C60 Moiety Research Articles

Electrocatalytic hydrogen evolution on the MoS2/C60 heterostructure: Reaction mechanism and activity improvement

Cheap materials are highly desirable to catalyze the important hydrogen evolution reaction (HER). Density functional theory calculations were carried out to investigate the HER on the new MoS2/C60 heterostructured catalyst. The C60 and MoS2 moieties are connected by van der Waals interactions and there is obvious charge transfer between them. They both exhibit enhanced hydrogen adsorption than the isolated components, but the activity of MoS2/C60 in experiment still may stem from the edge S sites of MoS2 with minor contribution from some C sites of C60. The activity could be effectively improved by doping boron on the MoS2 surface or exerting tensile strains, which bring more positive pz-band centers for all the MoS2/C60 sites. The boron doping also leads to electron-deficient fullerene surface due to increased charge transfer at the heterointerface. They thus further enhance the H adsorption on MoS2/C60 and achieve near-zero ΔGH* values. Importantly, an unexpected Transfer-Tafel mechanism was found at the interface and it could greatly decrease the energy barrier for H coupling. Our work elucidates the activity origin of the MoS2/C60 catalyst and provides promising strategies for activity improvement. The disclosed reaction mechanisms could guide the rational design of more heterostructured catalysts.

DFT-D3 study of two-dimensional polymerization of C60 crystal under high pressure

The high-pressure behavior of a monomer and 2D polymerized C60 crystals were investigated using DFT-D3 calculations. Although covalent bonds were not observed in monomer upon simple compression, C60 moieties in two-dimensional polymer phases (Immm and phases) exhibited intermolecular electron density, which indicates the formation of covalent bonds between C60 moieties. The C60 crystals were highly compressed under high pressure; however, small compression was observed at the C60 moieties. Both internal energies and PV terms contributed similarly to enthalpy. The deformation of crystals prevented polymerization. These results suggested a different behavior from that of typical inorganic materials.

An Unusual Fullerene–Carbene Adduct: Thermal Motion, Disorder, or Both?**

AbstractA single‐crystal X‐ray study of a fullerene‐imidazole adduct at nine temperatures (80 K≤T≤480 K), accompanied by energy calculations, strongly suggested thermal motion of the C60 moiety with respect to the imidazolium heterocycle. Analysis of the anisotropic displacement parameters, calculations of frequencies, and the refinement of disorder models for the crystal at four temperatures (230 K≤T≤380 K) lead to the conclusion that the rotator is moving at all temperatures. The rotation barrier is low, with one preferred crystallographic site and several other energy minima.

Formation and electrochemical properties of ternary mesoporous carbon, coordination C60Pd polymer and palladium nanoparticle composites

This work describes the preparation and properties of composites based on spherical mesoporous carbon nanoparticles and fullerene-coordinated C60Pd polymer. The composite material was synthesized under a multistep chemical procedure. In the first step, mesoporous carbon nanoparticles were synthesized via a template-assisted method. Next, the C60 fullerene was incorporated into mesoporous carbon pores, and then the polymerization process was carried out in a solution containing a Pd(0) complex. The composite material is electroactive in the negative potential range due to the faradaic reduction process of C60 moieties. At less negative potentials, a high capacity current related to the presence of mesoporous carbon is observed. Under voltammetric conditions, this system exhibits a high capacitance equal to 359 F g−1 in the potential range of C60Pd reduction at 0.1 V s−1. This value is 3 times higher than that of the pure polymeric material. Moreover, the composite system is more stable than pristine C60Pd. Capacitance retention, in this case, is approximately 30% higher than that of the C60Pd polymer after 6000 charging/discharging cycles at current density of 6.7 A g−1.

Fullerene-Perylenediimide (C60-PDI) Based Systems: An Overview and Synthesis of a Versatile Platform for Their Anchor Engineering.

