3‐dipolar cycloaddition reactions of azomethine ylides on Lu₃N@I_h‐C₈₀ and C₆₀. To the best of our knowledge, this is the first time that two fullerenes behaving as both electron donor (Lu₃N@I_h‐C₈₀) and acceptor (C₆₀) are forming an electroactive dumbbell. DFT calculations reveal up to 16 diastereomeric pairs, that is, 8 with syn and 8 with anti orientation, with the anti‐RSSS isomer being the most stable. Spectroelectrochemical absorption and femtosecond transient absorption experiments support the notion that a C₆₀ ^⋅−‐Lu₃N@I_h‐C₈₀ ^⋅+ charge‐separated state is formed. Spin conversion from the charge‐separated singlet state C₆₀ ^⋅−‐Lu₃N@I_h‐C₈₀ ^⋅+ into the corresponding triplet state is facilitated by the heavy‐atom effect stemming from the Lu₃N‐cluster, which, in turn, slows down the charge recombination by one order of magnitude.

On the right wavelength: Water‐soluble fullerenes prepared by using natural‐product‐based solubilizing agents have photoinduced cytotoxicities. In particular, C₆₀ derivatives and the combination of light‐harvesting liposomal photosensitizers with fullerenes result in extremely high photoinduced cytotoxicities upon exposure to light of λ>600 nm; thus making them suitable for photodynamic therapy (see figure).

Abstract

Water‐soluble fullerenes prepared by using solubilizing agents based on natural products are promising photosensitizers for photodynamic therapy. Cyclodextrin, β‐1,3‐glucan, lysozyme, and liposomes can stably solubilize not only C₆₀ and C₇₀, but also some C₆₀ derivatives in water. To improve the solubilities of fullerenes, specific methods have been developed for each solubilizing agent. Water‐soluble C₆₀ and C₇₀ exhibit photoinduced cytotoxicity under near‐ultraviolet irradiation, but not at wavelengths over 600 nm, which are the appropriate wavelengths for photodynamic therapy. However, dyad complexes of solubilized C₆₀ derivatives combined with light‐harvesting antenna molecules improve the photoinduced cytotoxicities at wavelengths over 600 nm. Furthermore, controlling the fullerene and antenna molecule positions within the solubilizing agents affects the performance of the photosensitizer.

The endohedral fullerene CH₄@C₆₀ has been synthesized for the first time using photochemical desulfinylation of an open fullerene as the key step. Methane is a much larger molecule than has been previously encapsulated in the closed C₆₀ cage and is amongst the largest of possible guests.

Abstract

The endohedral fullerene CH₄@C₆₀, in which each C₆₀ fullerene cage encapsulates a single methane molecule, has been synthesized for the first time. Methane is the first organic molecule, as well as the largest, to have been encapsulated in C₆₀ to date. The key orifice contraction step, a photochemical desulfinylation of an open fullerene, was completed, even though it is inhibited by the endohedral molecule. The crystal structure of the nickel(II) octaethylporphyrin/ benzene solvate shows no significant distortion of the carbon cage, relative to the C₆₀ analogue, and shows the methane hydrogens as a shell of electron density around the central carbon, indicative of the quantum nature of the methane. The ¹H spin‐lattice relaxation times (T ₁) for endohedral methane are similar to those observed in the gas phase, indicating that methane is freely rotating inside the C₆₀ cage. The synthesis of CH₄@C₆₀ opens a route to endofullerenes incorporating large guest molecules and atoms.

An unprecedented 1,4‐cycloadduct of C₆₀ and other sophisticated fullerene architectures were prepared through reductive functionalization. This method, starting with the two‐fold reduction of C₆₀ with potassium, closely resembles related reactions of carbon nanotubides and represents a so far only little explored concept of fullerene chemistry. Investigations on the scope of different electrophiles as addition partners including a series of tether systems with a predefined geometry provide both new insights of fullerene reactivity itself and new types of exohedral derivatives. More information can be found in the Full Paper by A. Hirsch et al. (DOI: https://doi.org/10.1002/chem.20180577710.1002/chem.201805777).

As Lei Fu and Jinxin Liu discuss in article number 1800690, the exciting progress in controlled growth, etching, self‐assembly, and delivery of graphene on a liquid surface can be achieved, promoting its future industrial applications. The poem in the cover translates as “The pools in south China are suitable for gathering lotus. How dense and flourishing are the lotus leaves!” The lotus leaves floating in the pools represent graphene single crystals grown on liquid substrates.

