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Sample records for gadolinium-containing endoedral metallofullerenes

  1. Endohedral metallofullerenes

    NASA Astrophysics Data System (ADS)

    Shinohara, H.

    2000-06-01

    Endohedral metallofullerenes (fullerenes with metal atom(s) encapsulated) are novel forms of fullerene-based materials which have attracted wide interest during the past eight years, not only in physics and chemistry but also in such interdisciplinary areas as materials and biological sciences. In this paper, advances in the production, separation (isolation) and various spectroscopic characterizations of endohedral metallofullerenes are presented in an attempt to clarify their structural, electronic and solid state properties. Endohedral metallofullerenes are normally produced by DC electric arc discharge of metal/graphite composite rods used as positive electrodes. The metallofullerenes can also be produced by the so-called laser furnace method which incorporates laser vaporization of the composite rods under high temperature (ca 1000 °C). The endohedral metallofullerenes so far produced are centred on group 2 and 3 metallofullerenes such as Sc, Y, La, Ca, Sr and Ba as well as lanthanide metallofullerenes (Ce-Lu). These metal atoms have been encapsulated in higher fullerenes, especially in C82. These metallofullerenes have easily been extracted by solvents from primary soot. By using an elaborate high-performance liquid chromatography technique, the metallofullerenes are completely purified and isolated like C60 and C70. Synchrotron x-ray diffraction, 13C NMR and ultra-high vacuum scanning tunnelling microscopy (UHV-STM) studies have revealed that metal atoms are indeed encapsulated by the carbon cage and that the metal atoms are not in the centre of the fullerene cage but very close to the carbon cage, indicating the presence of a strong metal-cage interaction. It has been revealed by electron spin resonance and also by theoretical calculations that substantial electron transfers take place from the encaged metal atom to the carbon cage: intrafullerene electron transfers. Good examples are lanthanum and yttrium metallofullerenes which have the charge states of

  2. Endohedral Metallofullerene Derivatives

    NASA Technical Reports Server (NTRS)

    Dorn, Harry C. (Inventor); Iezzi, Erick B. (Inventor); Duchamp, James (Inventor)

    2008-01-01

    Trimetallic nitride endohedral metallofullerene derivatives and their preparation are described. The trimetallic nitride endohedral metallofullerene derivatives have the general formula A(sub 3-n)X(sub n)@C(sub m)(R) where n ranges from 0 to 3, A and X may be trivalent metals and may be either rare earth metal or group IIIB metals, m is between about 60 and about 200, and R is preferably an organic group. Derivatives where the R group forms cyclized derivatives with the fullerene cage are also described.

  3. Production and characterization of metallofullerenes

    SciTech Connect

    Ross, M.M.; Nelson, H.H.; Callahan, J.H.; McElvany, S.W.

    1992-06-25

    Negative ion/description chemical ionization mass spectrometry was used in this paper to characterize La{sub x}@C{sub n} and Y{sub x}@C{sub n} fullerenes in soot generated from metal compound-impregnated graphite rods. La@C{sub 82} and La@C{sub 80} are extracted by pyridine from the soot, but La@C{sub 60} and La@C{sub 70} are not. There are greater abundances of metallofullerenes with the lower ionization potential metal atom in the pyridine extracts. These observations indicate that metallofullerenes exist as ionic complexes with fullerenes (La{sub x}@C{sub n}){sup +}C{sub n}{sup -}. 16 refs., 4 figs.

  4. Enantioselective synthesis of endohedral metallofullerenes.

    PubMed

    Sawai, Koji; Takano, Yuta; Izquierdo, Marta; Filippone, Salvatore; Martín, Nazario; Slanina, Zdenek; Mizorogi, Naomi; Waelchli, Markus; Tsuchiya, Takahiro; Akasaka, Takeshi; Nagase, Shigeru

    2011-11-01

    Endohedral metallofullerenes are promising materials in biomedical and material sciences. In particular, they are of interest as agents for magnetic resonance imaging (MRI), photovoltaic devices, and semimetallic components. The synthesis of chiral endofullerenes represents one step further in the potential use of these carbon allotropes; however, this step has not been addressed so far. In this regard, enantiopure endofullerenes are expected to open new avenues in fields in which chirality is a key issue. Here, the synthesis and characterization of the first chiral endohedral metallofullerenes, namely, chiral bis-adducts of La@C(72), are reported. Eight optically active isomers were obtained by enantioselective 1,3-dipolar cycloaddition of a N-metalated azomethine ylide onto a non-isolated-pentagon rule metallofullerene derivative, La@C(72)(C(6)H(3)Cl(2)), catalyzed by a copper chiral complex. The chiral bis-adducts of La@C(72), isolated by nonchiral HPLC, showed optical purities as high as 98% as revealed by the remarkable positive or negative Cotton effects observed in the circular dichroic spectra.

  5. Another big discovery-metallofullerenes.

    PubMed

    Shinohara, Hisanori

    2016-09-13

    Several days after the first experimental observation of the 'magic number' soccerball-shaped C60 in a laser-vaporized cluster beam mass spectrum by Kroto and co-workers (Heath et al 1985 J. Am. Chem. Soc. 107, 7779-7780. (doi:10.1021/ja00311a102)) they also found a magic number feature owing to La@C60 in a mass spectrum prepared by laser vaporization of a LaCl3-impregnated graphite rod. With the advent of macroscopic synthesis and the following successful separation and purification of metallofullerenes, both experimental and theoretical studies of metallofullerenes have developed quite rapidly to date so as to elucidate their structural, electronic, magnetic and transport properties. Furthermore, a bottom-up closed network growth mechanism has experimentally been shown to play a crucial role in generating various types of metallofullerenes.This article is part of the themed issue 'Fullerenes: past, present and future, celebrating the 30th anniversary of Buckminster Fullerene'.

  6. Another big discovery-metallofullerenes.

    PubMed

    Shinohara, Hisanori

    2016-09-13

    Several days after the first experimental observation of the 'magic number' soccerball-shaped C60 in a laser-vaporized cluster beam mass spectrum by Kroto and co-workers (Heath et al 1985 J. Am. Chem. Soc. 107, 7779-7780. (doi:10.1021/ja00311a102)) they also found a magic number feature owing to La@C60 in a mass spectrum prepared by laser vaporization of a LaCl3-impregnated graphite rod. With the advent of macroscopic synthesis and the following successful separation and purification of metallofullerenes, both experimental and theoretical studies of metallofullerenes have developed quite rapidly to date so as to elucidate their structural, electronic, magnetic and transport properties. Furthermore, a bottom-up closed network growth mechanism has experimentally been shown to play a crucial role in generating various types of metallofullerenes.This article is part of the themed issue 'Fullerenes: past, present and future, celebrating the 30th anniversary of Buckminster Fullerene'. PMID:27501973

  7. Electron Transfer and Localization in Endohederal Metallofullerenes

    NASA Astrophysics Data System (ADS)

    Yang, Shenyuan; Yoon, Mina; Hicke, Christian; Zhang, Zhenyu; Wang, Enge

    2008-03-01

    Endohedral metallofullerenes constitute an appealing class of nanoscale building blocks for fabrication of a wide range of noval materials. One open question of fundamental importance is the precise nature of charge redistribution with the carbon cages (Cn) upon metal encapsulation. Using ab initio density functional theory, we systematically study the electronic structure of metallofullerenes, focusing on the spatial charge redistribution. For all large metallofullerenes (n>32), the valence electrons of the metal atoms are all transferred to the fullerene states. Surprisingly, the transferred charge is found to be highly localized inside the cage near the metal cations, rather than uniformly distributed on the surfaces of the carbon cage as traditionally belied. This counterintuitive charge localization picture is attributed to the strong metal-cage interactions within the systems. These findings may prove to be instrumental in the design of novel fullerene-based functional nanomaterials.

  8. Tandem mass spectrometry studies of metallofullerenes

    SciTech Connect

    Callahan, J.H.; Nelson, H.; McElvany, S.W.; Ross, M.M.

    1993-12-31

    As interest in the chemistry of fullerenes grows, many laboratories are now directing their efforts toward the synthesis of fullerene derivatives such as metallofullerenes (endohedral complexes). Tandem mass spectrometry has proven useful in the characterization of such derivatives. In tandem mass spectrometry, ions of interest are selected with one mass analyzer, collided or reacted with a gas, and the products of the reaction are subsequently analyzed with an additional stage of mass analysis. The authors have used low- and high-energy collisions with reactive and inert target gas molecules to probe the structures, properties and reactivities of endohedral metallofullerene complexes. These studies have shown that metallofullerenes have properties similar to those of fullerenes, including the ability to take up He during keV collisions, forming complexes such as La{sub 2}He@C{sub 80} These studies indicate that the metal is not on the outside of the cage, although the formation of La{sub 2}He@C{sub 80} suggests that one of the metal atoms may be incorporated as part of the cage. Fragmentation processes in the metallofullerenes are similar to those of the fullerenes (e.g. successive C{sub 2} loss), lending further support for the proposed endohedral structure of the fullerenes. The behavior of the metallofullerenes in reactive collisions with oxygen has also been studied, indicating that their reactivities are similar to those of the fullerenes. Fourier transform spectroscopy studies are currently underway to further probe the reactivities, ionization energies and gas phase proton affinities of the metallofullerenes.

  9. Subcellular SIMS imaging of gadolinium isotopes in human glioblastoma cells treated with a gadolinium containing MRI agent

    NASA Astrophysics Data System (ADS)

    Smith, Duane R.; Lorey, Daniel R.; Chandra, Subhash

    2004-06-01

    Neutron capture therapy is an experimental binary radiotherapeutic modality for the treatment of brain tumors such as glioblastoma multiforme. Recently, neutron capture therapy with gadolinium-157 has gained attention, and techniques for studying the subcellular distribution of gadolinium-157 are needed. In this preliminary study, we have been able to image the subcellular distribution of gadolinium-157, as well as the other six naturally abundant isotopes of gadolinium, with SIMS ion microscopy. T98G human glioblastoma cells were treated for 24 h with 25 mg/ml of the metal ion complex diethylenetriaminepentaacetic acid Gd(III) dihydrogen salt hydrate (Gd-DTPA). Gd-DTPA is a contrast enhancing agent used for MRI of brain tumors, blood-brain barrier impairment, diseases of the central nervous system, etc. A highly heterogeneous subcellular distribution was observed for gadolinium-157. The nuclei in each cell were distinctly lower in gadolinium-157 than in the cytoplasm. Even within the cytoplasm the gadolinium-157 was heterogeneously distributed. The other six naturally abundant isotopes of gadolinium were imaged from the same cells and exhibited a subcellular distribution consistent with that observed for gadolinium-157. These observations indicate that SIMS ion microscopy may be a viable approach for subcellular studies of gadolinium containing neutron capture therapy drugs and may even play a major role in the development and validation of new gadolinium contrast enhancing agents for diagnostic MRI applications.

  10. Production and characterization of metallofullerene superatoms

    SciTech Connect

    Ying, Z.C.; Hettich, R.L.; Puretzky, A.A.; Haufler, R.E.; Compton, R.N.

    1994-09-01

    Lanthanum metallofullerenes, with the La atoms presumably located inside the carbon cages, were produced using the laser vaporization method with optimum parameters, and concentrated using vacuum sublimation. The obtained material was analyzed using Fourier transform mass spectrometry. The electron affinities of LaC{sub n} (n = 60, 70 {minus} 84) were determined, using the charge-transfer bracketing technique, to be in a range between 2.7 {plus_minus} 0.2 and 3.3 {plus_minus} 0.3 eV. The ionization potentials of these metallofullerenes were measured to be less than 6.2 eV.

  11. Interaction between hydrogen molecules and metallofullerenes.

    SciTech Connect

    Yoon, Mina; Yang, Shenyuan; Zhang, Zhenyu

    2009-01-01

    Within first-principles density functional theory, we explore the feasibility of using metallofullerenes as efficient hydrogen storage media. In particular, we systematically investigate the interaction between hydrogen molecules and La encapsulated all-carbon fullerenes, Cn (20≤n≤82), focusing on the role of transferred charges between the metal atoms and fullerenes on the affinity of hydrogen molecules to the metallofullerenes. Our calculations show that three electrons are transferred from La atom to fullerene cages, while the induced charges are mostly screened by the fullerene cages. We find the local enhancement of molecular hydrogen affinity to the fullerenes to be sensitively dependent on the local bonding properties, rather than on the global charging effects.

  12. Interaction between hydrogen molecules and metallofullerenes

    NASA Astrophysics Data System (ADS)

    Yoon, Mina; Yang, Shenyuan; Zhang, Zhenyu

    2009-08-01

    Within first-principles density functional theory, we explore the feasibility of using metallofullerenes as efficient hydrogen storage media. In particular, we systematically investigate the interaction between hydrogen molecules and La encapsulated all-carbon fullerenes, Cn (20≤n≤82), focusing on the role of transferred charges between the metal atoms and fullerenes on the affinity of hydrogen molecules to the metallofullerenes. Our calculations show that three electrons are transferred from La atom to fullerene cages, while the induced charges are mostly screened by the fullerene cages. We find the local enhancement of molecular hydrogen affinity to the fullerenes to be sensitively dependent on the local bonding properties, rather than on the global charging effects.

  13. Endohedral Metallofullerenes and Nano-Peapods

    NASA Astrophysics Data System (ADS)

    Kitaura, Ryo; Shinohara, Hisanori

    2007-03-01

    In this review article, we deal with the structures and properties of novel hybrid nanocarbon materials, which are created by the incorporation of atoms and molecules in hollow spaces of fullerenes and carbon nanotubes (CNTs); these hybrid materials are called endohedral metallofullerenes (in the case of metal atom incorporated fullerenes) and nano-peapods, respectively. Synthesis procedures, structural characterizations by synchrotron powder x-ray diffraction, electronic structures, and magnetic properties of endohedral metallofullerenes are discussed. The structure and properties of nano-peapods by high-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), scanning tunneling microscopy (STM) and field effect transistor (FET) transport measurements together with their synthesis procedures are described. The utilization of the low-dimensional nanosized spaces of CNTs to produce novel low-dimensional nanocluster, nanowire and nano-tube materials is also discussed.

  14. Interaction between hydrogen molecules and metallofullerenes.

    PubMed

    Yoon, Mina; Yang, Shenyuan; Zhang, Zhenyu

    2009-08-14

    Within first-principles density functional theory, we explore the feasibility of using metallofullerenes as efficient hydrogen storage media. In particular, we systematically investigate the interaction between hydrogen molecules and La encapsulated all-carbon fullerenes, C(n) (20 < or = n < or = 82), focusing on the role of transferred charges between the metal atoms and fullerenes on the affinity of hydrogen molecules to the metallofullerenes. Our calculations show that three electrons are transferred from La atom to fullerene cages, while the induced charges are mostly screened by the fullerene cages. We find the local enhancement of molecular hydrogen affinity to the fullerenes to be sensitively dependent on the local bonding properties, rather than on the global charging effects.

  15. Large fullerenes and metallofullerenes: Structure and stability

    SciTech Connect

    Achiba, Y.

    1993-12-31

    Isolation and characterization of large fullerenes up to n=160 is described. The fullerenes were extracted from carbon soot and isolated by a high performance liquid chromatography. Preparative amounts of well-separated large fullerenes were characterized by UV/visible absorption, IR, {sup 13}C NMR in solution, and VUV photoelectron measurements. Isolation and characterization of isomers on some of large fullerenes is also be described. Tentative report on the isolation of metallofullerenes such as LaC82 are presented.

  16. Electron Transfer and Localization in Endohederal Metallofullerenes

    SciTech Connect

    Yang, Shenyuan; Yoon, Mina; Hicke, Christian; Zhang, Zhenyu

    2008-01-01

    Endohedral metallofullerenes constitute an appealing class of nanoscale building blocks for fabrication of a wide range of noval materials. One open question of fundamental importance is the precise nature of charge redistribution with the carbon cages (Cn) upon metal encapsulation. Using ab initio density functional theory, we systematically study the electronic structure of metallofullerenes, focusing on the spatial charge redistribution. For all large metallofullerenes (n >32), the valence electrons of the metal atoms are all transferred to the fullerene states. Surprisingly, the transferred charge is found to be highly localized inside the cage near the metal cations, rather than uniformly distributed on the surfaces of the carbon cage as traditionally belied. This counterintuitive charge localization picture is attributed to the strong metal-cage interactions within the systems. These findings may prove to be instrumental in the design of novel fullerene-based functional nanomaterials. 1Supported by the DMSE program and grant no. DE-FG02-05ER46209 of USDOE, grant no. DMR-0606485 of USNSF, and NSF of China.

  17. Electron Transfer in Trimetal Nitride Metallofullerenes

    NASA Astrophysics Data System (ADS)

    Hagelberg, Frank; Wu, Jianhua

    2009-08-01

    Two classes of trimetal nitride metallofullerenes, Sc3N@Cn (n = 68, 78) and MxSc3-xN@C80 (x = 0-2), are investigated by Density Functional Theory with respect to their electronic properties and related geometric, energetic, and magnetic features. The substantial electron transfer from the metallic core to the fullerene cage makes these systems promising candidates for nonlinear optical devices. Pronounced magnetic effects associated with complexes that enclose lanthanide constituents suggest their suitability as contrast agents in biomedical imaging.

  18. Molecular magnetic switch for a metallofullerene

    PubMed Central

    Wu, Bo; Wang, Taishan; Feng, Yongqiang; Zhang, Zhuxia; Jiang, Li; Wang, Chunru

    2015-01-01

    The endohedral fullerenes lead to well-protected internal species by the fullerene cages, and even highly reactive radicals can be stabilized. However, the manipulation of the magnetic properties of these radicals from outside remains challenging. Here we report a system of a paramagnetic metallofullerene Sc3C2@C80 connected to a nitroxide radical, to achieve the remote control of the magnetic properties of the metallofullerene. The remote nitroxide group serves as a magnetic switch for the electronic spin resonance (ESR) signals of Sc3C2@C80 via spin–spin interactions. Briefly, the nitroxide radical group can ‘switch off’ the ESR signals of the Sc3C2@C80 moiety. Moreover, the strength of spin–spin interactions between Sc3C2@C80 and the nitroxide group can be manipulated by changing the distance between these two spin centres. In addition, the ESR signals of the Sc3C2@C80 moiety can be switched on at low temperatures through weakened spin–lattice interactions. PMID:25732144

  19. Synthesis, characterization, and neutron activation of holmium metallofullerenes

    SciTech Connect

    Cagle, D.W.; Thrash, T.P.; Wilson, L.J.; Alford, M.; Chibante, L.P.F.; Ehrhardt, G.J.

    1996-08-28

    Isolation of the first macroscopic quantities of endohedral holmium metallofullerenes (principally Ho@C{sub 82}, Ho{sub 2}@C{sub 82}, and Ho{sub 3}@C{sub 82} by LD-TOF mass spectrometry) has been accomplished by carbon-arc and preparative HPLC methodologies. The detailed procedure for production and isolation of the metallofullerenes includes a new technique whereby holmium-impregnated electrodes are prepared simply by soaking porous graphite rods in an ethanolic solution of Ho(NO{sub 3}){sub 3}.xH{sub 2}O. Monoisotopic {sup 165}Ho offers a unique combination of advantages for neutron-activation studies of metallofullerenes, and purified samples containing {sup 165}Ho@C{sub 82}, {sup 165}Ho{sub 2}@C{sub 82}, and {sup 165}Ho{sub 3}@C{sub 82} have been activated by high-flux neutron irradiation ({Phi} = 4 x 10{sup 13}n cm{sup -2} s{sup -1}) to generate {sup 166}Ho metallofullerenes, which undergo {beta}{sup -} decay to produce stable {sup 166}Er. Chemical workup of the irradiated samples, followed by re-irradiation, has been used to demonstrate that observed decomposition of holmium metallofullerenes is due mainly to `fast` neutron damage rather than to holmium atom nuclear recoil (E{sub max} = 200 eV). This implies that metallofullerene damage can be minimized by using neutron fluxes with the highest possible thermal component. 60 refs., 4 figs.

  20. Structures and Dynamics of Endohedral Scandium Metallofullerenes

    NASA Astrophysics Data System (ADS)

    Shinohara, H.; Tansho, M.; Inakuma, M.; Saito, Y.; Sato, H.; Hayashi, N.; Kato, T.; Hashizume, T.; Sakurai, T.

    The endohedral metallofullerenes, such as Sc@C82, Sc2@C84, and Sc3@C82, have been purified and isolated by using two-stage high-performance liquid chromatography (HPLC). The ESR spectrum of the isolated Sc3@C82 exhibits a perfectly symmetric 22 hyperfined splittings with an inherent linewidth of 0.77 Gauss at 220 K, which is consistent with a unique structure that three scandium atoms are encaged triangularly within the C3v isomer of C82. In addition, we report the direct imaging of the isolated discandium fullerene (Sc2@C84) on silicon clean surfaces in an ultrahigh-vacuum environment by utilizing scanning tunneling microscopy (STM). The STM images reveal spherical Sc2@C84 fullerenes, spaced 11.7 Å apart, stacked in close-packed arrays.

  1. Structural change of metallofullerene: an easier thermal decomposition.

    PubMed

    Zhao, Shixiong; Zhang, Jun; Guo, Xihong; Qiu, Xiaohui; Dong, Jinquan; Yuan, Bingkai; Ibrahim, Kurash; Wang, Jiaou; Qian, Haijie; Zhao, Yuliang; Yang, Shangyuan; Hao, Jian; Zhang, Hong; Yuan, Hui; Xing, Gengmei; Sun, Baoyun

    2011-10-01

    We have studied for the first time the structural change of high-purity metallofullerene (Gd@C(82)) upon heat treatment in an ultra-high vacuum system (10(-10) Torr) and examined the decomposition product through successive analysis with MS, IR, Raman, TEM, EDS and XPS. It was found that metallofullerene (Gd@C(82)) had fully collapsed at 580 °C which was lower than that for the complete destruction of C(60). The easier decomposition should be ascribed to the encapsulated metal in the carbon cage which could induce the deformation of the C-C bond. The analysis indicated that the broken metallofullerene (Gd@C(82)) became a kind of graphite-like material with a lot of defects. The Gd atoms leaked out from the carbon cage and aggregated together to form a regular arrangement. PMID:21860859

  2. Metallofullerenes: a new class of MRI agents and more?

    PubMed

    Fatouros, Panos P; Shultz, Michael D

    2013-11-01

    Metallofullerenes have incited research endeavors across many disciplines owing to their wide range of properties obtainable by altering the metal component inside the fullerene cage or by a variety of surface functionalities. With a metal component of gadolinium, gadofullerenes have particularly shown promise in MRI applications owing to their high proton relaxivity and isolation of the metal from the biological environment. This article aims to give a perspective on the development of metallofullerenes as MRI contrast agents and further applications that distinguish them as a new class of imaging agent.

  3. Investigation of the neutron activation of endohedral rare earth metallofullerenes

    SciTech Connect

    Shilin, V. A. Lebedev, V. T.; Kolesnik, S. G.; Kozlov, V. S.; Grushko, Yu. S.; Sedov, V. P.; Kukorenko, V. V.

    2011-12-15

    Endohedral lanthanide metallofullerenes and their water-soluble biocompatible derivatives have been synthesized. The effect that fast-neutron irradiation has on the stability and nuclear physical properties of endohedral metallofullerenes that are used as magnetocontrast materials ({sup 46}Sc, {sup 140}La, {sup 141}Nd, {sup 153}Sm, {sup 152}Eu, {sup 154}Eu, {sup 153}Sm, {sup 160}Tb, {sup 169}Yb, {sup 170}Tm (isomers I and III), and {sup 177}Lu) is studied. Our hypothesis, according to which carbon-shell relaxation is based on the fast nonradiative processes of an electron shake-off type, is confirmed.

  4. Structural and electronic properties of endohedral metallofullerenes.

    PubMed

    Akasaka, Takeshi; Lu, Xing

    2012-04-01

    This account presents an overview of our achievements in structural and chemical understanding of endohedral metallofullerenes (EMFs), a new class of metal-carbon hybrid materials formed by encapsulation of metals inside fullerene cavities. Structural determination of EMFs is of fundamental importance for understanding their intrinsic properties and the formation mechanism, and for broadening their applications. We have developed an effective method for determining the structures of paramagnetic EMFs, and also succeeded in observing the motion of cluster in a di-metal EMF for the first time. Recently, we unambiguously established the structures of some carbide EMFs which had been wrongly assumed as conventional EMFs previously. More importantly, we have obtained some insoluble EMF species which had never been explored or even expected before. Meanwhile, the chemical properties of various EMFs with different cage structures or different metallic cores have been systematically investigated by means of both covalent and supramolecular considerations, yielding many fascinating results relating to the dictating effect of internal metals. It is noteworthy that all these achievements are based on unambiguous X-ray results of pristine or functionalized EMFs.

  5. Endohedral metallofullerenes in self-assembled monolayers.

    PubMed

    Gimenez-Lopez, Maria Del Carmen; Gardener, Jules A; Shaw, Adam Q; Iwasiewicz-Wabnig, Agnieszka; Porfyrakis, Kyriakos; Balmer, Claire; Dantelle, Geraldine; Hadjipanayi, Maria; Crossley, Alison; Champness, Neil R; Castell, Martin R; Briggs, G Andrew D; Khlobystov, Andrei N

    2010-01-01

    A method has been developed for the attachment of a dithiolane group to endohedral metallofullerenes via a 1,3-dipolar cycloaddition reaction. This sulfur-containing functional group serves as an anchor, enabling efficient immobilisation of endohedral fullerenes on Au(111) surfaces at room temperature, directly from the solution phase. The functionalised fullerenes form disordered monolayers that exhibit no long-range ordering, which is attributed to both the strong bonding of the dithiolane anchor to the surface and to the conformational flexibility of the functional group. Endohedral fullerenes Er(3)N@C(80) and Sc(3)N@C(80) have been used as models for functionalisation and subsequent surface deposition. Their chemical reactivity towards dithiolane functionalisation and their surface behaviour have been compared to that of C(60). The endohedral fullerenes appear to be significantly less reactive towards the functionalisation than C(60), however they bind in a similar manner to a gold surface as their dithiolane terminated C(60) counterparts. The optical activity of Er(3)N@C(80) molecules is preserved after attachment of the functional group. We report a splitting of the endohedral Er(3+) emission lines due to the reduction in symmetry of the functionalised fullerene cage, as compared to the highly symmetrical icosahedral C(80) cage of pristine Er(3)N@C(80).

  6. Multiple reaction pathways of metallofullerenes investigated by transmission electron microscopy.

    PubMed

    Koshino, Masanori

    2014-05-28

    Recent advances in molecule-by-molecule transmission electron microscopy (TEM) have provided time-series structural information of individual molecules supported by nano-carbon materials, enabling researchers to trace their motions and reactions. In this paper, the chemical reactions of fullerenes and metallofullerene derivatives, focusing on their deformation process, are reviewed and discussed based on the single-molecule-resolved TEM analysis.

  7. Size-selective complexation and extraction of endohedral metallofullerenes with cycloparaphenylene.

    PubMed

    Nakanishi, Yusuke; Omachi, Haruka; Matsuura, Sanae; Miyata, Yasumitsu; Kitaura, Ryo; Segawa, Yasutomo; Itami, Kenichiro; Shinohara, Hisanori

    2014-03-17

    A new strategy for the non-chromatographic extraction of metallofullerenes from solutions of arc-processed raw soot is based on the size-selective complexation with cycloparaphenylene (CPP). [11]CPP has a high affinity for Mx @C82 (x=1, 2); for example, Gd@C82 can be selectively extracted from a fullerene mixture by the addition of [11]CPP. This approach should open new opportunities in metallofullerene chemistry, including for the bulk extraction of metallofullerenes. PMID:24616170

  8. Size-selective complexation and extraction of endohedral metallofullerenes with cycloparaphenylene.

    PubMed

    Nakanishi, Yusuke; Omachi, Haruka; Matsuura, Sanae; Miyata, Yasumitsu; Kitaura, Ryo; Segawa, Yasutomo; Itami, Kenichiro; Shinohara, Hisanori

    2014-03-17

    A new strategy for the non-chromatographic extraction of metallofullerenes from solutions of arc-processed raw soot is based on the size-selective complexation with cycloparaphenylene (CPP). [11]CPP has a high affinity for Mx @C82 (x=1, 2); for example, Gd@C82 can be selectively extracted from a fullerene mixture by the addition of [11]CPP. This approach should open new opportunities in metallofullerene chemistry, including for the bulk extraction of metallofullerenes.

  9. Computer simulation of the infrared spectra of endohedral metallofullerenes Li2C60 and Na2C60

    NASA Astrophysics Data System (ADS)

    Butyrskaya, E. V.; Zapryagaev, S. A.

    2009-03-01

    Using the Gaussian03 computer software, the infrared spectra of endohedral Li2C60 and Na2C60 are calculated by the Hartree-Fock method in the 3-21 G basis set. The calculation is carried out for three cases: (i) metallofullerenes without a solvent, (ii) metallofullerenes in a toluene solution, and (iii) metallofullerenes in a tetrahydrofuran solution. The effect of a solvent on the energetic, electrical, and spectral characteristics of the metallofullerenes is studied.

  10. Dynamics of paramagnetic metallofullerenes in carbon nanotube peapods.

    PubMed

    Warner, Jamie H; Watt, Andrew A R; Ge, Ling; Porfyrakis, Kyriakos; Akachi, Takao; Okimoto, Haruya; Ito, Yasuhiro; Ardavan, Arzhang; Montanari, Barbara; Jefferson, John H; Harrison, Nicholas M; Shinohara, Hisanori; Briggs, G Andrew D

    2008-04-01

    We filled SWNTs with the paramagnetic fullerene Sc@C82 to form peapods. The interfullerene 1D packing distance measured using TEM is d = 1.1 +/- 0.02 nm. The Sc@C82 in SWNT peapods continuously rotated during the 2 s TEM exposure time, and we did not see the Sc atoms. However, Sc@C82 metallofullerenes in MWNT peapods have periods of fixed orientation, indicated by the brief observation of Sc atoms. La@C82 peapods were also prepared and their rotational behavior examined. The interfullerene 1D packing of both La@C82 and Sc@C82 peapods is identical and thus independent of the charge transfer state for these paramagnetic fullerenes. The La@C82 metallofullerenes in the peapods have fixed orientations for extended periods of time, up to 50 s in some cases. The La@C82 spontaneously rotates rapidly between fixed orientations.

  11. Clusters encapsulated in endohedral metallofullerenes: how strained are they?

    PubMed

    Deng, Qingming; Popov, Alexey A

    2014-03-19

    Endohedral clusters in metallofullerenes can vary in a broad range of geometrical parameters following the size and shape of the host carbon cage. Obviously, distortions of the cluster may increase its energy and even destabilize the whole clusterfullerene molecule. However, direct evaluation of the magnitude of cluster strain energies has not been done because of the lack of a suitable computational scheme that would allow one to decouple cluster and fullerene distortions and hence estimate individual components. In this work we offer a simple and efficient scheme to calculate cluster distortion energies in endohedral metallofullerenes (EMFs). Using this scheme, we analyze distortions in three classes of EMFs with nitride, sulfide, and carbide clusters and different metal atoms (Sc, Y, Ti).

  12. Biomedical Activities of Endohedral Metallofullerene Optimized for Nanopharmaceutics

    PubMed Central

    Meng, Jie; Wang, Dong-liang; Wang, Paul C.; Jia, Lee; Chen, Chunying; Liang, Xing-Jie

    2011-01-01

    Endohedral metallofullerenes, a novel form of carbon-related nanomaterials, currently attract wide attention for their potential applications in biomedical fields such as therapeutic medicine. Most endohedral metallofullerenes are synthesized using C60 or higher molecular weight fullerenes because of the limited interior volume of fullerene. It is known that the encapsulated metal atom has strong electronic interactions with the carbon cage in metallofullerenes. Gd@C82 is one of the most important molecules in the metallofullerene family, known as Magnetic Resonance Imaging (MRI) contrast agent candidate for diagnostic imaging. Gadolinium endohedral metallofullerenol (e.g., Gd@C82(OH)22) is a functionalized fullerene with gadolinium trapped inside carbon cage. Our group previously demonstrated that the distinctive chemical and physical properties of Gd@C82(OH)22 are dependent on the number and position of the hydroxyl groups on the fullerene cage. The present article summarizes our latest findings of biomedical effects of Gd@C82(OH)22 and gives rise to a connected flow of the existing knowledge and information from experts in the field. It briefly narrates the synthesis and physico-chemical properties of Gd@C82(OH)22. The polyhydroxylated nanoparticles exhibit the enhanced water solubility and high purity, and were tested as a MRI contrast agent. Gd@C82(OH)22 treatment inhibited tumor growth in tumor-bearing nude mice. Although the precise mechanisms of this action are not well defined, our in vitro data suggest involvements of improved immunity and antioxidation by Gd@C82(OH)22 and its size-based selective targeting to tumor site. The review critically analyzed the relevant data instead of fact-listing, and explained the potential for developing Gd@C82(OH)22 into a diagnostic or therapeutic agent. PMID:21121373

  13. Structural studies of endohedral metallofullerenes by synchrotron radiation powder diffraction.

    PubMed

    Nishibori, E; Takata, M; Sakata, M; Shinohara, H

    1998-05-01

    The endohedral natures of the metallofullerenes Y@C(82) and Sc(2)@C(8)4 are described based on synchrotron radiation powder diffraction experiments. For structural analysis, a combination of the maximum-entropy method (MEM) and Rietveld refinement was employed to analyse the complicated powder pattern. The obtained MEM charge densities show a clear distinction of the endohedral natures of the mono- and dimetallofullerenes.

  14. Exohedral reactivity of trimetallic nitride template (TNT) endohedral metallofullerenes.

    PubMed

    Campanera, Josep M; Bo, Carles; Poblet, Josep M

    2006-01-01

    [structures: see text] Fullerenes containing a trimetallic nitride template (TNT) within the cage are a particularly interesting class of endohedral metallofullerenes. Recently two exohedral derivatives of the Sc3N@C80 fullerene have been synthesized: a Diels-Alder and a fulleropyrrolidine cycloadduct. The successful isolation, purification, and structural elucidation of these metallofullerenes derivatives have encouraged us to understand how the chemical reactivity is affected by TNT encapsulation. First of all, we predicted the most reactive exohedral sites, taking into account the double bond character and the pyramidalization angle of the C-C bonds. For this purpose, a full characterization of all different types of C-C bonds of the following fullerenes was carried out: I(h)-C60:1, D3-C68:6140, D3-Sc3N@C68, D(5h)-C70:1, D(3h')-C78:5, D(3h)-Sc3N@C78, I(h)-C80:7 and several isomers of Sc3N@C80. Finally the exohedral reactivity of these TNT endohedral metallofullerenes, via [4 + 2] cycloaddition reactions of 1,3-butadiene, was corroborated by means of DFT calculations.

  15. Non-HPLC rapid separation of metallofullerenes and empty cages with TiCl4 Lewis acid.

    PubMed

    Akiyama, Kazuhiko; Hamano, Tatsuyuki; Nakanishi, Yusuke; Takeuchi, Erina; Noda, Shoko; Wang, Zhiyong; Kubuki, Shiro; Shinohara, Hisanori

    2012-06-13

    Rapid and efficient separation/purification of pure metallofullerenes M(x)@C(n) (M = metal; x = 1, 2; n > 70) and carbide metallofullerenes of the type M(y)C(2)@C(n-2) (y = 2, 3, 4; n - 2 > 68) has been reported. The present method utilizes rapid and almost perfect preferential formation of TiCl(4) (generally known as a Lewis acid)-metallofullerene complexes, which easily decompose to provide pure metallofullerene powders by a simple water treatment. The present method enables one to separate the metallofullerenes up to >99% purity within 10 min without using any type of high-performance liquid chromatography (HPLC). It is found that the oxidation potentials of the metallofullerenes are crucial factors for efficient purification. The current separation/purification technique may open a brand-new era for inducing further applications and commercialization of endohedral metallofullerenes.

  16. Chemical, electrochemical, and structural properties of endohedral metallofullerenes.

    PubMed

    Chaur, Manuel N; Melin, Frederic; Ortiz, Angy L; Echegoyen, Luis

    2009-01-01

    Ever since the first experimental evidence of the existence of endohedral metallofullerenes (EMFs) was obtained, the search for carbon cages with encapsulated metals and small molecules has become a very active field of research. EMFs exhibit unique electronic and structural features, with potential applications in many fields. Furthermore, functionalized EMFs offer additional potential applications because of their higher solubility and their ease of characterization by X-ray crystallography and other techniques. Herein we review the general field of EMFs, particularly of functionalized EMFs. We also address their structures and their (electrochemical) properties, as well as applications of these fascinating compounds.