An overview of the different covalent bonding synthetic strategies of two electron acceptors leading to fullerene-perylenediimide (C60-PDI)-based systems, essentially dyads and triads, is presented, as well as their more important applications. To go further in the development of such electron and photoactive assemblies, an original aromatic platform 5-benzyloxy-3-formylbenzoic acid was synthesized to graft both the PDI dye and the fullerene C60. This new C60-PDI dyad exhibits a free anchoring phenolic function that could be used to attach a third electro- and photoactive unit to study cascade electron and/or energy transfer processes or to obtain unprecedented side-chain polymers in which the C60-PDI dyads are attached as pendant moieties onto the main polymer chain. This C60-PDI dyad was fully characterized, and cyclic voltammetry showed the concomitant reduction process onto both C60 and PDI moieties at identical potential. A quasi-quantitative quenching of fluorescence was demonstrated in this C60-PDI dyad, and an intramolecular energy transfer was suggested between these two units. After deprotection of the benzyloxy group, the free hydroxyl functional group of the platform was used as an anchor to reach a new side-chain methyl methacrylate-based polymer in which the PDI-C60 dyad units are located as pendants of the main polymer chain. Such polymer which associates two complementary acceptors could find interesting applications in optoelectronics and in particular in organic solar cells.

Selective population of tripletexcited states in heavy-atom-free BODIPY-C60based molecular assemblies.

Photophysical studies on a BODIPY-fullerene-distyryl BODIPY triad (BDP-C60-DSBDP) and its reference dyads (BODIPY-fullerene; BDP-C60 and distyryl BODIPY-fullerene; DSBDP-C60) are presented herein. In the triad, the association of the two chromophore units linked by a fullerene moiety leads to strong near UV-Visible light absorption from 300 to 700nm. The triplet-excited state was observed upon visible excitation in all these assemblies, and shown to be localized on the C60 or BODIPY moieties. Using quantitative nanosecond transient absorption, we provide a complete investigation on the lifetime and formation quantum yield of the triplet-excited state. In the BDP-C60 dyad, the tripletexcited state of C60 (τ = 7 ± 1μs) was obtained with a quantum yield of 40 ± 8%. For the DSBDP-C60 dyad and BDP-C60-DSBDP triad, a longer-lived tripletexcited state with a lifetime of around 250 ± 20μs centered on the DSBDP moiety was formed, with respective quantum yields of 37 ± 8 and 20 ± 4%. Triplet-triplet annihilation up-conversion is characterized in the BDP-C60 dyad and the bichromophoric triad in the presence of perylene and DSBDP-monomer as respective annihilators. The photo-induced formation of a long-lived 3DSBDP* in the triad coupled with panchromatic light absorption offers potential applications as a heavy-atom-free organic triplet photosensitizer.

A novel supramolecular porphyrin-fullerene compound: Crystal structure and photophysical properties

A novel porphyrin-(60)fullerene complex [bis(5,10,15,20-tetra-3-pyridinyl-21H, 23H-porphine)](60)-fullerene tetrahydrate, C60(Por)2·4H2O (1; Por ​= ​5,10,15,20-tetra-3-pyridinyl-21H,23H-porphine) was synthesized via a hydrothermal reaction of 5,10,15,20-tetra-3-pyridinyl-21H,23H-porphine, C60, xylene and distilled water. The crystal structure is characterized by single-crystal X-ray diffraction. Compound 1 is characteristic of an isolated structure and each molecule contains two 5,10,15,20-tetra-3-pyridinyl-21H,23H-porphine moieties surrounding one C60 moiety, accompanied by four lattice water molecules. The porphine molecule features a saddle-distorted nonplanar macrocycle. The molecules in 1 are interconnected through van der Waals interactions to yield a supramolecular network. The photophysical properties of 1 in ethanol solution have been studied by photoluminescence and UV–Vis–NIR absorbance. A solution photoluminescence measurement shows that compound 1 can emit red photoluminescence with the maximum peak locating at 656 ​nm. Compound 1 has CIE (Commission Internationale de I'Éclairage) chromaticity coordinates of 0.70 and 0.30. The lifetime is 1.501 us and the quantum yield of 1 is 0.9%.

Ionization and electron excitation of C60 in a carbon nanotube: A variable temperature/voltage transmission electron microscopic study

There is increasing attention to chemical applications of transmission electron microscopy, which is often plagued by radiation damage. The damage in organic matter predominantly occurs via radiolysis. Although radiolysis is highly important, previous studies on radiolysis have largely been descriptive and qualitative, lacking in such fundamental information as the product structure, the influence of the energy of the electrons, and the reaction kinetics. We need a chemically well-defined system to obtain such data and have chosen as a model a variable-temperature and variable-voltage (VT/VV) study of the [2 + 2] dimerization of a van der Waals dimer [60]fullerene (C60) to C120 in a carbon nanotube (CNT), as studied for several hundred individual reaction events at atomic resolution. We report here the identification of five reaction pathways that serve as mechanistic models of radiolysis damage. Two of them occur via a radical cation of the specimen generated by specimen ionization, and three involve singlet or triplet excited states of the specimen, as initiated by electron excitation of the CNT, followed by energy transfer to the specimen. The [2 + 2] product was identified by measuring the distance between the two C60 moieties, and the mechanisms were distinguished by the pre-exponential factor and the Arrhenius activation energy—the standard protocol of chemical kinetic studies. The results illustrate the importance of VT/VV kinetic analysis in the studies of radiation damage and show that chemical ionization and electron excitation are inseparable, but different, mechanisms of radiation damage, which has so far been classified loosely under the single term “ionization.”

