Y.F.Wang

A new purely organic supramolecular framework based on hexakis[60]fullerene is capable of absorbing and releasing chloroform through internal structural reorganization.

Abstract

The design of dynamic structures with high recognition host-guest materials capable to host selectively small volatile molecules is an emergent field of research with both fundamental and applied implications. The challenge of exploring novel materials with advanced functionalities has led to the development of dynamic crystalline structures promoted by soft interactions. Here, a new pure organic dynamic framework based on hexakis[60]fullerene that are held together by weak van der Waals interactions is described. This crystalline structure is capable of absorbing and releasing chloroform, through internal structural reorganization. This research provides new insight into the design of organic molecular crystals for selective adsorption applications.

The first C₇₀-based “ionic” endohedral fullerene, Li⁺@C₇₀, was synthesized and isolated as PF₆ ⁻ and TFSI⁻ salts. The 1 : 1 ion pair structures were fully confirmed by spectroscopic analyses and X-ray crystallography. Optical spectroscopy as well as electrochemical measurements revealed that the encapsulated Li⁺ strongly stabilized the orbital energy of C₇₀ through Coulomb interaction without changing the original energy gap and orbital degeneracy of the cage.

Abstract

Ion-endohedral-fullerene has attracted growing interest due to the unique electronic and structural characteristics arising from its distinctive ionic nature. Although there has been only one reported ion-encapsulated fullerene, Li⁺@C₆₀, a significant number of fundamental and applied studies have been conducted, making a substantial impact not only in chemistry and physics but also across various interdisciplinary research fields. Nevertheless, studies on ion-endohedral fullerenes are still in their infancy due to the limitations in variety, and hence, it remains an open question how the size and symmetry of fullerene, as well as the motion and position of the encapsulated ion, affect their physical/chemical properties. Herein, we report the synthesis of lithium-ion-endohedral [70]fullerene (Li⁺@C₇₀ X⁻, X=PF₆ ⁻ and TFSI⁻), a novel ionic endohedral fullerene. X-ray crystallography confirmed the encapsulation of Li⁺ by C₇₀ cage as well as its ion-pair structure stabilized by external TFSI⁻ counter anion. The encapsulated Li⁺ drastically lowered the orbital energy of the C₇₀ cage by Coulomb interactions but did not affect the orbital energy gap and degeneracy. DFT studies were also performed, which supported the experimentally observed electronic effects caused by the encapsulated Li⁺.

The covalent anchoring of electron acceptors derived of [6,6]-phenyl-fullerene-methyl butyrate (PC₆₁BM and PC₇₁BM) to carbon dots (CD) was carried out successfully and the obtained hybrid nanomaterials characterized by means of AFM microscopy, and FTIR and XPS spectroscopies. Electrochemical and photophysical studies confirmed the electronic communication between the covalently connected units and their promise for further photo- and electronic applications.

Abstract

The covalent incorporation of C₆₀ and C₇₀ derivatives of the well-known n-type organic semiconductor PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) onto carbon dots (CD) is described. Morphological and structural characterization reveal combined features of both pristine starting materials (CD and PCBM). Electrochemical investigations evidenced the existence of additional reduction processes to that of CD or PCBM precursors, showing rich electron-acceptor capabilities, with multistep processes in an affordable and narrow electrochemical window (ca. 1.5 V). Electronic communication in the obtained nanoconjugated species were derived from steady-state absorption and emission spectroscopies, which showed bathochromically shifted absorptions and emissions well entering the red region. Finally, the lower fluorescence quantum yield of CD-PCBM nanoconjugates, compared with CD, and the fast decay of the observed emission of CD, support the existence of an electronic communication between both CD and PCBM units in the excited state.

Nature Communications, Published online: 19 December 2023; doi:10.1038/s41467-023-44194-y

Shortening the inter-spin distance is an effective way to enhance magnetic coupling. However, it is typically challenging to change the inter-ion distance in most magnetic systems. Here, Huang et al present a strategy for enhancing magnetic interactions, by confining a molecular magnetic system inside a carbon fullerene cage, leading to enhanced magnetic properties.

Nature Communications, Published online: 15 January 2024; doi:10.1038/s41467-024-44834-x

Inter-fullerene conjugates are non-naturally occurring carbon allotropes. Here the authors report on the chemical synthesis and solid-state structure of three inter-[60]fullerene hybrids with inherent chirality.

A large-size amorphous carbon monolayer is fabricated by rapid pyrolyzing the fullerene monolayer. The amorphous carbon monolayer is metastable, insulating, and nanoporous with a cation selectivity of 26%. This work provides new insight into the controlled synthesis of large-size metastable amorphous carbon monolayer.