  17. Synthesis and characterization of the first trimetallic nitride templated pyrrolidino endohedral metallofullerenes.

    PubMed

    Cai, Ting; Ge, Zhongxin; Iezzi, Erick B; Glass, Thomas E; Harich, Kim; Gibson, Harry W; Dorn, Harry C

    2005-07-28

    New pyrrolidino derivatives of both diamagnetic and paramagnetic trimetallic nitride templated endohedral metallofullerenes were synthesized by the Prato reaction, isolated and characterized by means of MALDI-TOF MS, NMR and UV-vis spectroscopies.

  18. DFT calculations on the structural stability and infrared spectroscopy of endohedral metallofullerenes

    NASA Astrophysics Data System (ADS)

    Peng, Sheng; Zhang, Yan; Li, Xiao Jun; Ren, Yan; Zhang, Deng Xin

    2009-10-01

    Endohedral metallofullerenes M@C 24 (M = Li 0/+, Na 0/+, K 0/+, Be 0/2+, Mg 0/2+ and Ca 0/2+) with different spin configurations have been systematically investigated using the hybrid DFT-B3PW91 functional in conjunction with 6-31G(d) basis sets. Our theoretical studies show that Li@C 24, Be@C 24, Be 2+@C 24, and Mg 2+@C 24 are energetically favorable. In these endohedral metallofullerenes, only the encapsulated Be and Ca atoms can donate the electrons to the cage. With exception of Be 2+@C 24, the energy gaps of other charged compounds are larger than that of corresponding neutral compounds. We also find that some endohedral metallofullerenes have high energy gaps, but they are unlikely to show high thermodynamic stability. Additionally, the vibrational frequencies and active infrared intensities are also used as evidence to identify these endohedral metallofullerenes.

  19. DFT calculations on the structural stability and infrared spectroscopy of endohedral metallofullerenes.

    PubMed

    Peng, Sheng; Zhang, Yan; Li, Xiao Jun; Ren, Yan; Zhang, Deng Xin

    2009-10-01

    Endohedral metallofullerenes M@C(24) (M = Li(0/+), Na(0/+), K(0/+), Be(0/2+), Mg(0/2+) and Ca(0/2+)) with different spin configurations have been systematically investigated using the hybrid DFT-B3PW91 functional in conjunction with 6-31 G(d) basis sets. Our theoretical studies show that Li@C(24), Be@C(24), Be(2+)@C(24), and Mg(2+)@C(24) are energetically favorable. In these endohedral metallofullerenes, only the encapsulated Be and Ca atoms can donate the electrons to the cage. With exception of Be(2+)@C(24), the energy gaps of other charged compounds are larger than that of corresponding neutral compounds. We also find that some endohedral metallofullerenes have high energy gaps, but they are unlikely to show high thermodynamic stability. Additionally, the vibrational frequencies and active infrared intensities are also used as evidence to identify these endohedral metallofullerenes.

  20. Bottom-up formation of endohedral mono-metallofullerenes is directed by charge transfer.

    PubMed

    Dunk, Paul W; Mulet-Gas, Marc; Nakanishi, Yusuke; Kaiser, Nathan K; Rodríguez-Fortea, Antonio; Shinohara, Hisanori; Poblet, Josep M; Marshall, Alan G; Kroto, Harold W

    2014-01-01

    An understanding of chemical formation mechanisms is essential to achieve effective yields and targeted products. One of the most challenging endeavors is synthesis of molecular nanocarbon. Endohedral metallofullerenes are of particular interest because of their unique properties that offer promise in a variety of applications. Nevertheless, the mechanism of formation from metal-doped graphite has largely eluded experimental study, because harsh synthetic methods are required to obtain them. Here we report bottom-up formation of mono-metallofullerenes under core synthesis conditions. Charge transfer is a principal factor that guides formation, discovered by study of metallofullerene formation with virtually all available elements of the periodic table. These results could enable production strategies that overcome long-standing problems that hinder current and future applications of metallofullerenes.

  1. Bottom-up formation of endohedral mono-metallofullerenes is directed by charge transfer

    NASA Astrophysics Data System (ADS)

    Dunk, Paul W.; Mulet-Gas, Marc; Nakanishi, Yusuke; Kaiser, Nathan K.; Rodríguez-Fortea, Antonio; Shinohara, Hisanori; Poblet, Josep M.; Marshall, Alan G.; Kroto, Harold W.

    2014-12-01

    An understanding of chemical formation mechanisms is essential to achieve effective yields and targeted products. One of the most challenging endeavors is synthesis of molecular nanocarbon. Endohedral metallofullerenes are of particular interest because of their unique properties that offer promise in a variety of applications. Nevertheless, the mechanism of formation from metal-doped graphite has largely eluded experimental study, because harsh synthetic methods are required to obtain them. Here we report bottom-up formation of mono-metallofullerenes under core synthesis conditions. Charge transfer is a principal factor that guides formation, discovered by study of metallofullerene formation with virtually all available elements of the periodic table. These results could enable production strategies that overcome long-standing problems that hinder current and future applications of metallofullerenes.

  2. Endohedral metallofullerenes-filled fullerene derivatives towards multifunctional reaction center mimics.

    PubMed

    Rudolf, Marc; Wolfrum, Silke; Guldi, Dirk M; Feng, Lai; Tsuchiya, Takahiro; Akasaka, Takeshi; Echegoyen, Luis

    2012-04-23

    In recent years, endohedral metallofullerenes have attracted tremendous interest not only in physics and chemistry, but also in interdisciplinary areas, such as materials and biological sciences. In this concept article we highlight recent results on different endohedral metallofullerenes based on lanthanides and their derivatives. The chemical and excited state reactivities of endohedral metallofullerenes are discussed for various endohedral clusters. Most important is the part that covers spectroscopic and kinetic assays of reductive and oxidative charge transfer evolving from photoexcited electron donors and electron acceptors, respectively, in a variety of electron donor-acceptor conjugates. Towards this end, we refer to the applications of endohedral metallofullerenes in photovoltaic devices that feature greater efficiency than devices fabricated with empty fullerenes. Herein, we focus mainly on results obtained in the groups of Akasaka, Echegoyen, and Guldi.

  3. Bottom-up formation of endohedral mono-metallofullerenes is directed by charge transfer.

    PubMed

    Dunk, Paul W; Mulet-Gas, Marc; Nakanishi, Yusuke; Kaiser, Nathan K; Rodríguez-Fortea, Antonio; Shinohara, Hisanori; Poblet, Josep M; Marshall, Alan G; Kroto, Harold W

    2014-01-01

    An understanding of chemical formation mechanisms is essential to achieve effective yields and targeted products. One of the most challenging endeavors is synthesis of molecular nanocarbon. Endohedral metallofullerenes are of particular interest because of their unique properties that offer promise in a variety of applications. Nevertheless, the mechanism of formation from metal-doped graphite has largely eluded experimental study, because harsh synthetic methods are required to obtain them. Here we report bottom-up formation of mono-metallofullerenes under core synthesis conditions. Charge transfer is a principal factor that guides formation, discovered by study of metallofullerene formation with virtually all available elements of the periodic table. These results could enable production strategies that overcome long-standing problems that hinder current and future applications of metallofullerenes. PMID:25524825

  4. Electron transport through single endohedral Ce@C82 metallofullerenes

    NASA Astrophysics Data System (ADS)

    Kaneko, Satoshi; Wang, Lu; Luo, Guangfu; Lu, Jing; Nagase, Shigeru; Sato, Satoru; Yamada, Michio; Slanina, Zdenek; Akasaka, Takeshi; Kiguchi, Manabu

    2012-10-01

    The electron transport through a single endohedral Ce@C82 metallofullerene bridging between metal electrodes was investigated with experimental (break junction) as well as theoretical (density functional theory coupled with the nonequilibrium Green's function formalism) techniques. The single Ce@C82 molecule junction showing a high and fixed conductance value was fabricated by direct binding of the metallofullerene to Ag electrodes. The junction had a conductance of 0.28(±0.05)G0 (G0 = 2e2/h), which was much larger than that of single molecule junctions having anchoring groups (<0.01G0), but only half that of the single C60 molecule junction of 0.5G0. The unexpected reduced conductance of the single Ce@C82 molecule junction compared with that of the single C60 molecule junction was supported by the ab initio quantum transport calculations and was explained in terms of the localization of electrons in the C82 cage. In the case of the Au electrodes, the single Ce@C82 molecule junction was not formed by the break junction technique because the Ce@C82 molecule could not be trapped in the large Au nanogap, which was formed just after breaking the Au contacts.

  5. Bandgap modulation of carbon nanotubes by encapsulated metallofullerenes.

    PubMed

    Lee, Jhinhwan; Kim, H; Kahng, S-J; Kim, G; Son, Y-W; Ihm, J; Kato, H; Wang, Z W; Okazaki, T; Shinohara, H; Kuk, Young

    2002-02-28

    Motivated by the technical and economic difficulties in further miniaturizing silicon-based transistors with the present fabrication technologies, there is a strong effort to develop alternative electronic devices, based, for example, on single molecules. Recently, carbon nanotubes have been successfully used for nanometre-sized devices such as diodes, transistors, and random access memory cells. Such nanotube devices are usually very long compared to silicon-based transistors. Here we report a method for dividing a semiconductor nanotube into multiple quantum dots with lengths of about 10nm by inserting Gd@C82 endohedral fullerenes. The spatial modulation of the nanotube electronic bandgap is observed with a low-temperature scanning tunnelling microscope. We find that a bandgap of approximately 0.5eV is narrowed down to approximately 0.1eV at sites where endohedral metallofullerenes are inserted. This change in bandgap can be explained by local elastic strain and charge transfer at metallofullerene sites. This technique for fabricating an array of quantum dots could be used for nano-electronics and nano-optoelectronics.

  6. Chemical reactivity of a metallofullerene. EPR study of diphenylmethano-La @ C{sub 82} radicals

    SciTech Connect

    Suzuki, Toshiyasu; Maruyama, Yusei; Kato, Tatsuhisa; Akasaka, Takeshi; Kobayashi, Kaoru; Nagase, Shigeru; Yamamoto, Kazunori; Funasaka, Hideyuki; Takahashi, Takeshi

    1995-09-20

    We have synthesized the first methanofullerene derivatives of La@C{sub 82} and shown that the metallofullerene can be functionalized while retaining its unique electronic properties. We describe the first C-C bond formation on La@C{sub 82} and characterization of the products by EPR. We are currently applying the technology to produce water-soluble metallofullerenes. 22 refs., 3 figs., 1 tab.

  7. STM and STS Observation on Titanium-Carbide Metallofullerenes:. TI2C2@C78

    NASA Astrophysics Data System (ADS)

    Fukui, N.; Moribe, H.; Umemoto, H.; Shinohara, H.; Suwa, Y.; Heike, S.; Fujimori, M.; Hashizume, T.

    2009-06-01

    A metallofullerene Ti2C2@C78, in which two titanium atoms and C2 cluster are encapsulated, is studied by scanning tunneling microscopy and spectroscopy. Measurements of Ti2C2@C78 on Cu(111) surface reveal that their cage symmetry is C78-D3h. There is a preferential orientation of Ti2C2@C78 resulting from electrostatic interaction same as other metallofullerene.

  8. Extraction and chromatographic elution behavior of endohedral metallofullerenes: Inferences regarding effective dipole moments

    SciTech Connect

    Fuchs, D.; Rietschel, H.; Michel, R.H.; Fischer, A.; Weis, P.; Kappes, M.M.

    1996-01-11

    Chromatographic retention relationships between Ce-, Gd-, La-, and Y- containing endohedral metallofullerenes and a [2-(1-pyrenyl)ethyl]silyl-silica stationary phase were studied using toluene as eluent. Measurements are discussed in comparison to those of empty fullerenes. Both the extraction and chromatographic elution behaviour of the metallofullerenes reflect their polar nature and allow inferences regarding the presence of a dipole moment in M@C{sub 82}. 55 refs., 4 figs.

  9. Endohedral metallofullerenes: a unique host-guest association.

    PubMed

    Rodríguez-Fortea, Antonio; Balch, Alan L; Poblet, Josep M

    2011-07-01

    In this tutorial review taking X-ray crystallographically characterized compounds as a starting point a walk is taken through the electronic and structural properties of endohedral metallofullerenes. After classification of the fullerenes according to the encapsulated guest, particular attention is given to identifying factors that determine the selection of a particular carbon cage network by the internal metal cluster. Some of the physical rules that determine which particular fullerene cage is formed will be discussed. Concepts such as charge transfer between the cage and the guest metal ions, the topology of the cage, the separations between the 12 pentagons on the fullerene surface, and the effect of entropic factors are used to rationalize the selection of a particular cage. The roles of electrochemistry and vibrational spectroscopy in combination with theoretical calculations are considered in understanding the structures of the endohedral fullerenes.

  10. Current status and future developments of endohedral metallofullerenes.

    PubMed

    Lu, Xing; Feng, Lai; Akasaka, Takeshi; Nagase, Shigeru

    2012-12-01

    Endohedral metallofullerenes (EMFs), a new class of hybrid molecules formed by encapsulation of metallic species inside fullerene cages, exhibit unique properties that differ distinctly from those of empty fullerenes because of the presence of metals and their hybridization effects via electron transfer. This critical review provides a balanced but not an exhaustive summary regarding almost all aspects of EMFs, including the history, the classification, current progress in the synthesis, extraction, isolation, and characterization of EMFs, as well as their physiochemical properties and applications in fields such as electronics, photovoltaics, biomedicine, and materials science. Emphasis is assigned to experimentally obtained results, especially the X-ray crystallographic characterizations of EMFs and their derivatives, rather than theoretical calculations, although the latter has indeed enhanced our knowledge of metal-cage interactions. Finally, perspectives related to future developments and challenges in the research of EMFs are proposed. (381 references).

  11. Gadolinium Endohedral Metallofullerene-Based MRI Contrast Agents

    NASA Astrophysics Data System (ADS)

    Bolskar, Robert D.

    With the ability to encapsulate and carry the highly paramagnetic Gd3+ ion, gadolinium endohedral metallofullerenes or "gadofullerenes" are being explored as alternatives to the chelate complexes that are currently used for contrast-enhanced magnetic resonance imaging (MRI). Reviewed here are the various water-soluble derivatives of the gadofullerenes Gd@C82, Gd@C60, and Gd3N@C80 that have been investigated as MRI contrast agents. The water proton r1 relaxivities of gadofullerenes can be more than an order of magnitude higher than those of clinically used chelate agents. Gadofullerene relaxivity mechanisms have been studied, and multiple factors are found to contribute to their high relaxivities. In vitro and in vivoT1-weighted MRI tests of gadofullerene derivatives have shown their utility as bright image-enhancing agents. The gadofullerene MRI contrast agents are a promising new and unique style of gadolinium carrier for advanced imaging applications, including cellular and molecular imaging.

  12. Fractionation of rare-earth metallofullerenes via reversible uptake and release from reactive silica.

    PubMed

    Stevenson, Steven; Rottinger, Khristina A; Field, Jessica S

    2014-05-28

    Minimal research exists for non-chromatographic separations of rare-earth metallofullerenes containing di-metallic (M2), di-metallic carbide (M2C2), and tri-metallic nitride (M3N) clusters trapped inside fullerene cages. Herein, we demonstrate a non-HPLC method (i.e., SAFA, Stir and Filter Approach) for purifying Er3N@Ih-C80, a rare-earth, metallic nitride clusterfullerene. We describe a strategic method that chemically releases rare-earth metallofullerenes (e.g., M2@C2n, M3N@C2n) trapped by aminosilica during SAFA. Recovery of metallofullerenes from spent silica represents a "green approach" because the spent silica and its useful, immobilized rare-earth metallofullerenes would have been discarded as waste material. We observe selectivity during metallofullerene uptake to aminosilica and also during its release from spent silica via addition of CS2. We describe a procedure to obtain samples enriched in M2 and M3N endohedrals. M2C2n fractions from our SAFA release process contain a wide range of higher metallofullerenes (e.g., Gd2C90-Gd2C140 or Er2C76-Er2C122). It is facile to obtain samples enriched in M3N@C82-M3N@C92. Note that unreacted M3N@C80 remains in the filtrate. The strategy for handling rare-earth metallofullerenes with different degrees of reactivity toward aminosilica is also discussed.

  13. Fractionation of rare-earth metallofullerenes via reversible uptake and release from reactive silica.

    PubMed

    Stevenson, Steven; Rottinger, Khristina A; Field, Jessica S

    2014-05-28

    Minimal research exists for non-chromatographic separations of rare-earth metallofullerenes containing di-metallic (M2), di-metallic carbide (M2C2), and tri-metallic nitride (M3N) clusters trapped inside fullerene cages. Herein, we demonstrate a non-HPLC method (i.e., SAFA, Stir and Filter Approach) for purifying Er3N@Ih-C80, a rare-earth, metallic nitride clusterfullerene. We describe a strategic method that chemically releases rare-earth metallofullerenes (e.g., M2@C2n, M3N@C2n) trapped by aminosilica during SAFA. Recovery of metallofullerenes from spent silica represents a "green approach" because the spent silica and its useful, immobilized rare-earth metallofullerenes would have been discarded as waste material. We observe selectivity during metallofullerene uptake to aminosilica and also during its release from spent silica via addition of CS2. We describe a procedure to obtain samples enriched in M2 and M3N endohedrals. M2C2n fractions from our SAFA release process contain a wide range of higher metallofullerenes (e.g., Gd2C90-Gd2C140 or Er2C76-Er2C122). It is facile to obtain samples enriched in M3N@C82-M3N@C92. Note that unreacted M3N@C80 remains in the filtrate. The strategy for handling rare-earth metallofullerenes with different degrees of reactivity toward aminosilica is also discussed. PMID:24522624

  14. Cluster formation of endohedral metallofullerenes with Y, Gd, and Ho in a solution and on a solid surface

    NASA Astrophysics Data System (ADS)

    Kareev, I. E.; Bubnov, V. P.; Alidzhanov, E. K.; Pashkevich, S. N.; Lantukh, Yu. D.; Letuta, S. N.; Razdobreev, D. A.

    2016-09-01

    The formation of endohedral metallofullerene clusters with Y, Gd, and Ho in an N, N-dimethylformamide solution and on a mica substrate surface has been investigated using static and dynamic light scattering and atomic force microscopy, respectively. It has been found that the size distribution of the clusters depends on the concentration of endohedral metallofullerenes and on the exposure time of the solution. It has been shown that the clusters are resistant to high temperatures and ultrasound effects. The concentration of endohedral metallofullerenes at which only single clusters are formed in the solutions has been determined. It has been established that an increase in the concentration of endohedral metallofullerenes leads to the agglomeration of single clusters. The fractal dimension has been estimated, and the zeta potential of endohedral metallofullerene clusters has been measured.

  15. Studies of metallofullerene primary soots by laser and thermal desorption mass spectrometry

    SciTech Connect

    Moro, L.; Ruoff, R.S.; Becker, C.H.; Lorents, D.C.; Malhotra, R. )

    1993-07-01

    Laser desorption (LD) and thermal desorption (TD) mass spectra of the metallofullerenes found in arc-produced primary soots have been studied for a large variety of alkaline earth and lanthanide elements. The metallofullerene ratios found in the LD spectra indicate that two distinct groups are observed: Sc, Y, La, Ce, Pr, Nd, Gd, Tb, Ho, Er, and Lu (group A) and Ca, Sr, Sm, Eu, and Yb (group B). The TD spectra of most of these same soots also separate into two groups that contain the same elements as groups A and B. Group A metallofullerenes show strong signals in both LD and TD spectra. Group B metallofullerenes are distinguished by their presence in the LD spectra but absence in the TD spectra. From the general ionic behavior of the elements of these groups, and recent studies of the endohedral oxidation states, we propose that the oxidation states are +3 for group A and +2 for group B. C[sub 70] metallofullerenes are anomalous in that they are absent in TD spectra for all group A and B elements, even at T = 750[degrees]C, but present in LD spectra. 31 refs., 4 figs., 2 tabs.

  16. Smart Crystallography in Materials Science at SPring-8: In the case of Endohedral Metallofullerene

    NASA Astrophysics Data System (ADS)

    Nishibori, Eiji; Maki, Sachiko; Takata, Masaki

    Structural studies of endohedral metallofullerenes using synchrotron radiation powder profiles were described with two examples. A two-dimensional (2D) arrangement of metallofullerenes for both M@C82 (M = Y, La, Ce, Pr) and (M2Cy)@C82 (M = Er, y = 0, 2; M = Sc, y =2) is crystallized with 1 : 2 fullerene/toluene molecular ratio. The difference of the molecular arrangements strongly correlates with an orientation of metallofullerenes in the 2D layer. Systematically structural studies have been carried out for 24 different kinds of endohedral metallofullerenes, MxC2n (M = La, Y, Sc, Lu, Ti, Eu, Er, Hf, Sc3N; 34 ≤ n ≤ 43), as 1 : 1 co-crystals with solvent toluene molecules. It is found that the volume for one fullerene and one toluene molecule linearly depends on the number of carbon atoms in the fullerene cage. This linear dependence provides a metallofullerene diagnostics diagram that has universal importance for structural characterization of the cluster endohedral fullerenes.

  17. Electron spin coherence in metallofullerenes: Y, Sc, and La@C82

    NASA Astrophysics Data System (ADS)

    Brown, Richard M.; Ito, Yasuhiro; Warner, Jamie H.; Ardavan, Arzhang; Shinohara, Hisanori; Briggs, G. Andrew D.; Morton, John J. L.

    2010-07-01

    Endohedral fullerenes encapsulating a spin-active atom or ion within a carbon cage offer a route to self-assembled arrays such as spin chains. In the case of metallofullerenes the charge transfer between the atom and the fullerene cage has been thought to limit the electron spin phase coherence time (T2) to the order of a few microseconds. We study electron spin relaxation in several species of metallofullerene as a function of temperature and solvent environment, yielding a maximum T2 in deuterated o-terphenyl greater than 200μs for Y, Sc, and La@C82 . The mechanisms governing relaxation ( T1 , T2 ) arise from metal-cage vibrational modes, spin-orbit coupling and the nuclear spin environment. The T2 times are over 2 orders of magnitude longer than previously reported and consequently make metallofullerenes of interest in areas such as spin labeling, spintronics, and quantum computing.

  18. Electron transfer and localization in endohedral metallofullerenes: Ab initio density functional theory calculations

    NASA Astrophysics Data System (ADS)

    Yang, Shenyuan; Yoon, Mina; Hicke, Christian; Zhang, Zhenyu; Wang, Enge

    2008-09-01

    Endohedral metallofullerenes constitute an appealing class of nanoscale building blocks for fabrication of a wide range of materials. One open question of fundamental importance is the precise nature of charge redistribution within the carbon cages (Cn) upon metal encapsulation. Using ab initio density functional theory, we systematically study the electronic structure of metallofullerenes, focusing on the spatial charge redistribution. For large metallofullerenes (n>32) , the valence electrons of the metal atoms are all transferred to the fullerene states. Surprisingly, the transferred charge is found to be highly localized inside the cage near the metal cations rather than uniformly distributed on the surfaces of the carbon cage as traditionally believed. This counterintuitive charge localization picture is attributed to the strong metal-cage interactions within the systems. These findings may prove to be instrumental in the design of fullerene-based functional nanomaterials.

  19. Magneto-photoluminescence in lanthanide-bearing endohedral metallofullerenes with various cage symmetries

    NASA Astrophysics Data System (ADS)

    Merritt, Travis; Dorn, Harry; Khodaparast, Giti A.; McGill, Steve

    2012-02-01

    Taken as a family, endohedral metallofullerenes (EMF) nanomaterials provide opportunities for exquisite functional tunability at the nanoscale, enabling a wide range of synthetic nanoparticles with diverse sizes, symmetries, electronic, optical and, especially, magnetic properties. In particular, metallofullerenes incarcerating lanthanide ions will permit endohedral luminescence due to the 4f optically-active electrons being uninvolved in the stabilizing charge transfer between the endohedral guest and cage. In addition, if those lanthanide ions possess optical transitions beyond the absorption onset of the cage, a well-defined optical spectrum may be observed for the metallofullerene system. In this talk, several magneto-optical and time-resolved studies at high magnetic fields on lanthanide-based EMFs with different cage symmetries will be presented, where the residual magnetic degeneracies in the lanthanide ion energy levels are lifted and observed in the optical spectrum with magnetic field strengths in excess of 10 T.

  20. Two-dimensional coalescence dynamics of encapsulated metallofullerenes in carbon nanotubes.

    PubMed

    Allen, Christopher S; Ito, Yasuhiro; Robertson, Alex W; Shinohara, Hisanori; Warner, Jamie H

    2011-12-27

    We report on the coalescence of a two-dimensional (2D) chain of La@C(82) metallofullerene molecules encapsulated inside a single-wall carbon nanotube (SWNT). 2D packing of metallofullerenes is known to adopt a zigzag arrangement and cause elliptical distortion to the cross-section of the SWNT host. We show that after coalescence of the metallofullerenes into an inner nanotube the carbon nanotube host returns to its original circular cross-section. This is due to a relaxation of the strain caused by the packing of the encapsulated La@C(82) molecules into the nanotube. We identify the formation of some novel but transient fullerene-based structures formed during the intermediate stages of coalescence of the La@C(82) into an inner nanotube. These results highlight the flexible nature of SWNTs and their ability to adapt their cross-sectional profile depending upon forces induced by material encapsulated within.

  1. Isolation and spectroscopic characterization of two isomers of the metallofullerene Nd at C82

    SciTech Connect

    Porfyrakis, Kyriakos; Briggs, G. Andrew D.; Kanai, Mito; Dennis, T. John S.; Morley, Gavin W.; Ardavan, Arzhang

    2005-09-27

    For the first time, two types of the metallofullerene Nd at C82 have been isolated and characterized. HPLC was used to isolate Nd at C82(I, II). The two isomers were characterized by mass spectrometry and UV-Vis-NIR absorption spectroscopy. Nd at C82(I) was found to be similar in structure to the main isomer of other lanthanofullerenes such as La at C82, as was previously reported. We assign Nd at C82(I) to have a C2v cage symmetry. Nd at C82(II) showed a markedly different UV-Vis-NIR absorption spectrum to Nd at C82(I). Its spectrum is in good agreement with that of the minor isomer of metallofullerenes such as Pr at C82. We therefore assign Nd at C82(II) to have a Cs cage symmetry. In contrast to other metallofullerenes, both isomers appear to be equally abundant.

  2. Carbide cluster metallofullerenes: structure, properties, and possible origin.

    PubMed

    Lu, Xing; Akasaka, Takeshi; Nagase, Shigeru

    2013-07-16

    Endohedral metallofullerenes (EMFs) are hybrid molecules with different metallic species encapsulated inside the fullerene cages. In addition to conventional EMFs that contain only metal ions, researchers have constructed novel compounds that encapsulate metallic clusters of nitride, carbide, oxide, cyanide, and sulfide. Among these structures, carbide cluster metallofullerenes (CCMFs) are unique because their synthesis requires only graphite and the metal source. As a result the molecular structures of CCMFs are particularly difficult to characterize. Two carbon atoms are encapsulated inside the cage, but they do not participate in constructing the cage framework. Recent X-ray crystallographic studies of EMFs have allowed researchers to unambiguously identify CCMFs (MxC₂@C2n). Previously most of these structures had been described as conventional EMFs Mx@C2n+2. Most of these species are scandium-containing compounds such as Sc3C₂@Ih(7)-C₈₀ [not Sc₃@C3v(7)-C₈₂], Sc₂C₂@C2v(5)-C₈₀ [not Sc₂@C₈₂], Sc₂C₂@Cs(6)-C₈₂ [not Sc₂@Cs(10)-C₈₄], Sc₂C₂@C2v(9)-C₈₂ [not Sc₂@C2v(17)-C₈₄], Sc₂C₂@C3v(8)-C₈₂ [not Sc₂@D2d(23)-C₈₄], and Sc₂C₂@D2d(23)-C₈₄ [not Sc₂@C₈₆]. Additional examples of CCMFs include Gd₂C₂@D₃(85)-C₉₂, Sc₂C₂@C2v(6073)-C₆₈, Ti₂C₂@D3h(5)-C₇₈, M₂C₂@C3v(8)-C₈₂, M₂C₂@Cs(6)-C₈₂ (M = Y, Er, etc.), Y₂C₂@C₈₄, Y₂C₂@D₃(85)-C₉₂, Y₂C₂@D₅(450)-C₁₀₀, and Lu₃C₂@D₂(35)-C₈₈. The existence of so many CCMF species reminds us that the symbol '@' (which denotes the encapsulation status of EMFs) should be used with caution with species whose molecular structures have not been determined unambiguously. This Account presents a detailed summary of all aspects of CCMFs, including historically erroneous assignments and corrected structural characterizations, along with their intrinsic properties such as electrochemical and chemical

  3. Identification of metal-cage coupling in a single metallofullerene by inelastic electron tunneling spectroscopy

    NASA Astrophysics Data System (ADS)

    Jiang, J.; Gao, B.; Hu, Z. P.; Lu, Wei; Wu, Z. Y.; Yang, J. L.; Luo, Y.

    2010-06-01

    We report hybrid density functional theory calculations for inelastic electron tunneling spectroscopy (IETS) of a single metallofullerene Gd@C82. It is found that the metal atom inside the carbon cage can have significant impact on the IETS spectral profiles of the system, by modulating both the vibration and electron density. It is demonstrated that the IETS signals are very sensitive to the changes in the metal position and charge states, so that provide a unique tool for identifying the metal-cage coupling in metallofullerenes.

  4. Entrapping of exohedral metallofullerenes in carbon nanotubes: (CsC60)n@SWNT nano-peapods.

    PubMed

    Sun, Bao-Yun; Sato, Yuta; Suenaga, Kazutomo; Okazaki, Toshiya; Kishi, Naoki; Sugai, Toshiki; Bandow, Shunji; Iijima, Sumio; Shinohara, Hisanori

    2005-12-28

    Exohedral C60-based metallofullerenes, CsC60, have been synthesized and successfully encapsulated into single-wall carbon nanotubes (SWNTs) in high yield by reducing C60 molecules into anions. High-resolution transmission electron microscopy (HRTEM) images and in situ electron energy loss spectroscopy (EELS) indicate that Cs atoms and C60 molecules align within SWNTs as CsC60 exohedral metallofullerenes, and that the formal charge state of encaged CsC60 is expressed as Cs+1C60-1. The present peapods with the exohedral metallofullerenes provide a new insight and the possibility to fine-tune the electronic and transport properties of carbon nanotubes.

  5. Chemistry of endohedral metallofullerenes: the role of metals.

    PubMed

    Lu, Xing; Akasaka, Takeshi; Nagase, Shigeru

    2011-06-01

    Recent breakthroughs achieved in the chemical functionalization of endohedral metallofullerenes (EMFs), especially single crystallographic X-ray characterizations of their derivatives, have presented fundamentally new insights into the structures and properties of these metal-carbon hybrid molecules, and have also brought immense potential applications. In particular, the interplay between the encapsulated metallic species and the fullerene cage has been well investigated. On one hand, the position and motion of the encapsulated metals can be effectively controlled by exohedral modification. On the other hand, the cage structures, the chemical behaviours of cage carbons and thus the chemical reactivity of the whole molecule are also apparently influenced by the electronic configuration and geometrical conformation of the internal metals via strong metal-cage interactions. In this article, we contribute a systematic review of the important chemical transformations of EMFs reported to date, including disilylation, 1,3-dipolar cycloaddition with ylides, cyclopropanation with carbenes and carbanions, cycloaddition with dienes and benzyne, radical reactions, and other miscellaneous reactions, in addition to noncovalent interactions such as supramolecular complexation. The roles that internal metals play in controlling the reactivity of cage carbons are particularly emphasized. Finally, some applicable materials based on EMFs and their derivatives are summarized and practical perspectives are proposed.

  6. An Investigation of Magnetic, Electronic and Structural Properties of Metallofullerenes

    NASA Astrophysics Data System (ADS)

    Ong, S. Vincent; Qian, Meichun; Khanna, Shiv

    2008-03-01

    Gadolinium based endohedral metallofullerenes Gd3N@C80 functionalized with OH radicals have been found to enhance the relaxivity by orders of magnitude over conventional agents and are being sought as new contrast agents in magnetic resonance imaging (MRI). Using state of the art density functional theory (DFT) in the regime of the local density approximation with the on-site Coulomb interaction (LSDA+U), we have carried out theoretical studies to determine the electronic and magnetic properties of gadolinium-based and lutetium-based nitride fullerenes, namely Lu3-xGdxN@C80 (x = 1-2). While Gd3N@C80 has previously shown promising features as a contrast agent, the idea of replacing gadolinium atoms by lutetium has been proposed to result in a mixed-metal species for multi-modal imaging. Our results indicate that Lu2GdN@C80 is the most stable of all possible configurations with a binding energy 16.57 eV, can be considered for use as both an MRI contrast agent, due to gadolinium's high magnetic moment, and as a potential radioactive therapeutic or diagnostic agent, by neutron activation of a lutetium radioisotope. These results along with details of electronic structure will be presented.

  7. Chemical oxidation of endohedral metallofullerenes: identification and separation of distinct classes.

    PubMed

    Bolskar, Robert D; Alford, J Michael

    2003-06-01

    Chemical oxidation is useful for solubilizing and separating endohedral metallofullerenes, as demonstrated here by a separation of three categories of Gd@C2n species and by the solubilization of Tm@C60+ and Tm@C70+ for the first time.

  8. Efficient N,N-dimethylformamide extraction of endohedral metallofullerenes for HPLC purification

    SciTech Connect

    Ding, Junqi; Yang, Shihe

    1996-12-01

    Extraction of endohedral metallofullerenes using N,N-dimethylformamide was studied. Separation of Ce{sub 2}@C{sub 60}, Nd@C{sub 60}, and Pr@C{sub 60} was demonstrated. Excellent discrimination against native, non metallated fullerenes was observed.

  9. Maximum aromaticity or maximum pentagon separation; which is the origin behind the stability of endohedral metallofullerenes?

    PubMed

    Rodríguez-Fortea, Antonio; Poblet, Josep M

    2014-01-01

    Two different interpretations have been recently proposed to rationalize the stabilization of some hosting cages in endohedral metallofullerenes as a consequence of the larger localization of the negative charge on pentagonal rather than on hexagonal faces. We try to figure out the physical origin that mainly governs the stability of charged fullerenes; is it aromaticity or electrostatics?

  10. Regioselective synthesis and molecular structure of the first derivative of praseodymium-containing metallofullerenes.

    PubMed

    Zhou, Qin; Li, Hui; Lian, Yongfu; Suzuki, Mitsuaki; Bao, Lipiao; Cai, Wenting; Wang, Weiwei; Nagase, Shigeru; Lu, Xing; Akasaka, Takeshi

    2014-09-01

    Regioselective cycloaddition of adamantylidene carbene to Pr@C(2v)(9)-C82 affords the first derivative of praseodymium-containing metallofullerenes. Single-crystal X-ray crystallographic data in combination with theoretical studies demonstrate that the addition is dictated by the single metal ion encapsulated inside the fullerene cage.

  11. Maximum aromaticity or maximum pentagon separation; which is the origin behind the stability of endohedral metallofullerenes?

    PubMed

    Rodríguez-Fortea, Antonio; Poblet, Josep M

    2014-01-01

    Two different interpretations have been recently proposed to rationalize the stabilization of some hosting cages in endohedral metallofullerenes as a consequence of the larger localization of the negative charge on pentagonal rather than on hexagonal faces. We try to figure out the physical origin that mainly governs the stability of charged fullerenes; is it aromaticity or electrostatics? PMID:25467947

  12. Regioselective synthesis and molecular structure of the first derivative of praseodymium-containing metallofullerenes.

