Nitride Endohedral Fullerenes Research Articles

Amine Functionalized Trimetallic Nitride Endohedral Fullerenes: A Class of Nanoparticle to Tackle Low Back/Leg Pain.

Low back pain is the most common health problem with a prevalence of over 80% worldwide and an estimated annual cost of $100 billion in the United States. Intervertebral disc degeneration accounts for a major cause of low back pain. However, there is still a lack of safe and effective treatment to tackle this devastating condition. In this study, we synthesized four functionalized trimetallic nitride endohedral metallofullerenes (carboxyl-f-Sc3N@C80, carboxyl-f-Gd3N@C80, amino-f-Sc3N@C80, and amino-f-Gd3N@C80) and characterized them with X-ray photoelectron spectroscopy, matrix-assisted laser desorption/ionization-time of flight mass spectrometry, and UV-vis. Via electron paramagnetic resonance, all four metallofullerene derivatives possessed dose-dependent radical scavenging capabilities (hydroxyl radicals and superoxide anions), with the most promising radical scavenging properties shown in the amine functionalized C80 metallofullerenes. Both amino-f-Sc3N@C80 and amino-f-Gd3N@C80 at 1 μM significantly reduced lipopolysaccharide induced reactive oxygen species production and mRNA expressions of pro-inflammatory mediators (inos, tnf-α, il-1, and cox-2) in macrophages without apparent cytotoxicity through regulating activity of p38 MAPK, p65, and nuclear translocation of NF-κB. Furthermore, in an established mouse model of lumbar radiculopathy, amino-f-Sc3N@C80 and amino-f-Gd3N@C80 effectively alleviated ipsilateral mechanical hyperalgesia for up to 2 weeks. In dorsal root ganglia explant culture, we also showed that amino-f-Sc3N@C80 and amino-f-Gd3N@C80 ameliorated TNF-α elicited neuroinflammation. In summary, we presented results for a potent radical scavenging, anti-inflammatory and analgesic nanoparticle, amino-functionalized eighty-carbon metallofullerenes in vitro and in vivo. Our study provides important assets for developing pleiotropic treatment strategies to tackle the inflammation, a significant pathological hallmark in the intervertebral disc degeneration and associated pain.

Actinide Nitride Clusterfullerene: Synthesis, Isolation and Spectroscopic Characterization of U2N@C80

All the nitride clusterfullerenes discovered so far adopted a trimetallic nitride template. Here, we report that an unprecedented nitride cluster endohedral fullerene with only two metal atoms in the cluster, U2N@C80, has been successfully synthesized by a modified arc-discharge method and isolated by a multistage HPLC process. Mass spectroscopy, UV-vis-NIR absorption spectrometry and Raman spectroscopy were employed to investigate its structure and some intriguing properties have been revealed. The UV-vis-NIR absorption spectrum of U2N@C80 in CS2 is featured with two weak absorption peaks at 446nm and 680 nm. Compared with previously reported M3N@I h(7)-C80 (M= Tm, Gd, Y, Er, Dy) fullerenes, their overall absorption spectra, characteristic absorption peaks and optical band gaps are almost identical, providing evidence for a probable six-electron transfer from the interior cluster to the exterior fullerene cage. In addition, the features of the low energy Raman spectrum of U2N@C80 also show similarities to those of fullerenes with I h-C80 cage, which agree well with the UV-vis-NIR absorption study. However, in the range of 100-200 cm‒1, the peaks of the stretching metal-cage mode is observed at 119,135 cm‒1, which shows great difference from those of lanthanide endohedral fullerenes, M3N@I h(7)-C80 (M=Tm, Gd, Y, Er, Dy), indicating a quite different metal-to-cage interaction between the inner cluster and the I h(7)-C80 cage from that of the lanthanide nitride endohedral fullerenes.

Trimetallic Nitride Endohedral Fullerenes Carboxyl-Gd3N@C80: A New Theranostic Agent for Combating Oxidative Stress and Resolving Inflammation.