BOPHY-Fullerene C60 Dyad as a Photosensitizer for Antimicrobial Photodynamic Therapy.

A novel BOPHY-fullerene C60 dyad (BP-C60 ) was designed as a heavy-atom-free photosensitizer (PS) with potential uses in photodynamic treatment and reactive oxygen species (ROS)-mediated applications. BP-C60 consists of a BOPHY fluorophore covalently attached to a C60 moiety through a pyrrolidine ring. The BOPHY core works as a visible-light-harvesting antenna, while the fullerene C60 subunit elicits the photodynamic action. This fluorophore-fullerene cycloadduct, obtained by a straightforward synthetic route, was fully characterized and compared with its individual counterparts. The restricted rotation around the single bond connecting the BOPHY and pyrrolidine moieties led to the formation of two atropisomers. Spectroscopic, electrochemical, and computational studies disclose an efficient photoinduced energy/electron transfer process from BOPHY to fullerene C60 . Photodynamic studies indicate that BP-C60 produces ROS by both photomechanisms (type I and type II). Moreover, the dyad exhibits higher ROS production efficiency than its individual constitutional components. Preliminary screening of photodynamic inactivation on bacteria models (Staphylococcus aureus and Escherichia coli) demonstrated the ability of this dyad to be used as a heavy-atom-free PS. To the best of our knowledge, this is the first time that not only a BOPHY-fullerene C60 dyad is reported, but also that a BOPHY derivative is applied to photoinactivate microorganisms. This study lays the foundations for the development of new BOPHY-based PSs with plausible applications in the medical field.

Anthracene modified graphene for C60/C70 fullerenes capture and construction of energy storage materials

Graphene functionalized with dianthracene malonate was synthesized and used subsequently for construction of covalently bound graphene-fullerene hybrid nanomaterials. For this purpose, novel approach of Diels–Alder reaction of C60/C70 fullerene cores with anthracene moieties previously introduced onto graphene surface was successfully employed. Structure and composition of obtained graphene and its derivatives were characterized using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and FT-IR spectroscopy. Obtained results revealed that both C60 and C70 fullerenes were found to be capable of formation desired Diels–Alder adducts, yielding products of different morphology. Capacitive properties of the synthesized energy storage nanomaterials were determined by means of cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) measurements, revealing that functionalization of graphene with C60 moieties enhances its energy storage properties.

On the surface interaction of C60 with superalkalis: a computational approach

We study the surface interaction of C60 with superalkali (SA) clusters for SA = FLi2, OLi3 and NLi4 using a density functional approach and compare it with exohedral LiC60 complex. The interaction takes place via two or more Li–C bonds and leads to SAC60 complexes, which are stabilised by electron transfer from SA to C60 moieties. Thus, SAC60 complexes can be represented as (SA)+C60 − having enhanced dipole moment and the energy gap, unlike endohedral SA@C60 complexes with negligible dipole moment and lower energy gap. These findings suggest that C60 fullerene can be activated by the surface interaction with SA clusters.

Insights on the supramolecular polymorphism of poly(\u03b3-benzyl-L-glutamate) rod-like peptides from atomistic molecular dynamics simulations

This work reports an all-atom molecular dynamics study of the first stages of aggregation of poly(gamma-benzyl-L-glutamate)—PBLG—polymers end-capped with C60. PBLG self-assembles in water and shows polymorphism when specific changes in the molecular structure are made. Three variants of PBLG are compared, which differ for the location of the C60 moiety: N-terminus, C-terminus, or both. The aim of the computational experiments was to rationalize the key molecular properties that are relevant to the supramolecular polymorphism. Single-peptide simulations in tetrahydrofuran and in water allowed to quantify the strength of the self-assembly driving force in terms of the overall order parameter of the phenyl rings that are “coating” the peptides. Two-peptide simulations for the singly capped peptides showed that two kinds of aggregates can be formed: one “slow” thermodynamically more stable, and one “fast” kinetically favoured. These first-stage aggregates are interpreted as the seeds leading to different self-assemblies.Graphical abstract

Pentafluorophenyl Esters as Exchangeable Stoppers for the Construction of Photoactive [2]Rotaxanes.