    PubMed

    Zhou, Qin; Li, Hui; Lian, Yongfu; Suzuki, Mitsuaki; Bao, Lipiao; Cai, Wenting; Wang, Weiwei; Nagase, Shigeru; Lu, Xing; Akasaka, Takeshi

    2014-09-01

    Regioselective cycloaddition of adamantylidene carbene to Pr@C(2v)(9)-C82 affords the first derivative of praseodymium-containing metallofullerenes. Single-crystal X-ray crystallographic data in combination with theoretical studies demonstrate that the addition is dictated by the single metal ion encapsulated inside the fullerene cage. PMID:25026192

  13. Recent progress in the chemistry of endohedral metallofullerenes.

    PubMed

    Lu, Xing; Bao, Lipiao; Akasaka, Takeshi; Nagase, Shigeru

    2014-12-01

    Putting metal atoms or metallic clusters into fullerenes has generated a new class of hybrid molecules, defined as endohedral metallofullerenes (EMFs), possessing novel structures and fascinating properties which are different from those of empty fullerenes. In particular, it has been revealed that the chemical properties of the cage carbons of EMFs depend strongly on the nature of the internal metallic species, such as their electronic configuration, location and even motion. Since the first report describing the successful derivatization of La@C82 in 1995, great efforts have been devoted to the chemical modification of EMFs during the last two decades. Although earlier studies mainly focused on readily available species such as M@C82, M2@C80 and M3N@C80 and the related results have been systematically summarized in our previous review paper (Chem. Commun., 2011, 47, 5942-5957), recent concerns about some relatively rare EMFs have developed rapidly. Moreover, taking advantage of single crystal X-ray crystallography, we can now clearly demonstrate the mutual influences between the internal metallic species and the chemical behaviours of the surrounding cage carbons, and the addends as well. In this article, we present recent achievements in the chemical functionalization of EMFs, which were mainly published during the last four years. For consistency, we will still pay special attention to the role that the metals play in controlling the properties of the whole EMF molecules. In this review, however, we will not only focus on concrete experimental results such as X-ray crystallographic and NMR spectroscopic data but will also include computational studies which have indeed enhanced our understanding of the chemical properties of EMFs. Applicable materials based on EMFs are also mentioned but are not discussed in detail.

  14. The cage and metal effect: spectroscopy and electrochemical survey of a series of Sm-containing high metallofullerenes.

    PubMed

    Liu, Jia; Shi, Zujin; Gu, Zhennan

    2009-11-01

    A series of Sm-containing high metallofullerenes, namely, Sm@C82 (I, II, III, IV), Sm@C84 (I, II, III), Sm@C86, Sm@C88 (I, II, III), Sm@C90 (I, II, III), Sm@C92 (I, II), Sm@C94 (I, II, III), and Sm@C96, is successfully synthesized and characterized by UV/Vis/NIR absorption spectroscopy, and cyclic and differential pulse voltammetry. Sm-containing high metallofullerenes have a relatively larger number of isomers compared with other divalent ones. The highest boiling point of Sm among Group II metals may be responsible for this phenomenon. Comparing the spectroscopic and electrochemical behaviors of Sm-containing metallofullerenes with those of other divalent ones, it is seen that when the size of the carbon cage enlarges, different structures form stable molecules with different metals. Furthermore, there are also some important differences in the electrochemistry properties. The cage effect on the electronic structures of high metallofullerenes is also estimated from the differences in reduction potentials between metallofullerenes and their corresponding fullerenes. It is believed that the influence of transferred electrons from the metal to the carbon cage becomes much weaker for high fullerenes. The redox property of high metallofullerene is more dependent on the carbon-cage structure than the effect of electron transfer.

  15. Tuning the selectivity of Gd3N cluster endohedral metallofullerene reactions with Lewis acids.

    PubMed

    Stevenson, Steven; Rottinger, Khristina A; Fahim, Muska; Field, Jessica S; Martin, Benjamin R; Arvola, Kristine D

    2014-12-15

    We demonstrate the manipulation of the Lewis acid strength to selectively fractionate different types of Gd3N metallofullerenes that are present in complex mixtures. Carbon disulfide is used for all Lewis acid studies. CaCl2 exhibits the lowest reactivity but the highest selectivity by precipitating only those gadolinium metallofullerenes with the lowest first oxidation potentials. ZnCl2 selectively complexes Gd3N@C88 during the first 4 h of reaction. Reaction with ZnCl2 for an additional 7 days permits a selective precipitation of Gd3N@C84 as the dominant endohedral isolated. A third fraction is the filtrate, which possesses Gd3N@C86 and Gd3N@C80 as the two dominant metallofullerenes. The order of increasing reactivity and decreasing selectivity (left to right) is as follows: CaCl2 < ZnCl2 < NiCl2 < MgCl2 < MnCl2 < CuCl2 < WCl4 ≪ WCl6 < ZrCl4 < AlCl3 < FeCl3. As a group, CaCl2, ZnCl2, and NiCl2 are the weakest Lewis acids and have the highest selectivity because of their very low precipitation onsets, which are below +0.19 V (i.e., endohedrals with first oxidation potentials below +0.19 V are precipitated). For CaCl2, the precipitation threshold is estimated at a remarkably low value of +0.06 V. Because most endohedrals possess first oxidation potentials significantly higher than +0.06 V, CaCl2 is especially useful in its ability to precipitate only a select group of gadolinium metallofullerenes. The Lewis acids of intermediate reactivity (i.e., precipitation onsets estimated between +0.19 and +0.4 V) are MgCl2, MnCl2, CuCl2, and WCl4. The strongest Lewis acids (WCl6, ZrCl4, AlCl3, and FeCl3) are the least selective and tend to precipitate the entire family of gadolinium metallofullerenes. Tuning the Lewis acid for a specific type of endohedral should be useful in a nonchromatographic purification method. The ability to control which metallofullerenes are permitted to precipitate and which endohedrals would remain in solution is a key outcome of this work.

  16. Bingel-Hirsch addition on endohedral metallofullerenes: kinetic versus thermodynamic control.

    PubMed

    Alegret, Núria; Rodríguez-Fortea, Antonio; Poblet, Josep M

    2013-04-15

    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.

  17. Understanding the reactivity of endohedral metallofullerenes: C78 versus Sc3N@C78.

    PubMed

    Bickelhaupt, F Matthias; Solà, Miquel; Fernández, Israel

    2015-04-01

    The physical factors behind the reduced Diels-Alder reactivity of the Sc3N@C78 metallofullerene as compared with free C78 have been investigated in detail by means of computational tools. To this end, the reactions between 1,3-butadiene and free C78 and endohedral Sc3N@C78 have been analysed in terms of regioselectivity and reactivity by using the activation strain model of reactivity in combination with the energy decomposition analysis method. Additional factors such as the molecular orbital overlap or the aromaticity of the corresponding transition states have been also explored. Our results indicate that the lower reactivity of the metallofullerene finds its origin mainly in the less stabilizing interaction between the deformed reactants along the reaction coordinate induced by the triscandium nitride moiety.

  18. A piggyback ride for transition metals: encapsulation of exohedral metallofullerenes in carbon nanotubes.

    PubMed

    Chamberlain, Thomas W; Champness, Neil R; Schröder, Martin; Khlobystov, Andrei N

    2011-01-10

    We have developed a method that enables the efficient insertion of transition-metal atoms and their small clusters into carbon nanotubes. As a model system, Os complexes attached to the exterior of fullerene C60 (exohedral metallofullerenes) were shown to be dragged into the nanotube spontaneously and irreversibly due to strong van der Waals interactions, specific to fullerenes and carbon nanotubes. The size of the metal-containing groups attached to C60 was shown to be critical for successful insertion, as functional groups too bulky to enter the nanotube were stripped off the fullerene during the encapsulation process. Once inside the nanotube, Os atoms catalyse polymerisation and decomposition of fullerene cages, which is related to a much higher catalytic activity of metal atoms situated on the surface of the fullerene cage, as compared to metal atoms in endohedral fullerenes, such as M@C82. Thus, exohedral metallofullerenes show promise for applications in catalysis in carbon “nano” test tubes.

  19. The Regioselectivity of Bingel-Hirsch Cycloadditions on Isolated Pentagon Rule Endohedral Metallofullerenes.

    PubMed

    Garcia-Borràs, Marc; Cerón, Maira R; Osuna, Sílvia; Izquierdo, Marta; Luis, Josep M; Echegoyen, Luis; Solà, Miquel

    2016-02-12

    In this work, the Bingel-Hirsch addition of diethylbromomalonate to all non-equivalent bonds of Sc3N@D3h -C78 was studied using density functional theory calculations. The regioselectivities observed computationally allowed the proposal of a set of rules, the predictive aromaticity criteria (PAC), to identify the most reactive bonds of a given endohedral metallofullerene based on a simple evaluation of the cage structure. The predictions based on the PAC are fully confirmed by both the computational and experimental exploration of the Bingel-Hirsch reaction of Sc3N@D5h -C80, thus indicating that these rules are rather general and applicable to other isolated pentagon rule endohedral metallofullerenes.

  20. Metallofullerenes as fuel cell electrocatalysts: a theoretical investigation of adsorbates on C59Pt.

    PubMed

    Gabriel, Margaret A; Genovese, Luigi; Krosnicki, Guillaume; Lemaire, Olivier; Deutsch, Thierry; Franco, Alejandro A

    2010-08-28

    Nano-structured electrode degradation in state-of-the-art polymer electrolyte membrane fuel cells (PEMFCs) is one of the main shortcomings that limit the large-scale development and commercialization of this technology. During normal operating conditions of the fuel cell, the PEMFC lifetime tends to be limited by coarsening of the cathode's Pt-based catalyst and by corrosion of the cathode's carbon black support. Because of their chemical properties, metallofullerenes such as C(59)Pt may be more electrochemically stable than the Pt/C mixture. In this paper we investigate, by theoretical methods, the stability of oxygen reduction reaction (ORR) adsorbates on the metallofullerene C(59)Pt and evaluate its potential as a PEMFC fuel cell catalyst.

  1. The Regioselectivity of Bingel-Hirsch Cycloadditions on Isolated Pentagon Rule Endohedral Metallofullerenes.

    PubMed

    Garcia-Borràs, Marc; Cerón, Maira R; Osuna, Sílvia; Izquierdo, Marta; Luis, Josep M; Echegoyen, Luis; Solà, Miquel

    2016-02-12

    In this work, the Bingel-Hirsch addition of diethylbromomalonate to all non-equivalent bonds of Sc3N@D3h -C78 was studied using density functional theory calculations. The regioselectivities observed computationally allowed the proposal of a set of rules, the predictive aromaticity criteria (PAC), to identify the most reactive bonds of a given endohedral metallofullerene based on a simple evaluation of the cage structure. The predictions based on the PAC are fully confirmed by both the computational and experimental exploration of the Bingel-Hirsch reaction of Sc3N@D5h -C80, thus indicating that these rules are rather general and applicable to other isolated pentagon rule endohedral metallofullerenes. PMID:26765333

  2. Tuning electronic and magnetic properties of endohedral Co@B80 and exohedral Co-B80 metallofullerenes by positioning Co atom

    NASA Astrophysics Data System (ADS)

    Li, J. L.; Yang, G. W.

    2010-06-01

    We have performed a systematical study of the structural configurations, electronic and magnetic properties of the single Co-doped endohedral Co@B80 and exohedral Co-B80 metallofullerene complexes using spin-polarized density functional calculations. Our calculations revealed that there are four stable configurations of the Co-doped metallofullerenes depending on different positions of the doping Co atoms as follows. In the case of the exohedral Co-B80 metallofullerene complexes, Co atom energetically prefers standing near the centers of pentagon (pentagon-out) and hexagon (hexagon-out) on the surface of B80. In the case of the endohedral Co@B80 metallofullerene complexes, the encapsulated Co atom energetically prefers standing near the centers of pentagon (pentagon-in) and hexagon (hexagon-in) on the inner surface of the hollow cage of B80. Electronically, the energy gaps of the hexagon-near adsorbed metallofullerenes have been greatly modified compared with that of B80. At the same time, the magnetic moments of both of the exohedral Co-B80 metallofullerenes are one third of that of the isolated Co atom. The tunable electronic and magnetic properties of the Co-doped B80 metallofullerenes clearly showed that this new type of metallofullerenes may be a promising candidate for molecular devices, especially single molecular spin electronic devices.

  3. Efficient HPLC purification of endohedral metallofullerenes on a porphyrin-silica stationary phase

    SciTech Connect

    Xiao, Jie; Savina, M.R.; Martin, G.B.; Francis, A.H.; Meyerhoff, M.E. )

    1994-10-05

    Endohedral metallofullrenes are among the most fascinating materials to emerge from ongoing efforts to produce and characterize closed-cage carbon compounds. In this paper, we describe the use of a new tetraphenylporphyrin-silica support material for efficient HPLC purification of the metallofullerenes from crude soot extract. The true single-stage separation from pyridine extracts demonstrates the unique chemical selectivity exhibited by employing [pi]-electron-rich tetraphenylporphyrin-silica stationary phases in chemical purifications. 18 refs., 3 figs.

  4. Rates and energetics of intramolecular electron transfer processes in conjugated metallofullerenes.

    PubMed

    Schubert, Christina; Rudolf, Marc; Guldi, Dirk M; Takano, Yuta; Mizorogi, Naomi; Herranz, M Ángeles; Martín, Nazario; Nagase, Shigeru; Akasaka, Takeshi

    2013-09-13

    In this paper, we report on the design, redox potentials, excited state energies and radical ion pair state energies in electron donor-acceptor conjugates comprising the electron-donating π-extended tetrathiafulvalene and several electron-accepting fullerenes. To this end, we contrast an empty fullerene, that is, C₆₀, with two endohedral metallofullerenes, that is, open-shell La@C₈₂ and closed-shell La₂@C₈₀, in terms of charge separation and charge recombination dynamics.

  5. Near-Infrared Photoluminescence Properties of Endohedral Mono- and Dithulium Metallofullerenes.

    PubMed

    Wang, Zhiyong; Izumi, Noriko; Nakanishi, Yusuke; Koyama, Takeshi; Sugai, Toshiki; Tange, Masayoshi; Okazaki, Toshiya; Shinohara, Hisanori

    2016-04-26

    The optical properties of endohedral metallofullerene molecules can be tuned by changing the fullerene size as well as the number of metal atoms inside the fullerene cages. In this work we have synthesized and isolated a series of mono- and dithulium metallofullerenes, including Tm@C82 (isomers I, II, III, IV), Tm@C88 (I-IV), Tm2@C82 (I-III), and (Tm2C2)@C82 (I-III). Near-infrared photoluminescence is observed from the thulium metallofullerenes. By changing the number of Tm ion in the fullerene cage, we have found that one can vary and tune the photoluminescence from 1200 to 1300-2000 nm observed for Tm(2+) (4f(13)) in Tm@C88 and Tm(3+) (4f(12)) in (Tm2C2)@C82, respectively. The photoluminescence intensity depends sensitively on the fullerene cages. (Tm2C2)@C82 (III) exhibits the highest photoluminescence intensity among the three structural isomers because of its large HOMO-LUMO energy gap.

  6. Near-Infrared Photoluminescence Properties of Endohedral Mono- and Dithulium Metallofullerenes.

    PubMed

    Wang, Zhiyong; Izumi, Noriko; Nakanishi, Yusuke; Koyama, Takeshi; Sugai, Toshiki; Tange, Masayoshi; Okazaki, Toshiya; Shinohara, Hisanori

    2016-04-26

    The optical properties of endohedral metallofullerene molecules can be tuned by changing the fullerene size as well as the number of metal atoms inside the fullerene cages. In this work we have synthesized and isolated a series of mono- and dithulium metallofullerenes, including Tm@C82 (isomers I, II, III, IV), Tm@C88 (I-IV), Tm2@C82 (I-III), and (Tm2C2)@C82 (I-III). Near-infrared photoluminescence is observed from the thulium metallofullerenes. By changing the number of Tm ion in the fullerene cage, we have found that one can vary and tune the photoluminescence from 1200 to 1300-2000 nm observed for Tm(2+) (4f(13)) in Tm@C88 and Tm(3+) (4f(12)) in (Tm2C2)@C82, respectively. The photoluminescence intensity depends sensitively on the fullerene cages. (Tm2C2)@C82 (III) exhibits the highest photoluminescence intensity among the three structural isomers because of its large HOMO-LUMO energy gap. PMID:27057619

  7. Electrochemical survey: the effect of the cage size and structure on the electronic structures of a series of ytterbium metallofullerenes.

    PubMed

    Xu, Jianxun; Li, Meixian; Shi, Zujin; Gu, Zhennan

    2005-12-23

    The electrochemical properties of a series of metallofullerenes with different cages, namely, Yb@C74(II), Yb@C76(I, II), Yb@C78, Yb@C80, Yb@C82(I, II, III), and Yb@C84(II, III, IV), have been systematically investigated by cyclic and differential pulse voltammetry experiments for the first time. This article discusses the electronic structures of these metallofullerenes based on the results from these experiments. From previous electrochemical work and the above discussion, it is concluded that the nondegenerate LUMO is a common characteristic of the electronic structures of the higher fullerenes and monometallofullerenes. In addition, the effect of the cage on the electronic structure and properties of the metallofullerene is estimated from the plot of the reduction potential versus the carbon number of the metallofullerene. This estimation shows that usually the electronic structure and properties of the metallofullerene vary with cage size and structure. The cage structure is of particular importance for determining the electronic structure and properties. Moreover, an explanation concerning the abundance and stability of C82-based trivalent monometallofullerenes is given from an electronic structural standpoint.

  8. {sup 13}C-NMR study on the structure of isolated Sc{sub 2}@C{sub 84} metallofullerene

    SciTech Connect

    Yamamoto, Etsuji; Tansho, Masataka; Tomiyama, Tetsuo; Shinohara, Hisanori; Kawahara, Hironori; Kobayashi, Yuji

    1996-03-06

    Here we report the first {sup 13}C-NMR results on the metallofullerene, Sc{sub 2}@C{sub 84}, which determines an isomer cage structure for the metallofullerene. The Sc{sub 2}@C{sub 84} fullerene was separated and isolated from the various hollow fullerenes (C{sub 60}-C{sub 110}) and other scandium metallofullerenes by the multistage high-performance liquid chromatography (HPLC) method by using two complementary types of HPLC columns. The purity of Sc{sub 2}@C{sub 84} relative to other fullerenes was more than 99.9%. {sup 13}C-NMR measurements were made using a 600 MHz NMR (JEOL JNM-A600) at room temperature in CS{sub 2} solvent. 30 refs., 3 figs.

  9. Spectroscopic and structural study of Y 2C 2 carbide encapsulating endohedral metallofullerene: (Y 2C 2)@C 82

    NASA Astrophysics Data System (ADS)

    Inoue, Takashi; Tomiyama, Tetsuo; Sugai, Toshiki; Shinohara, Hisanori

    2003-12-01

    The first di-yttrium carbide endohedral metallofullerene has been produced and spectroscopically and structurally characterized. 13C NMR structural analyses reveal that di-yttrium endohedral metallofullerene having a molecular formula of Y 2C 84 has been found to possess an endohedral yttrium carbide structure, (Y 2C 2)@C 82, in which a Y 2C 2 species is encaged by a C 82-C 3v(8) fullerene. The encaged Y 2C 2 species should rapidly rotate in order to maintain the entire (Y 2C 2)@C 82 molecular symmetry unchanged at room temperature.

  10. Energy and optical absorption spectra of endohedral metallofullerenes with Gd or Ho as strongly correlated π-electron systems

    NASA Astrophysics Data System (ADS)

    Bubnov, V. P.; Kareev, I. E.; Lobanov, B. V.; Murzashev, A. I.; Nekrasov, V. M.

    2016-08-01

    Isomerically pure endohedral metallofullerenes Gd@C82(C2v), Ho@C82( C 2 v ), and their monoanions have been synthesized and separated. The optical absorption spectra of solutions of obtained compounds in o-dichlorobenzene have been studied. Within the Hubbard model, the energy spectrum of isomer of C 2 v symmetry (no. 9) of fullerene C82 has been calculated. Based on the obtained spectrum, optical absorption spectra of endohedral metallofullerenes Gd@C82 and Ho@C82 and their monoanions have been simulated. The calculated optical absorption spectra have been compared with experimental ones; it has been found that qualitative agreement between them is observed.

  11. Structural and magnetic properties of Tcn@C60 endohedral metallofullerenes: An ab initio study

    NASA Astrophysics Data System (ADS)

    Kim, Eunja; Weck, Philippe F.; Czerwinski, Kenneth R.; Tománek, David

    2010-03-01

    We use ab initio spin density functional calculations to study the equilibrium structure and magnetic properties of Tcn@C60 endohedral metallofullerenes. The radionuclide ^99mTc is well established in biomedicine as a potent in vivo diagnostic radiopharmaceutical; its encapsulation in the inert C60 shell is expected to limit possible cytotoxicity of radiometal nanoparticles catabolized by the biological host. We find that C60 can endohedrally accommodate Tcn clusters with up to n=7. The encapsulation does not change significantly the structure of the enclosed clusters, but reduces the magnetic moment due to a stronger Tc--C hybridization for the larger clusters.

  12. Determination of Gd and Sm contents in metallofullerenes on a total reflection X-ray fluorescence spectrometer with parallel beam

    NASA Astrophysics Data System (ADS)

    Tikhonova, A. E.; Kozlov, V. S.

    2014-01-01

    The contents of Gd and Sm have been determined quantitatively using the X-ray fluorescence analysis on a total reflection spectrometer with a parallel beam. It has been shown that the results can be used in developments of the technique for measuring the content of Gd metallofullerenes in powder samples several milligrams in weight and in liquid samples several microliters in volume.

  13. Thermodynamically stable [4 + 2] cycloadducts of lanthanum-encapsulated endohedral metallofullerenes

    PubMed Central

    Takano, Yuta; Nagashima, Yuki; Herranz, M Ángeles

    2014-01-01

    Summary The [4 + 2] cycloaddition of o-quinodimethanes, generated in situ from the sultine 4,5-benzo-3,6-dihydro-1,2-oxathiin 2-oxide and its derivative, to La metal-encapsulated fullerenes, La2@C80 or La@C82, afforded the novel derivatives of endohedral metallofullerenes (3a,b, 4a,b and 5b). Molecular structures of the resulting compounds were elucidated using spectroscopic methods such as MALDI–TOF mass, optical absorption, and NMR spectroscopy. The [4 + 2] adducts of La2@C80 (3a,b, and 4a,b) and La@C82 (5b), respectively, retain diamagnetic and paramagnetic properties, as confirmed by EPR spectroscopy. Dynamic NMR measurements of 4a at various temperatures demonstrated the boat-to-boat inversions of the addend. In addition, 5b revealed remarkable thermal stability in comparison with the reported [4 + 2] cycloadduct of pentamethylcyclopentadiene and La@C82 (6). These findings demonstrate the utility of sultines to afford thermodynamically stable endohedral metallofullerene derivatives for the use in material science. PMID:24778724

  14. A structural diagnostics diagram for metallofullerenes encapsulating metal carbides and nitrides.

    PubMed

    Maki, Sachiko; Nishibori, Eiji; Terauchi, Ikuya; Ishihara, Masayuki; Aoyagi, Shinobu; Sakata, Makoto; Takata, Masaki; Umemoto, Hisashi; Inoue, Takashi; Shinohara, Hisanori

    2013-01-16

    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.

  15. Thermodynamically stable [4 + 2] cycloadducts of lanthanum-encapsulated endohedral metallofullerenes.

    PubMed

    Takano, Yuta; Nagashima, Yuki; Herranz, M Ángeles; Martín, Nazario; Akasaka, Takeshi

    2014-01-01

    The [4 + 2] cycloaddition of o-quinodimethanes, generated in situ from the sultine 4,5-benzo-3,6-dihydro-1,2-oxathiin 2-oxide and its derivative, to La metal-encapsulated fullerenes, La2@C80 or La@C82, afforded the novel derivatives of endohedral metallofullerenes (3a,b, 4a,b and 5b). Molecular structures of the resulting compounds were elucidated using spectroscopic methods such as MALDI-TOF mass, optical absorption, and NMR spectroscopy. The [4 + 2] adducts of La2@C80 (3a,b, and 4a,b) and La@C82 (5b), respectively, retain diamagnetic and paramagnetic properties, as confirmed by EPR spectroscopy. Dynamic NMR measurements of 4a at various temperatures demonstrated the boat-to-boat inversions of the addend. In addition, 5b revealed remarkable thermal stability in comparison with the reported [4 + 2] cycloadduct of pentamethylcyclopentadiene and La@C82 (6). These findings demonstrate the utility of sultines to afford thermodynamically stable endohedral metallofullerene derivatives for the use in material science.

  16. A multicomponent molecular approach to artificial photosynthesis - the role of fullerenes and endohedral metallofullerenes.

    PubMed

    Rudolf, M; Kirner, S V; Guldi, D M

    2016-02-01

    In this review article, we highlight recent advances in the field of solar energy conversion at a molecular level. We focus mainly on investigations regarding fullerenes as well as endohedral metallofullerenes in energy and/or electron donor-acceptor conjugates, hybrids, and arrays, but will also discuss several more advanced systems. Hereby, the mimicry of the fundamental processes occurring in natural photosynthesis, namely light harvesting (LH), energy transfer (EnT), reductive/oxidative electron transfer (ET), and catalysis (CAT), which serve as a blue print for the rational design of artificial photosynthetic systems, stand at the focalpoint. Importantly, the key processes in photosynthesis, that is, LH, EnT, ET, and CAT, define the structure of this review with the only further differentiation in terms of covalent and non-covalent systems. Fullerenes as well as endohedral metallofullerenes are chosen by virtue of their small reorganization energies in electron transfer processes, on the one hand, and their exceptional redox behaviour, on the other hand.

  17. Development of water-soluble metallofullerenes as X-ray contrast media.

    PubMed

    Miyamoto, Akihiko; Okimoto, Haruya; Shinohara, Hisanori; Shibamoto, Yuta

    2006-05-01

    Fullerenes are a new carbonic allotrope having a cage structure. We investigated whether fullerenes containing one or two atoms of heavy metals could be an X-ray contrast material with little adverse effects. One or two atoms of dysprosium (Dy), erbium (Er), gadolinium (Gd), europium (Eu) and lutetium (Lu) were encapsulated into fullerene (C(82)), which was synthesized as a polyhydroxyl form (e.g., Gd@C(82)(OH)n, n=40, Gd - fullerenols). They were dissolved in water at maximum soluble concentrations and subjected to CT number analysis. The CT numbers of the solutions were measured using a 4- or 16-row multidetector CT scanner. The CT number of the water-soluble metallofullerenes were 56.0 HU for Dy@C(82)(OH)(40), 111.5 HU for Er@C(82)(OH)(40), 58.4 HU for Gd@C(82)(OH)(40), 100.9 HU for Eu@C(82)(OH)(40) and 23.3 HU for Lu(2)@C(82)(OH)(40). The CT numbers of the metallofullerenes investigated in the present study were not high enough to be used in the clinic in place of iodinated contrast materials. However, if nanotechnology progresses in the near future, it may prove to have a possibility as an X-ray contrast material.

  18. Endohedral metallofullerenes based on spherical I(h)-C(80) cage: molecular structures and paramagnetic properties.

    PubMed

    Wang, Taishan; Wang, Chunru

    2014-02-18

    Fullerenes are carbon cages assembled from fused hexagons andpentagons that have closed networks and conjugated π systems. The curve of the fullerene structure requires that the constituent carbon atoms take on a pyramidal shape and produces extra strain energy. However, the highly symmetrical geometry of the fullerene decreases the surface tension in these structures, so highly symmetrical fullerenes are usually very stable. For example, C60 with icosahedral symmetry (Ih) is the most stable fullerene molecule. However, another highly symmetrical fullerene, Ih-C80, is extremely unstable. The reason for this difference is the open-shell electronic structure of Ih-C80, which has a 4-fold degenerate HOMO occupied by only two electrons. Predictably, once the degenerate HOMO of Ih-C80 accepts six more electrons, it forms a closed-shell electronic structure similar to Ih-C60 and with comparable stability. Because the hollow structure of fullerenes can encapsulate metal atoms and those internal metals can transfer electrons to the fullerene cage, the encapsulation of metal clusters may provide an ideal technique for the stabilization of the Ih-C80 fullerenes. In this Account, we focus on the molecular structures and paramagnetic properties of spherical Ih-C80 endohedral fullerenes encaging a variety of metal moieties, such as metal atoms (Mn), metal nitride (M3N), metal carbide (MnC2), metal carbonitride (M3CN), and metal oxides (M4Om). We introduce several types of endohedral metallofullerenes such as Sc4C2@Ih-C80, which exhibits a Russian-doll-like structure, and Sc3CN@Ih-C80, which encapsulates a planar metal carbonitride cluster. In addition, we emphasize the paramagnetic properties of Ih-C80-based metallofullerenes, such as Sc3C2@Ih-C80, Y2@C79N, and M3N@Ih-C80, to show how those spin-active species can present a controllable paramagnetism. This Account highlights an inspiring molecular world within the spherical Ih-C80 cages of various metallofullerenes.

  19. C74 endohedral metallofullerenes violating the isolated pentagon rule: a density functional theory study

    NASA Astrophysics Data System (ADS)

    Zheng, Hong; Zhao, Xiang; Ren, Ting; Wang, Wei-Wei

    2012-07-01

    Precise studies on M2@C74 (M = Sc, La) series by means of DFT methods have disclosed that certain non-IPR isomers are more stable than the IPR structure. M2@C2(13295)-C74 and M2@C2(13333)-C74, both of which have two pentagon adjacencies (PA), present excellent thermodynamic stability with very small energy differences. Statistical mechanics calculations on the M2@C74 series reveal that M2@C2(13295)-C74 and M2@C2(13333)-C74 are quite favoured by entropy effects below 3000 K. Sc2@C74 and La2@C74 series are found to have similar electronic transfer but different electronic structures due to the distinct properties of scandium and lanthanum elements according to Natural Bond Orbital (NBO) analysis in conjunction with orbital interaction diagrams. Investigations of bonding energies reflect quite different influences of the two types of metal atoms to C74 metallo-fullerenes. Further examinations on C74 metallo-fullerenes uncover significant stabilization effects of metal atoms acting on PA fragments. Geometrical structures of certain non-IPR cages (from C72 to C76), which exhibit splendid stabilities when encapsulating metallo-clusters, are found to be related by Stone-Wales transformation and C2 addition. Furthermore, IR spectra and 13C NMR spectra of M2@C2(13295)-C74 and M2@C2(13333)-C74 have been simulated to assist further experimental characterization.Precise studies on M2@C74 (M = Sc, La) series by means of DFT methods have disclosed that certain non-IPR isomers are more stable than the IPR structure. M2@C2(13295)-C74 and M2@C2(13333)-C74, both of which have two pentagon adjacencies (PA), present excellent thermodynamic stability with very small energy differences. Statistical mechanics calculations on the M2@C74 series reveal that M2@C2(13295)-C74 and M2@C2(13333)-C74 are quite favoured by entropy effects below 3000 K. Sc2@C74 and La2@C74 series are found to have similar electronic transfer but different electronic structures due to the distinct properties of

  20. Development of Electron Cyclotron Resonance Ion Source for Synthesis of Endohedral Metallofullerenes

    SciTech Connect

    Tanaka, K.; Muramatsu, M.; Uchida, T.; Hanajiri, T.; Yoshida, Y.; Biri, S.; Kitagawa, A.; Kato, Y.

    2008-11-03

    A new electron cyclotron resonance ion source (ECRIS) has been constructed for synthesis of endohedral metallofullerenes. The main purpose of the ion source is to produce new biological and medical materials. The design is based on ECRIS for production of multicharged ion beams with a traditional minimum-B magnetic field. An 8-10 GHz traveling wave tube (TWT) amplifier and a 2.45 GHz magnetron have been applied as microwave sources. Fullerene and metal vapor are introduced with a filament heating micro-oven and an induction heating oven, respectively. In preliminary ion-extraction test, Ar{sup +} is 54 {mu}A. Many broken fullerenes such as C{sub 58} and C{sub 56} are observed in fullerene ion beams.

  1. Exchange interactions of spin-active metallofullerenes in solid-state carbon networks

    NASA Astrophysics Data System (ADS)

    Zaka, Mujtaba; Warner, Jamie H.; Ito, Yasuhiro; Morton, John J. L.; Rümmeli, Mark H.; Pichler, Thomas; Ardavan, Arzhang; Shinohara, Hisanori; Briggs, G. Andrew D.

    2010-02-01

    The electron paramagnetic resonance (EPR) of spin-active metallofullerenes (MFs) La@C82 and Sc@C82 diluted in solid-state C60 crystalline matrices with molar concentrations varying from 0.4% to 100% are investigated. For dilute concentrations, the hyperfine structure of the MFs is resolved, and as the concentration increases exchange narrowing is observed leading to a single peak in the EPR. Sc@C82 MFs are inserted into single-walled carbon nanotubes to form peapods with concentrations of 10% and 0.1%, diluted with C60 . For the case of peapods containing 10% Sc@C82 a strong narrow peak is observed in X -band CW EPR, but not pulsed measurements. Peapods containing Ce@C82 MFs are prepared and these also show similar CW EPR to the Sc@C82 , indicating the peak arises from charge transfer with the SWNT.

  2. Oriented cluster formation of endohedral Y@C{sub 82} metallofullerenes on clean surfaces

    SciTech Connect

    Shinohara, Hisanori; Inakuma, Masayasu; Kishida, Masaaki; Yamazaki, Souichi; Hashizume, Tomihiro; Sakurai, Toshio

    1995-09-21

    An oriented head-to-tail cluster formation of an endohedral yttrium metallofullerene, Y@C{sub 82}, on a Cu(111)I x 1 clean surface has been observed directly by the use of a scanning tunneling microscopy (STM) under ultrahigh-vacuum conditions. The STM observation reveals that the Y@C{sub 82} molecules preferentially form dimers and one-dimensional clusters at the step edge of the Cu(111) surface. The observed intermolecular distance (11.2 {+-} 0.5 A) is smaller than that of the simple Y@C{sub 82}, Y@C{sub 82} van der Waals distance (11.4 A), indicating the presence of a strong interfullerene interaction. The STM results suggest the presence of strong dipole-dipole and charge-transfer interactions among Y@C{sub 82} fullerenes. Such a molecule has a great similarity to the `superatom` features proposed theoretically in a semiconductor heterostructure. 30 refs., 5 figs.

  3. The maximum pentagon separation rule provides a guideline for the structures of endohedral metallofullerenes

    NASA Astrophysics Data System (ADS)

    Rodríguez-Fortea, Antonio; Alegret, Núria; Balch, Alan L.; Poblet, Josep M.

    2010-11-01

    Fullerenes tend to follow the isolated pentagon rule, which requires that each of the 12 pentagons is surrounded only by hexagons. Over the past decade many violations to this rule were reported for endohedral fullerenes. Based on the ionic model M3N6+@C2n6- and the orbital energies of the isolated cages, in 2005 we formulated a molecular orbital rule to identify the most suitable hosting cages in endohedral metallofullerenes. Now, we give physical support to the orbital rule, and we propose the maximum pentagon separation rule, which can be applied to either isolated pentagon rule cages or to non-isolated pentagon rule cages with the same number of adjacent pentagon pairs. The maximum pentagon separation rule can be formulated as 'The electron transfer from the internal cluster to the fullerene host preferentially adds electrons to the pentagons; therefore, the most suitable carbon cages are those with the largest separations among the 12 pentagons'.

  4. Development of Electron Cyclotron Resonance Ion Source for Synthesis of Endohedral Metallofullerenes

    NASA Astrophysics Data System (ADS)

    Tanaka, K.; Muramatsu, M.; Uchida, T.; Biri, S.; Asaji, T.; Shima, K.; Hanajiri, T.; Kitagawa, A.; Kato, Y.; Yoshida, Y.

    2008-11-01

    A new electron cyclotron resonance ion source (ECRIS) has been constructed for synthesis of endohedral metallofullerenes. The main purpose of the ion source is to produce new biological and medical materials. The design is based on ECRIS for production of multicharged ion beams with a traditional minimum-B magnetic field. An 8-10 GHz traveling wave tube (TWT) amplifier and a 2.45 GHz magnetron have been applied as microwave sources. Fullerene and metal vapor are introduced with a filament heating micro-oven and an induction heating oven, respectively. In preliminary ion-extraction test, Ar+ is 54 μA. Many broken fullerenes such as C58 and C56 are observed in fullerene ion beams.

