Y.F.Wang

Imitation game : A charge‐separating chlorophyll dimer with a structure resembling natural chlorophyll pairs in photosynthetic reaction centers is reported. Structural, electrochemical, and spectrometric analyses revealed the similarity between the artificial and natural pair. Pairing the chlorophyll‐a derivatives with an N‐alkylamide group provided geometry and properties that duplicate those of the natural chlorophyll pair.

Abstract

Accurately mimicking structure and function of natural chlorophyll (Chl) assemblies is very challenging. Herein, we report the synthesis of a fullerene‐appended Chl dimer being capable of intramolecular photoinduced charge separation (CS) with a unique structure reminiscent of reaction centers (RCs) in phototrophs. Structural analyses revealed that the Chl dimer adopts a bird‐like structure in which two Chl components overlapped partially with one of the four pyrrole rings in a Chl ring similar to in a Chl pair in the natural RC complexes. A comparative study including voltammetry and spectrometric analyses using the Chl dimer and its corresponding monomer with and without a fullerene moiety was performed to gain insight into the effect of Chl pairing on (photo)redox properties. Our results suggest that the present dimer motif that closely resemble the Chl pair in natural RCs lead to more facile oxidation and lower energy of the CS state of the Chl dimer than those of the Chl monomer, resulting in its photoredox behavior different from that of the monomer Chl.

PET in cationic complexes: The recently designed triquinoline cationic moiety (TQ⋅H⁺) has strong electron‐acceptor properties, which make this cation a unique element in nanochemistry. Advanced computational studies revealed photoinduced electron transfer (PET) in supramolecular complexes of TQ⋅H⁺ with coronene and cycloparaphenylene molecules. Computed ET rates show that electron transfer occurs in the normal or inverted Marcus region, depending on the partner.

Abstract

A triquinoline cationic moiety (TQ⋅H⁺) has recently been designed as a novel molecular unit for supramolecular chemistry. In addition to some useful features, TQ⋅H⁺ has strong electron‐acceptor properties, which renders the molecular cation a unique element in nanochemistry. TQ⋅H⁺ is found to form complexes with coronene (COR) and cycloparaphenylene (CPP). In this work, we report a computational study of photoinduced electron transfer in supramolecular complexes TQ⋅H⁺‐COR, TQ⋅H⁺⊂[12]CPP and (TQ⋅H⁺‐COR)⊂[12]CPP. The electron‐transfer rates are estimated by using the semi‐classical approach. The results are compared with the data previously obtained for a structurally similar inclusion complex Li⁺@C₆₀⊂[10]CPP. In particular, we found a red solvatochromic shift for charge‐shift bands in the TQ⋅H⁺‐complexes unlike a blueshift showed by Li⁺@C₆₀⊂[10]CPP. This distinction is explored in terms of electronic and structural features of the systems.

Pore craftsmen: Two‐dimensional mesoporous carbon materials derived from self‐assembled C₆₀ microsheets are fabricated in a controlled way. These act as efficient and robust electrode materials for efficient oxygen‐reduction‐reaction catalysts and high‐performance supercapacitors.

Abstract

Porous carbon materials rich in defects are promising candidates in energy storage and conversion applications. Herein, a facile template‐free approach is reported for the synthesis of a two‐dimensional (2 D) mesoporous carbon material derived from fullerene (C₆₀) microsheets (FMSs) through simple heat treatment. The sample obtained at 1000 °C (FMS1000) shows a large surface area of 1507.6 m² g⁻¹ owing to the presence of mesopores and rich defects, which promote electron and mass transfer in the electrocatalytic process of the oxygen reduction reaction (ORR), showing an excellent performance with an onset potential of 0.95 V, a half‐wave potential of 0.85 V, and long‐term durability of 2000 cycles, comparable to the performance of commercial Pt/C. Moreover, FMS1000 displays a remarkable supercapacitive property with a specific capacitance of 330.7 F g⁻¹ at 0.2 A g⁻¹ and good long‐term stability with a capacitance retention of 97 % over 50 000 cycles. Thus, a practical strategy for the production of mesoporous carbon materials with different morphological structures and porous defects as high‐performance energy materials is advanced.