Antioxidative and anti-inflammatory effects of trimetallic nitride endohedral fullerenes carboxyl-Gd3N@C80, a newly developed magnetic resonance imaging (MRI) contrast agent, were investigated. All hydrochalarone and carboxyl-functionalized fullerenes showed effective radical (hydroxyl and superoxide anion) scavenging, whereas the carboxyl-Gd3N@C80 more efficiently attenuated lipopolysaccharide (LPS) induced oxidative stress in macrophages. Carboxyl-Gd3N@C80 also suppressed LPS-elicited mRNA expression of pro-inflammatory inducible nitric oxide synthase and tumor necrosis factor-alpha, and upregulated antioxidative enzyme axis Nrf2 and heme oxygenase-1, possibly via ERK but not AKT signaling pathways. Therefore, carboxyl-Gd3N@C80 held a great promise in becoming a novel theranostic nanoplatform for simultaneously deliver MRI contrast and therapeutic functions to inflammation-related diseases.

Awaking N-hyperfine couplings in charged yttrium nitride endohedral fullerenes.

The electron spin properties of endohedral metallofullerene molecules have broad potential applications in quantum information and magnetic induction systems due to the high stability and sensitivity. Herein, we synthesized a series of Y3N@C2n (n = 40-44) molecules and studied the hyperfine structures of their anion radicals via ESR measurements and DFT calculations. N-Hyperfine couplings were clearly observed in the ESR spectra of charged Y3N@C80 and Y3N@C86 anion radicals, which are not found in the other metallofullerenes. The ESR results revealed size-dependent spin distributions and hyperfine structures, which are sensitive to subtle changes in the carbon cage and the configuration of the yttrium nitride cluster. BOMD cluster trajectories simulations indicated that the Y3N cluster almost rotates freely in neutral Y3N@C80 but there is a certain degree of limitation in the Y3N@C80 anion.

Catching metallic nitride endohedral fullerenes in organic and aqueous media

Two bis-tetraphenylporphyrin tweezers-like conjugates bearing different linkers have been characterized by means of electrochemical and photophysical methods. The thrust of this work was the complexation of these bis-porphyrins with C[Formula: see text] and metallic nitride endohedral fullerenes (MNEF) like Sc3N@C[Formula: see text] in organic and in aqueus media — studied by a combination of steady-state and time-resolved spectroscopies. In the context of charge separation evidence for the formation of the 1a[Formula: see text]-Sc3N@C[Formula: see text] and 1c[Formula: see text]-Sc3N@C[Formula: see text] charge separated states in organic and aqueous media, respectively, came from transient absorption spectroscopy. Multi-wavelength analyses afforded charge separated state lifetimes of around 400 ps.

Site specific atomic polarizabilities in endohedral fullerenes and carbon onions.

We investigate the polarizability of trimetallic nitride endohedral fullerenes by partitioning the total polarizability into site specific components. This analysis indicates that the polarizability of the endohedral fullerene is essentially due to the outer fullerene cage and has insignificant contribution from the encapsulated unit. Thus, the outer fullerene cages effectively shield the encapsulated clusters and behave like Faraday cages. The polarizability of endohedral fullerenes is slightly smaller than the polarizability of the corresponding bare carbon fullerenes. The application of the site specific polarizabilities to C60@C240 and C60@C180 onions shows that, compared to the polarizability of isolated C60 fullerene, the encapsulation of the C60 in C240 and C180 fullerenes reduces its polarizability by 75% and 83%, respectively. The differences in the polarizability of C60 in the two onions is a result of differences in the bonding (intershell electron transfer), fullerene shell relaxations, and intershell separations. The site specific analysis further shows that the outer atoms in a fullerene shell contribute most to the fullerene polarizability.