  5. The maximum pentagon separation rule provides a guideline for the structures of endohedral metallofullerenes.

    PubMed

    Rodríguez-Fortea, Antonio; Alegret, Núria; Balch, Alan L; Poblet, Josep M

    2010-11-01

    Fullerenes tend to follow the isolated pentagon rule, which requires that each of the 12 pentagons is surrounded only by hexagons. Over the past decade many violations to this rule were reported for endohedral fullerenes. Based on the ionic model M(3)N(6+)@C(2n)(6-) and the orbital energies of the isolated cages, in 2005 we formulated a molecular orbital rule to identify the most suitable hosting cages in endohedral metallofullerenes. Now, we give physical support to the orbital rule, and we propose the maximum pentagon separation rule, which can be applied to either isolated pentagon rule cages or to non-isolated pentagon rule cages with the same number of adjacent pentagon pairs. The maximum pentagon separation rule can be formulated as 'The electron transfer from the internal cluster to the fullerene host preferentially adds electrons to the pentagons; therefore, the most suitable carbon cages are those with the largest separations among the 12 pentagons'.

  6. Metallofullerene-Nanoplatform-Delivered Interstitial Brachytherapy Improved Survival in a Murine Model of Glioblastoma Multiforme

    PubMed Central

    Wilson, John D.; Broaddus, William C.; Dorn, Harry C.; Fatouros, Panos P.; Chalfant, Charles E.; Shultz, Michael D.

    2012-01-01

    Fullerenes are used across scientific disciplines because of their diverse properties gained by altering encapsulated or surface bound components. In this study, the recently developed theranostic agent based on a radiolabeled functionalized metallofullerene (177Lu-DOTA-f-Gd3N@C80) was synthesized with high radiochemical yield and purity. The efficacy of this agent was demonstrated in two orthotopic xenograft brain tumor models of glioblastoma multiforme (GBM). A dose-dependent improvement in survival was also shown. The in vivo stability of the agent was verified through dual label measurements of biological elimination from the tumor. Overall, these results provide evidence that nanomaterial platforms can be used to deliver effective interstitial brachytherapy. PMID:22881865

  7. C₇₄ endohedral metallofullerenes violating the isolated pentagon rule: a density functional theory study.

    PubMed

    Zheng, Hong; Zhao, Xiang; Ren, Ting; Wang, Wei-Wei

    2012-08-01

    Precise studies on M(2)@C(74) (M = Sc, La) series by means of DFT methods have disclosed that certain non-IPR isomers are more stable than the IPR structure. M(2)@C(2)(13295)-C(74) and M(2)@C(2)(13333)-C(74), both of which have two pentagon adjacencies (PA), present excellent thermodynamic stability with very small energy differences. Statistical mechanics calculations on the M(2)@C(74) series reveal that M(2)@C(2)(13295)-C(74) and M(2)@C(2)(13333)-C(74) are quite favoured by entropy effects below 3000 K. Sc(2)@C(74) and La(2)@C(74) series are found to have similar electronic transfer but different electronic structures due to the distinct properties of scandium and lanthanum elements according to Natural Bond Orbital (NBO) analysis in conjunction with orbital interaction diagrams. Investigations of bonding energies reflect quite different influences of the two types of metal atoms to C(74) metallo-fullerenes. Further examinations on C(74) metallo-fullerenes uncover significant stabilization effects of metal atoms acting on PA fragments. Geometrical structures of certain non-IPR cages (from C(72) to C(76)), which exhibit splendid stabilities when encapsulating metallo-clusters, are found to be related by Stone-Wales transformation and C(2) addition. Furthermore, IR spectra and (13)C NMR spectra of M(2)@C(2)(13295)-C(74) and M(2)@C(2)(13333)-C(74) have been simulated to assist further experimental characterization.

  8. Modifying the endohedral La-ion location in both neutral and positively charged polyhydroxylated metallofullerenes

    NASA Astrophysics Data System (ADS)

    Rodríguez-Zavala, J. G.; Padilla-Osuna, I.; Guirado-López, R. A.

    2008-10-01

    We present extensive ab initio density-functional theory calculations in order to analyze the structure and energetics of both neutral and positively charged highly hydroxylated La@C60(OH)32+q and La@C82(OH)20+q ( q=0 , 1, 2, 4, 6, and 8) metallofullerenes. Interestingly we obtain, for the neutral hydroxylated structures, that the location of the encapsulated La atom strongly depends on the precise distribution of the OH groups on the carbon surface. Actually, we found atomic configurations in which the La ion is attached to different regions of the inner surface as well as atomic arrays in which weakly bonded endohedral species are obtained, being located near the center of the structure. The previous strong variations in the endohedral position of the lanthanum atom leads to sizable modifications in its valence state as well as to notable changes in the electronic spectra and in the lowest-energy spin configuration of the molecules, which are all facts that could be used to better identify the atomic structure of these highly relevant metallofullerenes. The positive charging (by means of simply electron detachment) of our here-considered La@C60(OH)32 compounds reveals that the rupture of various C-C bonds of the carbon network can be achieved. However, even if the previous bond breakage leads to the formation of sizable holes in the C60 cavity (made of nine-membered rings), we obtain that the encapsulated La atom was unable to escape from the cage. In contrast, in the polyhydroxylated La@C82(OH)20 fullerene, no C-C bond breakage is induced with increasing charge state of the cage, defining thus a more stable molecular compound. The previous results are expected to be of fundamental importance in medical and biological applications where the permanent encapsulation of these highly toxic atomic species is required.

  9. Molecular Location Sensing Approach by Anisotropic Magnetism of an Endohedral Metallofullerene.

    PubMed

    Takano, Yuta; Tashita, Ryo; Suzuki, Mitsuaki; Nagase, Shigeru; Imahori, Hiroshi; Akasaka, Takeshi

    2016-06-29

    Location recognition at the molecular scale provides valuable information about the nature of functional molecular materials. This study presents a novel location sensing approach based on an endohedral metallofullerene, Ce@C82, using its anisotropic magnetic properties, which lead to temperature-dependent paramagnetic shifts in (1)H NMR spectra. Five site-isomers of Ce@C82CH2-3,5-C6H3Me2 were synthesized to demonstrate the spatial sensing ability of Ce@C82. Single-crystal structures, absorption spectra, and density functional theory calculations were used to select the plausible addition positions in the radical coupling reaction, which preferentially happens on the carbon atoms with high electron density of the singly occupied molecular orbital (SOMO) and positive charge. Temperature-dependent NMR measurements demonstrated unique paramagnetic shifts of the (1)H peaks, which were derived from the anisotropic magnetism of the f-electron in the Ce atom of the isomers. It was found that the magnetic anisotropy axes can be easily predicted by theoretical calculations using the Gaussian 09 package. Further analysis revealed that the temperature-dependent trend in the shifts is clearly predictable from the distance and relative position of the proton from the Ce atom. Hence, the Ce-encapsulated metallofullerene Ce@C82 can provide spatial location information about nearby atoms through the temperature-dependent paramagnetic shifts of its NMR signals. It can act as a molecular probe for location sensing by utilizing the anisotropic magnetism of the encapsulated Ce atom. The potentially low toxicity and stability of the endohedral fullerene would make Ce@C82 suitable for applications in biology and material science.

  10. Isolation and monitoring of the endohedral metallofullerenes YC{sub 82} and Sc{sub 3}C{sub 82}. On-line chromatographic separation with EPR detection

    SciTech Connect

    Stevenson, S.; Dorn, H.C.; Burbank, P.; Harich, K.; Sun, Z.; Kiang, C.H.; Salem, J.R.; DeVries, M.S.; Loosdrecht, P.H.M. van; Johnson, R.D.; Yannoni, C.S.; Bethune, D.S.

    1994-09-01

    The direct coupling of high-performance liquid chromatography (HPLC) with on-line electron paramagnetic resonance (EPR) detection is demonstrated for monitoring separations of endohedral metallofullerenes (MC{sub 2a}). The HPLC-EPR approach readily permits detection of the paramagnetic species, such as YC{sub 82} and Sc{sub 3}C{sub 82}, in the presence of the dominant empty-cage fullerenes (C{sub 60}, C{sub 70}) and diamagnetic metallofullerenes (e.g., M{sub 2}C{sub 2n}). The results indicate that on-line EPR provides a noninvasive, selective detector for HPLC metallofullerene separations that is readily adaptable to air-sensitive and/or labile compounds. Specifically, the `EPR-active` metallofullerenes, YC{sub 82} and Sc{sub 3}C{sub 82}, are selectively monitored on-line for an initial separation of the metallofullerene fraction from the dominant empty-cage fullerenes utilizing a combination of polystyrene columns. This preparative `cleanup` procedure is followed by HPLC-EPR separation and monitoring of YC{sub 82} and Sc{sub 3}C{sub 82} species using a selective tripodal {pi}-acidic-phase column (Trident-Tri-DNP) for the final stages of isolation. 30 refs., 8 figs.

  11. Manganese(III)-catalyzed free radical reactions on trimetallic nitride endohedral metallofullerenes.

    PubMed

    Shu, Chunying; Cai, Ting; Xu, Liaosa; Zuo, Tianming; Reid, Jonathan; Harich, Kim; Dorn, Harry C; Gibson, Harry W

    2007-12-19

    The first reactions of trimetallic nitride templated endohedral metallofullerenes (TNT EMFs) with carbon radicals generated from diethyl malonate catalyzed by manganese(III) acetate are reported. Two methano monoadducts, Sc3N@C80-A and Sc3N@C80-B, were isolated and characterized. Sc3N@C80-A contains two ester moieties, whereas Sc3N@C80-B contains only one ester group and a hydrogen atom on the central carbon of the addend. NMR spectroscopy of the two monoadducts suggests that the addition occurs regioselectively at a 6,6-ring juncture on the surface of the icosahedrally (Ih) symmetric Sc3N@C80, forming the first 6,6-ring-bridged methano Ih Sc3N@C80 derivatives. The measured 1J(C,H) = 147 Hz for the methano carbon with its hydrogen in monoadduct Sc3N@C80-B nearly perfectly matches the data for pi-homoaromatic systems, indicating an open [6,6]-methano structure. Geometry optimization also found that the "closed" [6,6]-methano structures were energetically unstable and always led to the open forms. Thus, an "open" [6,6]-methanofulleride structure is proposed, which was induced by the norcaradiene rearrangement, resulting in the cleavage of the cyclopropane ring and the formation of energetically stable open cage fullerene derivatives. These are the first examples of thermodynamically stable adducts of the "open" type at the 6,6-ring juncture of Ih Sc3N@C80, differing greatly from the "closed" 5,6-ring juncture adducts reported previously. In addition, bis-, tri-, and up to octaadducts of Sc3N@C80 were detected by matrix-assisted laser desorption ionization time-of-flight mass spectrometry; this synthetic method was also applied to Lu3N@C80, producing adducts with up to 10 substituents on the carbon cage. These are the highest levels of substitution of TNT metallofullerenes reported so far.

  12. Visible-Light Photoexcited Electron Dynamics of Scandium Endohedral Metallofullerenes: The Cage Symmetry and Substituent Effects.

    PubMed

    Wu, Bo; Hu, Jiahua; Cui, Peng; Jiang, Li; Chen, Zongwei; Zhang, Qun; Wang, Chunru; Luo, Yi

    2015-07-15

    Endohedral metallofullerenes (EMFs) have become an important class of molecular materials for optoelectronic applications. The performance of EMFs is known to be dependent on their symmetries and characters of the substituents, but the underlying electron dynamics remain unclear. Here we report a systematic study on several scandium EMFs and representative derivatives to examine the cage symmetry and substituent effects on their photoexcited electron dynamics using ultrafast transient absorption spectroscopy. Our attention is focused on the visible-light (530 nm as a demonstration) photoexcited electron dynamics, which is of broad interest to visible-light solar energy harvesting but is considered to be quite complicated as the visible-light photons would promote the system to a high-lying energy region where dense manifolds of electronic states locate. Our ultrafast spectroscopy study enables a full mapping of the photoinduced deactivation channels involved and reveals that the long-lived triplet exciton plays a decisive role in controlling the photoexcited electron dynamics under certain conditions. More importantly, it is found that the opening of the triplet channels is highly correlated to the fullerene cage symmetry as well as the electronic character of the substituents.

  13. Paramagnetic water-soluble metallofullerenes having the highest relaxivity for MRI contrast agents.

    PubMed

    Mikawa, M; Kato, H; Okumura, M; Narazaki, M; Kanazawa, Y; Miwa, N; Shinohara, H

    2001-01-01

    Water-soluble gadolinium (Gd) endohedral metallofullerenes have been synthesized as polyhydroxyl forms (Gd@C(82)(OH)(n)(), Gd-fullerenols) and their paramagnetic properties were evaluated by in vivo as well as in vitro for the novel magnetic resonance imaging (MRI) contrast agents for next generation. The in vitro water proton relaxivity, R(1) (the effect on 1/T(1)), of Gd-fullerenols is significantly higher (20-folds) than that of the commercial MRI contrast agent, Magnevist (gadolinium-diethylenetriaminepentaacetic acid, Gd-DTPA) at 1.0 T close to the common field of clinical MRI. This unusually high proton relaxivity of Gd-fullerenols leads to the highest signal enhancement at extremely lower Gd concentration in MRI studies. The strong signal was confirmed in vivo MRI at lung, liver, spleen, and kidney of CDF1 mice after i.v. administration of Gd-fullerenols at a dose of 5 micromol Gd/kg, which was 1/20 of the typical clinical dose (100 micromol Gd/kg) of Gd-DTPA.

  14. Trimetallic nitride endohedral metallofullerenes: reactivity dictated by the encapsulated metal cluster.

    PubMed

    Cardona, Claudia M; Kitaygorodskiy, Alex; Echegoyen, Luis

    2005-07-27

    The first derivatives of Y(3)N@C(80) have been synthesized and fully characterized. 1,3-Dipolar cycloaddition of N-ethylazomethine ylide yielded mainly the pyrrolidine monoadduct of the icosahedral (I(h)()) symmetry cage exclusively at a [6,6] double bond. The same regioselectivity on a [6,6] double bond was observed when the endohedral compound was cyclopropanated with diethyl bromomalonate. These results are in pronounced contrast to those observed for icosahedral symmetry Sc(3)N@C(80), for which all reported derivatives add completely regioselectively to [5,6] double bonds. (1)H NMR, (13)C NMR, and HMQC spectroscopy revealed that the addition pattern on Y(3)N@C(80) resulted in a pyrrolidinofullerene derivative with unsymmetric pyrrolidine carbons and symmetric geminal protons. The cyclopropanated monoadduct exhibited symmetric ethyl groups on the malonate, consistent with regioselective addition at a [6,6] double bond. Attempts to perform the same cyclopropanation reaction on (I(h)()) Sc(3)N@C(80) failed to yield any identifiable products. These observations clearly indicate that the reactivity of trimetallic nitride endohedral metallofullerenes toward exohedral chemical functionalization is profoundly affected and effectively controlled by the nature of the endohedral metal cluster.

  15. Exploration in metallic nitride fullerenes and oxometallic fullerenes: A new class of metallofullerenes

    NASA Astrophysics Data System (ADS)

    Mackey, Mary Alice

    2011-07-01

    Research groups around the world have taken an interest in the synthesis, purification, characterization, and functionalization of Metallic Nitride Fullerenes (MNFs) since their discovery in 1999. This dissertation details the discovery of another new class of molecules---Oxometallic Fullerenes (OMFs). There are many groups worldwide doing research on MNFs, and there is a large database of published MNF research, but we have had a unique opportunity to fill a research void on OMFs as at present no one else is doing research on these molecules; herein we take molecules that we discover and perform seminal research relating to them. MNF research is closely tied to this project; MNFs are a stepping stone because of their greater abundance and similar reactivity. Building off of previously developed techniques, we are able to create new methods for the separation and isolation of MNFs and OMFs. We studied the reactivity differences of various MNFs and OMFs in order to utilize Lewis acid chemistry as a tool for the enrichment and purification of both MNFs and OMFs, eventually resulting in a detailed separations technique. We have also begun studies to functionalize the carbon cage of endohedral metallofullerenes---this research includes using Lewis acids and various aromatic solvents via Friedel-Crafts reactions.

  16. Nonchromatographic "stir and filter approach" (SAFA) for isolating Sc3N@C80 metallofullerenes.

    PubMed

    Stevenson, Steven; Harich, Kim; Yu, Hua; Stephen, Ryan R; Heaps, David; Coumbe, Curtis; Phillips, J Paige

    2006-07-12

    Separation difficulties have led to a paucity of purified metallic nitride fullerenes (MNFs). Fundamental research and application development has been hampered with limited sample availability. Separation techniques designed to remove contaminant empty-cage fullerenes (e.g., C(60), C(70)...C(2)(n)) and classical metallofullerenes (e.g., non-MNFs) traditionally require expensive and tedious chromatographic methods. Our motivation is an alternative purification approach to minimize dependence on HPLC. Herein we report the use of cyclopentadienyl (CPD) and amino functionalized silica to selectively bind contaminant fullerenes. This "Stir and Filter Approach" (SAFA) provides purified MNF samples at ambient and reflux conditions. Under reflux conditions, purified MNFs (80% recovery, 41 h) are obtained using CPD silica. However, at room temperature, there is an equilibrium established between fullerenes and CPD silica, and no purified MNF samples are obtained using SAFA. In contrast, purified MNF samples (99+%) are readily obtained at room temperature using amino, diamino, and triamino silica at recoveries of 93% (11 h), 76% (9 h), and 50% (6 h), respectively.

  17. Metabolizer in vivo of fullerenes and metallofullerenes by positron emission tomography.

    PubMed

    Li, Juan; Yang, Wenjiang; Cui, Rongli; Wang, Dongliang; Chang, Yanan; Gu, Weihong; Yin, Wenyan; Bai, Xue; Chen, Kui; Xia, Lin; Geng, Huan; Xing, Gengmei

    2016-04-15

    Fullerenes (C60) and metallofullerenes (Gd@C82) have similar chemical structure, but the bio-effects of both fullerene-based materials are distinct in vivo. Tracking organic carbon-based materials such as C60 and Gd@C82 is difficult in vivo due to the high content of carbon element in the living tissues themselves. In this study, the biodistribution and metabolism of fullerenes (C60 and Gd@C82) radiolabeled with (64)Cu were observed by positron emission tomography (PET). (64)Cu-C60 and (64)Cu-Gd@C82 were prepared using 1, 4, 7, 10-tetrakis (carbamoylmethyl)-1, 4, 7, 10-tetra-azacyclodo-decanes grafted on carbon cages as a chelator for (64)Cu, and were obtained rapidly with high radiochemical yield (≥90%). The new radio-conjugates were evaluated in vivo in the normal mouse model and tissue distribution by small animal PET/CT imaging and histology was carried out. The PET imaging, the biodistribution and the excretion of C60 and Gd@C82 indicated that C60 samples have higher blood retention and lower renal clearance than the Gd@C82 samples in vivo and suggested that the differences in metabolism and distribution in vivo were caused by the structural differences of the groups on the fullerene cages though there is chemical similarity between C60 and Gd@C82.

  18. Enhanced dipole moments in trimetallic nitride template endohedral metallofullerenes with the pentalene motif.

    PubMed

    Zhang, Jianyuan; Bearden, Daniel W; Fuhrer, Tim; Xu, Liaosa; Fu, Wujun; Zuo, Tianming; Dorn, Harry C

    2013-03-01

    Although not found to date in empty-cage fullerenes, the fused pentagon motifs (pentalenes) are allowed in endohedral metallofullerenes (EMFs). We have found that members of the trimetallic nitride template (TNT) EMF Y3N@C2n (n = 39-44) family that contain pentalene motifs exhibit significant dipole moments. This finding is predicted to be significant for other EMFs with a metal atom orientated toward the pentalene motif. Chromatographic retention data and computational results for Y3N@C2-C78, Y3N@Cs-C82, and Y3N@Cs-C84 are examples that pentalene groups lead to a significant induced dipole moment (∼1D). A special case is the Y3N@C2-C78 that contains two pentalenes in a relatively small cage. The (13)C NMR spectrum for Y3N@C2-C78 exhibits strongly deshielded signals for the fullerene cage (155-170 ppm) supporting the presence of the pentalene motif. In addition, a lengthening of the covalent M-N bond in the internal M3N cluster is found for all reported TNT EMFs that contain one or two pentalene motifs.

  19. Magnetic properties of endohedral metallofullerenes based on asymmetric nitride yttrium cluster within azafullerenes

    NASA Astrophysics Data System (ADS)

    Nakagawa, Hitoshi; Suzuki, Atsushi; Oku, Takeo

    2013-04-01

    Magnetic properties of endohedral metallofullerene based on asymmetric triyttrium cluster of Y3N within azafullerene cage of C79N were studied to control spin-flop of nuclear magnetic resonance quantum computer. Difference of nuclear magnetic resonance peaks were exerted by symmetry of structure, electron density distribution and magnetic interaction. In the present calculation, magnetic properties of Y3N@C80, (Y3N@C80)-1, Y3N@C80 (CF3)2, Y3N@C79N and (C79N)+1 were compared for spin controlling in nuclear magnetic resonance quantum computers. The chemical shift of Y3N@C79N appeared the highest magnetic field side. Difference of electron density and magnetic parameters are cause of this result. The chemical shift of Y3N@C80 (CF3)2 had the widest peak in all of samples. Substituent groups of (CF3)2 caused the wide peaks by breaking symmetry of the an fullerene cages. The effect of difference of fullerene cage was shown in NMR chemical shift.

  20. Key Structural Motifs To Predict the Cage Topology in Endohedral Metallofullerenes.

    PubMed

    Wang, Yang; Díaz-Tendero, Sergio; Martín, Fernando; Alcamí, Manuel

    2016-02-10

    We show that the relative isomer stability of fullerene anions is essentially governed by a few simple structural motifs, requiring only the connectivity information between atoms. Relative energies of a large number of isomers of fullerene anions, C(2n)(q) (2n = 68-104; q = -2, -4, -6), can be satisfactorily reproduced by merely counting the numbers of seven kinds of hexagon-based motifs. The dependence of stability on these motifs varies with the charge state, which reflects the fact that the isomeric form of the carbon cage in endohedral metallofullerenes (EMFs) often differs from that in neutral empty fullerenes. The chemical origin of the stabilization differences between motifs is discussed on the basis of electronic and strain effects as well as aromaticity. On the basis of this simple model, the extraordinary abundance of the icosahedral C80 cage in EMFs can be easily understood. We also provide an explanation for why the well-known isolated pentagon rule is often violated in smaller EMFs. Finally, simple topological indices are proposed for quantitatively predicting the relative stability of fullerene anions, allowing a rapid determination of suitable hosting cages in EMFs by just counting three simple structural motifs.

  1. Visible-Light Photoexcited Electron Dynamics of Scandium Endohedral Metallofullerenes: The Cage Symmetry and Substituent Effects.

    PubMed

    Wu, Bo; Hu, Jiahua; Cui, Peng; Jiang, Li; Chen, Zongwei; Zhang, Qun; Wang, Chunru; Luo, Yi

    2015-07-15

    Endohedral metallofullerenes (EMFs) have become an important class of molecular materials for optoelectronic applications. The performance of EMFs is known to be dependent on their symmetries and characters of the substituents, but the underlying electron dynamics remain unclear. Here we report a systematic study on several scandium EMFs and representative derivatives to examine the cage symmetry and substituent effects on their photoexcited electron dynamics using ultrafast transient absorption spectroscopy. Our attention is focused on the visible-light (530 nm as a demonstration) photoexcited electron dynamics, which is of broad interest to visible-light solar energy harvesting but is considered to be quite complicated as the visible-light photons would promote the system to a high-lying energy region where dense manifolds of electronic states locate. Our ultrafast spectroscopy study enables a full mapping of the photoinduced deactivation channels involved and reveals that the long-lived triplet exciton plays a decisive role in controlling the photoexcited electron dynamics under certain conditions. More importantly, it is found that the opening of the triplet channels is highly correlated to the fullerene cage symmetry as well as the electronic character of the substituents. PMID:26097975

  2. Electron transport in endohedral metallofullerene Ce@C{sub 82} single-molecule transistors

    SciTech Connect

    Okamura, Naoya; Yoshida, Kenji; Sakata, Shuichi; Hirakawa, Kazuhiko

    2015-01-26

    We have investigated the electron transport in endohedral metallofullerene Ce@C{sub 82} single-molecule transistors (SMTs) together with that in reference C{sub 84} SMTs. The vibrational modes (bending and stretching) of the encapsulated single Ce atom in the C{sub 82} cage appear in Coulomb stability diagrams for the single-electron tunneling through Ce@C{sub 82} molecules, demonstrating the single-atom sensitivity of the transport measurements. When a bias voltage larger than 100 mV is applied across the source/drain electrodes, large hysteretic behavior is observed in the current-voltage (I-V) characteristics. At the same time, the pattern in the Coulomb stability diagram is changed. No such hysteretic behavior is observed in the I-V curves of hollow-cage C{sub 84} SMTs, even when the bias voltage exceeds 500 mV. This hysteretic change in the I-V characteristics is induced by a nanomechanical change in the configuration of the Ce@C{sub 82} molecule in the nanogap electrode due to the electric dipole that exists in Ce@C{sub 82}.

  3. Metabolizer in vivo of fullerenes and metallofullerenes by positron emission tomography

    NASA Astrophysics Data System (ADS)

    Li, Juan; Yang, Wenjiang; Cui, Rongli; Wang, Dongliang; Chang, Yanan; Gu, Weihong; Yin, Wenyan; Bai, Xue; Chen, Kui; Xia, Lin; Geng, Huan; Xing, Gengmei

    2016-04-01

    Fullerenes (C60) and metallofullerenes (Gd@C82) have similar chemical structure, but the bio-effects of both fullerene-based materials are distinct in vivo. Tracking organic carbon-based materials such as C60 and Gd@C82 is difficult in vivo due to the high content of carbon element in the living tissues themselves. In this study, the biodistribution and metabolism of fullerenes (C60 and Gd@C82) radiolabeled with 64Cu were observed by positron emission tomography (PET). 64Cu-C60 and 64Cu-Gd@C82 were prepared using 1, 4, 7, 10-tetrakis (carbamoylmethyl)-1, 4, 7, 10-tetra-azacyclodo-decanes grafted on carbon cages as a chelator for 64Cu, and were obtained rapidly with high radiochemical yield (≥90%). The new radio-conjugates were evaluated in vivo in the normal mouse model and tissue distribution by small animal PET/CT imaging and histology was carried out. The PET imaging, the biodistribution and the excretion of C60 and Gd@C82 indicated that C60 samples have higher blood retention and lower renal clearance than the Gd@C82 samples in vivo and suggested that the differences in metabolism and distribution in vivo were caused by the structural differences of the groups on the fullerene cages though there is chemical similarity between C60 and Gd@C82.

  4. Key Structural Motifs To Predict the Cage Topology in Endohedral Metallofullerenes.

    PubMed

    Wang, Yang; Díaz-Tendero, Sergio; Martín, Fernando; Alcamí, Manuel

    2016-02-10

    We show that the relative isomer stability of fullerene anions is essentially governed by a few simple structural motifs, requiring only the connectivity information between atoms. Relative energies of a large number of isomers of fullerene anions, C(2n)(q) (2n = 68-104; q = -2, -4, -6), can be satisfactorily reproduced by merely counting the numbers of seven kinds of hexagon-based motifs. The dependence of stability on these motifs varies with the charge state, which reflects the fact that the isomeric form of the carbon cage in endohedral metallofullerenes (EMFs) often differs from that in neutral empty fullerenes. The chemical origin of the stabilization differences between motifs is discussed on the basis of electronic and strain effects as well as aromaticity. On the basis of this simple model, the extraordinary abundance of the icosahedral C80 cage in EMFs can be easily understood. We also provide an explanation for why the well-known isolated pentagon rule is often violated in smaller EMFs. Finally, simple topological indices are proposed for quantitatively predicting the relative stability of fullerene anions, allowing a rapid determination of suitable hosting cages in EMFs by just counting three simple structural motifs. PMID:26762322

  5. Use of trimetasphere metallofullerene MRI contrast agent for the non-invasive longitudinal tracking of stem cells in the lung.

    PubMed

    Murphy, Sean V; Hale, Austin; Reid, Tanya; Olson, John; Kidiyoor, Amritha; Tan, Josh; Zhou, Zhiguo; Jackson, John; Atala, Anthony

    2016-04-15

    Magnetic Resonance Imaging (MRI) is a commonly used, non-invasive imaging technique that provides visualization of soft tissues with high spatial resolution. In both a research and clinical setting, the major challenge has been identifying a non-invasive and safe method for longitudinal tracking of delivered cells in vivo. The labeling and tracking of contrast agent labeled cells using MRI has the potential to fulfill this need. Contrast agents are often used to enhance the image contrast between the tissue of interest and surrounding tissues with MRI. The most commonly used MRI contrast agents contain Gd(III) ions. However, Gd(III) ions are highly toxic in their ionic form, as they tend to accumulate in the liver, spleen, kidney and bones and block calcium channels. Endohedral metallofullerenes such as trimetallic nitride endohedral metallofullerenes (Trimetasphere®) are one unique class of fullerene molecules where a Gd3N cluster is encapsulated inside a C80 carbon cage referred to as Gd3N@C80. These endohedral metallofullerenes have several advantages over small chelated Gd(III) complexes such as increased stability of the Gd(III) ion, minimal toxic effects, high solubility in water and high proton relativity. In this study, we describe the evaluation of gadolinium-based Trimetasphere® positive contrast agent for the ​in vitro labeling and in vivo tracking of human amniotic fluid-derived stem cells within lung tissue. In addition, we conducted a 'proof-of-concept' experiment demonstrating that this methodology can be used to track the homing of stem cells to injured lung tissue and provide longitudinal analysis of cell localization over an extended time course.

  6. Use of trimetasphere metallofullerene MRI contrast agent for the non-invasive longitudinal tracking of stem cells in the lung.

    PubMed

    Murphy, Sean V; Hale, Austin; Reid, Tanya; Olson, John; Kidiyoor, Amritha; Tan, Josh; Zhou, Zhiguo; Jackson, John; Atala, Anthony

    2016-04-15

    Magnetic Resonance Imaging (MRI) is a commonly used, non-invasive imaging technique that provides visualization of soft tissues with high spatial resolution. In both a research and clinical setting, the major challenge has been identifying a non-invasive and safe method for longitudinal tracking of delivered cells in vivo. The labeling and tracking of contrast agent labeled cells using MRI has the potential to fulfill this need. Contrast agents are often used to enhance the image contrast between the tissue of interest and surrounding tissues with MRI. The most commonly used MRI contrast agents contain Gd(III) ions. However, Gd(III) ions are highly toxic in their ionic form, as they tend to accumulate in the liver, spleen, kidney and bones and block calcium channels. Endohedral metallofullerenes such as trimetallic nitride endohedral metallofullerenes (Trimetasphere®) are one unique class of fullerene molecules where a Gd3N cluster is encapsulated inside a C80 carbon cage referred to as Gd3N@C80. These endohedral metallofullerenes have several advantages over small chelated Gd(III) complexes such as increased stability of the Gd(III) ion, minimal toxic effects, high solubility in water and high proton relativity. In this study, we describe the evaluation of gadolinium-based Trimetasphere® positive contrast agent for the ​in vitro labeling and in vivo tracking of human amniotic fluid-derived stem cells within lung tissue. In addition, we conducted a 'proof-of-concept' experiment demonstrating that this methodology can be used to track the homing of stem cells to injured lung tissue and provide longitudinal analysis of cell localization over an extended time course. PMID:26546729

  7. Use of trimetasphere metallofullerene MRI contrast agent for the non-invasive longitudinal tracking of stem cells in the lung

    PubMed Central

    Murphy, Sean V.; Hale, Austin; Reid, Tanya; Olson, John; Kidiyoor, Amritha; Tan, Josh; Zhou, Zhiguo; Jackson, John; Atala, Anthony

    2016-01-01

    Magnetic Resonance Imaging (MRI) is a commonly used, non-invasive imaging technique that provides visualization of soft tissues with high spatial resolution. In both a research and clinical setting, the major challenge has been identifying a non-invasive and safe method for longitudinal tracking of delivered cells in vivo. The labeling and tracking of contrast agent labeled cells using MRI has the potential to fulfill this need. Contrast agents are often used to enhance the image contrast between the tissue of interest and surrounding tissues with MRI. The most commonly used MRI contrast agents contain Gd(III) ions. However, Gd(III) ions are highly toxic in their ionic form, as they tend to accumulate in the liver, spleen, kidney and bones and block calcium channels. Endohedral metallofullerenes such as trimetallic nitride endohedral metallofullerenes (Trimetasphere®) are one unique class of fullerene molecules where a Gd3N cluster is encapsulated inside a C80 carbon cage referred to as Gd3N@C80. These endohedral metallofullerenes have several advantages over small chelated Gd(III) complexes such as increased stability of the Gd(III) ion, minimal toxic effects, high solubility in water and high proton relativity. In this study, we describe the evaluation of gadolinium-based Trimetasphere® positive contrast agent for the in vitro labeling and in vivo tracking of human amniotic fluid-derived stem cells within lung tissue. In addition, we conducted a ‘proof-of-concept’ experiment demonstrating that this methodology can be used to track the homing of stem cells to injured lung tissue and provide longitudinal analysis of cell localization over an extended time course. PMID:26546729

  8. In Vitro and In Vivo Studies of Single-Walled Carbon Nanohorns with Encapsulated Metallofullerenes and Exohedrally Functionalized Quantum Dots

    SciTech Connect

    Zhang, Jianfei; Ge, Jiechao; Shultz, M.D.; Chung, Eunna; Singh, Gurpreet; Shu, Chunying; Deck, Paul; Fatouros, Panos; Henderson, Scott; Corwin, Frank; Geohegan, David B; Rouleau, Christopher M; More, Karren Leslie; Rylander, Nichole M; Rylander, Christopher; Gibson, Harry W; Dorn, Harry C

    2010-07-01

    Single-walled carbon nanohorns (SWNHs) are new carbonaceous materials. In this paper, we report the first successful preparation of SWNHs encapsulating trimetallic nitride template endohedral metallofullerenes (TNT-EMFs). The resultant materials were functionalized by a high-speed vibration milling method and conjugated with CdSe/ZnS quantum dots (QDs). The successful encapsulation of TNT-EMFs and external functionalization with QDs provide a dual diagnostic platform for in vitro and in vivo biomedical applications of these new carbonaceous materials.

  9. In vitro and in vivo studies of single-walled carbon nanohorns with encapsulated metallofullerenes and exohedrally functionalized quantum dots.

    PubMed

    Zhang, Jianfei; Ge, Jiechao; Shultz, Michael D; Chung, Eunna; Singh, Gurpreet; Shu, Chunying; Fatouros, Panos P; Henderson, Scott C; Corwin, Frank D; Geohegan, David B; Puretzky, Alex A; Rouleau, Christopher M; More, Karren; Rylander, Christopher; Rylander, Marissa Nichole; Gibson, Harry W; Dorn, Harry C

    2010-08-11

    Single-walled carbon nanohorns (SWNHs) are new carbonaceous materials. In this paper, we report the first successful preparation of SWNHs encapsulating trimetallic nitride template endohedral metallofullerenes (TNT-EMFs). The resultant materials were functionalized by a high-speed vibration milling method and conjugated with CdSe/ZnS quantum dots (QDs). The successful encapsulation of TNT-EMFs and external functionalization with QDs provide a dual diagnostic platform for in vitro and in vivo biomedical applications of these new carbonaceous materials.

  10. Ab initio investigations of the charge transport properties of endohedral M@C20 (M = Na and K) metallofullerenes

    NASA Astrophysics Data System (ADS)

    An, Yi-Peng; Yang, Chuan-Lu; Wang, Mei-Shan; Ma, Xiao-Guang; Wang, De-Hua

    2010-11-01

    Using density functional theory and quantum transport calculations based on nonequilibum Green's function formalism, we investigate the charge transport properties of endohedral M@C20(M = Na and K) metallofullerenes. Our results show that the conductance of C20 fullerene can be obviously improved by insertion of alkali atom at its centre. Both linear and nonlinear sections are found on the I—V curves of the Au-M@C20-Au two-probe systems. The novel negative differential resistance behaviour is also observed in Na@C20 molecule but not in K@C20.

  11. In Vitro and In Vivo Studies of Single-Walled Carbon Nanohorns with Encapsulated Metallofullerenes and Exohedrally Functionalized Quantum Dots

    PubMed Central

    Zhang, Jianfei; Ge, Jiechao; Shultz, Michael D.; Chung, Eunna; Singh, Gurpreet; Shu, Chunying; Deck, Paul A.; Fatouros, Panos P.; Henderson, Scott C.; Corwin, Frank D.; Geohegan, David B.; Puretzky, Alex A.; Rouleau, Christopher M.; More, Karren; Rylander, Christopher; Rylander, Marissa Nichole; Gibson, Harry W.; Dorn, Harry C.