Speeding addition to fullerenes: Similar to the Diels–Alder (DA) cycloaddition, the Bingel–Hirsch (BH) addition of bromomalonate to C₆₀ is accelerated by the presence of monocations (Li⁺, Na⁺, K⁺) encapsulated in the fullerene. However, at variance with the DA cycloaddition, the performance of the BH deteriorates when changing the monocations to dications (Mg²⁺, Ca²⁺) owing to the increase of the energy barriers in the last step of the BH addition.

Abstract

In the last 30 years, fullerene‐based materials have become popular building blocks for devices with a broad range of applications. Among fullerene derivatives, endohedral metallofullerenes (EMFs, M@C _x ) have been widely studied owing to their unique properties and reactivity. For real applications, fullerenes and EMFs must be exohedrally functionalized. It has been shown that encapsulated metal cations facilitate the Diels–Alder reaction in fullerenes. Herein, the Bingel–Hirsch (BH) addition of ethyl bromomalonate over a series of ion‐encapsulated M@C₆₀ (M=Ø, Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, and Cl⁻; Ø@C₆₀ stands for C₆₀ without any endohedral metal) is quantum mechanically explored to analyze the effect of these ions on the BH addition. The results show that the incarcerated ion has a very important effect on the kinetics and thermodynamics of this reaction. Among the systems studied, K⁺@C₆₀ is the one that leads to the fastest BH reaction, whereas the slowest reaction is given by Cl⁻@C₆₀.

Cycloparaphenylenes and their complexes in the gas phase : A straightforward method—(MA)LDI—is introduced to characterize CPPs and their host–guest complexes either with another ring size or with different fullerenes. The method enables the detection of thus far unknown complexes. Fragmentation experiments and DFT calculations provide insight into geometries, binding and fragmentation energies as well as charge location of CPP host–guest complexes.

Abstract

[n ]Cycloparaphenylenes ([n ]CPPs) with n =5, 8, 10 and 12 and their noncovalent ring‐in‐ring and [m ]fullerene‐in‐ring complexes with m =60, 70 and 84 have been studied by direct and matrix‐assisted laser desorption ionization ((MA)LDI) and density‐functional theory (DFT). LDI is introduced as a straightforward approach for the sensitive analysis of CPPs, free from unwanted decomposition and without the need of a matrix. The ring‐in‐ring system of [[10]CPP⊃[5]CPP]^+. was studied in positive‐ion MALDI. Fragmentation and DFT indicate that the positive charge is exclusively located on the inner ring, while in [[10]CPP⊃C₆₀]^+. it is located solely on the outer nanohoop. Positive‐ion MALDI is introduced as a new sensitive method for analysis of CPP⊃fullerene complexes, enabling the detection of novel complexes [[12]CPP⊃C_{60, 70 and 84}]^+. and [[10]CPP⊃C₈₄]^+.. Selective binding can be observed when mixing one fullerene with two CPPs or vice versa, reflecting ideal size requirements for efficient complex formation. Geometries, binding and fragmentation energies of CPP⊃fullerene complexes from DFT calculations explain the observed fragmentation behavior.

Turn and flip : A C₅₉N⁺ cation has been trapped by ethanol or water in a tubular host to fix an oxy substituent on the fullerene guest. The substituent was found to modulate the guest motion, with the up‐and‐down flipping motions of the guest facilitated by the OH group sliding along the inner wall of the host while staying attached through OH‐π hydrogen bonds, whereas an ethoxy substituent halted such motions.

Abstract

A supramolecular/synthetic method has been devised to affix a sterically hindered substituent onto a fullerene guest encapsulated in a tubular host. A two‐wheeled complex of (C₅₉N)‐(C₅₉N) with a tubular host was oxidatively bisected to afford a C₅₉N⁺ cation captured in the tube. The C₅₉N⁺ cation in the tube was then trapped by ethanol or water, which led to an oxy substituent pinned on the guest. The guest motions within the tube were modulated by the pinned substituent, and up‐and‐down flipping motions were halted by an ethoxy substituent. A hydroxy substituent, however, was ineffective in halting the flipping motions, despite the tight‐fitting relationship between the tubular host and the spherical guest. Theoretical calculations of the dynamics revealed that the flipping motions were assisted by OH‐π hydrogen bonds between the guest and the carbon‐rich wall and that sliding motions of the OH group were also facilitated by deformations of the tube.

The big bucks: A wide range of fullerenes (buckyballs; C₃₀–C₁₁₄) and their building blocks (buckybowls with a stoichiometry of C_10x H₁₀) were detected in heavy crude oil by ultrahigh‐resolution mass spectrometry. Structural findings are supported by high‐level calculations at the DLPNO‐CCSD(T) level of theory, revealing for the first time the presence of fullerenes in low‐energy fossil materials on a molecular level.