Bingel–Hirsch Addition on Endohedral Metallofullerenes: Kinetic Versus Thermodynamic Control

An extensive theoretical study of the Bingel-Hirsch addition of bromomalonate on scandium nitride endohedral fullerenes has been carried out. The prototypical and highly symmetrical Sc3N@I(h)-C80, with a structure that satisfies the isolated pentagon rule (IPR), and the non-IPR Sc3N@D3(6140)-C68 fullerene show analogous reaction paths despite the distinct topology of the carbon networks and different rotation freedom of the internal nitride cluster. For the two metallofullerenes, our results predict that the reaction takes place under kinetic control yielding open-cage fulleroids on [6,6] bonds, which is in good agreement with experimental data. The theoretical studies also show that predicting the reactivity of endohedral metallofullerenes is not straightforward and often an accurate analysis of the potential energy surface is required.

A Structural Diagnostics Diagram for Metallofullerenes Encapsulating Metal Carbides and Nitrides

Systematic structural studies of 24 different kinds of endohedral metallofullerenes, M(x)C(2n) (M = La, Y, Sc, Lu, Ti, Eu, Er, Hf, Sc(3)N; 34 ≤ n ≤ 43), as 1:1 cocrystals with solvent toluene molecules have been carried out using synchrotron radiation powder diffraction. Thirteen of the 24 molecular structures, including five metal carbides, one metal nitride endohedral fullerene, and one hollow fullerene, have been determined by a combination of the maximum entropy method and Rietveld refinement of the X-ray diffraction data obtained. We have found that the volume for one fullerene and one toluene molecule depends linearly on the number of carbon atoms in the fullerene cage. Fifteen different kinds of metal carbide endohedral fullerenes have been identified, which can be structurally characterized from the obtained lattice constants using only this linear dependence. The linear dependence found in the present study provides a metallofullerene diagnostics diagram that may have universal importance for structural characterization of the so-called cluster endohedral fullerenes.

Free Energies of Electron Transfer, Electron Transfer Kinetic Theoretical and Quantitative Structural Relationships and Electrochemical Properties Studies of Gadolinium Nitride Cluster Fullerenes Gd3N@Cn in [X-UT-Y][Gd3N@Cn](n = 80, 82, 84, 86 and 88) Supramolecular Complexes

Organometal derivatization of fullerene species is essential to construct novel organo-metallofullerene materials for a variety of applications. Gadolinium nitride endohedral fullerenes Gd3N@Cn are one of the interesting types of metallofullerenes due to their interesting electronic properties. The synthesis of these compounds allows the encapsulation of different metals such as Gadolinium, inside fullerenes making it possible to combine the properties of the metal with those of the fullerene. Their interesting electrochemical and optical features make them potential candidates for several applications, such as molecular electronics, biomedical imaging, nonlinear optical devices and MRI agents. Electron transfer between C80, C82, C84, C86 and C88 derivatives such as nitride Gadolinium cluster Gd3N@C80 (n = 80, 82, 84, 86 and 88) and other molecules is thought to involve the transfer of electrons between molecules surrounding the fullerene cage. One class of electron-transfer molecules is the [X-UT-Y][Gd3N@Cn](n = 80, 82, 84, 86 and 88). The supramolecular complexes [X-UT-Y] 1–9 and Gd3N@C80 (n = 80, 82, 84, 86 and 88) are shown to possess a previously unreported host-guest interaction for electron transfer processes. The unsaturated, cis-geometry, thiocrown ethers, (1–9), (described as [X-UT-Y], where X and Y indicate the numbers of carbon and sulfur atoms, respectively), are a group of crown ethers that display interesting physiochemical properties in light of their conformational restriction compared to a corresponding saturated system, as well as the sizes of their cavities. Topological indices have been successfully used to construct mathematical methods that relate structural data to various chemical and physical properties. To establish a good relationship between the structures of 1–9 with derivatives of nitride metal cluster as Gd3N@C80 (n = 80, 82, 84, 86 and 88) 10–14, an index is utilized, μ cs . This index (μcs) is a topological index defined by the ratio of the sum of the number of carbon atoms (nc ) and the number of sulfur atoms (ns ) with the product of these two numbers for 1–9. In this study, the relationships between this index and oxidation potential ( ox E 1 ) of 1–9, as well as the first and second free energies of electron transfer (ΔGet(n) , for n = 1, 2, which is given by the Rehm-Weller equation) between 1–9 and the nitride Gadolinium cluster Gd3N@C80 (n = 80, 82, 84, 86 and 88) 10–14 derivatives as [X-UT-Y][Gd3N@Cn](n = 80, 82, 84, 86 and 88) 15a–i –19a–i supramolecular complexes are presented and investigated. The first and second free energies of electron transfer and kinetic rate constants of the electron transfers, ΔG# et(n) and k et (n = 1,2), respectively, were also calculated in this study for [X-UT-Y][M3N@C80-R] and in accordance with the Marcus theory.