    2010-01-01

    Single-walled carbon nanohorns (SWNHs) are new carbonaceous materials. In this paper, we report the first successful preparation of SWNHs encapsulating trimetallic nitride template endohedral metallofullerenes (TNT-EMFs). The resultant materials were functionalized by a high-speed vibration milling method and conjugated with CdSe/ZnS quantum dots (QDs). The successful encapsulation of TNT-EMFs and external functionalization with QDs provide a dual diagnostic platform for in vitro and in vivo biomedical applications of these new carbonaceous materials. PMID:20698597

  12. The metallofullerene field-induced single-ion magnet HoSc2 N@C80.

    PubMed

    Dreiser, Jan; Westerström, Rasmus; Zhang, Yang; Popov, Alexey A; Dunsch, Lothar; Krämer, Karl; Liu, Shi-Xia; Decurtins, Silvio; Greber, Thomas

    2014-10-13

    The low-temperature magnetic properties of the endohedral metallofullerene HoSc2 N@C80 have been studied by superconducting quantum interference device (SQUID) magnetometry. Alternating current (ac) susceptibility measurements reveal that this molecule exhibits slow relaxation of magnetization in a small applied field with timescales in the order of milliseconds. The equilibrium magnetic properties of HoSc2 N@C80 indicate strong magnetic anisotropy. The large differences in magnetization relaxation times between the present compound and the previously investigated DySc2 N@C80 are discussed. PMID:25164532

  13. Highly regioselective 1,3-dipolar cycloaddition of diphenylnitrilimine to Sc3N@I(h)-C80 affording a very stable, unprecedented pyrazole-ring fused derivative of endohedral metallofullerenes.

    PubMed

    Liu, Bin; Cong, Hailin; Li, Xiaofang; Yu, Bing; Bao, Lipiao; Cai, Wenting; Xie, Yunpeng; Lu, Xing

    2014-10-28

    Formation of a very stable, unprecedented pyrazole-ring fused derivative of endohedral metallofullerenes was achieved by the first 1,3-dipolar cycloaddition reaction of Sc3N@C80 with diphenylnitrilimine in a highly regioselective manner.

  14. Metallofullerene and fullerene formation from condensing carbon gas under conditions of stellar outflows and implication to stardust

    PubMed Central

    Dunk, Paul W.; Adjizian, Jean-Joseph; Kaiser, Nathan K.; Quinn, John P.; Blakney, Gregory T.; Ewels, Christopher P.; Marshall, Alan G.; Kroto, Harold W.

    2013-01-01

    Carbonaceous presolar grains of supernovae origin have long been isolated and are determined to be the carrier of anomalous 22Ne in ancient meteorites. That exotic 22Ne is, in fact, the decay isotope of relatively short-lived 22Na formed by explosive nucleosynthesis, and therefore, a selective and rapid Na physical trapping mechanism must take place during carbon condensation in supernova ejecta. Elucidation of the processes that trap Na and produce large carbon molecules should yield insight into carbon stardust enrichment and formation. Herein, we demonstrate that Na effectively nucleates formation of Na@C60 and other metallofullerenes during carbon condensation under highly energetic conditions in oxygen- and hydrogen-rich environments. Thus, fundamental carbon chemistry that leads to trapping of Na is revealed, and should be directly applicable to gas-phase chemistry involving stellar environments, such as supernova ejecta. The results indicate that, in addition to empty fullerenes, metallofullerenes should be constituents of stellar/circumstellar and interstellar space. In addition, gas-phase reactions of fullerenes with polycyclic aromatic hydrocarbons are investigated to probe “build-up” and formation of carbon stardust, and provide insight into fullerene astrochemistry. PMID:24145444

  15. Intrafullerene electron transfers in Sm-containing metallofullerenes: Sm@C2n (74 < or = 2n < or = 84).

    PubMed

    Okazaki, T; Suenaga, K; Lian, Y; Gu, Z; Shinohara, H

    2001-01-01

    The electronic properties of Sm-containing metallofullerenes, Sm@C74, Sm@C76 (I, II), Sm@C78, Sm@C80, Sm@C82 (I, II, III) and Sm@C84 (I, II, III), are characterized by UV-Vis-NIR absorption spectroscopy and electron energy-loss spectroscopy (EELS). The UV-Vis-NIR absorption spectra of Sm@C74, Sm@C80, Sm@C82 (I, II, III) and Sm@C84 (I, II) are quite similar to those of the corresponding Ca, Sr, Ba, Eu, Tm, Yb-based metallofullerenes. In contrast, the absorption spectra of Sm@C76 (I, II), Sm@C78 and Sm@C84(III) show a novel feature: the onset for Sm@C78 is observed approximately 2600 nm, which corresponds to a small band gap (approximately 0.5 eV). Furthermore, the oxidation states of Sm atom in the various fullerene cages are investigated by EELS, which reveals that the Sm atom takes +2 oxidation state in the fullerene cages. A probable rationale for the tendency to have the Sm2+ state is presented based on a simple thermochemical cycle model.

  16. A missing link in the transformation from asymmetric to symmetric metallofullerene cages implies a top-down fullerene formation mechanism

    NASA Astrophysics Data System (ADS)

    Zhang, Jianyuan; Bowles, Faye L.; Bearden, Daniel W.; Ray, W. Keith; Fuhrer, Tim; Ye, Youqing; Dixon, Caitlyn; Harich, Kim; Helm, Richard F.; Olmstead, Marilyn M.; Balch, Alan L.; Dorn, Harry C.

    2013-10-01

    Although fullerenes were discovered nearly three decades ago, the mechanism of their formation remains a mystery. Many versions of the classic ‘bottom-up’ formation mechanism have been advanced, starting with C2 units that build up to form chains and rings of carbon atoms and ultimately form those well-known isolated fullerenes (for example, Ih-C60). In recent years, evidence from laboratory and interstellar observations has emerged to suggest a ‘top-down’ mechanism, whereby small isolated fullerenes are formed via shrinkage of giant fullerenes generated from graphene sheets. Here, we present molecular structural evidence for this top-down mechanism based on metal carbide metallofullerenes M2C2@C1(51383)-C84 (M = Y, Gd). We propose that the unique asymmetric C1(51383)-C84 cage with destabilizing fused pentagons is a preserved ‘missing link’ in the top-down mechanism, and in well-established rearrangement steps can form many well-known, high-symmetry fullerene structures that account for the majority of solvent-extractable metallofullerenes.

  17. Automated HPLC separation of endohedral metallofullerene ScC{sub 2n} and YC{sub 2n} fractions

    SciTech Connect

    Stevenson, S.; Dorn, H.C.; Burbank, P.; Harich, K.; Haynes, J. Jr.; Kiang, C.H.; Salem, J.R.; DeVries, M.S.; Loosdrecht, P.H.M. van; Johnson, R.D.; Yannoni, C.S.; Bethune, D.S.

    1994-09-01

    We describe an automated HPLC separation of the endohedral metallofullerenes such as SCC{sub 2n} and YC{sub 2n} from empty-cage fullerenes utilizing two polystyrene chromatographic columns (500 and 1000 A) in series. Rapid separation of the metallofullerene fraction from the empty-cage fullerenes (e.g., C{sub 60}) under anaerobic conditions is achieved. For the isolated SCC{sub 2n} fraction, all even-carbon-membered species from Sc{sub 2}C{sub 74} to Sc{sub 2}C{sub 104} were identified by negative-ion chemical ionization mass spectrometry. In addition, Sc{sub 3}C{sub 82} was a prominent component of this fraction. For the separated YC{sub 2n} sample, the mass spectral data indicate the presence of YC{sub 82} and all even-carbon-numbered diyttrium species from Y{sub 2}C{sub 82} to Y{sub 2}C{sub 104}. 14 refs., 7 figs.

  18. Metallofullerene and fullerene formation from condensing carbon gas under conditions of stellar outflows and implication to stardust.

    PubMed

    Dunk, Paul W; Adjizian, Jean-Joseph; Kaiser, Nathan K; Quinn, John P; Blakney, Gregory T; Ewels, Christopher P; Marshall, Alan G; Kroto, Harold W

    2013-11-01

    Carbonaceous presolar grains of supernovae origin have long been isolated and are determined to be the carrier of anomalous (22)Ne in ancient meteorites. That exotic (22)Ne is, in fact, the decay isotope of relatively short-lived (22)Na formed by explosive nucleosynthesis, and therefore, a selective and rapid Na physical trapping mechanism must take place during carbon condensation in supernova ejecta. Elucidation of the processes that trap Na and produce large carbon molecules should yield insight into carbon stardust enrichment and formation. Herein, we demonstrate that Na effectively nucleates formation of Na@C60 and other metallofullerenes during carbon condensation under highly energetic conditions in oxygen- and hydrogen-rich environments. Thus, fundamental carbon chemistry that leads to trapping of Na is revealed, and should be directly applicable to gas-phase chemistry involving stellar environments, such as supernova ejecta. The results indicate that, in addition to empty fullerenes, metallofullerenes should be constituents of stellar/circumstellar and interstellar space. In addition, gas-phase reactions of fullerenes with polycyclic aromatic hydrocarbons are investigated to probe "build-up" and formation of carbon stardust, and provide insight into fullerene astrochemistry.

  19. Metallofullerene and fullerene formation from condensing carbon gas under conditions of stellar outflows and implication to stardust.

    PubMed

    Dunk, Paul W; Adjizian, Jean-Joseph; Kaiser, Nathan K; Quinn, John P; Blakney, Gregory T; Ewels, Christopher P; Marshall, Alan G; Kroto, Harold W

    2013-11-01

    Carbonaceous presolar grains of supernovae origin have long been isolated and are determined to be the carrier of anomalous (22)Ne in ancient meteorites. That exotic (22)Ne is, in fact, the decay isotope of relatively short-lived (22)Na formed by explosive nucleosynthesis, and therefore, a selective and rapid Na physical trapping mechanism must take place during carbon condensation in supernova ejecta. Elucidation of the processes that trap Na and produce large carbon molecules should yield insight into carbon stardust enrichment and formation. Herein, we demonstrate that Na effectively nucleates formation of Na@C60 and other metallofullerenes during carbon condensation under highly energetic conditions in oxygen- and hydrogen-rich environments. Thus, fundamental carbon chemistry that leads to trapping of Na is revealed, and should be directly applicable to gas-phase chemistry involving stellar environments, such as supernova ejecta. The results indicate that, in addition to empty fullerenes, metallofullerenes should be constituents of stellar/circumstellar and interstellar space. In addition, gas-phase reactions of fullerenes with polycyclic aromatic hydrocarbons are investigated to probe "build-up" and formation of carbon stardust, and provide insight into fullerene astrochemistry. PMID:24145444

  20. Bonding in endohedral metallofullerenes as studied by quantum theory of atoms in molecules.

    PubMed

    Popov, Alexey A; Dunsch, Lothar

    2009-09-28

    Metal-cage and intracluster bonding was studied in detail by quantum theory of atoms in molecules (QTAIM) for the four major classes of endohedral metallofullerenes (EMFs), including monometallofullerenes Ca@C(72), La@C(72), M@C(82) (M=Ca, Sc, Y, La), dimetallofullerenes Sc(2)@C(76), Y(2)@C(82), Y(2)@C(79)N, La(2)@C(78), La(2)@C(80), metal nitride clusterfullerenes Sc(3)N@C(2n) (2n=68, 70, 78, 80), Y(3)N@C(2n) (2n=78, 80, 82, 84, 86, 88), La(3)N@C(2n) (2n=88, 92, 96), metal carbide clusterfullerenes Sc(2)C(2)@C(68), Sc(2)C(2)@C(82), Sc(2)C(2)@C(84), Ti(2)C(2)@C(78), Y(2)C(2)@C(82), Sc(3)C(2)@C(80), as well as Sc(3)CH@C(80) and Sc(4)O(x)@C(80) (x=2, 3), that is, 42 EMF molecules and ions in total. Analysis of the delocalization indices and bond critical point (BCP) indicators such as G(bcp)/rho(bcp), H(bcp)/rho(bcp), and |V(bcp)|/G(bcp), revealed that all types of bonding in EMFs exhibit a high degree of covalency, and the ionic model is reasonable only for the Ca-based EMFs. Metal-metal bonds with negative values of the electron-density Laplacian were found in Y(2)@C(82), Y(2)@C(79)N, Sc(4)O(2)@C(80), and anionic forms of La(2)@C(80). A delocalized nature of the metal-cage bonding results in a topological instability of the electron density in EMFs with an unpredictable number of metal-cage bond paths and large elipticity values.

  1. Trimetallic nitride template endohedral metallofullerenes: discovery, structural characterization, reactivity, and applications.

    PubMed

    Zhang, Jianyuan; Stevenson, Steven; Dorn, Harry C

    2013-07-16

    Shortly after the discovery of the carbon fullerene allotrope, C₆₀, researchers recognized that the hollow spheroidal shape could accommodate metal atoms, or clusters, which quickly led to the discovery of endohedral metallofullerenes (EMFs). In the past 2 decades, the unique features of EMFs have attracted broad interest in many fields, including inorganic chemistry, organic chemistry, materials chemistry, and biomedical chemistry. Some EMFs produce new metallic clusters that do not exist outside of a fullerene cage, and some other EMFs can boost the efficiency of magnetic resonance (MR) imaging 10-50-fold, in comparison with commercial contrast agents. In 1999, the Dorn laboratory discovered the trimetallic nitride template (TNT) EMFs, which consist of a trimetallic nitride cluster and a host fullerene cage. The TNT-EMFs (A₃N@C2n, n = 34-55, A = Sc, Y, or lanthanides) are typically formed in relatively high yields (sometimes only exceeded by empty-cage C₆₀ and C₇₀, but yields may decrease with increasing TNT cluster size), and exhibit high chemical and thermal stability. In this Account, we give an overview of TNT-EMF research, starting with the discovery of these structures and then describing their synthesis and applications. First, we describe our serendipitous discovery of the first member of this class, Sc₃N@Ih-C₈₀. Second, we discuss the methodology for the synthesis of several TNT-EMFs. These results emphasize the importance of chemically adjusting plasma temperature, energy, and reactivity (CAPTEAR) to optimize the type and yield of TNT-EMFs produced. Third, we review the approaches that are used to separate and purify pristine TNT-EMF molecules from their corresponding product mixtures. Although we used high-performance liquid chromatography (HPLC) to separate TNT-EMFs in early studies, we have more recently achieved facile separation based on the reduced chemical reactivity of the TNT-EMFs. These improved production yields and

  2. Preparation and characterization of two new water-soluble endohedral metallofullerenes as magnetic resonance imaging contrast agents.

    PubMed

    Zhang, Er-Yun; Shu, Chun-Ying; Feng, Lai; Wang, Chun-Ru

    2007-12-27

    Two new water-soluble Gd-containing endohedral metallofullerenes [ScxGd3-xN@C80OmOHn (x = 1, 2; m approximately 12; n approximately 26)] were synthesized in a simple one-step reaction and characterized by Fourier transform (FT)-IR as well as X-ray photoelectron spectroscopy (XPS). Their observed longitudinal relaxivities (R1) for water protons are 20.7 and 17.6 mM(-1) s(-1), respectively, which are significantly higher than that of the commercial magnetic resonance imaging (MRI) contrast agent (Gd-DTPA, 3.2 mM(-1) s(-1)). These results indicate these trimetallic nitride endohedral fullerenols are potential next-generation high-efficiency MRI contrast agents.

  3. Sm@C1(153491)-C94: A missing isomer from Sm@C94 mono-metallofullerenes

    NASA Astrophysics Data System (ADS)

    Zhao, Pei; Guo, Yi-Jun; Zhao, Rui-Sheng; Zhao, Xiang

    2016-01-01

    The Sm-containing endohedral metallofullerene (EMF) Sm@C94 has been investigated by quantum chemical and statistical thermodynamic methods. Sm@C1(153491)-C94 and Sm@C3v(153493)-C94 which both satisfy the isolated-pentagon rule (IPR) are exposed to possess considerable thermodynamic stabilities within the fullerene-formation temperature region (500-3000 K). Sm@C3v(153493)-C94 has been indeed determined experimentally, and a novel structure, Sm@C1(153491)-C94, is reported for the first time. These two isomers are related by a single Stone-Wales transformation. Meanwhile, frontier molecular orbital, natural electron configuration, and Mayer bond order analyses were employed to uncover their electronic properties. In addition, their optical spectra were simulated to support experimental identification and characterization.

  4. Endohedral metallofullerenes, M@C60 (M = Ca, Na, Sr): selective adsorption and sensing of open-shell NOx gases.

    PubMed

    Tawfik, Sherif Abdulkader; Cui, X Y; Ringer, S P; Stampfl, C

    2016-08-21

    Based on density-functional theory and non-equilibrium Green's function calculations, we demonstrate that endohedral metallofullerenes (EMFs) are reactive to open-shell gases, and therefore have the potential application as selective open-shell gas sensors. The adsorption of eight gas species (CO, H2O, H2S, NO2, NO, SO2, O2 and NH3) on three EMFs (M@C60, M = Ca, Na and Sr) shows that the adsorption energies of the EMFs towards NO2 and NO are significantly higher than the closed-shell species. Moreover, the high selectivity appears relatively insensitive to the inserted metal atoms. The calculated current-voltage characteristics of gold-M@C60-gold structures (M = Ca, Na) show that the adsorption of NO2 leads to significant change in conductivity, suggesting a potential application as an EMF gas resistive sensing device. PMID:27426253

  5. Endohedral metallofullerenes, M@C60 (M = Ca, Na, Sr): selective adsorption and sensing of open-shell NOx gases.

    PubMed

    Tawfik, Sherif Abdulkader; Cui, X Y; Ringer, S P; Stampfl, C

    2016-08-21

    Based on density-functional theory and non-equilibrium Green's function calculations, we demonstrate that endohedral metallofullerenes (EMFs) are reactive to open-shell gases, and therefore have the potential application as selective open-shell gas sensors. The adsorption of eight gas species (CO, H2O, H2S, NO2, NO, SO2, O2 and NH3) on three EMFs (M@C60, M = Ca, Na and Sr) shows that the adsorption energies of the EMFs towards NO2 and NO are significantly higher than the closed-shell species. Moreover, the high selectivity appears relatively insensitive to the inserted metal atoms. The calculated current-voltage characteristics of gold-M@C60-gold structures (M = Ca, Na) show that the adsorption of NO2 leads to significant change in conductivity, suggesting a potential application as an EMF gas resistive sensing device.

  6. Production and EPR characterization of exohedrally perfluoroalkylated paramagnetic lanthanum metallofullerenes: (La@C 82)-(C 8F 17) 2

    NASA Astrophysics Data System (ADS)

    Tagmatarchis, Nikos; Taninaka, Atsushi; Shinohara, Hisanori

    2002-04-01

    A strategy to chemically derivatize the outer sphere of endohedral metallofullerenes by using a fluorous synthesis-partitioning approach has been developed. The newly synthesized materials were found to be paramagnetic species and were characterized by electron paramagnetic resonance spectroscopy (EPR), laser desorption time-of-flight spectrometry (LD-TOF) and electronic absorption spectroscopy (UV-VIS-NIR). The fluorous-phase partitioning method (or liquid-liquid extraction), successfully applied for the first time in fullerene chemistry, aided by multi-stage recycling high performance liquid chromatography (HPLC) resulted in their isolation in isomer-free form. The present study opens the way to organic transformations of fullerene-based materials as a powerful separation technique.

  7. Theoretical Insight into the Ambiguous Endohedral Metallofullerene Er3C74: Covalent Interactions among Three Lanthanide Atoms.

    PubMed

    Guo, Yi-Jun; Zheng, Hong; Yang, Tao; Nagase, Shigeru; Zhao, Xiang

    2015-08-17

    All of C74-based endohedral metallofullerenes (EMFs) are found to be monometallofullerenes with the same D3h(14246)-C74 cage so far. An opening question is whether other C74 cages could survive during the production of some novel C74-EMFs. Theoretically, we studied the trimetallic endohedral fullerene Er3C74, the existence of which had been proven without any further characterizations. Two thermodynamically stable Er3C74 isomers were obtained, both of which could be expressed as Er3@C74, meaning that previously synthesized Er3C74 is indeed an endohedral trierbium fullerene. Besides the isomer with well-known D3h(14246)-C74 cage which obeys isolated pentagon rule (IPR), another one possesses the C1(13771)-C74 cage with two adjacent pentagons. Notably, it is the first time an endohedral metallofullerene containing the C1(13771)-C74 cage has been reported. Frontier orbitals analysis, bonding analysis in terms of quantum theory of atoms-in-molecule (QTAIM) and Mayer bond order, together with two-dimensional maps of electron localization function (ELF) and Laplacian of electron density of Er3@D3h(14246)-C74 and Er3@C1(13771)-C74 show obvious covalent interactions not only between metallic atoms and carbon cage but also among three erbium atoms. Finally, simulated IR spectra of Er3@D3h(14246)-C74 and Er3@C1(13771)-C74 were simulated, which should be useful to distinguish those two isomers. PMID:26230214

  8. Relevance of thermal effects in the formation of endohedral metallofullerenes: the case of Gd3N@C(s)(39663)-C82 and other related systems.

    PubMed

    Mulet-Gas, Marc; Rodríguez-Fortea, Antonio; Echegoyen, Luis; Poblet, Josep M

    2013-02-18

    Thermal contributions to the free energy have to be taken into account to rationalize the formation of Gd(3)N@C(s)(39663)-C(82), a nitride endohedral metallofullerene that shows a carbon cage with two fused pentagons which is not predicted to have the lowest electronic energy among the isomers of C(82). The lower symmetry and the larger number of pyracylene units of C(s)(39663)-C(82) with respect to the cage in the lowest-energy metallofullerene, C(2v)(39705)-C(82), favor its formation at high temperatures, as seen for other similar cage isomers that encapsulate metal clusters within the C(80) and C(82) families. These cages, which share common motifs with the prototypical I(h)(7)-C(80), are all related by C(2) insertions/extrusions and Stone-Wales transformations.

  9. Isolated pentagon rule violating endohedral metallofullerenes explained using the Hückel rule: a statistical mechanical study of the C84 Isomeric Set.

    PubMed

    Fuhrer, Timothy J; Lambert, Angel M

    2015-01-30

    Fullerenes and their structure and stability have been a major topic of discussion and research since their discovery nearly 30 years ago. The isolated pentagon rule (IPR) has long served as a guideline for predicting the most stable fullerene cages. More recently, endohedral metallofullerenes have been discovered that violate the IPR. This article presents a systematic, temperature dependent, statistical thermodynamic study of the 24 possible IPR isomers of C84 as well as two of the experimentally known non-IPR isomers (51365 and 51383), at several different charges (0, -2, -4, and -6). From the results of this study, we conclude that the Hückel rule is a valid simpler explanation for the stability of fused pentagons in endohedral metallofullerenes.

  10. Production and isolation of Ca@C{sup 82} (I-IV) and Ca@C{sup 84} (I,II) metallofullerenes

    SciTech Connect

    Xu, Z.; Nakane, Tomoyasu; Shinohara, Hisanori

    1996-11-13

    Almost all of the metallofullerenes prepared so far have incorporated La, Y, and Sc or several lanthanide elements such as Gd and Pr. The endohederal structures of Y@C{sup 82} and Sc{sup 2}@C{sup 84} have been finally confirmed by recent synchrotron X-ray powder diffraction and {sup 13}C NMR studies, respectively. This paper reports the first production, isolation, and spectroscopic study on several structural isomers of Ca@C{sup 82} and Ca@C{sup 84}. The details of the production and separation/isolation of endohedral metallofullerenes have been described elsewhere. Briefly, soot-containing Ca@C{sup 82}, Ca@C{sup 84}, and other calcium metallofullerenes was produced in direct-current (350-400 A) arc-discharge of a calcium/graphite composite rod (Toyo Tanso Co. Ltd., 12.5 x 12.5 x 240 mm, 0.3 atomic %) under He flow (8-10 L/min) at 50 Torr. The soot was collected under totally anaerobic conditions and was extracted by CS{sup 2}. The Ca@C{sup 82} and Ca@C{sup 84} fullerenes were separated by the two-stage high-performance liquid chromatography (HPLC) method. The retention times of the present isomers are very close to each other; therefore the final isolation of the isomers was achieved by recycling (2-9 times) the HPLC process to increase the resolution. 23 refs., 3 figs.

  11. Application of MCD spectroscopy and TD-DFT to endohedral metallofullerenes for characterization of their electronic transitions.

    PubMed

    Yamada, Michio; Slanina, Zdenek; Mizorogi, Naomi; Muranaka, Atsuya; Maeda, Yutaka; Nagase, Shigeru; Akasaka, Takeshi; Kobayashi, Nagao

    2013-03-14

    We describe, for the first time, the application of magnetic circular dichroism (MCD) spectroscopy and time-dependent density functional theory (TD-DFT) calculations using B3LYP and M06-2X functionals to characterize the electronic transitions of endohedral metallofullerenes (EMFs). Results revealed that the electronic transitions of La@C(2v)-C(82), La(2)@I(h)-C(80), and Sc(3)N@I(h)-C(80) can be assigned using these techniques. Particularly, a difference in the electronic transitions between La(2)@I(h)-C(80) and Sc(3)N@I(h)-C(80), which is invisible in absorption spectra, was observed clearly in MCD spectra. The observed MCD bands agree well with the oscillator strengths calculated using the B3LYP functional. In addition, the MCD bands of La(2)@I(h)-C(80) were altered upon [5,6]-addition, demonstrating that the MCD spectroscopy is sensitive to chemical functionalization of EMFs, and that it is therefore powerful to distinguish [5,6]-adducts from pristine La(2)@I(h)-C(80), although no marked difference exists in their absorption spectra.

  12. Low-toxic and safe nanomaterials by surface-chemical design, carbon nanotubes, fullerenes, metallofullerenes, and graphenes.

    PubMed

    Yan, Liang; Zhao, Feng; Li, Shoujian; Hu, Zhongbo; Zhao, Yuliang

    2011-02-01

    The toxicity grade for a bulk material can be approximately determined by three factors (chemical composition, dose, and exposure route). However, for a nanomaterial it depends on more than ten factors. Interestingly, some nano-factors (like huge surface adsorbability, small size, etc.) that endow nanomaterials with new biomedical functions are also potential causes leading to toxicity or damage to the living organism. Is it possible to create safe nanomaterials if such a number of complicated factors need to be regulated? We herein try to find answers to this important question. We first discuss chemical processes that are applicable for nanosurface modifications, in order to improve biocompatibility, regulate ADME, and reduce the toxicity of carbon nanomaterials (carbon nanotubes, fullerenes, metallofullerenes, and graphenes). Then the biological/toxicological effects of surface-modified and unmodified carbon nanomaterials are comparatively discussed from two aspects: the lowered toxic responses or the enhanced biomedical functions. We summarize the eight biggest challenges in creating low-toxicity and safer nanomaterials and some significant topics of future research needs: to find out safer nanofactors; to establish controllable surface modifications and simpler chemistries for low-toxic nanomaterials; to explore the nanotoxicity mechanisms; to justify the validity of current toxicological theories in nanotoxicology; to create standardized nanomaterials for toxicity tests; to build theoretical models for cellular and molecular interactions of nanoparticles; and to establish systematical knowledge frameworks for nanotoxicology.

  13. Low-toxic and safe nanomaterials by surface-chemical design, carbon nanotubes, fullerenes, metallofullerenes, and graphenes

    NASA Astrophysics Data System (ADS)

    YanEqual Contribution, Liang; Zhao, Feng; Li, Shoujian; Hu, Zhongbo; Zhao, Yuliang

    2011-02-01

    The toxicity grade for a bulk material can be approximately determined by three factors (chemical composition, dose, and exposure route). However, for a nanomaterial it depends on more than ten factors. Interestingly, some nano-factors (like huge surface adsorbability, small size, etc.) that endow nanomaterials with new biomedical functions are also potential causes leading to toxicity or damage to the living organism. Is it possible to create safe nanomaterials if such a number of complicated factors need to be regulated? We herein try to find answers to this important question. We first discuss chemical processes that are applicable for nanosurface modifications, in order to improve biocompatibility, regulate ADME, and reduce the toxicity of carbon nanomaterials (carbon nanotubes, fullerenes, metallofullerenes, and graphenes). Then the biological/toxicological effects of surface-modified and unmodified carbon nanomaterials are comparatively discussed from two aspects: the lowered toxic responses or the enhanced biomedical functions. We summarize the eight biggest challenges in creating low-toxicity and safer nanomaterials and some significant topics of future research needs: to find out safer nanofactors; to establish controllable surface modifications and simpler chemistries for low-toxic nanomaterials; to explore the nanotoxicity mechanisms; to justify the validity of current toxicological theories in nanotoxicology; to create standardized nanomaterials for toxicity tests; to build theoretical models for cellular and molecular interactions of nanoparticles; and to establish systematical knowledge frameworks for nanotoxicology.

  14. Electronic structure and magnetic properties of endohedral metallofullerenes based on mixed metal cluster within fullerene cage with trifluoromethyl groups

    NASA Astrophysics Data System (ADS)

    Suzuki, A.; Oku, T.

    2013-04-01

    Endohedral metallofullerenes based on encapsulated nitride scandium cluster within C80 fullerene cage with trifluoromethyl group of CF3 were characterized as a candidate model for controlling nuclear spin gate in NMR quantum computers. Effects of yttrium in nitride scandium cluster of Sc3N within the fullerene cage with trifluoromethyl group on electronic structures and magnetic properties were investigated. Electronic structure and chemical shifts in 45Sc, 89Y, 19F, 13C and 14N atoms were calculated by quantum calculation using density functional theory. Addition of yttrium in nitride scandium cluster of Sc3N within the fullerene cage provided a different position of chemical shift in 45Sc, 89Y, 19F, 13C and 14N atoms. This result was originated in magnetic interaction with spin-local interaction, dipole-dipole interaction and nuclear quadrupole interaction based on nuclear quadrupole moment and asymmetry of electron field gradient with a bias value of charge and spin density distribution of spd-hybrid orbital by inductive effect.

  15. Electronic transport properties of the first all-boron fullerene B40 and its metallofullerene Sr@B40.

    PubMed

    An, Yipeng; Zhang, Mengjun; Wu, Dapeng; Fu, Zhaoming; Wang, Tianxing; Xia, Congxin

    2016-04-28

    The newly-discovered B40 is the first experimentally observed all-boron fullerene and has potential applications in molecular devices. Herein, we report the electronic transport properties of B40 and its metallofullerene, Sr@B40, using the first-principles technique. We obtain the conductance of B40 fullerene, which is about 130 μS and can be increased by embedding a strontium metal atom in the cage due to the decreased energy gap. Both the current-voltage (I-V) curves of B40 and Sr@B40 present perfect linear characteristics. Intuitively, it is assumed that the electron currents pass through the B40 fullerene mainly along the surface B-B bonds, while two types of new B-Sr-B bond currents and B→Sr→B hopping currents are presented for Sr@B40 due to Sr acting as a bridge. This study provides valuable information for the potential applications of future borospherene-based molecular devices. PMID:27067381

  16. A complete guide on the influence of metal clusters in the Diels-Alder regioselectivity of I(h)-C80 endohedral metallofullerenes.

    PubMed

    Garcia-Borràs, Marc; Osuna, Sílvia; Luis, Josep M; Swart, Marcel; Solà, Miquel

    2013-10-25

    The chemical functionalization of endohedral metallofullerenes (EMFs) has aroused considerable interest due to the possibility of synthesizing new species with potential applications in materials science and medicine. Experimental and theoretical studies on the reactivity of endohedral metallofullerenes are scarce. To improve our understanding of the endohedral metallofullerene reactivity, we have systematically studied with DFT methods the Diels-Alder cycloaddition between s-cis-1,3-butadiene and practically all X@I(h)-C80 EMFs synthesized to date: X=Sc3N, Lu3N, Y3N, La2, Y3, Sc3C2, Sc4C2, Sc3CH, Sc3NC, Sc4O2 and Sc4O3. We have studied both the thermodynamic and kinetic regioselectivity, taking into account the free rotation of the metallic cluster inside the fullerene. This systematic study has been made possible through the use of the frozen cage model (FCM), a computationally cheap approach to accurately predicting the exohedral regioselectivity of cycloaddition reactions in EMFs. Our results show that the EMFs are less reactive than the hollow I(h)-C80 cage. Except for the Y3 cluster, the additions occur predominantly at the [5,6] bond. In many cases, however, a mixture of the two possible regioisomers is predicted. In general, [6,6] addition is favored in EMFs that have a larger charge transfer from the metal cluster to the cage or a voluminous metal cluster inside. The present guide represents the first complete and exhaustive investigation of the reactivity of I(h)-C80-based EMFs.

  17. Metallofullerenes encaging mixed-metal clusters: synthesis and structural studies of Gdx Ho3-x N@C80 and Gdx Lu3-x N@C80.

    PubMed

    Zhang, Zhuxia; Liu, Yang; Han, Peide; Zhuang, Shengyi; Wang, Taishan; Luo, Shuchang; Xu, Bingshe

    2015-02-01

    Metallofullerenes of Gdx Ho3-x N@C80 and Gdx Lu3-x N@C80 encapsulating mixed-metal nitride clusters were synthesized. Spectroscopic characterization of Gdx Ho3-x N@C80 and Gdx Lu3-x N@C80 was employed to reveal their structural and vibrational properties. The structural properties of these species were analyzed by using theoretical calculations. The studies of Gdx Ho3-x N@C80 and Gdx Lu3-x N@C80 laid the foundations for these species to be used as multifunctional molecules.

  18. Bingel-Hirsch addition on non-isolated-pentagon-rule Gd3N@C2n (2n = 82 and 84) metallofullerenes: products under kinetic control.

    PubMed

    Alegret, Núria; Salvadó, Patricia; Rodríguez-Fortea, Antonio; Poblet, Josep M

    2013-10-01

    Bingel-Hirsch reactions on fullerenes take place under kinetic control. We here predict, by means of DFT methodology, the products of the Bingel-Hirsch addition on non-isolated-pentagon-rule (non-IPR) metallofullerenes Gd3N@C2n (2n = 82, 84), as modeled by closed-shell Y3N@C2n systems. Adducts on [6,6] B-type bonds placed near the pentalene unit are predicted for the two cages, as found for other non-IPR endohedral fullerenes such as Sc3N@C68.

  19. Self-assembly of endohedral metallofullerenes: a decisive role of cooling gas and metal-carbon bonding

    NASA Astrophysics Data System (ADS)

    Deng, Qingming; Heine, Thomas; Irle, Stephan; Popov, Alexey A.

    2016-02-01

    The endohedral metallofullerene (EMF) self-assembly process in Sc/carbon vapor in the presence and absence of an inert cooling gas (helium) is systematically investigated using quantum chemical molecular dynamics simulations. It is revealed that the presence of He atoms accelerates the formation of pentagons and hexagons and reduces the size of the self-assembled carbon cages in comparison with analogous He-free simulations. As a result, the Sc/C/He system simulations produce a larger number of successful trajectories (i.e. leading to Sc-EMFs) with more realistic cage-size distribution than simulations of the Sc/C system. The main Sc encapsulation mechanism involves nucleation of several hexagons and pentagons with Sc atoms already at the early stages of carbon vapor condensation. In such proto-cages, both Sc-C σ-bonds and coordination bonds between Sc atoms and the π-system of the carbon network are present. Sc atoms are thus rather labile and can move along the carbon network, but the overall bonding is sufficiently strong to prevent dissociation even at temperatures around 2000 kelvin. Further growth of the fullerene cage results in the encapsulation of one or two Sc atoms within the fullerene. In agreement with experimental studies, an extension of the simulations to Fe and Ti as the metal component showed that Fe-EMFs are not formed at all, whereas Ti is prone to form Ti-EMFs with small cage sizes, including Ti@C28-Td and Ti@C30-C2v(3).The endohedral metallofullerene (EMF) self-assembly process in Sc/carbon vapor in the presence and absence of an inert cooling gas (helium) is systematically investigated using quantum chemical molecular dynamics simulations. It is revealed that the presence of He atoms accelerates the formation of pentagons and hexagons and reduces the size of the self-assembled carbon cages in comparison with analogous He-free simulations. As a result, the Sc/C/He system simulations produce a larger number of successful trajectories (i

  20. Enhanced 1520 nm photoluminescence from Er3+ ions in di-erbium-carbide metallofullerenes (Er2C2)@C82 (isomers I, II, and III).