Abstract

Carbon materials derived from fullerene are reported recently with unique structures and properties. However, only micrometer size samples can be obtained that limits the studying and exploration for membrane applications. Here, the preparation of a centimeter-size nanoporous amorphous carbon monolayer is reported by rapid pyrolyzing a Langmuir–Blodgett film of fullerene. The sample is fully characterized and the results indicate that the amorphous carbon monolayer derived from fullerene is metastable and insulating. The ionic transmembrane transport study demonstrates that the membrane is porous and cation selective with a selectivity of 26%. This work provides new insights into the controlled synthesis of large-size metastable amorphous carbon monolayer.

Metal-free photoredox catalyst C₇₀ was introduced for the facile construction of pyrrolo[2,1-a]isoquinolines under mild conditions, yielding a diverse library of pyrrolo[2,1-a]isoquinolines. Low catalyst loading, gram scale synthesis, and broad substrate scope (48 examples) demonstrate the synthetic utility of the protocol and encourage its future application as a photoredox catalyst in organic transformations.

Abstract

Herein, fullerene (C₇₀) is introduced as an effective photoredox catalyst for the construction of a highly functionalised pyrrolo[2,1-a]isoquinoline framework by 1,3-dipolar cycloaddition-aromatisation reaction sequence. The ability of C₇₀ to efficiently harvest visible light, its long-triplet state lifetime, good photostability, and strong singlet oxygen generation potential (Φ_▵≈1), make it an efficient photoredox catalyst. Upon photoirradiation, C₇₀ promotes the formation of singlet oxygen and superoxide radical by energy transfer (EnT) and single electron transfer (SET) mechanism. The superoxide radical acts as a potential oxidant in the formation of azomethine ylide through the oxidation-deprotonation tandem process. Azomethine ylide further participates in [3+2]-cycloaddition reaction protocol with alkene/alkyne to give the corresponding pyrrolo[2,1-a]isoquinolines. Interestingly, this protocol allows the activation of a wide range of substrates giving access to a diverse library of 48 well-decorated pyrrolo[2,1-a]isoquinolines with good functional group tolerance.

Molecular interactions are a combination of different attractive and repulsive forces. We have studied the delicate balance within a supramolecular [10]cycloparaphenylene–fullerene complex—both functionalized with alkyl esters—to evaluate the attractive and repulsive interplay between the substituents on the components. More information can be found in the Research Article by H. A. Wegner and co-workers (DOI: 10.1002/chem.202300268).

Efficient charge separation and low sensitivity to the spatial orientation of monomeric units in tetramer make host–guest complexes of cyclic dibenzopyrrolo[3,2-b]pyrroles attractive for photovoltaic applications.

Abstract

An approach to modulating the properties of carbon nanorings by incorporating pyrrolo[3,2-b]pyrrole units is of particular interest due to the combined effect of heteroatom and antiaromatic character on electronic properties. The inclusion of units other than phenylene leads to the formation of stereoisomers. In this work, we computationally study how the spatial orientation of monomeric units in the ring affects the properties of cyclic dibenzopyrrolo[3,2-b]pyrroles and their complexes with C₆₀ fullerene. For [4]PP and [4]DHPP, the most symmetrical AAAA isomer is the most stable and forms stronger interactions with fullerene than the isomers where one or two monomeric units are flipped, mostly due to less Pauli repulsion. π-Electron delocalization in the monomeric unit is crucial for directing the electron transfer (from or to nanoring). The energy of excited states with charge transfer depends on the HOMO–LUMO gap, which varies from one stereoisomer to another only for [4]DHPP⊃C₆₀ with aromatic 1,4-dihydropyrrolo[3,2-b]pyrrole units. The rates of electron transfer and charge recombination reactions are relatively weakly dependent of the spatial isomerism of nanorings.

By employing torsion balance molecules, we effectively measured the magnitude of the dispersion forces involved in the non-covalent interactions between substituted arene and fullerene. In addition, our findings indicate that solvation is of paramount importance in the anionic arene–fullerene interaction between thiophenolate and fullerene.

Abstract

We employ a molecular torsion balance displaying bifurcated conformational isomerism to quantitatively evaluate the non-covalent interactions between the fullerene surface and substituted arene moieties containing elements with high atomic numbers, as well as the thermodynamic processes involved in the folding equilibrium using nuclear magnetic resonance spectroscopy. The interaction between fullerene and haloaryl groups was stronger in cases where the introduced halogen had a higher atomic number, indicating that dispersion forces play a significant role in the interaction between fullerenes and 4-haloaryl groups. The dispersion term also significantly contributed to the interaction between fullerene and the 4-mercaptophenyl group. Moreover, the addition of an appropriate base to the 4-mercaptophenyl-appended torsion balance formed the corresponding thiophenolate anion, resulting in a large negative change in the folding free energy in CDCl₃. Detailed analysis suggested that the observed attractive anionic arene–fullerene interactions predominantly originated from solvation effects.