Stable pillar[5]arene-containing [2]rotaxane building blocks with pentafluorophenyl ester stoppers have been efficiently prepared on a multi-gram scale. Reaction of these building blocks with various nucleophiles gave access to a wide range of [2]rotaxanes with amide, ester or thioester stoppers in good to excellent yields. The rotaxane structure is fully preserved during these chemical transformations. Actually, the addition-elimination mechanism at work during these transformations totally prevents the unthreading of the axle moiety of the mechanically interlocked system. The stopper exchange reactions were optimized both in solution and under mechanochemical solvent-free conditions. While amide formation is more efficient in solution, the solvent-free conditions are more powerful for the transesterification reactions. Starting from a fullerene-functionalized pillar[5]arene derivative, this new strategy gave easy access to a photoactive [2]rotaxane incorporating a C60 moiety and two Bodipy stoppers. Despite the absence of covalent connectivity between the Bodipy and the fullerene moieties in this photoactive molecular device, efficient through-space excited state interactions have been evidenced in this rotaxane.

Pomegranate-like C60@cobalt/nitrogen-codoped porous carbon for high-performance oxygen reduction reaction and lithium-sulfur battery

Porous carbon materials play essential roles in electrocatalysis and electrochemical energy storage. It is of significant importance to rationally design and tune their porous structure and active sites for achieving high electrochemical activity and stability. Herein, we develop a novel approach to tune the morphology of porous carbon materials (PCM) by embedding fullerene C60, achieving improved performance of oxygen reduction reaction (ORR) and lithium-sulfur (Li-S) battery. Owing to the strong interaction between C60 and imidazole moieties, pomegranate-like hybrid of C60-embedded zeolitic imidazolate framework (ZIF-67) precursor is synthesized, which is further pyrolyzed to form C60-embedded cobalt/nitrogen-codoped porous carbon materials (abbreviated as C60@Co-N-PCM). Remarkably, the unique structure of C60@Co-N-PCM offers excellent ORR electrocatalytic activity and stability in alkaline solutions, outperforming the commercial Pt/C (20 wt.%) catalyst. Besides, C60@Co-N-PCM as a novel cathode delivers a high specific capacity of ∼ 900 mAh·g−1 at 0.2 C rate in Li-S batteries, which is superior to the pristine ZIF-67-derived PCM without embedding C60.

Photoinduced Electron Transfer and Energy Transfer Processes in a Flexible BODIPY-C60 Dyad.

A new donor-acceptor dyad composed of a BODIPY (4,4'-difluoro-4-bora-3a,4a-diaza-s-indacene) donor and a fullerene C60 acceptor has been synthesized and characterized. This derivative has been prepared using a clickable fullerene building block that bears an alkyne moiety and a maleimide unit. The post-functionalization of the maleimide group by a BODIPY thiol leads to a BODIPY-C60 dyad, leaving the alkyne moiety for further functional arrangement. On the basis of the combination of semi-empirical and density functional theory (DFT) calculations, spectroelectrochemical experiments, and steady-state and time-resolved spectroscopies, the photophysical properties of this new BODIPY-C60 dyad were thoroughly studied. By using semi-empirical calculations, the equilibrium of three conformations of the BODIPY-C60 dyad has been deduced, and their molecular orbital structures have been analyzed using DFT calculations. Two short fluorescence lifetimes were attributed to two extended conformers displaying variable donor-acceptor distances (17.5 and 20.0 Å). Additionally, the driving force for photoinduced electron transfer from the singlet excited state of BODIPY to the C60 moiety was calculated using redox potentials determined with electrochemical studies. Spectroelectrochemical measurements were also carried out to investigate the absorption profiles of radicals in the BODIPY-C60 dyad in order to assign the transient species in pump-probe experiments. Under selective photoexcitation of the BODIPY moiety, occurrences of both energy and electron transfers were demonstrated for the dyad by femtosecond and nanosecond transient absorption spectroscopies. Photoinduced electron transfer occurs in the folded conformer, while energy transfer is observed in extended conformers.