    PubMed

    Ito, Yasuhiro; Okazaki, Toshiya; Okubo, Shingo; Akachi, Masahiro; Ohno, Yutaka; Mizutani, Takashi; Nakamura, Tetsuya; Kitaura, Ryo; Sugai, Toshiki; Shinohara, Hisanori

    2007-12-01

    Di-erbium and di-erbium-carbide endohedral metallofullerenes with a C(82) cage such as Er(2)@C(82) (isomers I, II, and III) and (Er(2)C(2))@C(82) (isomers I, II, and III) have been synthesized and chromatographically isolated (99%). The structures of Er(2)@C(82) (I, II, III) and (Er(2)C(2))@C(82) (I, II, III) metallofullerenes are characterized by comparison with the UV-vis-NIR absorption spectra of (Y(2)C(2))@C(82) (I, II, III), where molecular symmetries of the structures are determined to be C(s), C(2v) and C(3v), respectively. Furthermore, enhanced near-infrared photoluminescence (PL) at 1520 nm from Er(3+) ions in Er(2)@C(82) (I, III) and (Er(2)C(2))@C(82) (I, III) have been observed at room temperature. The PL intensities have been shown to depend on the symmetry of the C(82) cage. In particular, the PL intensity of (Er(2)C(2))@C(82) (III) has been the strongest among the isomers of Er(2)@C(82) and (Er(2)C(2))@C(82). Optical measurements indicate that the PL properties of Er(2)@C(82) (I, II, III) and (Er(2)C(2))@C(82) (I, II, III) correlate strongly with the absorbance at 1520 nm and the HOMO-LUMO energy gap of the C(82) cage.

  1. Chemical understanding of carbide cluster metallofullerenes: a case study on Sc2C2@C2v(5)-C80 with complete X-ray crystallographic characterizations.

    PubMed

    Kurihara, Hiroki; Lu, Xing; Iiduka, Yuko; Nikawa, Hidefumi; Mizorogi, Naomi; Slanina, Zdenek; Tsuchiya, Takahiro; Nagase, Shigeru; Akasaka, Takeshi

    2012-02-15

    Little is known about the chemical properties of carbide cluster metallofullerenes (CCMFs). Here we report the photochemical reaction of a newly assigned CCMF Sc(2)C(2)@C(2v)(5)-C(80) with 2-adamantane-2,3-[3H]-diazirine (AdN(2), 1), which provides a carbene reagent under irradiation. Five monoadduct isomers (2a-2e), with respective abundances of 20%, 40%, 25%, 5%, and 10%, were isolated and characterized with a combination of experimental techniques including unambiguous single-crystal X-ray crystallography. Results show that the two Sc atoms of the bent Sc(2)C(2) cluster tend to move in most cases, whereas the C(2)-unit is almost fixed. Accordingly, it is difficult to explain the addition patterns by considering the strain and charge density on the cage with a fixed cluster, and thus a moving cluster may account for the addition patterns. These results show that the situation of CCMFs is more complicated than those in other metallofullerenes. Furthermore, a thermal isomerization process from 2b to 2c was observed, confirming that the most abundant isomer 2b is a kinetically favored adduct. Finally, it is revealed that the electronic and electrochemical properties of pristine Sc(2)C(2)@C(2v)(5)-C(80) have been markedly altered by exohedral modification.

  2. Bonding between strongly repulsive metal atoms: an oxymoron made real in a confined space of endohedral metallofullerenes.

    PubMed

    Popov, Alexey A; Avdoshenko, Stas M; Pendás, Angel Martín; Dunsch, Lothar

    2012-08-21

    Endohedral metallofullerenes (EMFs) are able to encapsulate up to four metal atoms. In EMFs, metal atoms are positively charged because of the electron transfer from the endohedral metal atoms to the carbon cage. It results in the strong Coulomb repulsion between the positively charged ions trapped in the confined inner space of the fullerene. At the same time, in many EMFs, such as Lu(2)@C(76), Y(2)@C(79)N, M(2)@C(82) (M = Sc, Y, Lu, etc.), Y(3)@C(80), or Sc(4)O(2)@C(80), metals do not adopt their highest oxidation states, thus yielding a possibility of the covalent metal-metal bonding. In some other EMFs (e.g., La(2)@C(80)), metal-metal bonding evolves as the result of the electrochemical or chemical reduction, which leads to the population of the metal-based LUMO with pronounced metal-metal bonding character. This article highlights different aspects of the metal-metal bonding in EMFs. It is concluded that the valence state of the metal atoms in dimetallofullerenes is not dependent on their third ionization potential, but is determined by their ns(2)(n- 1)d(1)→ns(1)(n- 1)d(2) excitation energies. Peculiarities of the metal-metal bonding in EMFs are described in terms of molecular orbital analysis as well as topological approaches such as Quantum Theory of Atoms in Molecules and Electron Localization Function. Interplay of Coulomb repulsion and covalent bonding is analyzed in the framework of the Interacting Quantum Atom approach.

  3. Self-assembly of endohedral metallofullerenes: a decisive role of cooling gas and metal-carbon bonding.

    PubMed

    Deng, Qingming; Heine, Thomas; Irle, Stephan; Popov, Alexey A

    2016-02-14

    The endohedral metallofullerene (EMF) self-assembly process in Sc/carbon vapor in the presence and absence of an inert cooling gas (helium) is systematically investigated using quantum chemical molecular dynamics simulations. It is revealed that the presence of He atoms accelerates the formation of pentagons and hexagons and reduces the size of the self-assembled carbon cages in comparison with analogous He-free simulations. As a result, the Sc/C/He system simulations produce a larger number of successful trajectories (i.e. leading to Sc-EMFs) with more realistic cage-size distribution than simulations of the Sc/C system. The main Sc encapsulation mechanism involves nucleation of several hexagons and pentagons with Sc atoms already at the early stages of carbon vapor condensation. In such proto-cages, both Sc-C σ-bonds and coordination bonds between Sc atoms and the π-system of the carbon network are present. Sc atoms are thus rather labile and can move along the carbon network, but the overall bonding is sufficiently strong to prevent dissociation even at temperatures around 2000 kelvin. Further growth of the fullerene cage results in the encapsulation of one or two Sc atoms within the fullerene. In agreement with experimental studies, an extension of the simulations to Fe and Ti as the metal component showed that Fe-EMFs are not formed at all, whereas Ti is prone to form Ti-EMFs with small cage sizes, including Ti@C28-Td and Ti@C30-C2v(3).

  4. Metallofullerene-based Nanoplatform for Brain Tumor Brachytherapy and Longitudinal Imaging in a Murine Orthotopic Xenograft Model

    PubMed Central

    Shultz, Michael D.; Wilson, John D.; Fuller, Christine E.; Zhang, Jianyuan; Dorn, Harry C.

    2011-01-01

    Purpose: To demonstrate in an orthotopic xenograft brain tumor model that a functionalized metallofullerene (f-Gd3N@C80) can enable longitudinal tumor imaging and, when radiolabeled with lutetium 177 (177Lu) and tetraazacyclododecane tetraacetic acid (DOTA) (177Lu-DOTA-f-Gd3N@C80), provide an anchor to deliver effective brachytherapy. Materials and Methods: All experiments involving the use of mice were carried out in accordance with protocols approved by the institutional animal care and use committee. Human glioblastoma U87MG cells were implanted by using stereotactic procedures into the brains of 37 female athymic nude-Foxn1nu mice and allowed to develop into a tumor for 8 days. T1- and T2-weighted magnetic resonance (MR) imaging was performed in five mice. Biodistribution studies were performed in 12 mice at four time points over 7 days to evaluate gadolinium content. Survival studies involved 20 mice that received infusion of a nanoplatform by means of convection-enhanced delivery (CED) 8 days after tumor implantation. Mice in survival studies were divided into two groups: one comprised untreated mice that received f-Gd3N@C80 alone and the other comprised mice treated with brachytherapy that received 1.11 MBq of 177Lu-DOTA-f-Gd3N@C80. Survival data were evaluated by using Kaplan-Meier statistical methods. Results: MR imaging showed extended tumor retention (25.6% ± 1.2 of the infused dose at 52 days, confirmed with biodistribution studies) of the f-Gd3N@C80 nanoplatform, which enabled longitudinal imaging. Successful coupling of 177Lu to the f-Gd3N@C80 surface was achieved by using a bifunctional macrocyclic chelator. The extended tumor retention allowed for effective brachytherapy, as indicated by extended survival time (>2.5 times that of the untreated group) and histologic signs of radiation-induced tumor damage. Conclusion: The authors have developed a multimodal nanoplatform and have demonstrated longitudinal tumor imaging, prolonged intratumoral probe

  5. Effect of cage charges on multiphoton absorptions: first-principles study on metallofullerenes Sc(2)C(2)@C(68) and Sc(3)N@C(68).

    PubMed

    Cheng, W-D; Hu, H; Wu, D-S; Wang, J-Y; Huang, S-P; Xe, Z; Zhang, H

    2009-05-21

    A combined method of the time-dependent density functional theory (TDDFT) and sum-overstate (SOS) formula was implemented to model multiphoton absorption spectra, including two-photon absorption (2PA) and three-photon absorption (3PA), of Sc(2)C(2)@C(68) and Sc(3)N@C(68) endohedral metallofullerenes (EMFs). This method has been proved to be effective by comparisons between the calculated and experimental results of trans-4,4'-bis[diphenylamino]stilbene. It was found that the multiphoton absorption cross sections were larger for Sc(2)C(2)@C(68) than that of Sc(3)N@C(68). The electronic origin of multiphoton absorption has been identified with respect to the molecular orbitals involved in charge transfer process. It shows that the increase of pi-charges on the cage of C(68) results in a large multiphoton absorption cross section in EMFs.

  6. First soluble M@C60 derivatives provide enhanced access to metallofullerenes and permit in vivo evaluation of Gd@C60[C(COOH)2]10 as a MRI contrast agent.

    PubMed

    Bolskar, Robert D; Benedetto, Angelo F; Husebo, Lars O; Price, Roger E; Jackson, Edward F; Wallace, Sidney; Wilson, Lon J; Alford, J Michael

    2003-05-01

    M@C(60) and related endohedral metallofullerenes comprise a significant portion of the metallofullerene yield in the traditional arc synthesis, but their chemistry and potential applications have been largely overlooked because of their sparse solubility. In this work, procedures are described to solublize Gd@C(60) species for the first time by forming the derivative, Gd@C(60)[C(COOCH(2)CH(3))(2)](10), and its hydrolyzed water-soluble form, Gd@C(60)[C(COOH)(2)](10). Imparting water solubility to Gd@C(60) permits its evaluation as a magnetic resonance imaging (MRI) contrast agent. Relaxometry measurements for Gd@C(60)[C(COOH)(2)](10) reveal it to possess a relaxivity (4.6 mM(-1) s(-1) at 20 MHz and 40 degrees C) comparable to that of commercially available Gd(III) chelate-based MRI agents. An in vivo MRI biodistribution study in a rodent model reveals Gd@C(60)[C(COOH)(2)](10) to possess the first non-reticuloendothelial system (RES) localizing behavior for a water-soluble endohedral metallofullerene species, consistent with its lack of intermolecular aggregation in solution as determined by light-scattering measurements. This first derivatization and use of a M@C(60) species suggests new potential for metallofullerene technologies by reducing reliance on the chromatographic purification procedures normally employed for the far less abundant M@C(82) and related endohedrals. The recognition that water-soluble fullerene derivatives can be designed to avoid high levels of RES uptake is an important step toward fullerene-based pharmaceutical development.

  7. Entrapping a Group-VB Transition Metal, Vanadium, within an Endohedral Metallofullerene: V(x)Sc(3-x)N@I(h)-C80 (x = 1, 2).

    PubMed

    Wei, Tao; Wang, Song; Lu, Xing; Tan, Yuanzhi; Huang, Jing; Liu, Fupin; Li, Qunxiang; Xie, Suyuan; Yang, Shangfeng

    2016-01-13

    So far the entrapped metals for the isolated endohedral metallofullerenes (EMFs) are primarily limited to rare earth metals, whereas except group-IVB metals, whether it is possible to entrap other d-block transition metals remains unclear. Herein we report the successful entrapment of the group-VB transition metal vanadium(V) into fullerene cage, affording the heretofore unknown V-containing EMFs. Two novel V-containing EMFs--V(x)Sc(3-x)N@C80 (x = 1, 2)--were isolated, and their molecular structures were unambiguously determined by X-ray crystallography to be I(h)(7)-C80 cage entrapping the planar VSc2N/V2ScN clusters. V(x)Sc(3-x)N@I(h)(7)-C80 (x = 1, 2) were further characterized by UV-vis-NIR and ESR spectroscopies and electrochemistry, revealing that the electronic and magnetic properties of V(x)Sc(3-x)N@I(h)(7)-C80 (x = 1, 2) are tunable upon varying the number of entrapped V atoms (i.e., x value). The molecular structures and electronic properties of V(x)Sc(3-x)N@I(h)(7)-C80 (x = 1, 2) were further compared with those of the reported analogous EMFs based on lanthanide metals and the adjacent group-IVB transition metal Ti, revealing the peculiarity of the group-VB transition metal V-based EMFs. PMID:26645852

  8. The Frozen Cage Model: A Computationally Low-Cost Tool for Predicting the Exohedral Regioselectivity of Cycloaddition Reactions Involving Endohedral Metallofullerenes.

    PubMed

    Garcia-Borràs, Marc; Romero-Rivera, Adrian; Osuna, Sílvia; Luis, Josep M; Swart, Marcel; Solà, Miquel

    2012-05-01

    Functionalization of endohedral metallofullerenes (EMFs) is an active line of research that is important for obtaining nanomaterials with unique properties that might be used in a variety of fields, ranging from molecular electronics to biomedical applications. Such functionalization is commonly achieved by means of cycloaddition reactions. The scarcity of both experimental and theoretical studies analyzing the exohedral regioselectivity of cycloaddition reactions involving EMFs translates into a poor understanding of the EMF reactivity. From a theoretical point of view, the main obstacle is the high computational cost associated with this kind of studies. To alleviate the situation, we propose an approach named the frozen cage model (FCM) based on single point energy calculations at the optimized geometries of the empty cage products. The FCM represents a fast and computationally inexpensive way to perform accurate qualitative predictions of the exohedral regioselectivity of cycloaddition reactions in EMFs. Analysis of the Dimroth approximation, the activation strain or distortion/interaction model, and the noncluster energies in the Diels-Alder cycloaddition of s-cis-1,3-butadiene to X@D3h-C78 (X = Ti2C2, Sc3N, and Y3N) EMFs provides a justification of the method.

  9. Regiospecific coordination of Re(3) clusters with the sumanene-type hexagons on endohedral metallofullerenes and higher fullerenes that provides an efficient separation method.

    PubMed

    Chen, Chia-Hsiang; Lin, Dong-Yui; Yeh, Wen-Yann

    2014-05-01

    The reactions of [(μ-H)3 Re3 (CO)11 (NCMe)] with Sc2 @C82 -C3v (8), Sc2 C2 @C80 -C2v (5), Sc2 O@C82 -Cs (6), C86 -C2 (17), and C86 -Cs (16) have been carried out to produce face-capping cluster complexes. The Re3 triangles are found to bind to the sumanene-type hexagons on the fullerene surface regiospecifically. In contrast, Sc3 N@C78 -D3h (5) and Sc3 N@C80 -Ih show no reactivity toward [(μ-H)3 Re3 (CO)11 (NCMe)], probably due to electronic and steric factors. These complexes can be easily purified by using HPLC. Carbonylation of each complex releases the corresponding higher fullerene or endohedral metallofullerene in pure form. Remarkably, the C86 -C2 (17) and C86 -Cs (16) isomers were successively separated through Re3 cluster complexation/decomplexation. This unique bonding feature may provide an attractive general strategy to purify as yet unresolved fullerene mixtures.

  10. (2 + 2) Cycloaddition of Benzyne to Endohedral Metallofullerenes M3N@C80 (M = Sc, Y): A Rotating-Intermediate Mechanism.

    PubMed

    Yang, Tao; Nagase, Shigeru; Akasaka, Takeshi; Poblet, Josep M; Houk, K N; Ehara, Masahiro; Zhao, Xiang

    2015-06-01

    The reaction mechanism and origin of regioselectivity of (2 + 2) cycloadditions of benzyne to endohedral metallofullerenes M3N@C80 (M = Sc, Y) were investigated with density functional calculations. The reaction was demonstrated to follow a diradical mechanism rather than a carbene mechanism, in which the formation of the diradical intermediate is the rate-determining step. Through rotation of benzyne moiety on the fullerene surface, the diradical intermediate on 566 site could isomerize to two new diradical intermediates which give rise to two distinct [5,6] and [6,6] benzoadducts, respectively. However, the diradical intermediate on 666 site only produces the [6,6] benzoadduct. The nature of the endohedral cluster not only influences the regioselectivity, but also determines the cycloadduct geometry. For Sc3N@C80, the [5,6] benzoadduct is preferred kinetically and thermodynamically, whereas in the case of Y3N@C80, both [5,6] and [6,6] benzoadducts are favorable. In contrast to closed-cage benzoadducts of Sc3N@C80, Y3N@C80 affords open-cage benzoadducts, making it the first example that the endohedral cluster could alter cycloadducts from the closed cage to open cage. With further analysis, it is revealed that the origin of regioselectivity results from the local strain energy of the fullerene cage.

  11. X-ray structures of Sc2C2@C2n (n = 40-42): in-depth understanding of the core-shell interplay in carbide cluster metallofullerenes.

    PubMed

    Kurihara, Hiroki; Lu, Xing; Iiduka, Yuko; Nikawa, Hidefumi; Hachiya, Makoto; Mizorogi, Naomi; Slanina, Zdenek; Tsuchiya, Takahiro; Nagase, Shigeru; Akasaka, Takeshi

    2012-01-01

    X-ray analyses of the cocrystals of a series of carbide cluster metallofullerenes Sc(2)C(2)@C(2n) (n = 40-42) with cobalt(II) octaethylporphyrin present new insights into the molecular structures and cluster-cage interactions of these less-explored species. Along with the unambiguous identification of the cage structures for the three isomers of Sc(2)C(2)@C(2v)(5)-C(80), Sc(2)C(2)@C(3v)(8)-C(82), and Sc(2)C(2)@D(2d)(23)-C(84), a clear correlation between the cluster strain and cage size is observed in this series: Sc-Sc distances and dihedral angles of the bent cluster increase along with cage expansion, indicating that the bending strain within the cluster makes it pursue a planar structure to the greatest degree possible. However, the C-C distances within Sc(2)C(2) remain unchanged when the cage expands, perhaps because of the unusual bent structure of the cluster, preventing contact between the cage and the C(2) unit. Moreover, analyses revealed that larger cages provide more space for the cluster to rotate. The preferential formation of cluster endohedral metallofullerenes for scandium might be associated with its small ionic radius and the strong coordination ability as well.

  12. Magnetism of the endohedral metallofullerenes M@C82 (M=Gd,Dy) and the corresponding nanoscale peapods: Synchrotron soft x-ray magnetic circular dichroism and density-functional theory calculations

    NASA Astrophysics Data System (ADS)

    Kitaura, R.; Okimoto, H.; Shinohara, H.; Nakamura, T.; Osawa, H.

    2007-11-01

    Synchrotron soft x-ray magnetic circular dichroism (SXMCD) spectroscopy at the Gd and Dy M5 edges is reported on endohedral metallofullerenes ( M@C82 , M=Gd and Dy) and the corresponding nanopeapods [ (M@C82)@SWNT , SWNT represents single wall carbon nanotube] in a temperature range between 10 and 40K . The magnetic moment has also been determined by theoretical calculations, which are based on the Hartree-Fock approximation with relativistic corrections. Because of the element-specific measurement of SXMCD, magnetization processes of Gd and Dy ions of nanopeapods have been selectively observed. The temperature dependence of magnetic moments of the metallofullerenes and nanopeapods follows the Curie-Weiss law with a small Weiss temperature, indicating that the magnetic interaction between encapsulated rare-earth metal atoms is relatively weak. Although the observed differences in Curie constants and Weiss temperatures between Gd@C82 and (Gd@C82)@SWNT are small, those of Dy@C82 and (Dy@C82)@SWNT are significant. This observation is consistently explained by charge transfer-induced crystal-field effects.

  13. Mass spectroscopic and ESR characterization of soluble yttrium-containing metallofullerenes YC{sub 82} and Y{sub 2}C{sub 82}

    SciTech Connect

    Shinohara, Hisanori; Sato, Hiroyasu; Saito, Yahachi

    1992-04-30

    Solvent soluble, yttrium-containing fullerenes are extracted from yttrium/carbon soot produced by the carbon-arc fullerene generation method. An yttrium-graphite composite yields solvent extractable molecules such as YC{sub 82} and Y{sub 2}C{sub 82} as evidenced by a laser desorption time-of-flight (LD-TOF) mass spectroscopic analysis of the extracts. This is consistent with the very recent results by Smalley et al. where YC{sub 82} and Y{sub 2}C{sub 82} are prepared by laser vaporization of yttrium-graphite rods. The present extracts are souble by both toluene and carbon disulfide, but the solubility is much higher is CS{sub 2} than toluene. LD-TOF mass spectra also show the presence of a series of peaks due to the dimetallofullerens Y{sub 2}C{sub 2n}(2n = 84; 90 {le} 2n {le}140). The metallofullerenes YC{sub 60} and YC{sub 70} are not observed in the mildest possible LD conditions under which YC{sub 82} and the dimetallofullerenes Y{sub 2}C{sub 82} and Y{sub 2}C{sub 2n} are readily observed. ESR spectral results are also reported for the present yttrium-fullerene complexes and indicate the charge separation state of Y{sup 3+}C{sub 82}{sup 3-} as has been found for La{sup 3+}C{sub 82}{sup 3-} by Johnson et. al. 13 refs., 4 figs.

  14. Gd@C82 metallofullerenes for neutron capture therapy—fullerene solubilization by poly(ethylene glycol)-block-poly(2-(N, N-diethylamino)ethyl methacrylate) and resultant efficacy in vitro

    NASA Astrophysics Data System (ADS)

    Horiguchi, Yukichi; Kudo, Shinpei; Nagasaki, Yukio

    2011-08-01

    Poly(ethylene glycol)-block-poly(2-(N,N-diethylamino)ethyl methacrylate) (PEG-b-PAMA) was found to solubilize fullerenes such as C60, and this technique was applied to metallofullerenes. Gd@C82 was easily dissolved in water in the presence of PEG-b-PAMA without any covalent derivatization, forming a transparent complex about 20-30 nm in diameter. Low cytotoxicity was confirmed in vitro. Neutron irradiation of cultured cells (colon-26 adenocarcinoma) with Gd@C82-PEG-b-PAMA-complexed nanoparticles showed effective cytotoxicity, indicating the effective emission of gamma rays and internal conversion electrons produced from the neutron capture reaction of Gd. This result suggests a potentially valuable approach to gadolinium-based neutron capture therapy.

  15. Tunable charge-transport properties of I(h)-C80 endohedral metallofullerenes: investigation of La2@C80, Sc3N@C80, and Sc3C2@C80.

    PubMed

    Sato, Satoru; Seki, Shu; Luo, Guangfu; Suzuki, Mitsuaki; Lu, Jing; Nagase, Shigeru; Akasaka, Takeshi

    2012-07-18

    Fullerene crystals or films have drawn much interest because they are good candidates for use in the construction of electronic devices. The results of theoretical calculations revealed that the conductivity properties of I(h)-C(80) endohedral metallofullerenes (EMFs) vary depending on the encapsulated metal species. We experimentally investigated the solid-state structures and charge-carrier mobilities of I(h)-C(80) EMFs La(2)@C(80), Sc(3)N@C(80), and Sc(3)C(2)@C(80). The thin film of Sc(3)C(2)@C(80) exhibits a high electron mobility μ = 0.13 cm(2) V(-1) s(-1) under normal temperature and atmospheric pressure, as determined using flash-photolysis time-resolved microwave conductivity measurements. This electron mobility is 2 orders of magnitude higher than the mobility of La(2)@C(80) or Sc(3)N@C(80).

  16. Full exploration of the Diels-Alder cycloaddition on metallofullerenes M3N@C80 (M = Sc, Lu, Gd): the D(5h) versus I(h) isomer and the influence of the metal cluster.

    PubMed

    Osuna, Sílvia; Valencia, Ramón; Rodríguez-Fortea, Antonio; Swart, Marcel; Solà, Miquel; Poblet, Josep M

    2012-07-16

    In this work a detailed investigation of the exohedral reactivity of the most important and abundant endohedral metallofullerene (EMF) is provided, that is, Sc(3)N@I(h)-C(80) and its D(5h) counterpart Sc(3)N@D(5h)-C(80) , and the (bio)chemically relevant lutetium- and gadolinium-based M(3)N@I(h)/D(5h)-C(80) EMFs (M = Sc, Lu, Gd). In particular, we analyze the thermodynamics and kinetics of the Diels-Alder cycloaddition of s-cis-1,3-butadiene on all the different bonds of the I(h)-C(80) and D(5h)-C(80) cages and their endohedral derivatives. First, we discuss the thermodynamic and kinetic aspects of the cycloaddition reaction on the hollow fullerenes and the two isomers of Sc(3)N@C(80). Afterwards, the effect of the nature of the metal nitride is analyzed in detail. In general, our BP86/TZP//BP86/DZP calculations indicate that [5,6] bonds are more reactive than [6,6] bonds for the two isomers. The [5,6] bond D(5h)-b, which is the most similar to the unique [5,6] bond type in the icosahedral cage, I(h)-a, is the most reactive bond in M(3)N@D(5h)-C(80) regardless of M. Sc(3)N@C(80) and Lu(3)N@C(80) give similar results; the regioselectivity is, however, significantly reduced for the larger and more electropositive M = Gd, as previously found in similar metallofullerenes. Calculations also show that the D(5h) isomer is more reactive from the kinetic point of view than the I(h) one in all cases which is in good agreement with experiments.

  17. In-depth understanding of the chemical properties of rarely explored carbide cluster metallofullerenes: a case study of Sc2 C2 @C3v (8)-C82 that reveals a general rule.

    PubMed

    Cai, Wenting; Chen, Muqing; Bao, Lipiao; Xie, Yunpeng; Akasaka, Takeshi; Lu, Xing

    2015-02-16

    The chemical properties of carbide-cluster metallofullerenes (CCMFs) remain largely unexplored, although several new members of CCMFs have been discovered recently. Herein, we report the reaction between Sc2 C2 @C3v (8)-C82 , which is viewed as a prototypical CCMF because of its high abundance, and 3-triphenylmethyl-5-oxazolidinone (1) to afford the corresponding pyrrolidino derivative Sc2 C2 @C3v (8)-C82 (CH2 )2 NTrt (2; Trt=triphenylmethyl). Single-crystal X-ray crystallography studies of 2 revealed that the reaction takes place at a [6,6]-bond junction, which is directly over the encapsulated C2 unit and is far from either of the two scandium atoms. On the basis of theoretical calculations and by considering previously reports, we have found that a hexagonal carbon ring on the cage of Sc2 C2 @C3v (8)-C82 is highly reactive toward different reagents due to the overlap of high p-orbital axis vector (POAV) angles and large LUMO coefficients. We propose that this highly concentrated area of reactivity is generated by the encapsulation of the Sc2 C2 cluster because this region is absent from the empty fullerene C3v (8)-C82 . Moreover, the absorption and electrochemical results confirm that derivative 2 is more stable than pristine Sc2 C2 @C3v (8)-C82 , thus illuminating its potential applications.

  18. Magnetic properties of rare-earth metallofullerenes

    SciTech Connect

    Funasaka, Hideyuki; Sugiyama, Kenji; Yamamoto, Kazunori; Takahashi, Takeshi )

    1995-02-16

    Bulk amounts of La C[sub 82] and Gd C[sub 82] have been isolated in pure form from various hollow fullerenes. Magnetization data for these powder samples, an isolated La C[sub 82] isomer and a Gd C[sub 82] isomer, have been obtained employing a SQUID magnetometer at temperatures ranging from 3 to 300 K. For La C[sub 82] the inverse susceptibility as a function of temperature follows a Curie-Weiss law. The effective magnetic moment per La C[sub 82] is 0.38 [mu][sub B]. For Gd C[sub 32] the magnetization data fall on a universal curve which is fitted to a Brillouin function in correspondence with the Gd[sup 3+] free ion ground state values of J = 3.38 and g = 2. 33 refs., 6 figs.

  19. Magnetic Endohedral Metallofullerenes with Floppy Interiors

    NASA Astrophysics Data System (ADS)

    Qian, Meichun; Khanna, Shiv; Knickelbein, Mark

    2007-03-01

    Investigations on the electronic structure and magnetic properties of a free Gd3N and Gd3N@C80 have been carried out using to examine the stability and the electronic and magnetic properties of the endohedral species. Using a synergistic approach combining Stern-Gerlach experiments in beams and first principles electronic structure studies, it is demonstrated that an isolated Gd3N has a ground state spin moment of 23 μB followed by a non-collinear state of 17.2 μB only 88 meV above the ground state. The large moment is largely due to localized f-electrons. As a Gd3N is embedded inside a C80 cage, the localized f-electrons maintain the magnetic character while the hybridization between the s,d states of isolated Gd3N and p-states of C80 leads to a strongly bound motif with an interaction energy of 13.63 eV and a large HOMO-LUMO gap of 1.48 eV. Gd3N@C80 is further shown to possess two isomers corresponding to the location of the N atom on either side of the Gd3 triangle with an appreciable electric dipole moment and a low barrier of 91 meV for transition between them offering potential for a fluctuating dipole.

  20. Magnetic endohedral metallofullerenes with floppy interiors

    NASA Astrophysics Data System (ADS)

    Qian, Meichun; Ong, Stephen V.; Khanna, Shiv N.; Knickelbein, Mark B.

    2007-03-01

    It is shown that Gd3N@C80 is a highly magnetic and very stable motif that allows enhanced contrast magnetic resonance imaging and electric dipole moment with potential for cancer treatment. Using a synergistic approach combining Stern-Gerlach experiments in beams and first-principles electronic structure studies, it is demonstrated that an isolated Gd3N has a ground state spin moment of 23μB followed by a noncollinear state of 17.2μB only 88meV above the ground state. The large moment is largely due to localized f electrons. As a Gd3N is embedded inside a C80 cage, the localized f electrons maintain the magnetic character while the hybridization between the s , d states of isolated Gd3N and p states of C80 leads to a strongly bound motif with an interaction energy of 13.63eV and a large highest-occupied-molecular-orbital-lowest-unoccupied-molecular-orbital gap of 1.48eV . Gd3N@C80 is further shown to possess two isomers corresponding to the location of the N atom on either side of the Gd3 triangle with an appreciable electric dipole moment and a low barrier of 91meV for transition between them offering potential for a fluctuating dipole.

  1. Rotational dynamics of fullerenes and metallofullerenes

    SciTech Connect

    Johnson, R.D.; Salem, J.R.; Vries, M.S. de; Hoinkis, M.; Crowder, M.; Bethune, D.S.; Yannonni, C.S.

    1993-12-31

    The authors have investigated the rotational dynamics of C{sub 60} both in solution and the solid state, using {sup 13}C NMR. The rotational correlation times and activation energies of C{sub 60} in several solvents will be reported, and the results compared to measurements in the solid state. These results will then be used to interpret both EPR and NMR experiments on Scandium clusters encapsulated in fullerene cages. Measurement of {sup 45}Sc NMR relaxation rates are found to support conclusions from EPR experiments that the metal clusters form molecules inside the carbon cages.

  2. Diagnostic Magnetic Resonance Imaging of Atherosclerosis in Apolipoprotein E Knockout Mouse Model Using Macrophage-Targeted Gadolinium-Containing Synthetic Lipopeptide Nanoparticles

    PubMed Central

    Shen, Zu T.; Zheng, Shaokuan; Gounis, Matthew J.; Sigalov, Alexander B.

    2015-01-01

    Cardiovascular disease is the leading cause of death in Western cultures. The vast majority of cardiovascular events, including stroke and myocardial infarction, result from the rupture of vulnerable atherosclerotic plaques, which are characterized by high and active macrophage content. Current imaging modalities including magnetic resonance imaging (MRI) aim to characterize anatomic and structural features of plaques rather than their content. Previously, we reported that macrophage-targeted delivery of gadolinium (Gd)-based contrast agent (GBCA-HDL) using high density lipoproteins (HDL)-like particles significantly enhances the detection of plaques in an apolipoprotein (apo) E knockout (KO) mouse model, with an atherosclerotic wall/muscle normalized enhancement ratio (NER) of 120% achieved. These particles are comprised of lipids and synthetic peptide fragments of the major protein of HDL, apo A-I, that contain a naturally occurring modification which targets the particles to macrophages. Targeted delivery minimizes the Gd dose and thus reduces the adverse effects of Gd. The aims of the current study were to test whether varying the GBCA-HDL particle shape and composition can further enhance atherosclerotic plaque MRI and control organ clearance of these agents. We show that the optimized GBCA-HDL particles are efficiently delivered intracellularly to and uptaken by both J774 macrophages in vitro and more importantly, by intraplaque macrophages in vivo, as evidenced by NER up to 160% and higher. This suggests high diagnostic power of our GBCA-HDL particles in the detection of vulnerable atherosclerotic plaques. Further, in contrast to discoidal, spherical GBCA-HDL exhibit hepatic clearance, which could further diminish adverse renal effects of Gd. Finally, activated macrophages are reliable indicators of any inflamed tissues and are implicated in other areas of unmet clinical need such as rheumatoid arthritis, sepsis and cancer, suggesting the expanded diagnostic and prognostic use of this method. PMID:26569115

  3. Self-assembly of endohedral metallofullerenes: a decisive role of cooling gas and metal–carbon bonding† †Electronic supplementary information (ESI) available: Additional information on metal–carbon bonding and MD simulations. See DOI: 10.1039/c5nr08645k Click here for additional data file.

    PubMed Central

    Deng, Qingming; Heine, Thomas

    2016-01-01

    The endohedral metallofullerene (EMF) self-assembly process in Sc/carbon vapor in the presence and absence of an inert cooling gas (helium) is systematically investigated using quantum chemical molecular dynamics simulations. It is revealed that the presence of He atoms accelerates the formation of pentagons and hexagons and reduces the size of the self-assembled carbon cages in comparison with analogous He-free simulations. As a result, the Sc/C/He system simulations produce a larger number of successful trajectories (i.e. leading to Sc-EMFs) with more realistic cage-size distribution than simulations of the Sc/C system. The main Sc encapsulation mechanism involves nucleation of several hexagons and pentagons with Sc atoms already at the early stages of carbon vapor condensation. In such proto-cages, both Sc–C σ-bonds and coordination bonds between Sc atoms and the π-system of the carbon network are present. Sc atoms are thus rather labile and can move along the carbon network, but the overall bonding is sufficiently strong to prevent dissociation even at temperatures around 2000 kelvin. Further growth of the fullerene cage results in the encapsulation of one or two Sc atoms within the fullerene. In agreement with experimental studies, an extension of the simulations to Fe and Ti as the metal component showed that Fe-EMFs are not formed at all, whereas Ti is prone to form Ti-EMFs with small cage sizes, including Ti@C28-T d and Ti@C30-C 2v(3). PMID:26815243

  4. Electronic Structure of Endohedral Metallofullerenes: Evidences of the Ionic Model

    NASA Astrophysics Data System (ADS)

    Rodríguez-Fortea, Antonio; Valencia, Ramón; Poblet, Josep M.

    2009-08-01

    The electronic structure of the metal nitride M3N and metal carbide M2C2 endohedral fullerenes is rationalized by means of the simple ionic model that assumes a charge transfer from the internal metal cluster to the carbon framework. Experimental evidences of such an ionic model are also presented.

  5. Production and EPR spectroscopy of lanthanum an metallofullerenes

    SciTech Connect

    Bethune, D.S.; Yannoni, C.S.; Hoinkis, M.