Elusive β‐siteisomers are now the main products! PCBM‐like [70]methanofullerenes have been prepared from sulfur ylides in both site‐isomeric forms depending on the solvent polarity. Their use as template agent in perovskite solar cells afford high efficiency values (PCE∼20 %) depending on the site‐isomer.

Abstract

We report on the site‐selective synthesis of PCBM‐like [70]fullerene site‐isomers, where the elusive β‐site‐isomers are, for the first time, the major product in a (cyclo)addition chemical reaction involving [70]fullerene. The reaction involves an straightforward cyclopropanation of [70]fullerene from sulfonium salts, affording a mixture of α and β site‐isomers in good yields. Amazingly, the preference for the α‐ or β‐site‐isomer can be efficiently controlled by means of the solvent polarity! DFT theoretical calculations (DMF and toluene) nicely predict that, although the formation of the α‐adduct is, as expected, thermodynamically favored, the selectivity of the process is determined by the energy difference of the respective transition states. Furthermore, the employ of α or/and β site‐isomers, as pure materials or as a mixture of them, used as templating agent, has been evaluated in perovskite solar cells. The positive influence of the [70]fullerenes by passivating the voids/pin‐holes and/or deep slits, is reflected in highly efficient and stable bulk heterojunction perovskite solar cells, whose performance (around 20 %) is slightly but consistently depending on the isomeric fullerene composition. These experimental findings pave the way to investigate a new reactivity on C₇₀ and to explore the properties of the less‐known β‐derivatives.

Crystalline functionalized endohedral C₆₀ metallofullerides

Crystalline functionalized endohedral C₆₀ metallofullerides, Published online: 06 August 2018; doi:10.1038/s41467-018-05496-8

While endohedral metallofullerenes have demonstrated advantageous electronic and magnetic properties, the isolation of monomeric M@C60 remains highly challenging. Here, the authors prepare trifluoromethylated Gd@C60 and La@C60, where the functionalization of C60 allows for the stabilization of these otherwise reactive species.

Abstract

Tailored interfaces of unencapsulated perovskite solar cells for >1,000 hour operational stability

Tailored interfaces of unencapsulated perovskite solar cells for >1,000 hour operational stability, Published online: 09 January 2018; doi:10.1038/s41560-017-0067-y

The stability of perovskite solar cells depends on each layer and interface in the device. Here, Christians et al. systematically design the entire device stack focusing on stability, creating cells that retain 88% of their initial efficiency on average, after 1,000 h of unencapsulated operation.

Systematic investigation of the impact of operation conditions on the degradation behaviour of perovskite solar cells

Systematic investigation of the impact of operation conditions on the degradation behaviour of perovskite solar cells, Published online: 01 January 2018; doi:10.1038/s41560-017-0060-5

Perovskite solar cells suffer from poor operational stability. Stability measurement conditions used in various studies differ widely. Here, Domanski et al. systematically study environmentally induced degradation in an effort to drive the community towards a consensus on how to age perovskite solar cells.

Abstract

Nature Materials. doi:10.1038/nmat4946

Authors: Takashi Kodama, Masato Ohnishi, Woosung Park, Takuma Shiga, Joonsuk Park, Takashi Shimada, Hisanori Shinohara, Junichiro Shiomi & Kenneth E. Goodson

The potential impact of encapsulated molecules on the thermal properties of individual carbon nanotubes (CNTs) has been an important open question since the first reports of the strong modulation of electrical properties in 2002. However, thermal property modulation has not been demonstrated experimentally because of the difficulty of realizing CNT-encapsulated molecules as part of thermal transport microstructures. Here we develop a nanofabrication strategy that enables measurement of the impact of encapsulation on the thermal conductivity (κ) and thermopower (S) of single CNT bundles that encapsulate C 60, Gd@C 82 and Er 2@C 82. Encapsulation causes 35–55% suppression in κ and approximately 40% enhancement in S compared with the properties of hollow CNTs at room temperature. Measurements of temperature dependence from 40 to 320 K demonstrate a shift of the peak in the κ to lower temperature. The data are consistent with simulations accounting for the interaction between CNTs and encapsulated fullerenes.

Abstract

Abstract