Functionalization of Endohedral Metallofullerenes

Since the serendipitous discovery of C60 and subsequent finding of other fullerenes, scientists have focused on the discovery of the physical and chemical properties of these nanomaterials and their incorporation in biomaterials and nanodevices [1,2]. The development of a particular family of fullerenes which incarcerates a metal, metals, or a metallic cluster in the interior of their carbon cages, the endohedral metallofullerenes, is quickly becoming one of the most interesting research areas within the field of carbon-based compounds because of the scope of electronic properties not accessible with empty-cage fullerenes [3-7]. Even though mass spectrometric evidence of their existence was already available in the first paper reporting the discovery of Buckminsterfullerene in 1985 [8, 9], there was controversy about the location of the metals, since fullerenes with exohedral metals were also observed. It was not until 1991 that Smalley and coworkers unequivocally showed that a lanthanum atom was encapsulated in a C82 fullerene shell as La@C82 [10], and since then, many analogous species have been isolated. However, the exploration of the physical, chemical and electronic properties of endohedral metallofullerenes has become a reality only in the last few years when technological advances have been made in the production of macroscopic quantities of these nanomaterials [11, 12]. In this section, an overall view of the effect of the encapsulated metal species on the exohedral reactivity of the carbon cages will be addressed and the differences between empty cage fullerenes and endohedral metallofullerenes will be emphasized. It is our intent to suggest that endohedral metallofullerenes are the fullerenes of the future. Keywords: Fullerenes, Endohedral fullerenes, Trimetallic nitride endohedral fullerenes

Density functional theory characterization of lanthanum nitride endohedral fullerene: La3N@C92

Systemic investigations on lanthanum nitride endohedral metallofullerene La3N@C92 are carried out by a hybrid density functional theory technique combined with statistical mechanics treatment. A novel isolated-pentagon-rule (IPR) isomer with C2 symmetry is determined as the most suitable host cage for the encapsulation of La3N with the lowest energy and predominant thermodynamic stability related to fullerene formation. Natural electron configuration analyses reveal that electron transfer between the La3N cluster and C92 cage is mainly contributed by the 6s orbital of lanthanum atoms. The present work may supply some information reliable for synthesis and experimental characterization of large trimetallic nitride endohedral fullerenes.

Triplet Exciton Generation in Bulk-Heterojunction Solar Cells Based on Endohedral Fullerenes

Organic bulk-heterojunctions (BHJ) and solar cells containing the trimetallic nitride endohedral fullerene 1-[3-(2-ethyl)hexoxy carbonyl]propyl-1-phenyl-Lu(3)N@C(80) (Lu(3)N@C(80)-PCBEH) show an open circuit voltage (V(OC)) 0.3 V higher than similar devices with [6,6]-phenyl-C[61]-butyric acid methyl ester (PC(61)BM). To fully exploit the potential of this acceptor molecule with respect to the power conversion efficiency (PCE) of solar cells, the short circuit current (J(SC)) should be improved to become competitive with the state of the art solar cells. Here, we address factors influencing the J(SC) in blends containing the high voltage absorber Lu(3)N@C(80)-PCBEH in view of both photogeneration but also transport and extraction of charge carriers. We apply optical, charge carrier extraction, morphology, and spin-sensitive techniques. In blends containing Lu(3)N@C(80)-PCBEH, we found 2 times weaker photoluminescence quenching, remainders of interchain excitons, and, most remarkably, triplet excitons formed on the polymer chain, which were absent in the reference P3HT:PC(61)BM blends. We show that electron back transfer to the triplet state along with the lower exciton dissociation yield due to intramolecular charge transfer in Lu(3)N@C(80)-PCBEH are responsible for the reduced photocurrent.