    1992-12-01

    The authors report bulk preparation of LaC{sub 82} and ESR spectra of this species in solution and in the solid state. Samples were prepared and the soot was extracted with toluene. The extract contained only C{sub 60}, C{sub 70} and LA@C{sub 82}. The X band (9.112 GHz) ESR spectra of the degassed dry powder is centered at g = 2.001, in the region characteristic of fullerene anion radicals. In solution the spectrum consists of eight extremely narrow equally spaced (1.25 gauss interval) lines of equal intensity centered at g = 2.0010, unambiguously diagnostic for hyperfine coupling to a nuclear magnetic moment with spin 7/2 of {sup 139}La. The hyperfine coupling constant (1.25 gauss) is very small indicating that the unpaired electron resides primarily on the carbon atom and the La is in the +3 oxidation state.

  6. Physical and electrical properties of trimetallic nitride template endohedral metallofullerenes and their polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Ahmed, Hanaa Mohammed

    The main objective of this study was characterization of pure metallic nitride fullerene, MNF, and MNF containing polymers to evaluate these materials as suitable devices for tunable applications. Polymer-fullerene nanocomposites consisting of linear polyurethane (PU) segments crosslinked via polyhydroxylated fullerenes (C60 and Sc3N C 80, a metallic nitride fullerene) were prepared and characterized for their mechanical and dielectric properties using dynamic mechanical analysis (DMA) and broadband dielectric spectroscopic techniques. Polyhydroxylated fullerenes C60(OH)29 and Sc3N C80(OH) 18 were synthesized in a high yield through a solid-state high sheer ball-milling procedure and were characterized using a verity of techniques, such as FT-R, mass spectroscopy (MS) and thermal gravimetric analysis (TGA), to elucidate their structures. A difunctional isocyanate-terminated prepolymer was prepared from the reaction of poly(tetramethylene oxide) glycol (PTMO, ˜2000 g/mol) and methylene bis(4-isocyanatobenzene) (MDI) followed by the addition of the crosslinking fullerene agent. Fullerene-polymer networks [C60 -PU and Sc3N C80-PU] having high gel fractions and good mechanical properties and thermal stabilities were produced. Dynamic mechanical analyses of (C60 or Sc3N C80)-PU networks indicated a glass transition temperature, Tg, of -50°C with a sub-Tg relaxation due to local chain motions. Broadband dielectric spectroscopic analyses of the nanoparticles prior to incorporation into the networks revealed one relaxation and large epsilon' values in hydroxylated C60 relative to unfunctionalized C60. The analogous hydroxylated Sc3N C80 exhibited two relaxations, and the extra relaxation may be due to reorientations of cage-encapsulated Sc 3N clusters. Permittivity values (epsilon') for Sc3N C 80-PU were found to be higher than the corresponding values for C 60-PU, likely because of the rotationally mobile dipoles. For temperature < 0°C there was a dielectric loss peak due to the glass transition of the PU matrix and another at a lower temperature due to short range chain motions. The loss-frequency spectra of all prepared samples were analyzed sing the Kramers-Kronig transformation and Havriliak-Negami (HN) equation to extract information about relaxation processes taken place in these samples. Capacitance-voltage characteristics of the fullerene-PUs did not show any significant change with the applied dc bias voltage in the range of our instrument window (-30 to +30 volt). A general conclusion is that this class of materials can be rendered quite polarizable.

  7. Thermoelectricity at the molecular scale: a large Seebeck effect in endohedral metallofullerenes.

    PubMed

    Lee, See Kei; Buerkle, Marius; Yamada, Ryo; Asai, Yoshihiro; Tada, Hirokazu

    2015-12-28

    Single molecule devices provide a unique system to study the thermoelectric energy conversion at an atomistic level and can provide valuable information for the design of organic thermoelectric materials. Here we present a comprehensive study of the thermoelectric transport properties of molecular junctions based on C(82), Gd@C(82), and Ce@C(82). We combine precise scanning tunneling microscope break-junction measurements of the thermopower and conductance with quantitatively accurate self-energy-corrected first-principles transport calculations. We find that all three fullerene derivatives give rise to a negative thermopower (n-conducting). The absolute value, however, is much larger for the Gd@C(82) and Ce@C(82) junctions. The conductance, on the other hand, remains comparable for all three systems. The power factor determined for the Gd@C(82) based junction is so far the highest obtained for a single-molecule device. Although the encapsulated metal atom does not directly contribute to the transport, we show that the observed enhancement of the thermopower for Gd@C(82) and Ce@C(82) is elucidated by the substantial changes in the electronic- and geometrical structure of the fullerene molecule induced by the encapsulated metal atom. PMID:26583505

  8. Functionalization of gadolinium metallofullerenes for detecting atherosclerotic plaque lesions by cardiovascular magnetic resonance

    PubMed Central

    2013-01-01

    Background The hallmark of atherosclerosis is the accumulation of plaque in vessel walls. This process is initiated when monocytic cells differentiate into macrophage foam cells under conditions with high levels of atherogenic lipoproteins. Vulnerable plaque can dislodge, enter the blood stream, and result in acute myocardial infarction and stroke. Imaging techniques such as cardiovascular magnetic resonance (CMR) provides one strategy to identify patients with plaque accumulation. Methods We synthesized an atherosclerotic-targeting contrast agent (ATCA) in which gadolinium (Gd)-containing endohedrals were functionalized and formulated into liposomes with CD36 ligands intercalated into the lipid bilayer. In vitro assays were used to assess the specificity of the ATCA for foam cells. The ability of ATCA to detect atherosclerotic plaque lesions in vivo was assessed using CMR. Results The ATCA was able to detect scavenger receptor (CD36)-expressing foam cells in vitro and were specifically internalized via the CD36 receptor as determined by focused ion beam/scanning electron microscopy (FIB-SEM) and Western blotting analysis of CD36 receptor-specific signaling pathways. The ATCA exhibited time-dependent accumulation in atherosclerotic plaque lesions of ApoE −/− mice as determined using CMR. No ATCA accumulation was observed in vessels of wild type (C57/b6) controls. Non-targeted control compounds, without the plaque-targeting moieties, were not taken up by foam cells in vitro and did not bind plaque in vivo. Importantly, the ATCA injection was well tolerated, did not demonstrate toxicity in vitro or in vivo, and no accumulation was observed in the major organs. Conclusions The ATCA is specifically internalized by CD36 receptors on atherosclerotic plaque providing enhanced visualization of lesions under physiological conditions. These ATCA may provide new tools for physicians to non-invasively detect atherosclerotic disease. PMID:23324435

  9. Evolution of plasmonic and hybrid photoionization properties of alkaline earth metallofullerenes with the increasing fullerene size

    NASA Astrophysics Data System (ADS)

    Patel, Aakash; Chakraborty, Himadri

    2013-05-01

    A theoretical study of the photoionization of endohedral fullerenes with a selection of fullerene molecules of increasing size and with confined alkaline earth atoms like Be and Mg is carried out. The fullerene ion cores, comprised of C4+ ions, are smudged into a continuous jellium charge distribution, while the delocalized cloud of carbon valence electrons plus the electrons of the encaged atom are treated in the Kohn-Sham local density approximation (LDA). Only the spherical geometry is considered. The photoionization spectra are calculated by the time-dependent LDA that includes essential electron correlations. A systematic evolution of the mixing of valence atomic levels with states of fullerene single-electron bands is found along the sequence. This hybridization as a function of the fullerene size is seen to primarily define the properties of the subshell-differential ionization spectra both in the low energy plasmonic as well as the high energy oscillatory regions. Supported by NSF and DOE.

  10. Thermoelectricity at the molecular scale: a large Seebeck effect in endohedral metallofullerenes.

    PubMed

    Lee, See Kei; Buerkle, Marius; Yamada, Ryo; Asai, Yoshihiro; Tada, Hirokazu

    2015-12-28

    Single molecule devices provide a unique system to study the thermoelectric energy conversion at an atomistic level and can provide valuable information for the design of organic thermoelectric materials. Here we present a comprehensive study of the thermoelectric transport properties of molecular junctions based on C(82), Gd@C(82), and Ce@C(82). We combine precise scanning tunneling microscope break-junction measurements of the thermopower and conductance with quantitatively accurate self-energy-corrected first-principles transport calculations. We find that all three fullerene derivatives give rise to a negative thermopower (n-conducting). The absolute value, however, is much larger for the Gd@C(82) and Ce@C(82) junctions. The conductance, on the other hand, remains comparable for all three systems. The power factor determined for the Gd@C(82) based junction is so far the highest obtained for a single-molecule device. Although the encapsulated metal atom does not directly contribute to the transport, we show that the observed enhancement of the thermopower for Gd@C(82) and Ce@C(82) is elucidated by the substantial changes in the electronic- and geometrical structure of the fullerene molecule induced by the encapsulated metal atom.

  11. Structures and formation of small LaC[sub n][sup +] metallofullerenes

    SciTech Connect

    Shelimov, K.B.; Clemmer, D.E.; Jarrold, M.F. )

    1994-12-08

    Injected ion drift tube techniques have been used to probe LaC[sub n][sup +] clusters in the size range around LaC[sub 36][sup +] where the fullerene cage becomes too small to accommodate a La atom. Mobility measurements show that as the fullerene cage shrinks, the La atom moves out of the cage into the carbon network, stabilizing clusters with an odd number of carbon atoms. Annealing studies demonstrate that in this size range the presence of the La atom dramatically enhances the efficiency of conversion of bicyclic and monocyclic LaC[sub n][sup +] rings into fullerenes and graphite sheets. 20 refs., 4 figs.

  12. Endohedral metallofullerene Sc3NC@C82: A theoretical prediction

    NASA Astrophysics Data System (ADS)

    Meng, Qing-Ya; Sun, Xiao-Yuan; Wang, Cui-Yan; Wang, Dong-Lai

    2014-10-01

    All nine IPR C82 isomers and two non-IPR C82 isomers (C2v(39705) and Cs(39663)) are considered to explore that which one has the more possibility of encapsulating Sc3NC cluster in the C82 fullerene. Significantly, the favorable binding energies and large HOMO-LUMO energy gaps suggest two non-IPR Sc3NC@C2v(39705)sbnd C82 and Sc3NC@Cs(39663)sbnd C82 should be found among the possible structures of Sc3NC@C82. Furthermore, Raman spectra and 13C NMR spectra have also been explored to assist future experimental characterization.

  13. C68 fullerene isomers, anions, and their metallofullerenes: charge-stabilizing different isomers.

    PubMed

    Chen, De-Li; Tian, Wei Quan; Feng, Ji-Kang; Sun, Chia-Chung

    2008-02-22

    The complete set of 6332 classical isomers of the fullerene C(68) as well as several non-classical isomers is investigated by PM3, and the data for some of the more stable isomers are refined by the DFT-based methods HCTH and B3LYP. C(2):0112 possesses the lowest energy of all the neutral isomers and it prevails in a wide range of temperatures. Among the fullerene ions modeled, C(68) (2-), C(68) (4-) and C(68) (6-), the isomers C(68) (2-)(C(s):0064), C(68) (4-)(C(2v):0008), and C(68) (6-)(D(3):0009) respectively, are predicted to be the most stable. This reveals that the pentagon adjacency penalty rule (PAPR) does not necessarily apply to the charged fullerene cages. The vertical electron affinities of the neutral C(s):0064, C(2v):0008, and D(3):0009 isomers are 3.41, 3.29, and 3.10 eV, respectively, suggesting that they are good electron acceptors. The predicted complexation energy, that is, the adiabatic binding energy between the cage and encapsulated cluster, of Sc(2)C(2)@C(68)(C(2v):0008) is -6.95 eV, thus greatly releasing the strain of its parent fullerene (C(2v):0008). Essentially, C(68) fullerene isomers are charge-stabilized. Thus, inducing charge facilitates the isolation of the different isomers. Further investigations show that the steric effect of the encaged cluster should also be an important factor to stabilize the C(68) fullerenes effectively.

  14. Thermoelectricity at the molecular scale: a large Seebeck effect in endohedral metallofullerenes

    NASA Astrophysics Data System (ADS)

    Lee, See Kei; Buerkle, Marius; Yamada, Ryo; Asai, Yoshihiro; Tada, Hirokazu

    2015-12-01

    Single molecule devices provide a unique system to study the thermoelectric energy conversion at an atomistic level and can provide valuable information for the design of organic thermoelectric materials. Here we present a comprehensive study of the thermoelectric transport properties of molecular junctions based on C82, Gd@C82, and Ce@C82. We combine precise scanning tunneling microscope break-junction measurements of the thermopower and conductance with quantitatively accurate self-energy-corrected first-principles transport calculations. We find that all three fullerene derivatives give rise to a negative thermopower (n-conducting). The absolute value, however, is much larger for the Gd@C82 and Ce@C82 junctions. The conductance, on the other hand, remains comparable for all three systems. The power factor determined for the Gd@C82 based junction is so far the highest obtained for a single-molecule device. Although the encapsulated metal atom does not directly contribute to the transport, we show that the observed enhancement of the thermopower for Gd@C82 and Ce@C82 is elucidated by the substantial changes in the electronic- and geometrical structure of the fullerene molecule induced by the encapsulated metal atom.Single molecule devices provide a unique system to study the thermoelectric energy conversion at an atomistic level and can provide valuable information for the design of organic thermoelectric materials. Here we present a comprehensive study of the thermoelectric transport properties of molecular junctions based on C82, Gd@C82, and Ce@C82. We combine precise scanning tunneling microscope break-junction measurements of the thermopower and conductance with quantitatively accurate self-energy-corrected first-principles transport calculations. We find that all three fullerene derivatives give rise to a negative thermopower (n-conducting). The absolute value, however, is much larger for the Gd@C82 and Ce@C82 junctions. The conductance, on the other hand, remains comparable for all three systems. The power factor determined for the Gd@C82 based junction is so far the highest obtained for a single-molecule device. Although the encapsulated metal atom does not directly contribute to the transport, we show that the observed enhancement of the thermopower for Gd@C82 and Ce@C82 is elucidated by the substantial changes in the electronic- and geometrical structure of the fullerene molecule induced by the encapsulated metal atom. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05394c

  15. Metallofullerene nanoparticles promote osteogenic differentiation of bone marrow stromal cells through BMP signaling pathway

    NASA Astrophysics Data System (ADS)

    Yang, Kangning; Cao, Weipeng; Hao, Xiaohong; Xue, Xue; Zhao, Jing; Liu, Juan; Zhao, Yuliang; Meng, Jie; Sun, Baoyun; Zhang, Jinchao; Liang, Xing-Jie

    2013-01-01

    Although endohedral metallofullerenol [Gd@C82(OH)22]n nanoparticles have anti-tumor efficiency and mostly deposit in the bones of mice, how these nanoparticles act in bone marrow stromal cells (MSCs) remains largely unknown. Herein, we observed that [Gd@C82(OH)22]n nanoparticles facilitated the differentiation of MSCs toward osteoblasts, as evidenced by the enhancement of alkaline phosphatase (ALP) activity and mineralized nodule formation upon [Gd@C82(OH)22]n nanoparticle treatment. Mechanistically, the effect of [Gd@C82(OH)22]n nanoparticles on ALP activity was inhibited by the addition of noggin as an inhibitor of the BMP signaling pathway. Moreover, the in vivo results of the ovariectomized rats further indicated that [Gd@C82(OH)22]n nanoparticles effectively improved bone density and prevented osteoporosis.Although endohedral metallofullerenol [Gd@C82(OH)22]n nanoparticles have anti-tumor efficiency and mostly deposit in the bones of mice, how these nanoparticles act in bone marrow stromal cells (MSCs) remains largely unknown. Herein, we observed that [Gd@C82(OH)22]n nanoparticles facilitated the differentiation of MSCs toward osteoblasts, as evidenced by the enhancement of alkaline phosphatase (ALP) activity and mineralized nodule formation upon [Gd@C82(OH)22]n nanoparticle treatment. Mechanistically, the effect of [Gd@C82(OH)22]n nanoparticles on ALP activity was inhibited by the addition of noggin as an inhibitor of the BMP signaling pathway. Moreover, the in vivo results of the ovariectomized rats further indicated that [Gd@C82(OH)22]n nanoparticles effectively improved bone density and prevented osteoporosis. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr33575a

  16. Mass spectroscopic characterization of yttrium-containing metallofullerene YC82 using resonant laser ablation

    SciTech Connect

    Wang Shiliang; Tian Jiahe; Dai Songtao; Chen Dieyan; Luo Chuping; Tan Haisong; Gan Liangbing; Huang Chunhui

    1995-04-01

    In this paper, resonant laser ablation time-of-flight mass spectroscopy (RLA-TOF-MS) has been used to mass spectroscopic characterization of yttrium-containing fullerenes. Solvent soluble, yttrium-containing fullerenes are extracted from yttrium/carbon soot produced by the carbon-arc fullerene generation method. The RLA-TOF mass spectra indicate the presence of YC82. The metallofullerences YC60, YC70, Y2C82 and a series of Y2C2n are not observed by RLA-TOF-MS. This result is consistent with the ESR spectral result reported by Shinohara et al.

  17. In-Plane Intermolecular Interaction Assisted Assembly and Modified Electronic States of Metallofullerene Gd@C₈₂.

    PubMed

    Chen, Jian; Qin, Zhihui; Pan, Jinbo; Huang, Min; Du, Shixuan; Cao, Gengyu

    2015-10-27

    Orientational configuration and electronic states of Gd@C82 bonding to Cu(111) have been thoroughly investigated by low-temperature scanning tunneling microscopy/spectroscopy (LT-STM/S) and differential conductance mapping complemented by first-principles calculations. We clarify that individual Gd@C82 energetically adopts tilting adsorption configuration with the scanning tunneling spectroscopy (STS) states readily assigned to the C82 cage/Cu(111) hybrid states and the Gd/cage hybrid states, respectively. Moreover, upon assembling and sufficient thermal activation, Gd@C82 fullerenes are inclined to restore the energetically favored tilting orientational configuration similar to an individual one. This suggests the feasibility of high-level integration of single-Gd@C82 based moletronic device with the performances almost unchanged by two-dimensional arrangement. Furthermore, by rationalizing the inter-Gd@C82 interaction induced slight energy offset of the electronic states, we qualitatively confirm the shown electronic hybrid states as Cu(111)-, C82 cage- and Gd-dominant hybrid states, respectively. PMID:26457573

  18. Atom-Cage Charge Transfer in Endohedral Metallofullerenes: Trapping Atoms Within a Sphere-Like Ridge of Avoided Crossings.

    PubMed

    Tishchenko, Oksana; Truhlar, Donald G

    2013-02-01

    Endohedral fullerences have great potential for a variety of techological applications. Here we consider B@C60 and show that the amount of charge transfer from the semimetal boron atom to the cage is a strong function of the radial distance of the atom from the center of the fullerene, and it is controlled by multistate conical intersections whose associated ridge of avoided crossings has the topology of a Euclidean sphere. The potential energy surfaces of B@C60 are characterized by two kinds of local minima: those with a boron atom located in the geometric center of the fullerene, and those with a boron atom bound to the fullerene inner wall. At the lowest-energy minimum, at the center, the boron atom is neutral, whereas the transition to the wall is accompanied by an electron transfer from boron to the fullerene cage. The two kinds of minima are separated by a ridge of avoided crossings that forms a surface with a nearly spherical shape. The properties of such systems may be altered by controlling the populations of the two kinds of minima, for example, by application of an external field. Such switchable atom-cage charge transfer may find applications in novel molecular devices.

  19. In-Plane Intermolecular Interaction Assisted Assembly and Modified Electronic States of Metallofullerene Gd@C₈₂.

    PubMed

    Chen, Jian; Qin, Zhihui; Pan, Jinbo; Huang, Min; Du, Shixuan; Cao, Gengyu

    2015-10-27

    Orientational configuration and electronic states of Gd@C82 bonding to Cu(111) have been thoroughly investigated by low-temperature scanning tunneling microscopy/spectroscopy (LT-STM/S) and differential conductance mapping complemented by first-principles calculations. We clarify that individual Gd@C82 energetically adopts tilting adsorption configuration with the scanning tunneling spectroscopy (STS) states readily assigned to the C82 cage/Cu(111) hybrid states and the Gd/cage hybrid states, respectively. Moreover, upon assembling and sufficient thermal activation, Gd@C82 fullerenes are inclined to restore the energetically favored tilting orientational configuration similar to an individual one. This suggests the feasibility of high-level integration of single-Gd@C82 based moletronic device with the performances almost unchanged by two-dimensional arrangement. Furthermore, by rationalizing the inter-Gd@C82 interaction induced slight energy offset of the electronic states, we qualitatively confirm the shown electronic hybrid states as Cu(111)-, C82 cage- and Gd-dominant hybrid states, respectively.

  20. Probing the role of encapsulated alkaline earth metal atoms in endohedral metallofullerenes M@C76 (M = Ca, Sr, and Ba) by first-principles calculations.

    PubMed

    Yang, Tao; Zhao, Xiang; Xu, Qian; Zheng, Hong; Wang, Wei-Wei; Li, Sheng-Tao

    2012-05-01

    By means of density functional theory and statistical mechanics, we investigate the geometric and electronic structures, thermodynamic stability and infrared (IR) vibrational frequencies of alkaline earth metal endohedral fullerenes, M@C(76) (M = Ca, Sr, and Ba). The results reveal that M@C(1)(17,459)-C(76) possesses the lowest energy followed by M@C(2v)(19,138)-C(76) with a very small energy difference. Both the structures have a pair of adjacent pentagons and are related by a single Stone-Wales transformation. Equilibrium statistical thermodynamic analyses based on Gibbs energy treatments suggest that M@C(1)(17,459)-C(76) has a prominent thermodynamic stability at higher temperatures, in contrast with M@C(2v)(19,138)-C(76) whose thermodynamic stability is affected by the encapsulated metal atom. The encapsulated metallic atoms as well as cage structures significantly influence the electronic properties of endohedral fullerenes such as electron affinities and ionization potentials. On the other hand, the singlet-triplet splitting energy ΔE(S-T) depends on the cage structures. In addition, IR spectra and chemical shifts of these compounds have been computed to assist further experimental characterization.

  1. Fourier transform microwave/millimeter-wave spectroscopy of the ScC2 (XA1) radical: A model system for endohedral metallofullerenes

    NASA Astrophysics Data System (ADS)

    Min, J.; Halfen, D. T.; Ziurys, L. M.

    2014-08-01

    The pure rotational spectrum of the ScC2 radical (XA1) has been measured using Fourier transform microwave/millimeter-wave techniques in the frequency range 15-63 GHz - the first high-resolution spectroscopic study of a 3d dicarbide species. ScC2 was created in a supersonic expansion from laser-ablated scandium and CH4 in the presence of a DC discharge. Four transitions, NKa,Kc = 101 → 000 through 404 → 303, were recorded, each consisting of multiple fine/hyperfine components; rotational, fine structure, and Sc(I = 7/2) hyperfine constants were determined. These measurements confirm the T-shaped geometry for ScC2, and suggest the molecule has significant covalent character.

  2. ESR study of the electronic structures of metallofullerenes. A comparison between La C[sub 82] and Sc C[sub 82

    SciTech Connect

    Kato, Tatsuhisa ); Suzuki, Shinzo; Kikuchi, Koichi; Achiba, Yohji )

    1993-12-23

    The line widths of the hyperfine components of ESR spectra of La C[sub 82] and Sc C[sub 82] in CS[sub 2] and toluene solutions have been measured as a function of temperature. The extent of line broadening due not only to the insufficient rotational averaging of g and hyperfine tensors but also to the spin-rotation coupling interaction have been determined. The values of anisotropy for the g and hyperfine tensors are deduced by analysis according to Kivelson's formalism for these line broadening mechanisms. Although the two spectra for La C[sub 82] and Sc C[sub 82] in solution at room temperature look similar to each other, the different electronic structure for each endohedral metal is reflected in their differing values for the anisotropy of the g and hyperfine tensors. The electronic structures of La C[sub 82] and Sc C[sub 82] are discussed comparatively in terms of a theoretical interpretation for the anisotropic correction of the g factor and the hyperfine coupling constant. The results exhibit different electronic structures for La C[sub 82] and Sc C[sub 82]; the radical electron is assigned to a [pi] orbital of the C[sub 82] cage for La C[sub 82] but to a orbital of the metal for Sc C[sub 82]. 16 refs., 4 figs., 1 tab.

  3. Isolation and Crystallographic Characterization of the Labile Isomer of Y@C82 Cocrystallized with Ni(OEP): Unprecedented Dimerization of Pristine Metallofullerenes.

    PubMed

    Bao, Lipiao; Pan, Changwang; Slanina, Zdenek; Uhlik, Filip; Akasaka, Takeshi; Lu, Xing

    2016-08-01

    Although the major isomers of M@C82 (namely M@C2v (9)-C82 , where M is a trivalent rare-earth metal) have been intensively investigated, the lability of the minor isomers has meant that they have been little studied. Herein, the first isolation and crystallographic characterization of the minor Y@C82 isomer, unambiguously assigned as Y@Cs (6)-C82 by cocrystallization with Ni(octaethylporphyrin), is reported. Unexpectedly, a regioselective dimerization is observed in the crystalline state of Y@Cs (6)-C82 . In sharp contrast, no dimerization occurs for the major isomer Y@C2v (9)-C82 under the same conditions, indicating a cage-symmetry-induced dimerization process. Further experimental and theoretical results disclose that the regioselective dimer formation is a consequence of the localization of high spin density on a special cage-carbon atom of Y@Cs (6)-C82 which is caused by the steady displacement of the Y atom inside the Cs (6)-C82 cage.

  4. Isolation and Crystallographic Characterization of the Labile Isomer of Y@C82 Cocrystallized with Ni(OEP): Unprecedented Dimerization of Pristine Metallofullerenes.

    PubMed

    Bao, Lipiao; Pan, Changwang; Slanina, Zdenek; Uhlik, Filip; Akasaka, Takeshi; Lu, Xing

    2016-08-01

    Although the major isomers of M@C82 (namely M@C2v (9)-C82 , where M is a trivalent rare-earth metal) have been intensively investigated, the lability of the minor isomers has meant that they have been little studied. Herein, the first isolation and crystallographic characterization of the minor Y@C82 isomer, unambiguously assigned as Y@Cs (6)-C82 by cocrystallization with Ni(octaethylporphyrin), is reported. Unexpectedly, a regioselective dimerization is observed in the crystalline state of Y@Cs (6)-C82 . In sharp contrast, no dimerization occurs for the major isomer Y@C2v (9)-C82 under the same conditions, indicating a cage-symmetry-induced dimerization process. Further experimental and theoretical results disclose that the regioselective dimer formation is a consequence of the localization of high spin density on a special cage-carbon atom of Y@Cs (6)-C82 which is caused by the steady displacement of the Y atom inside the Cs (6)-C82 cage. PMID:27305624

  5. M2@C79N (M = Y, Tb): Isolation and Characterization of Stable Endohedral Metallofullerenes Exhibiting M-M Bonding Interactions Inside Aza[80]Fullerene Cages

    PubMed Central

    Zuo, Tianming; Xu, Liaosa; Beavers, Christine M.; Olmstead, Marilyn M.; Fu, Wujun; Crawford, T. Daniel; Dorn, Harry C.

    2009-01-01

    Y2@C79N and Tb2@C79N have been prepared by conducting the Krätschmer-Huffman electric arc-process under 20 torr of N2 and 280 torr of He with metal oxide doped graphite rods. These new heterofullerenes were separated from the resulting mixture of empty cage fullerenes and endohedral fullerenes by chemical separation and a two stage chromatographic process. Crystallographic data for Tb2@C79N • Ni(OEP) • 2C6H6 demonstrate the presence of an 80-atom cage with idealized Ih symmetry and two, widely separated Tb atoms inside with a Tb---Tb separation of 3.9020(10) Å for the major terbium sites. The EPR spectrum of the odd-electron Y2@C79N indicates that the spin density largely resides on the two, equivalent yttrium ions. Computational studies on Y2@C79N suggest that the nitrogen atom resides at a 665 ring junction in the equator on the fullerene cage and that the unpaired electron is localized in a bonding orbital between the two yttrium ions of this stable radical. Thus, the Tb-Tb bond length of the single-electron bond is the longest metal-metal bond reported so far. PMID:18774804

  6. Quantum-chemical calculations of the metallofullerene yields in the X@C{sub 74}, L@C{sub 74}, and Z@C{sub 82} series

    SciTech Connect

    Uhlík, Filip; Slanina, Zdeněk; Nagase, Shigeru

    2015-01-22

    The contribution reports computations for Al@C{sub 82}, Sc@C{sub 82}, Y@C{sub 82} and La@C{sub 82} based on encapsulation into the IPR (isolated pentagon rule) C{sub 2ν} C{sub 82} cage and also on Mg@C{sub 74}, Ca@C{sub 74}, Sr@C{sub 74} and Ba@C{sub 74} based on encapsulation into the only C{sub 74} IPR cage as well as for three selected lanthanoids La@C{sub 74}, Yb@C{sub 74}, and Lu@C{sub 74}. Their structural and energetic characteristics are used for evaluations of the relative production yields, using the encapsulation Gibbs-energy and saturated metal pressures. It is shown that the results can be well related to the ionization potentials of the free metal atoms.

  7. EPR spectrum of the Y@C82 metallofullerene isolated in solid argon matrix: hyperfine structure from EPR spectroscopy and relativistic DFT calculations.

    PubMed

    Misochko, Eugenii Ya; Akimov, Alexander V; Belov, Vasilii A; Tyurin, Daniil A; Bubnov, Vyacheslav P; Kareev, Ivan E; Yagubskii, Eduard B

    2010-08-21

    The EPR spectrum of the Y@C(82) molecules isolated in solid argon matrix was recorded for the first time at a temperature of 5 K. The isotropic hyperfine coupling constant (hfcc) A(iso) = 0.12 +/- 0.02 mT on the nucleus (89)Y as derived from the EPR spectrum is found in more than two times greater than that obtained in previous EPR measurements in liquid solutions. Comparison of the measured hfcc on a metal atom with that predicted by density-functional theory calculations (PBE/L22) indicate that relativistic method provides good agreement between experiment in solid argon and theory. Analysis of the DFT calculated dipole-dipole hf-interaction tensor and electron spin distribution in the endometallofullerenes with encaged group 3 metal atoms Sc, Y and La has been performed. It shows that spin density on the scandium atom represents the Sc d(yz) orbital lying in the symmetry plane of the C(2v) fullerene isomer and interacting with two carbon atoms located in the para-position on the fullerene hexagon. In contrast, the configuration of electron spin density on the heavier atoms, Y and La, is associated with the hybridized orbital formed by interaction of the metal d(yz) and p(y) electronic orbitals.

  8. Sc2@C3v(8)-C82 vs. Sc2C2@C3v(8)-C82: drastic effect of C2 capture on the redox properties of scandium metallofullerenes.

    PubMed

    Kurihara, Hiroki; Lu, Xing; Iiduka, Yuko; Mizorogi, Naomi; Slanina, Zdenek; Tsuchiya, Takahiro; Nagase, Shigeru; Akasaka, Takeshi

    2012-01-30

    We describe the first example of scandium dimetallofullerenes, Sc(2)@C(3v)(8)-C(82), which has the same cage as the previously assigned scandium carbide cluster fullerene Sc(2)C(2)@C(3v)(8)-C(82) but they exhibit distinctly different electronic configurations and electronic behaviours, confirming the drastic influence of the internal C(2) unit.

  9. Magnetism in Endohedral Metallofullerenes TM@Cn for n = 20, 28, 32, 36 where TM = Ti, V, Cr, Mn, Fe, Co, Ni and Cu: A Spin Polarized Density Functional Study

    NASA Astrophysics Data System (ADS)

    Sharma, Hitesh; Garg, Isha; Dharamvir, Keya; Jindal, V. K.

    2010-10-01

    A systematic investigation of 3d transition metal (TM)encapsulated inside small fullerene cages has been performed to calculate their magnetic properties using first principle methods. The total magnetic moment (MM) of TM@Cn complexes is delocalized between TM site and induced MM on carbon (C) atoms. There is a significant MM of 0.12-0.05μB induced on the cage C atoms. The 3d TM atoms interact ferromagnetically (FM) with C atoms of C20 and C32 cage except for Ni@C28 which interacts anti-ferromagnetically. The magnetic interactions are found to change from FM to AFM in C32 for Ti, V, Cr and Mn and the MM gets quenched for Ni@Cn for n>32. The total MM does not show any change in Mn@Cn for all cages although FM to AFM change does take place for n = 32. The cohesive energy of TM@Cn suggests Ti and V are stable inside all the cages considered.

  10. Kinetic Stability of Non-IPR Fullerene Molecular Ions.

    PubMed

    Aihara, Jun-ichi; Nakagami, Yuto; Sekine, Rika

    2015-06-18

    Many fullerenes that violate the isolated pentagon rule (IPR) form stable metallofullerenes. In general, a fullerene cage is kinetically stabilized by acquiring a given number of electrons. Kinetic stability of negatively charged non-IPR fullerenes, including the recently isolated endohedral metallofullerene with a heptagonal face, was rationalized in terms of bond resonance energy (BRE). Interestingly, molecular anions of conventional fullerenes found in most isolated metallofullerenes are kinetically stable with large positive BREs for all CC bonds. As we pointed out in 1993, the IPR does not apply to charged fullerenes because π-bonds shared by two five-membered rings are aromatized to varying extents. PMID:26020361

  11. Encapsulation of radioactive [sup 159]Gd and [sup 161]Tb atoms in fullerene cages

    SciTech Connect

    Kikuchi, Koichi; Kobayashi, Kanako; Sueki, Keisuke; Suzuki, Shinzo; Nakahara, Hiromichi; Achiba, Yohji; Katada, Motomi ); Tomura, Kenji )

    1994-10-19

    We demonstrate a novel form of metallofullerenes, namely, those with radioactive atoms encapsulated in the C[sub 82]cage. The metal atoms were made radioactive by a neutron capture reaction or through a nuclear decay process. The most important and intriguing finding of the present study is that the endohedral form of metallofullerenes is not affected by the recoil energy of the metal atom resulting from emission of electrons in the [beta] decay. Such a stability of the cage against the recoil energy of the encapsulated atom was confirmed by the elution behavior of the metallofullerene in liquid chromatography. Successful encapsulation of radioactive atoms inside the fullerene cage will greatly widen the potential use of endohedral metallofullerenes not only in basic science and technology but also in other areas, such as medicine. 14 refs., 3 figs.

  12. Transmission electron microscopy: Visualizing fullerene chemistry

    NASA Astrophysics Data System (ADS)

    Terrones, Mauricio

    2010-02-01

    Chemical reactions of fullerenes and metallofullerenes lined up inside single-walled carbon nanotubes can be monitored at the atomic scale inside an aberration-corrected transmission electron microscope.

  13. Design parameters for carbon nanobottles to absorb and store methane.

    PubMed

    Lee, Richard K F; Hill, James M

    2011-08-01

    We investigate the internal mechanics for methane storage in a nanobottle, which is assumed to comprise a metallofullerene located inside a carbon nanobottle, which is constructed from a half-fullerene as the base, and two nanotubes which are joined by a nanocone. The interaction potential energy for the metallofullerene is obtained from the 6-12 Lennard-Jones potential and the continuum approximation, which assumes that a discrete atomic structure can be replaced by an average atomic surface density. This potential energy shows that the metallofullerene has two minimum energy positions, which are located close to the neck of the bottle and at the base of the nanobottle, and therefore it may be used as a bottle-stopper to open or to close the nanobottle. At the neck of the bottle, the encapsulated metallofullerene closes the nanobottle, and by applying an external electrical force, the metallofullerene can overcome the energy barrier of the nanotube, and pass from the neck of the nanobottle to the base so that the nanobottle is open. For methane storage, the metallofullerene serves the dual purposes of opening and closing the nanobottle, as well as an attractor for the methane gas. The analytical formulation gives rise to a rapid computational capacity, and enables the direct determination of the optimal dimensions necessary to ensure the correct working function of the nanobottle, and specific ranges for the critical parameters are formulated. PMID:22103096

  14. Role of OH Adsorption on the Properties of MRI contrast agent Gd3N@C80

    NASA Astrophysics Data System (ADS)

    Ong, Vince; Khanna, Shiv; Fatouros, Panos

    2009-03-01

    Endohedral metallofullerenes Gd3N@C80 decorated with hydroxyl groups are now known to be excellent contrast enhancement agents for Magnetic Resonance Imaging (MRI) leading to strong relaxivity enhancements. One of the outstanding issues is the nature of OH adsorption and its effect on the properties of endohedral Gd3N motif. We have carried out theoretical studies on the electronic structure and magnetic properties of the endohedral metallofullerenes functionalized with hydroxyl groups to demonstrate that the nature of OH can have significant effect on the magnetic spin density. The new findings may provide physical insight into the observed strong relaxivity enhancements.

