Trimetallic 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.

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.

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.

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.

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

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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.

Charged States of Sc3N@C68: An In Situ Spectroelectrochemical Study of the Radical Cation and Radical Anion of a Non-IPR Fullerene

The redox behavior of Sc 3N@C 68 is studied systematically by means of electrochemistry, in situ ESR/Vis-NIR spectroelectrochemistry, and detailed theoretical treatment. Formation of the negatively and positively charged paramagnetic species for the same trimetallic nitride endohedral fullerene is demonstrated for the first time. The electrochemical study of Sc 3N@C 68 exhibits two electrochemically irreversible but chemically reversible reduction steps and two reversible oxidation steps. A double-square reaction scheme is proposed to explain the observed redox reaction at cathodic potentials involving the reversible dimerisation of the Sc 3N@C 68 monoanion. The spin state of the radical cation and the radical anion is probed by ESR spectroscopy, indicating that in both states, the large part of the unpaired spin is delocalized on the fullerene cage. The charged states of the non-isolated pentagon rule fullerene are characterized furthermore by in situ absorption spectroscopy. The interpretation of experimental data is supported by the density functional theory (DFT) calculations of the spin distribution in the anion and cation radicals of Sc 3N@C 68 and time-dependent DFT calculations of the absorption spectra of the charged species.

Characterization of magnetic and electronic properties of trimetallic nitride endohedral fullerenes by SQUID magnetometry and electron paramagnetic resonance

Magnetic and electronic properties of high-purity trimetallic nitride endohedral fullerenes Er3N@C80, Lu3N@C80, Sc3N@C80 diluted in a diamagnetic host were characterized by SQUID DC magnetometry and electron paramagnetic resonance (EPR) at multiple frequencies. The Er3N@C80 sample followed the Curie–Weiss law with negligible Weiss temperature of 0.16K. Based on temperature dependence and isothermal saturation magnetization the effective magnetic moment of Er3N@C80 was estimated as 10.2μB. The magnetic behavior of these fullerenes is ascribed to quenching of the orbital moment of the metal ions due to interactions between the metal centers with the nitrogen and the fullerene cage.

Gd3N@C2n (n = 40, 42, and 44): Remarkably Low HOMO−LUMO Gap and Unusual Electrochemical Reversibility of Gd3N@C88

High-performance liquid chromatography was used to isolate two new trimetallic nitride endohedral fullerenes, Gd3N@C2n (n = 42 and 44), and they were characterized by MALDI-TOF mass spectrometry, UV-vis-NIR, and cyclic voltammetry. It was found that their electronic HOMO-LUMO gaps depend pronouncedly on the size of the cage, from a large band gap for Gd3N@C80 (2.02 V) to a small band gap for Gd3N@C88 (1.49 V). The electrochemical properties also change dramatically with the size of the cage, going from irreversible for the C80 cage to reversible for Gd3N@C88. The latter is the largest trimetallic cluster inside C88 isolated and characterized to date. Gd3N@C88 has one of the lowest electrochemical energy gaps for a nonderivatized metallofullerene.

A Large Family of Dysprosium-based Trimetallic Nitride Endohedral Fullerenes: Dy3N@C2n

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Isolation of News Fullerene Cage Isomers: Dysprosium-based Trimetallic Nitride Endohedral Fullerenes

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A Large Family of Dysprosium-based Trimetallic Nitride Endohedral Fullerenes: Dy3N@C2n (39 ≤ n ≤ 44)

Dysprosium-based trimetallic nitride endohedral fullerenes (clusterfullerenes)-the Dy(3)N@C(2)(n) (38 </= n </= 49) family-have been produced at overwhelming yields compared to the empty fullerenes for the first time. The Dy(3)N@C(2)(n) family represents the largest clusterfullerene family explored up to now, even in comparison with the Tm(3)N@C(2)(n) (38 </= n </= 44) family which was discovered very recently. A series of 10 Dy(3)N@C(2)(n) clusterfullerenes (39 </= n </= 44, 1-9) have been isolated successfully and characterized by HPLC, mass spectrometry, and UV-vis-NIR spectroscopy. The study on the HPLC elution behavior reveals that there are two isomers for Dy(3)N@C(78) and Dy(3)N@C(84). Furthermore, a third isomer of Dy(3)N@C(80) is isolated for the first time. The optimum production conditions (Dy:C = 1:15, NH(3) pressure = 20 mbar) have been determined by investigating the effects of the Dy:C ratio and NH(3) pressure on the yields of the Dy(3)N@C(2)(n) clusterfullerenes. UV-vis-NIR spectroscopic study indicates that the Dy(3)N@C(2)(n) clusterfullerenes with small cages (n = 39-41) are large band-gap (1.38 approximately 1.51 eV) materials, while the band-gaps for those with larger cages (n = 42-44) are significantly smaller (0.80 approximately 0.84 eV).