Complexation of Sc3N@C80 Endohedral Fullerene with Cyclic Zn-Bisporphyrins: Solid State and Solution Studies

We report the synthesis of two cyclic β-pyrrole unsubstituted meso-tetraphenyl bisporphyrins in which the porphyrin units are connected by two 2,3-hexadiynyl-1,6-dioxo or two hexyl-1,6-dioxo spacers, respectively. Both cyclic porphyrin dimers exist in solution as mixtures of two conformational isomers. In the solid state, the receptor with diynyl spacers forms a 1:1 complex with the icosahedral (I(h)) isomer of the trimetallic nitride endohedral fullerene Sc(3)N@C(80). In this complex the receptor adopts a scoop-shaped conformation having a dihedral angle of 87.25° between the two porphyrin planes. The hexyl spaced analogue, however, adopts a similar conformation upon encapsulation of one molecule of Sc(3)N@C(80) in a self-assembled dimeric capsule. The capsular complexes pack in columns and render the fullerene units completely isolated. In toluene solution, (1)H NMR experiments indicate that the endohedral fullerene Sc(3)N@C(80) is exclusively bound by the expanded isomer of both dimers. UV-vis and fluorescence titration experiments confirmed the existence of strong π-π interactions between the fullerene Sc(3)N@C(80) and the flexible bisporphyrin dimer with hexyl spacers. At micromolar concentration, the flexible receptor forms only a 1:1 complex with the endohedral fullerene with stability constant value of K(a) = 2.6 ± 0.3 × 10(5) M(-1).

Fullerene derivative acceptors for high performance polymer solar cells

Polymer solar cells (PSCs) are composed of a blend film of a conjugated polymer donor and a soluble fullerene derivative acceptor sandwiched between a PEDOT : PSS coated ITO positive electrode and a low workfunction metal negative electrode. The conjugated polymer donor and the fullerene derivative acceptor are the key photovoltaic materials for high performance PSCs. For the acceptors, although [6,6]-phenyl-C(61)-butyric acid methyl ester (PC(60)BM) and its corresponding C(70) derivative PC(70)BM are dominantly used as the acceptors in PSC at present, several series of new fullerene derivatives with higher-lying LUMO energy level and better solubility were reported in recent years for further improving the power conversion efficiency of the PSCs. In this perspective paper, we reviewed the recent research progress on the new fullerene derivative acceptors, including various PC(60)BM-like C(60) derivatives, PC(60)BM bisadduct, PC(70)BM bisadduct, indene-C(60) bisadduct and indene-C(70) bisadduct, trimetallic nitride endohedral fullerenes and other C(60) derivatives with multi side chains. The synthesis and physicochemical properties of PC(60)BM and PC(70)BM were also introduced considering the importance of the two fullerene acceptors.

Electronic Structure and Redox Properties of Metal Nitride Endohedral Fullerenes M3N@C2n (M=Sc, Y, La, and Gd; 2n=80, 84, 88, 92, 96)

An extensive study of the redox properties of metal nitride endohedral fullerenes (MNEFs) based on DFT computational calculations has been performed. The electronic structure of the singly oxidized and reduced MNEFs has been thoroughly analyzed and the first anodic and cathodic potentials, as well as the electrochemical gaps, have been predicted for a large number of M(3)N@C(2n) systems (M=Sc, Y, La, and Gd; 2n=80, 84, 88, 92, and 96). In particular, calculations that include thermal and entropic effects correctly predict the different anodic behavior of the two isomers (I(h) and D(5h)) of Sc(3)N@C(80), which is the basis for their electrochemical separation. Important differences were found in the electronic structure of reduced M(3)N@C(80) when M=Sc or when M is a more electropositive metal, such as Y or Gd. Moreover, the changes in the electrochemical gaps within the Gd(3)N@C(2n) series (2n=80, 84, and 88) have been rationalized and the use of Y-based computational models to study the Gd-based systems has been justified. The redox properties of the largest MNEFs characterized so far, La(3)N@C(2n) (2n=92 and 96), were also correctly predicted. Finally, the quality of these predictions and their usefulness in distinguishing the carbon cages for MNEFs with unknown structures is discussed.