A novel superlattice containing 3 hydrocarbon single layers alternating with 4 fullerene 2D crystals can be generated in a wide range of fullerene block molecules (n=10 or 12; m=5–7), owing to the cooperative effect of a long spacer and short terminal tails. This offers a practical way to construct unconventional semi-conductive superstructures.

Abstract

Here the supramolecular liquid crystalline (LC) phase behavior of a series of fullerene block molecules was investigated regarding spacer length, alkyl tail length and temperature. These compounds exhibit several lamellar LC phases with different packings of self-organized fullerene two-dimensional (2D) crystals. With a short hexamethylene spacer, they form sandwich-like structures with triple or quadruple fullerene layers. By increasing the spacer length to 10 or 12 carbons, a composite layers-in-lamella superlattice structure with alternating soft hydrocarbon single layers and fullerene single or double layers was obtained. As the molecular configurational freedom between incompatible moieties was enhanced by the elongated spacer, the required cross-sectional fullerene-to-hydrocarbon ratio for the superlattice could be achieved despite of different volume fractions of the blocks. The superlattice phase range is efficiently widened by the design principle of constructing LC molecules with a long spacer, which also provides a facile way to tailor novel superstructures.

Novel sugar-bridged fullerene dumbbells were synthesized and fully characterized. Methano- and furan-fused C₆₀ interacted with [10]CPP, an electron-donating nanoring, to form bis-pseudorotaxanes. Interestingly, the methano-dumbbell molecules showed a different binding behaviour as mono-, bis-pseudorotaxanes as well as oligomers (polymers) were detected.

Abstract

The synthesis and characterization of four dumbbell-shaped fullerene molecules connected by isosorbide and isomannide moieties is presented. Additionally, their electrochemical behavior and their ability to form complexes with [10]cycloparaphenylene ([10]CPP) were investigated. The cyclic voltammetry (CV) results of the fullerene dumbbells demonstrate a high electron affinity, indicating their strong interaction with electron-donating counterparts such as carbon nanorings, which possess complementary charge and shape properties. To study the thermodynamic and kinetic parameters of complexation, isothermal titration calorimetry (ITC) was employed. NMR titration experiments provided further insights into the binding stoichiometries. Two distinct approaches were utilized to create bridged structures: one based on cyclopropane and the other based on furan. Regardless of the type of linker used, all derivatives formed conventional 2 : 1 complexes denoted as [10]CPP₂⊃C_60derivative. However, the methano-dumbbell molecules exhibited distinct binding behavior, resulting in the formation of mono- and bis-pseudorotaxanes, as well as oligomers (polymers). The formation of linear polymers holds significant potential for applications in solar energy conversion processes.

A series of fullerene-derived molecular torsion balances have been synthesized to quantitatively evaluate the contribution of the dispersion force to the arene—fullerene interaction. The torsion balance with a mercaptophenyl group was converted to the corresponding thiophenolate anion by adding an amine. Consequently, the anionic arene—fullerene interactions were elucidated. More information can be found in the Research Article by M. Yamada and co-workers (DOI: 10.1002/chem.202300877).

The cover picture represents the fascinating interaction between novel sugar-bridged fullerene dumbbells and the [10]cycloparaphenylene nanoring. It visually depicts the formation of mono- and bis-pseudorotaxanes, which exhibit variations depending on the sugar moiety and anchoring strategy employed. Additionally, the artwork highlights the formation of methano-dumbbell oligomers, emphasizing their potential application in sustainable solar energy conversion. More information can be found in the Research Article by M. E. Pérez-Ojeda, A. Mitrović, V. Maslak and co-workers (DOI: 10.1002/chem.202301061).

Nature Communications, Published online: 23 November 2022; doi:10.1038/s41467-022-34651-5

Diatomic actinide molecules are ideal models for studying rare multiple-bond motifs. Here, the authors report host-guest structures of metastable charged U≡N diatoms confined in fullerene cages and stabilized by coordinative electron transfer.

Nature Chemistry, Published online: 22 December 2022; doi:10.1038/s41557-022-01103-y

The enantioselective functionalization of C60 is highly challenging, typically requiring complex chiral tethers or demanding chromatography. Fullerenes have now been shown to undergo Diels–Alder reactions in a chemo-, regio- and enantio-selective fashion through confinement within an enantiopure metal–organic cage functionalized with a chiral formylpyridine group.