Abstract

Buckyballs (fullerenes) were first reported over 30 years ago, but still little is known regarding their natural occurrence, since they have so far only been found at sites of high‐energy incidents, such as lightning strikes or meteor impacts, but have not been reported in low‐energy materials like fossil fuels. Using ultrahigh‐resolution mass spectrometry, a wide range of fullerenes from C₃₀ to C₁₁₄ was detected in the asphaltene fraction of a heavy crude oil, together with their building blocks of C_10nH₁₀ stoichiometry. High‐level DLPNO‐CCSD(T) calculations corroborate their stability as spherical and hemispherical species. Interestingly, the maximum intensity of the fullerenes was found at C₄₀ instead of the major fullerene C₆₀. Hence, experimental evidence supported by calculations show the existence of not only buckyballs but also buckybowls as 3‐dimensional polyaromatic compounds in fossil materials.

Porous carbon materials with rich defects are promising candidates in energy storage and conversion applications. Herein, we report a facile template‐free approach for the synthesis of a two‐dimensional (2D) mesoporous carbon material derived from fullerene (C60) microsheets (FMSs) by simple heat‐treatment. The sample obtained at 1000 o C (FMS1000) shows a large surface area of 1507.6 m 2 g ‐1 due to the presence of mesopores and rich defects which promote the electron and mass transfer in the electrocatalysis process of oxygen reduction reactions (ORR) showing excellent performances with an onset potential of 0.95 V, half‐wave potential of 0.85 V and long‐term durability of 2000 cycles which are comparable to that of commercial Pt/C. Moreover, FMS1000 displays a remarkable supercapacitive property with specific capacitance of 330.7 F g ‐1 at 0.2 A g ‐1 and long‐term stability with capacitance retention of 97% over 50,000 cycles. Thus, a practical strategy for the production of mesoporous carbon materials with different morphological structures and porous defects as high‐performance energy materials is advanced.

Endohedral metallofullerenes (EMFs) serve as an ideal platform for the study of otherwise unstable metallic clusters owing to the protection afforded by fullerene cages. Herein, a systematic and comprehensive summary of the recent results of EMFs is presented according to the categories of monometallofullerenes, dimetallofullerenes, carbide clusterfullerenes, and nitride clusterfullerenes.

Abstract

Endohedral metallofullerenes (EMFs), namely fullerenes with metallic species encapsulated inside, represent an ideal platform to investigate metal–metal or metal–carbon interactions at the sub‐nanometer scale by means of single‐crystal X‐ray diffraction (XRD) crystallography. Herein, recent progress in the identification of new structures and unprecedented properties are discussed according to the categories of monometallofullerenes, dimetallofullerenes, carbide clusterfullerenes, and nitride clusterfullerenes. In particular, the dimerization and the cage‐isomer dependent oxidation state of the inner metal atom are summarized in terms of pristine monometallofullerenes. Metal–metal bonds involving lanthanide–lanthanides or actinide–actinides are discussed based on both experimental and theoretical studies. The cluster–cage matching and/or mutual selections, as well as the rarely seen M=C double bonds, are discovered in M₂C₂@C_2n , U₂C@C₈₀, M₂TiC@C₈₀, and Ti₃C₃@C₈₀. Subsequently, the geometries of different M₃N clusters in various cages are discussed, revealing size‐matching between the internal M₃N cluster and the outer cage induced by the planarity of the cluster. Finally, an outlook regarding the future developments of the molecular structures and applications of EMFs is presented.

Endohedral metallofullerenes (EMFs) encaging otherwise unstable metallic clusters represent an ideal platform for the investigation of unconventional chemical interactions inside the cages, the inter‐molecular dimerization, and the cluster–cage mutual fitting in different forms. In their Minireview on https://doi.org/10.1002/chem.201905306page 5748 ff., Xing Lu and colleagues discuss the recent progress in new hybrid molecules and unprecedented properties according to the categories of monometallofullerenes, dimetallofullerenes, carbide clusterfullerenes, and nitride clusterfullerenes. Finally, perspectives for the future development of EMFs are proposed.