A Fullerene‐Based Molecular Torsion Balance for Investigating Noncovalent Interactions at the C60 Surface

AbstractTo investigate the nature and strength of noncovalent interactions at the fullerene surface, molecular torsion balances consisting of C60 and organic moieties connected through a biphenyl linkage were synthesized. NMR and computational studies show that the unimolecular system remains in equilibrium between well‐defined folded and unfolded conformers owing to restricted rotation around the biphenyl C−C bond. The energy differences between the two conformers depend on the substituents and is ascribed to differences in the intramolecular noncovalent interactions between the organic moieties and the fullerene surface. Fullerenes favor interacting with the π‐faces of benzenes bearing electron‐donating substituents. The correlation between the folding free energies and corresponding Hammett constants of the substituents in the arene‐containing torsion balances reflects the contributions of the electrostatic interactions and dispersion force to face‐to‐face arene–fullerene interactions.

A Fullerene-Based Molecular Torsion Balance for Investigating Noncovalent Interactions at the C60 Surface.

To investigate the nature and strength of noncovalent interactions at the fullerene surface, molecular torsion balances consisting of C60 and organic moieties connected through a biphenyl linkage were synthesized. NMR and computational studies show that the unimolecular system remains in equilibrium between well-defined folded and unfolded conformers owing to restricted rotation around the biphenyl C-C bond. The energy differences between the two conformers depend on the substituents and is ascribed to differences in the intramolecular noncovalent interactions between the organic moieties and the fullerene surface. Fullerenes favor interacting with the π-faces of benzenes bearing electron-donating substituents. The correlation between the folding free energies and corresponding Hammett constants of the substituents in the arene-containing torsion balances reflects the contributions of the electrostatic interactions and dispersion force to face-to-face arene-fullerene interactions.

Synthesis and Photophysical Study of [60]Fullerene-Maleimide Dyads.

Novel [60]fullerene-maleimide dyads were synthesized by covalent linking of maleimide fluorophore to the [60]fullerene (C60) via Bingel reaction. The dyads were well characterized and studied for their absorption and emission properties. The fluorescence quenching of maleimide moiety by C60 was observed, indicating the intramolecular energy transfer from maleimide fluorophore to C60 moiety.

A Tunable, Fullerene-Based Molecular Amplifier for Vibrational Circular Dichroism.

Vibrational circular dichroism (VCD) studies are reported on a chiral compound in which a fullerene C60 moiety is used as an electron acceptor and local VCD amplifier for an alanine‐based peptide chain. Four redox states are investigated in this study, of which three are reduced species that possess low‐lying electronic states as confirmed by UV/Vis spectroelectrochemistry. VCD measurements in combination with (TD)DFT calculations are used to investigate (i) how the low‐lying electronic states of the reduced species modulate the amplification of VCD signals, (ii) how this amplification depends on the distance between oscillator and amplifier, and (iii) how the spatial extent of the amplifier influences amplification. These results pave the way for further development of tailored molecular VCD amplifiers.

Effect of the dual incorporation of fullerene and polyethyleneimine moieties into SBA-15 materials as platforms for drug delivery

Mesostructured SBA-15 silica materials have been successfully dual functionalized with polyethyleneimine (PEI) groups and C60 fullerene moieties to allow an evaluation of their properties as nanovehicles for controlled drug delivery. Methylprednisolone sodium succinate was selected as a model drug for adsorption on the surface of functionalized SBA-15 silica materials. The resulting dual-functionalized SBA-15 silica materials exhibit mesoscopic arrangements, although with a remarkable reduction in their textural properties as compared to pure silica SBA-15. The adsorption capacity of methylprednisolone on functionalized SBA-15-PEI improved remarkably compared with that of raw SBA-15, while the drug release rate slowed, as the amount of PEI anchored in the SBA-15 increased. The strong attractive electrostatic interactions between methylprednisolone and the silica surfaces of SBA-15-PEI materials, measured by zeta potential, account for these results. In a second step, wherein C60 fullerene species in combination with PEI were grafted to the silica, the results establish that the steric effects and hydrophobicity of the C60 moieties hinder methylprednisolone transport within the silica pores. The kinetic parameters obtained from the drug release profiles, fitted to four kinetic models, show that the incorporation of C60 species yields lower methylprednisolone release rates from SBA-15-PEI-C60 materials than from SBA-15-PEI materials. Additionally, the incorporation of fullerene groups into PEI-modified materials provides an increment in cell viability. Confocal microscopy evidences the cellular internalization of the dual-functionalized mesoporous SBA-15 materials inside the plasmatic membrane.