Looking inside an endohedral fullerene: Inter- and intramolecular ordering ofDy3N@C80(Ih)on Cu(111)

The inter- and intramolecular ordering of the trimetallic nitride endohedral fullerene ${\text{Dy}}_{3}\text{N}@{\text{C}}_{80}$ with icosahedral cage symmetry ${I}_{h}$ on Cu(111) has been studied by scanning tunneling microscopy and synchrotron-based x-ray photoelectron diffraction (XPD). ${\text{Dy}}_{3}\text{N}@{\text{C}}_{80}$ $({I}_{h})$ is found to form ordered islands consisting of domains of equally oriented molecules. As for ${\text{C}}_{60}$ on the same substrate, the cage is facing with a hexagon toward the surface, which is however slightly tilted for ${\text{C}}_{80}$. The endohedral nitrogen atom remains at a position close to the geometrical center of the cage. Resonant XPD on the ${\text{M}}_{\text{V}}$ edge shows that the encaged ${\text{Dy}}_{3}\text{N}$ unit takes well-defined orientations with respect to the ${\text{C}}_{80}$ cage and the Cu(111) substrate.

High Efficiency Organic Photovoltaic Devices Based on Derivatives of Trimetallic Nitride Endohedral Fullerenes

not Available.

Endohedral fullerenes for organic photovoltaic devices

So far, one of the fundamental limitations of organic photovoltaic (OPV) device power conversion efficiencies (PCEs) has been the low voltage output caused by a molecular orbital mismatch between the donor polymer and acceptor molecules. Here, we present a means of addressing the low voltage output by introducing novel trimetallic nitride endohedral fullerenes (TNEFs) as acceptor materials for use in photovoltaic devices. TNEFs were discovered in 1999 by Stevenson et al. ; for the first time derivatives of the TNEF acceptor, Lu(3)N@C(80), are synthesized and integrated into OPV devices. The reduced energy offset of the molecular orbitals of Lu(3)N@C(80) to the donor, poly(3-hexyl)thiophene (P3HT), reduces energy losses in the charge transfer process and increases the open circuit voltage (Voc) to 260 mV above reference devices made with [6,6]-phenyl-C(61)-butyric methyl ester (C(60)-PCBM) acceptor. PCEs >4% have been observed using P3HT as the donor material. This work clears a path towards higher PCEs in OPV devices by demonstrating that high-yield charge separation can occur with OPV systems that have a reduced donor/acceptor lowest unoccupied molecular orbital energy offset.

Trimetallic Nitride Endohedral Fullerenes: Experimental and Theoretical Evidence for the M3N6+@C2n6− model

Size doesn't matter: Metallic nitride endohedral fullerenes (MNEFs) exhibit redox properties that are not dependent on the size of the carbon cage, but on its electronic properties. These findings support the ionic model of MNEFs.

Metallic nitride endohedral fullerenes: synthesis and electrochemical properties

Metallic nitride endohedral fullerenes (MNEFs) are one of the most interesting types of metallofullerenes due to their high yields and interesting electronic properties. The synthesis of these compounds allows the encapsulation of different metals inside fullerenes making it possible to combine the properties of the metal with those of the fullerene. Their interesting electrochemical and optical features make them potential candidates for several applications such as molecular electronics, biomedical imaging, non-linear optical devices, and MRI agents. We report herein the synthesis, isolation, and electrochemical properties of the larger MNEFs including Gd 3N@C 82 and Gd 3N@C 86, reported here for the first time.