An efficient method for the fabrication of the single‐walled carbon nanotube (SWCNT) thin film using cross‐linking methoxycarbonyl polyallylamine (Moc‐PAA) was developed. The amine‐terminated surface of cross‐linked Moc‐PAA enables the formation of the highly dense and uniform thin film of SWCNT networks. The thin film transistor using the fabricated SWCNT film exhibited an excellent performance with a small variability.

Abstract

Owing to their remarkable properties, single‐walled carbon nanotube thin‐film transistors (SWCNT‐TFTs) are expected to be used in various flexible electronics applications. To fabricate SWCNT channel layers for TFTs, solution‐based film formation on a self‐assembled monolayer (SAM) covered with amino groups is commonly used. However, this method uses highly oxidized surfaces, which is not suitable for flexible polymeric substrates. In this work, a solution‐based SWCNT film fabrication using methoxycarbonyl polyallylamine (Moc‐PAA) is reported. The NH₂‐terminated surface of the cross‐linked Moc‐PAA layer enables the formation of highly dense and uniform SWCNT networks on both rigid and flexible substrates. TFTs that use the fabricated SWCNT thin film exhibited excellent performance with small variations. The presented simple method to access SWCNT thin film accelerates the realization of flexible nanoelectronics.

Self‐assembly is a process in which a disordered system spontaneously develops ordered structures without external directions. In materials science and technology, self‐assembly in the bulk has been extensively utilized to fabricate desired microscopic structures. Rodlike molecules have emerged as one of the most promising molecular building blocks to construct functional materials. Although the self‐assembly of conventional molecules containing rodlike components generally results in nematic or layered smectic phases, extensive efforts have revealed that rational molecular design provides a versatile platform to engineer rich self‐assembled structures. In their Review article on https://doi.org/10.1002/chem.201905432page 6741 ff., Feng, Lin and Cheng et al. summarize the first successes achieved in polyphilic liquid crystals and rod–coil block systems. Special attention is paid to recent progress in the conjugation of rodlike building blocks with other molecular building blocks through the molecular Lego approach.

The valence isomerization of norbornadiene (NBD) and quadricyclane (QC) has been widely studied as a potential molecular solar thermal (MOST) energy storage and release system. By combining this interconversion couple with C₆₀ fullerene, a hybrid system with novel properties was created. Within this system, light‐induced switching between NBD and QC in both directions is possible, thereby transforming the former photo/thermal system into a pure photoswitch. More information can be found in the Full Paper by P. Lorenz and A. H. Hirsch on https://doi.org/10.1002/chem.201904679page 5220.

Switching! The synthesis of several norbornadiene (NBD)–fullerene adducts is herein reported. Within these new hybrid systems, the photochemical isomerization of NBD is combined with the electron affinity of C₆₀. This enables the selective light‐induced isomerization of the NBD derivative to its corresponding quadricyclane (QC) counterpart and the back conversion of the latter mediated by the photochemically excited fullerene core.

Abstract

The synthesis and properties of various norbornadiene/quadricyclane (NBD/QC) fullerene hybrids are reported. By cyclopropanation of C₆₀ with malonates carrying the NBD scaffold a small library of NBD–fullerene monoadducts and NBD–fullerene hexakisadducts was established. The substitution pattern of the NBD scaffold, as well as the electron affinity of the fullerene core within these hybrid systems, has a pronounced impact on the properties of the corresponding energy rich QC derivatives. Based on this, the first direct photoisomerization of NBD–fullerene hybrids to their QC derivatives was achieved. Furthermore, it was possible to use the redox‐active fullerene core of a QC–fullerene monoadduct to enable the back reaction to form the corresponding NBD–fullerene monoadduct. Combining these two processes enables switching between NBD and QC simply by changing the irradiation wavelength between 310 and 400 nm. Therefore, turning this usually photo/thermal switch into a pure photoswitch. This not only simplifies the investigation of the underlying processes of the NBD–QC interconversion within the system, but also renders such hybrids interesting for applications as molecular switches.

The Isolated‐Pentagon Rule (IPR) governs a nearly whole chemistry of C₆₀ fullerene. High‐temperature chlorination of IPR C₆₀ enables the formation of non‐IPR derivatives with fused pentagons in the carbon cage. Thus, non‐IPR ¹⁸⁰⁹C₆₀Cl₁₆, ¹⁸¹⁰C₆₀Cl₂₄, and ¹⁸⁰⁵C₆₀Cl₂₄ were isolated, whereas trifluoromethylation of chlorination products afforded ¹⁸⁰⁷C₆₀(CF₃)₁₂. The experimentally isolated derivatives of non‐IPR cages contain two, three, four, and five fused pentagon pairs.

Abstract

The carbon cage of buckminsterfullerene I _h‐C₆₀, which obeys the Isolated‐Pentagon Rule (IPR), can be transformed to non‐IPR cages in the course of high‐temperature chlorination of C₆₀ or C₆₀Cl₃₀ with SbCl₅. The non‐IPR chloro derivatives were isolated chromatographically (HPLC) and characterized crystallographically as ¹⁸⁰⁹C₆₀Cl₁₆, ¹⁸¹⁰C₆₀Cl₂₄, and ¹⁸⁰⁵C₆₀Cl₂₄, which contain, respectively two, four, and four pairs of fused pentagons in the carbon cage. High‐temperature trifluoromethylation of the chlorination products with CF₃I afforded a non‐IPR CF₃ derivative, ¹⁸⁰⁷C₆₀(CF₃)₁₂, which contains four pairs of fused pentagons in the carbon cage. Addition patterns of non‐IPR chloro and CF₃ derivatives were compared and discussed in terms of the formation of stabilizing local substructures on fullerene cages. A detailed scheme of the experimentally confirmed non‐IPR C₆₀ isomers obtained by Stone–Wales cage transformations is presented.

Faraday nanocages: If carbon nano‐onions behave as ideal Faraday cages, the reactivity of the C₂₄₀ cage should be the same in Li⁺@C₂₄₀ and Li⁺@C₆₀@C₂₄₀. These results show significant differences between the reactivity of Li⁺@C₂₄₀ and Li⁺@C₆₀@C₂₄₀ indicating that C₆₀@C₂₄₀ does not act as an ideal Faraday cage.

Abstract

From the analysis of the polarizability of carbon nano‐onions (CNOs), it was concluded that CNOs behave as near perfect nanoscopic Faraday cages. If CNOs behave as ideal Faraday cages, the reactivity of the C₂₄₀ cage should be the same in Li⁺@C₂₄₀ and Li⁺@C₆₀@C₂₄₀. In this work, the Diels–Alder reaction of cyclopentadiene to the free C₂₄₀ cage and the C₆₀@C₂₄₀ CNO together with their Li⁺‐doped counterparts were analyzed using DFT. It was found that in all cases the preferred cycloaddition is on bond [6,6] of type B of C₂₄₀. Encapsulation of Li⁺ results in lower enthalpy barriers due to the decrease of the energy of the LUMO orbital of the C₂₄₀ cage. When the Li⁺ is placed inside the CNO C₆₀@C₂₄₀, the decrease in enthalpy barrier is similar to that of Li⁺@C₂₄₀. However, the location of Li⁺ in Li⁺@C₂₄₀ (off‐centered) and Li⁺@C₆₀@C₂₄₀ (centered) is quite different. When Li⁺ was placed in the center of the C₂₄₀ cage in Li⁺@C₂₄₀, the barriers increased significantly. Taking into account this effect, the barriers in Li⁺@C₂₄₀ and Li⁺@C₆₀@C₂₄₀ differ by about 4 kcal mol⁻¹. This result can be attributed to the shielding effect of C₆₀ in Li⁺@C₆₀@C₂₄₀. As a result, we conclude that this CNO does not act as a perfect Faraday cage.

The carbon cage of buckminsterfullerene I h ‐C 60 , which obeys the Isolated‐Pentagon Rule (IPR), can be transformed to non‐IPR cages in the course of high‐temperature chlorination of C 60 or C 60 Cl 30 with SbCl 5 . The non‐IPR chloro derivatives were isolated chromatographically (HPLC) and characterized crystallographically as 1809 C 60 Cl 16 , 1810 C 60 Cl 24 , and 1805 C 60 Cl 24 , which contain respectively two, four, and four pairs of fused pentagons in the carbon cage. High‐temperature trifluoromethylation of the chlorination products with CF 3 I afforded a non‐IPR CF 3 derivative, 1807 C 60 (CF 3 ) 12 , which contains four pairs of fused pentagons in the carbon cage. Addition patterns of non‐IPR chloro and CF 3 derivatives were compared and discussed in terms of the formation of stabilizing local substructures on fullerene cages. A detailed scheme of the experimentally confirmed non‐IPR C 60 isomers obtained by Stone‐Wales cage transformations is presented.