  15. Charge-Transfer Satellite in Ce@C82 Probed by Resonant X-ray Emission Spectroscopy

    NASA Astrophysics Data System (ADS)

    Yamaoka, Hitoshi; Kotani, Akio; Kubozono, Yoshihiro; Vlaicu, Aurel Mihai; Oohashi, Hirofumi; Tochio, Tatsuki; Ito, Yoshiaki; Yoshikawa, Hideki

    2011-01-01

    The electronic structure of metallofullerene Ce@C82 is probed by resonant x-ray emission spectroscopy at the Ce L3 absorption edge. We observed a satellite structure in x-ray absorption and resonant emission spectra for Ce@C82, which, we show, corresponds to the charge transfer induced by the core--hole potential in the final state, similarly to Pr@C82. This charge-transfer satellite may be a common feature in metallofullerenes. The temperature dependence of the electronic structure is also investigated.

  16. Tuneable dynamics of a scandium nitride cluster inside an Ih-C80 cage.

    PubMed

    Feng, Yongqiang; Wang, Taishan; Xiang, Junfeng; Gan, Lihua; Wu, Bo; Jiang, Li; Wang, Chunru

    2015-02-01

    The internal clusters in metallofullerenes usually exhibit certain motion that is potentially usable in molecular gyroscopes and nano-machines. Based on (45)Sc NMR, the motion of the scandium nitride cluster within the C80 cage was investigated via varying the temperature and modifying the cage, and by changing the cluster size.

  17. Voltammetry of Sc{sub 3}@C{sub 82}

    SciTech Connect

    Anderson, M.R.; Dorn, H.C.; Stevenson, S.; Burbank, P.M.; Gibson, J.R.

    1997-01-15

    This paper describes the first electrochemical data for a polymetallic endohedral metallofullerene. The voltammetric behavior of Sc{sub 3}@C{sub 82} resembles that for La@C{sub 82} and Y@C{sub 82}, indicating that the identity of the metal does not influence dramatically the energies of the metallofullerene molecular orbitals. The three Sc atoms, however, transfer more electrons from the encapsulated metals to the cage than the monometallic counterparts, accounting for the differences in the voltammetry for Sc{sub 3}@C{sub 82}. The similarity of the voltammetry of Sc{sub 3}@C{sub 82} with that of the monometallic fullerenes suggests that Sc{sub 3}{sup +4}@C{sub 82}{sup 4-} may describe the formal charges on the Sc trimer and the C{sub 82} cage of these species. Metallofullerene electronic structure and physical properties should be better understood as more metallofullerenes become available for investigation. 31 refs., 1 fig., 1 tab.

  18. Anaerobic sampling and characterization of lanthanofullerenes: Extraction of LaC{sub 76} and other LaC{sub 2n}

    SciTech Connect

    Bandow, S.; Kitagawa, H.; Mitani, T.; Inokuchi, H.

    1992-11-26

    The authors report the extraction of several lanthanum metallofullerenes by toluene, and ESR and mass spectroscopic observations on these samples in anaerobic conditions. They infer hyperfine coupling constants and g values for the molecules, and offer probable candidates for the observed molecules. They find that the ESR signals exhibit strong degradation if the samples are exposed to air for periods of several days.

  19. Current progress on the chemical functionalization and supramolecular chemistry of M@C82

    NASA Astrophysics Data System (ADS)

    Maeda, Yutaka; Tsuchiya, Takahiro; Lu, Xing; Takano, Yuta; Akasaka, Takeshi; Nagase, Shigeru

    2011-06-01

    Since the first discovery of fullerenes in 1985, the insertion of one or more atoms into a hollow fullerene cage has been attempted. Furthermore, synthesis and extraction of metallofullerene, La@Cn, were reported in 1991. Recent successful isolation and purification of metallofullerenes have facilitated the investigation of their chemical properties. This mini-review presents a summary of the recent progress of chemical functionalization and supramolecular chemistry of M@C82. Selective functionalization and successful structural analysis of derivatives have revealed their chemical features arising from endohedral metal doping.Since the first discovery of fullerenes in 1985, the insertion of one or more atoms into a hollow fullerene cage has been attempted. Furthermore, synthesis and extraction of metallofullerene, La@Cn, were reported in 1991. Recent successful isolation and purification of metallofullerenes have facilitated the investigation of their chemical properties. This mini-review presents a summary of the recent progress of chemical functionalization and supramolecular chemistry of M@C82. Selective functionalization and successful structural analysis of derivatives have revealed their chemical features arising from endohedral metal doping. This article was submitted as part of a collection highlighting papers from the Fullerene Silver Anniversary Symposium Conference held in Crete in October 2010.

  20. Metal-containing carbon clusters. Structures, isomerization, and formation of NbC{sub n}{sup +} clusters

    SciTech Connect

    Clemmer, D.E.; Jarrold, M.E.

    1995-08-30

    Injected ion drift tube techniques, including ion mobility measurements and annealing and fragmentation studies, have been used to examine the isomers present for NbC{sub n}{sup +} (n = 15-50) clusters. Isomers attributed to niobium-containing monocyclic and bicyclic rings, graphitic sheets, and metallofullerenes have been identified. Monocyclic rings, where the niobium atom appears to be either inserted into or bound to the outside of the ring, dominate for NbC{sub n}{sup +} with n < 22. Isomers assigned to bicyclic rings are first observed and become dominant around NbC{sub 22}{sup +}. They probably consist of two rings joined together by a niobium atom. An isomer attributed to NbC{sub n}{sup +} graphitic sheets is present for n > 22 and becomes important for clusters with around 30 carbon atoms. Metallofullerenes are first observed for NbC{sub 28}{sup +} and become a major isomer for clusters with n > 31. Both endohedral metallofullerenes and networked metallofullerenes (where the metal atom is part of the cage) have been identified. For clusters with more than around 30 carbon atoms the NbC{sub n}{sup +} bicyclic rings can be annealed into metallofullerenes and, for the smaller ones, metal-containing graphitic sheets. The isomers observed for NbC{sub n}{sup +} are similar to those found for pure C{sub n}{sup +} and LaC{sub n}{sup +}, but the niobium atom has a substantial effect on the properties and the abundances of the different isomers. 47 refs., 11 figs., 1 tab.

  1. Energy stabilization of the s -symmetry superatom molecular orbital by endohedral doping of C 82 fullerene with a lanthanum atom

    SciTech Connect

    Feng, Min; Shi, Yongliang; Lin, Chungwei; Zhao, Jin; Liu, Fupin; Yang, Shangfeng; Petek, Hrvoje

    2013-08-01

    Energy stabilization of the superatom molecular orbitals (SAMOs) in fullerenes is investigated with the goal of involving their nearly free-electron bands in practical charge transport applications. Combining low-temperature scanning tunneling microscopy-based spectroscopic methods and density functional theory calculations on an endohedral metallofullerene La@C82, we confirm that the s-SAMO of C82 fullerene is stabilized by as much as 2 eV with respect to that of C60 by endohedral doping with the La atom. On the copper metal substrate, the s-SAMO energy is further lowered to just 1 eV above the Fermi level, making the applications of s-SAMO state in transport more plausible. We conclude that in an endohedral metallofullerene, the s-SAMO state is stabilized through the hybridization with the s-symmetry valence state of the metal atom and the stabilization energy correlates with the ionization potential of the free atom.

  2. Theoretical prediction of the structures and properties of metal sulfide fullerene Sc2S@C80

    NASA Astrophysics Data System (ADS)

    Gan, Li-Hua; Lei, Dan; Zhao, Chong; Guo, Xiao

    2014-06-01

    Sc2S@C80 has been detected but not been isolated and characterized. To investigate the structures and properties of Sc2S@C80, a density functional theory study on fullerene C80 and metallofullerene Sc2S@C80 was carried out. The calculations demonstrate that Sc2S prefers to be encapsulated inside D5h-C80 and C2v-C80, instead of the well-known Ih-C80. The two lowest-energy isomers of Sc2S@C80 may coexist in the soot. The calculations reveal that there exists strong covalent interaction between the cage and Sc2S cluster, suggesting Sc2S@C80 may have different properties from those usual C80-based metallofullerenes. Raman spectra are provided to help future experimental identification of Sc2S@C80.

  3. Explosion Production of Fullerenes from Carbonaceous Bullet in Vacuum Using Rail Gun

    NASA Astrophysics Data System (ADS)

    Mieno, Tetsu; Yamori, Akira

    2006-04-01

    A carbonaceous bullet is accelerated using a rail gun in vacuum and collides with a metal or carbon target at a speed of approximately 6 km/s, at which the bullet explodes and the high-temperature reaction of carbon particles takes place. As a result, C60 and higher fullerenes are produced. Using a carbonaceous bullet containing metal-oxide powder, endohedral metallofullerenes are also produced by this method.

  4. Synthesis and development of novel fullerene-based structures for photovoltaics, electronic applications and MRI contrast agents

    NASA Astrophysics Data System (ADS)

    Chaur, Manuel N.

    Metallic nitride endohedral metallofullerenes (EMFs) 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 magnetic resonance imaging (MRI) agents. This thesis reports the synthesis of novel metallic nitride EMFs based on Gd, Nd, Pr, Ce and La. These families of metallofullerenes were characterized by different techniques such as X-ray diffraction, MALDI-TOF mass spectrometry, HPLC, electrochemistry and UV/Vis-NIR spectroscopy. The reactivity study of the Gd nitride EMF family and the synthesis of a third generation dendrimer that is attached to EMFs in order to obtain water soluble structures that can be used in MRI applications is also covered. Finally, a comprehensive electrochemical study of carbon rich macrocycles is reported.

  5. Defect Induced Electronic Structure of Uranofullerene

    PubMed Central

    Dai, Xing; Cheng, Cheng; Zhang, Wei; Xin, Minsi; Huai, Ping; Zhang, Ruiqin; Wang, Zhigang

    2013-01-01

    The interaction between the inner atoms/cluster and the outer fullerene cage is the source of various novel properties of endohedral metallofullerenes. Herein, we introduce an adatom-type spin polarization defect on the surface of a typical endohedral stable U2@C60 to predict the associated structure and electronic properties of U2@C61 based on the density functional theory method. We found that defect induces obvious changes in the electronic structure of this metallofullerene. More interestingly, the ground state of U2@C61 is nonet spin in contrast to the septet of U2@C60. Electronic structure analysis shows that the inner U atoms and the C ad-atom on the surface of the cage contribute together to this spin state, which is brought about by a ferromagnetic coupling between the spin of the unpaired electrons of the U atoms and the C ad-atom. This discovery may provide a possible approach to adapt the electronic structure properties of endohedral metallofullerenes. PMID:23439318

  6. Endohedral fullerene with μ3-carbido ligand and titanium-carbon double bond stabilized inside a carbon cage.

    PubMed

    Svitova, A L; Ghiassi, K B; Schlesier, C; Junghans, K; Zhang, Y; Olmstead, M M; Balch, A L; Dunsch, L; Popov, A A

    2014-01-01

    In all metallofullerenes known before this work, metal atoms form single highly polar bonds with non-metal atoms in endohedral cluster. This is rather surprising for titanium taking into account the diversity of organotitanium compounds. Here we show that the arc-discharge synthesis of mixed titanium-lutetium metallofullerenes in the presence of ammonia, melamine or methane unexpectedly results in the formation of TiLu2C@I(h)-C80 with an icosahedral Ih(7) carbon cage. Single-crystal X-ray diffraction and spectroscopic studies of the compound reveal an unprecedented endohedral cluster with a μ3-carbido ligand and Ti-C double bond. The Ti(IV) in TiLu2C@I(h)-C80 can be reversibly reduced to the Ti(III) state. The Ti = C bonding and Ti-localized lowest unoccupied molecular orbital in TiLu2C@Ih-C80 bear a certain resemblance to titanium alkylidenes. TiLu2C@I(h)-C80 is the first metallofullerene with a multiple bond between a metal and the central, non-metal atom of the endohedral cluster.

  7. Endohedral fullerene with μ3-carbido ligand and titanium-carbon double bond stabilized inside a carbon cage.

    PubMed

    Svitova, A L; Ghiassi, K B; Schlesier, C; Junghans, K; Zhang, Y; Olmstead, M M; Balch, A L; Dunsch, L; Popov, A A

    2014-01-01

    In all metallofullerenes known before this work, metal atoms form single highly polar bonds with non-metal atoms in endohedral cluster. This is rather surprising for titanium taking into account the diversity of organotitanium compounds. Here we show that the arc-discharge synthesis of mixed titanium-lutetium metallofullerenes in the presence of ammonia, melamine or methane unexpectedly results in the formation of TiLu2C@I(h)-C80 with an icosahedral Ih(7) carbon cage. Single-crystal X-ray diffraction and spectroscopic studies of the compound reveal an unprecedented endohedral cluster with a μ3-carbido ligand and Ti-C double bond. The Ti(IV) in TiLu2C@I(h)-C80 can be reversibly reduced to the Ti(III) state. The Ti = C bonding and Ti-localized lowest unoccupied molecular orbital in TiLu2C@Ih-C80 bear a certain resemblance to titanium alkylidenes. TiLu2C@I(h)-C80 is the first metallofullerene with a multiple bond between a metal and the central, non-metal atom of the endohedral cluster. PMID:24699547

  8. Ultraviolet photoelectron spectra of (YC)2 @ C82 and Y2 @ C82

    NASA Astrophysics Data System (ADS)

    Hino, Shojun; Wanita, Norihiko; Iwasaki, Kentaro; Yoshimura, Daisuke; Akachi, Takao; Inoue, Takeshi; Ito, Yasuhiro; Sugai, Toshiki; Shinohara, Hisanori

    2005-11-01

    Ultraviolet photoelectron spectra (UPS) of metallofullerenes, (YC)2@C82 (III) and Y2@C82 (III) were measured using a synchrotron radiation light source. The spectral onset energy of (YC)2@C82 (III) was determined to be 0.8 eV below the Fermi level, and that of Y2@C82 (III) was 0.45eV , indicating the semiconductive nature of these metallofullerenes. The UPS consisted of numerous crests and troughs. Further, a change in intensity upon tuning the excitation energy was observed; however, the intensity of the change was not as large as those observed for other fullerenes. The UPS of two metallofullerenes basically resemble each other, although there are minute differences between them. The UPS of (YC)2@C82 (III) was easily reproduced by a simulated spectrum obtained by molecular orbital calculations assuming a C3v (8) cage structure with four additional electrons on the cage. A difference spectrum between the UPS of (YC)2@C82 (III) and Y2@C82 (III) indicates the existence of additional electrons on the cage of Y2@C82 .

  9. Application of extracellular gadolinium-based MRI contrast agents and the risk of nephrogenic systemic fibrosis.

    PubMed

    Heverhagen, J T; Krombach, G A; Gizewski, E

    2014-07-01

    Nephrogenic systemic fibrosis (NSF) is a serious, sometimes fatal disease. Findings in recent years have shown that a causal association between gadolinium containing contrast media and NSF is most likely. Therefore, the regulatory authorities have issued guidelines on the use of gadolinium-containing contrast media which have reduced the number of new cases of NSF to almost zero. However, it is for precisely this reason that the greatest care must still be taken to ensure that these guidelines are complied with. The most important factors are renal function, the quantity of gadolinium administered and coexisting diseases such as inflammation. All of these factors crucially influence the quantity of gadolinium released from the chelat in the body. This free gadolinium is thought to be the trigger for NSF. Other important factors are the stability of the gadolinium complex and furthermore the route of its elimination from the body. Partial elimination via the liver might be an additional protective mechanism. In conclusion, despite the NSF risk, contrast-enhanced MRI is a safe diagnostic procedure which can be used reliably and safely even in patients with severe renal failure, and does not necessarily have to be replaced by other methods.

  10. CuCl2 for the isolation of a broad array of endohedral fullerenes containing metallic, metallic carbide, metallic nitride, and metallic oxide clusters, and separation of their structural isomers.

    PubMed

    Stevenson, Steven; Rottinger, Khristina A

    2013-08-19

    A typical arc-synthesis generates many types of fullerenes and endohedrals. Resulting soot extracts contain a complex mixture of >50 types of fullerenes, metallofullerenes, and their structural isomers. Prior to application development, novel separation methods are required to fractionate this rich array of metallic, metallic carbide, metallic nitride, and metallic oxide endohedrals, all of which can be present in a single, soot extract. Herein, we report the discovery of CuCl2 as a Lewis acid that will selectively precipitate only the more reactive members of each of these endohedral families. The more reactive Sc4O2@Ih-C80, Sc3C2@Ih-C80, and Sc3N@D3h-C78 endohedrals are quickly removed from extracts to greatly decrease the number of endohedrals present in a sample. Experiments indicate that enrichment factors of several orders of magnitude can be achieved within minutes of reaction time. CuCl2 also has sufficient selectivity to resolve and separate structural isomers, as demonstrated with Er2@C82 (isomer I, Cs(6)-C82 versus isomer III). The selective complexation of CuCl2 with fullerenes can be correlated to their first oxidation potential. We estimate a significantly lower threshold of precipitation for CuCl2 (<0.19 V) compared to stronger Lewis acids. Fullerenes and metallofullerenes having first oxidation potentials above 0.19 V tend to remain unreacted in solution. In contrast, species with first oxidation potentials below 0.19 V (vs Fc/Fc(+)) precipitate via complexation, and are easily decomplexed. CuCl2 is compared to Lewis acids having higher precipitation thresholds (e.g., FeCl3) in our goal to predict a priori which endohedrals would remain in solution versus which endohedral species would complex and precipitate. The ability to predict endohedral precipitation a priori is beneficial to the design of purification strategies for metallofullerenes. PMID:23952569

  11. Gd-containing conjugated polymer nanoparticles: bimodal nanoparticles for fluorescence and MRI imaging

    NASA Astrophysics Data System (ADS)

    Hashim, Zeina; Green, Mark; Chung, Pei Hua; Suhling, Klaus; Protti, Andrea; Phinikaridou, Alkystis; Botnar, Rene; Khanbeigi, Raha Ahmad; Thanou, Maya; Dailey, Lea Ann; Nicola J., Commander; Rowland, Caroline; Scott, Jo; Jenner, Dominic

    2014-06-01

    Aqueous bifunctional semiconductor polymer nanoparticles (SPNs), approximately 30 nm in diameter (as measured from electron microscopy), were synthesised using hydrophobic conjugated polymers, amphiphilic phospholipids and a gadolinium-containing lipid. Their fluorescence quantum yields and extinction coefficients were determined, and their MRI T1-weighted relaxation times in water were measured. The bimodal nanoparticles were readily taken up by HeLa and murine macrophage-like J774 cells as demonstrated by confocal laser scanning microscopy, and were found to be MRI-active, generating a linear relationship between T1-weighted relaxation rates and gadolinium concentrations The synthesis is relatively simple, and can easily result in milligrams of materials, although we fully expect scale-up to the gram level to be easily realised.

  12. Application of fullerenes in nanomedicine: an update.

    PubMed

    Dellinger, Anthony; Zhou, Zhiguo; Connor, James; Madhankumar, A B; Pamujula, Sarala; Sayes, Christie M; Kepley, Christopher L

    2013-07-01

    Fullerenes are carbon spheres presently being pursued globally for a wide range of applications in nanomedicine. These molecules have unique electronic properties that make them attractive candidates for diagnostic, therapeutic and theranostic applications. Herein, the latest research is discussed on developing fullerene-based therapeutics as antioxidants for inflammatory diseases, their potential as antiviral/bacterial agents, utility as a drug delivery device and the promise of endohedral fullerenes as new MRI contrast agents. The recent discovery that certain fullerene derivatives can stabilize immune effector cells to prevent or inhibit the release of proinflammatory mediators makes them potential candidates for several diseases such as asthma, arthritis and multiple sclerosis. Gadolinium-containing endohedral fullerenes are being pursued as diagnostic MRI contrast agents for several diseases. Finally, a new class of fullerene-based theranostics has been developed, which combine therapeutic and diagnostic capabilities to specifically detect and kill cancer cells.

  13. Plasma Measurement of Electron Cyclotron Resonance Ion Source for New Materials Production

    NASA Astrophysics Data System (ADS)

    Tanaka, Kiyokatsu; Uchida, Takashi; Minezaki, Hidekazu; Uchiyama, Hidefumi; Asaji, Toyohisa; Muramatsu, Masayuki; Kitagawa, Atsushi; Kato, Yushi; Yoshida, Yoshikazu

    An electron cyclotron resonance ion source (ECRIS) has been designed and developed for a synthesis of new materials such as endohedral metallofullerenes. The plasma chamber diameter is 140 mm in order to produce large m/q ions, like singly charged C60 ions effectively. In this study, we examined the performance of our ECRIS by plasma measurements using a Langmuir probe. The plasma density increased with increasing Ar pressure and reached to 6.1×1017 m-3 at a pressure of 5.0×10-3 Pa. The plasma was produced over a large volume compared with conventional ECRISs.

  14. Magnetic properties of ErSc2N@C80, Er2ScN@C80 and Er3N@C80 fullerenes

    NASA Astrophysics Data System (ADS)

    Tiwari, Archana; Dantelle, Geraldine; Porfyrakis, Kyriakos; Watt, Andrew A. R.; Ardavan, Arzhang; Briggs, G. Andrew D.

    2008-12-01

    The magnetic properties of ErScN@C, ErScN@C and ErN@C metallofullerenes are characterized in the temperature range 2 to 300 K up to a magnetic field of 7 T. The magnetic susceptibility of these fullerenes follows the Curie-Weiss law. The fitting parameters to the Curie-Weiss law provide an effective magnetic moment μ of Er ion in each of the fullerenes. The magnetic moment decreases with the increase in number of Er ions inside the cage. This is related to crystal-field effects, intramolecular interactions and the local quenching of the angular momentum of the ion within the fullerene cage.

  15. Isolation and characterization of Pr@C{sup 82} and Pr{sup 2}@C{sup 80}

    SciTech Connect

    Ding, J.; Yang, S.

    1996-11-13

    Pr@C{sup 82} and Pr{sup 2}@C{sup 80} have been isolated with a purity of >99.0% by an efficient solvent extraction procedure, followed by HPLC separation. UV-VIS-NIR spectra of the metallofullerenes were measured in the wavelength range from 300 to 2100 nm. The X-ray photoelectron spectra of Pr@C{sup 82} and Pr{sup 2}@C{sup 80} suggest that the Pr atoms inside the carbon cages all exist in a cationic form represented by Pr{sup 3+}. 32 refs., 5 figs.

  16. Partial separation of fullerenes by gradient sublimation

    SciTech Connect

    Yeretzian, C.; Wiley, J.B.; Holczer, K.; Su, T.; Nguyen, S.; Kaner, R.B.; Whetten, R.L. )

    1993-09-30

    An experimental technique is investigated to separate/enrich fullerenes of metallofullerenes, exploiting differences in sublimation temperatures without the use of solvents. Fullerenes are sublimed out of the soot and deposited on a quartz rod along a temperature gradient (gradient sublimation). In a position-sensitive experiment the composition of the deposit on the rod is monitored by laser-desorption mass spectrometry. Strongly enriched regions containing specific fullerene molecules (i.e., C[sub 84] or LaC[sub 82]) are observed. Furthermore, C[sub 74], which could not be extracted from the soot by organic solvents, sublimes out of the soot. 26 refs., 6 figs.

  17. Substrate-induced array of quantum dots in a single-walled carbon nanotube

    NASA Astrophysics Data System (ADS)

    Shin, Hyung-Joon; Clair, Sylvain; Kim, Yousoo; Kawai, Maki

    2009-09-01

    Single-walled carbon nanotubes are model one-dimensional structures. They can also be made into zero-dimensional structures; quantum wells can be created in nanotubes by inserting metallofullerenes, by mechanical cutting or by the application of mechanical strain. Here, we report that quantum dot arrays can be produced inside nanotubes simply by causing a misalignment between the nanotube and the <100> direction of a supporting silver substrate. This method does not require chemical or physical treatment of either the substrate or the nanotube. A short quantum dot confinement length of 6 nm results in large energy splittings.

  18. Production of C58 and C56 Ions by Using Electron Cyclotron Resonance Ion Source

    NASA Astrophysics Data System (ADS)

    Tanaka, Kiyokatsu; Uchida, Takashi; Minezaki, Hidekazu; Muramatsu, Masayuki; Biri, Sandor; Asaji, Toyohisa; Shima, Kazushi; Kitagawa, Atsushi; Kato, Yushi; Yoshida, Yoshikazu

    An electron cyclotron resonance ion source (ECRIS) has been developed for a synthesis of endohedral metallofullerenes. The ECRIS has a traditional minimum-B magnetic field and an 8-10 GHz traveling wave tube (TWT) amplifier as a microwave source. C60 plasmas have been generated at the first experiment. Many broken fullerenes C58 and C56 are observed in fullerene ion beams. We investigated the fullerene ion beams against pressures in the ion source. From the results, these fullerene ion currents increase as the decrease of the pressure and the maximum current is 0.81 μA of C602+.

  19. Ultraviolet photoelectron spectra of mono-metal endohedral fullerene Er@C 82 (I)

    NASA Astrophysics Data System (ADS)

    Miyazaki, Takafumi; Sumii, Ryohei; Umemoto, Hisashi; Okimoto, Haruya; Ito, Yasuhiro; Sugai, Toshiki; Shinohara, Hisanori; Hino, Shojun

    2010-12-01

    Ultraviolet photoelectron spectra (UPS) of Erbium endohedral fullerene Er@C 82 (I) were measured using a synchrotron radiation light source. The spectral onset of Er@C 82 (I) was 0.4 eV, which is smaller than those of divalent atom endohedral metallofullerenes and analogous to those of trivalent atom endohedral metallofullerenes. The upper valence structure ( Eb < 5 eV) of Er@C 82 (I) was almost identical with those of C 2v-Tb@C 82 and C 2v-La@C 82. The oxidation states of Er in Er@C 82 from the analogy of the oxidation state of Tb in Tb@C 82 and La in La@C 82 is estimated to be +3. The UPS of Er@C 82 (I) differs from those of Tm@C 82 isomers. The reason of the difference is attributed to differences in their cage structures and oxidation states. The upper valence UPS of Er@C 82 (I) could be well reproduced by a simulated spectrum obtained with a Gaussian03 program module assuming C 82-C 2v cage structure with three additional electrons.

  20. Fullerenes and their derivatives as inhibitors of tumor necrosis factor-α with highly promoted affinities.

    PubMed

    Wu, Gaoyin; Gao, Xuejiao J; Jang, Joonkyung; Gao, Xingfa

    2016-07-01

    Tumor necrosis factor-α (TNF-α) is a cell signalling protein involved in systemic inflammation in infectious and other malignant diseases. Physiologically, it plays an important role in regulating host defence, but its overexpression can lead to serious illnesses including cancer, autoimmune disease and inflammatory disease. Gadolinium-based metallofullerenols, e.g., Gd@C82(OH) x (x ≈ 22), are well known for their abundant biological activities with low toxicity experimentally and theoretically; however, their activity in direct TNF-α inhibition has not been explored. In this work, we investigated the inhibiting effects of four types of fullerene-based ligands: fullerenes, fullerenols, metallofullerenes, and metallofullerenols. We reported previously that fullerenes, metallofullerenes and their hydroxylated derivatives (fullerenols) can reside in the same pocket of the TNF-α dimer as that of SPD304-a known inhibitor of TNF-α [He et al. (2005) Science 310:1022, 18]. Ligand docking and binding free energy calculations suggest that, with a similar nonpolar interaction dominated binding pattern, the fullerene-based ligands, C60, C60(OH)12, Gd@C60, C82, C82(OH)12, Gd@C82, Gd@C82(OH)13 and Gd@C82(OH)21, have larger affinity than currently known inhibitors, and could be used to design novel inhibitors of TNF-α in the future. Graphical Abstract Fullerene-material/TNF-α.

  1. Nanoscale fullerene compression of an yttrium carbide cluster.

    PubMed

    Zhang, Jianyuan; Fuhrer, Tim; Fu, Wujun; Ge, Jiechao; Bearden, Daniel W; Dallas, Jerry; Duchamp, James; Walker, Kenneth; Champion, Hunter; Azurmendi, Hugo; Harich, Kim; Dorn, Harry C

    2012-05-23

    The nanoscale parameters of metal clusters and lattices have a crucial influence on the macroscopic properties of materials. Herein, we provide a detailed study on the size and shape of isolated yttrium carbide clusters in different fullerene cages. A family of diyttrium endohedral metallofullerenes with the general formula of Y(2)C(2n) (n = 40-59) are reported. The high field (13)C nuclear magnetic resonance (NMR) and density functional theory (DFT) methods are employed to examine this yttrium carbide cluster in certain family members, Y(2)C(2)@D(5)(450)-C(100), Y(2)C(2)@D(3)(85)-C(92), Y(2)C(2)@C(84), Y(2)C(2)@C(3v)(8)-C(82), and Y(2)C(2)@C(s)(6)-C(82). The results of this study suggest that decreasing the size of a fullerene cage with the same (Y(2)C(2))(4+) cluster results in nanoscale fullerene compression (NFC) from a nearly linear stretched geometry to a constrained "butterfly" structure. The (13)C NMR chemical shift and scalar (1)J(YC) coupling parameters provide a very sensitive measure of this NFC effect for the (Y(2)C(2))(4+) cluster. The crystal structural parameters of a previously reported metal carbide, Y(2)C(3) are directly compared to the (Y(2)C(2))(4+) cluster in the current metallofullerene study.

  2. Sm@C2v(3)-C80: site-hopping motion of endohedral Sm atom and metal-induced effect on redox profile

    NASA Astrophysics Data System (ADS)

    Xu, Wei; Niu, Ben; Shi, Zujin; Lian, Yongfu; Feng, Lai

    2012-10-01

    A new metallofullerene Sm@C2v(3)-C80 was synthesized and characterized. X-Ray analysis showed that the endohedral Sm atom undergoes a hopping motion between several off-center sites, even at low temperature. In addition, a comparative electrochemical study between Sm@C2v(3)-C80 and Yb@C2v(3)-C80 revealed their different redox potentials, suggesting a metal-induced effect on their redox profiles.A new metallofullerene Sm@C2v(3)-C80 was synthesized and characterized. X-Ray analysis showed that the endohedral Sm atom undergoes a hopping motion between several off-center sites, even at low temperature. In addition, a comparative electrochemical study between Sm@C2v(3)-C80 and Yb@C2v(3)-C80 revealed their different redox potentials, suggesting a metal-induced effect on their redox profiles. CCDC reference number 894168. For crystallographic data in CIF or other electronic format see DOI: 10.1039/c2nr32193a

  3. Fullerenes and their derivatives as inhibitors of tumor necrosis factor-α with highly promoted affinities.

    PubMed

    Wu, Gaoyin; Gao, Xuejiao J; Jang, Joonkyung; Gao, Xingfa

    2016-07-01

    Tumor necrosis factor-α (TNF-α) is a cell signalling protein involved in systemic inflammation in infectious and other malignant diseases. Physiologically, it plays an important role in regulating host defence, but its overexpression can lead to serious illnesses including cancer, autoimmune disease and inflammatory disease. Gadolinium-based metallofullerenols, e.g., Gd@C82(OH) x (x ≈ 22), are well known for their abundant biological activities with low toxicity experimentally and theoretically; however, their activity in direct TNF-α inhibition has not been explored. In this work, we investigated the inhibiting effects of four types of fullerene-based ligands: fullerenes, fullerenols, metallofullerenes, and metallofullerenols. We reported previously that fullerenes, metallofullerenes and their hydroxylated derivatives (fullerenols) can reside in the same pocket of the TNF-α dimer as that of SPD304-a known inhibitor of TNF-α [He et al. (2005) Science 310:1022, 18]. Ligand docking and binding free energy calculations suggest that, with a similar nonpolar interaction dominated binding pattern, the fullerene-based ligands, C60, C60(OH)12, Gd@C60, C82, C82(OH)12, Gd@C82, Gd@C82(OH)13 and Gd@C82(OH)21, have larger affinity than currently known inhibitors, and could be used to design novel inhibitors of TNF-α in the future. Graphical Abstract Fullerene-material/TNF-α. PMID:27316702

  4. Cage-Core Interactions in Fullerenes Enclosing Metal Clusters with Multiple Scandium and Yttrium Atoms.

    NASA Astrophysics Data System (ADS)

    Dan, Liu; Hagelberg, Frank

    2007-03-01

    Pronounced stability has been reported for metallofullerenes of the form NSc3@CN (N = 68, 78) /1/. In response of these and related findings, Density Functional Theory studies have been performed on the relation between cage-core interactions and the geometry as well as stability of endofullerenes with metal impurities containing Sc and Y. Substantial electron transfer from the metal core to the fullerene cage combines with electron backdonation, involving the interaction between the occupied orbitals of the negatively charged cage and the unoccupied d orbitals of the positively charged core. The Hueckel 4n+2 rule, well established in organic chemistry, is shown to provide a valuable heuristic tool for understanding the intramolecular electron transfer and the related stability gain /1/. The usefulness of the aromaticity concept for explaining and predicting the architecture of metallofullerenes is further exemplified by the units Sc2@C84 and Y2@C84 which were analyzed in spin triplet and singlet conditions. The Sc2 core turns out to be realized by two separated ions, while Y2 forms a bound subunit. These findings are in agreement with conclusions based on the 4n + 2 rule, assisted by Nucleus Independent Chemical Shift (NICS) calculations. /1/ Stevenson, S.; Fowler, P.W.; Heine, T.; Duchamp, J.C.; Rice, G.; Glass, T.; Harich, K.; Hadju, F.; Bible, R.; Dorn, H.C. Nature, 2000, 408, 427, /2/ S. S. Park, D. Liu, F. Hagelberg, J. Phys. Chem. A 109, 8865 (2005).

  5. "Dancing inside the ball": the structures and nonlinear optical properties of three Sc2S@C3v(8)-C82 isomers.

    PubMed

    Gao, Feng-Wei; Gao, Ying; Wang, Li-Jie; Xu, Hong-Liang; Sun, Shi-Ling; Su, Zhong-Min

    2015-10-01

    Recently, the crystal structures and electrochemical properties of the isomers (Sc2S "trapped" in C82) have been reported, in which the Sc2S is located inside the different positions of the C82 cage. In the present work, three isomers of endohedral metallofullerenes Sc2S@C3v(8)-C82 (A, B, and C) have been designed to explore the effect of the position of Sc2S on their interaction energies and nonlinear optical properties. Among three isomers, the Sc2S is located in different positions of the C82 cage: the angles of Sc-S-Sc in A, B, and C are 104.9, 114.8, and 115.7°, respectively. Furthermore, the analysis of natural bond orbital (NBO) charge indicates that the electron-transfer is from the Sc2S to the adjacent carbon atoms of the C82 cage. The interaction energy of B is the smallest among three isomers which is -226.2 kcal mol(-1). It was worth mentioning that their first hyperpolarizabilities (β tot) were studied, we found that their β tot values were related to the positions of Sc2S: C (2100) > B (1191) > A (947 au). We hope that the present work can provide a new strategy to promote the nonlinear optical properties of endohedral metallofullerenes by changing the positions of the encapsulated molecular. Graphical abstract Three isomers of endohedral metallofullerenes Sc2S@C3v(8)-C82 (A, B, and C) have been designed to explore the position effect of Sc2S on the interaction energies and nonlinear optical properties. Among three isomers, the Sc2S in B has the most stable position. Significantly, the first hyperpolarizability is related to the position of Sc2S inside the C82 cage, which provides a novel strategy to enhance the first hyperpolarizability by the Sc2S revolving inside the C82 cage.

  6. Synthesis and radiation resistance of fullerenes and fullerene derivatives

    NASA Astrophysics Data System (ADS)

    Shilin, V. A.; Lebedev, V. T.; Sedov, V. P.; Szhogina, A. A.

    2016-07-01

    The parameters of an electric-arc facility for the synthesis of fullerenes and endohedral metallofullerenes are optimized. The resistance of C60 and C70 fullerenes and C60(OH)30 and C70(OH)30 fullerenols against neutron irradiation is studied. It is established that the radiation resistance of the fullerenes is higher than that of the fullerenols, but the radiation resistance of the Gd@C2 n endometallofullerenes is lower than that of the corresponding Gd@C2 n (OH)38 fullerenols. The radiation resistance of mixtures of Me@C2 n (OH)38 ( Me = Gd, Tb, Sc, Fe, and Pr) endometallofullerenes with C60(OH)30 is determined. The factors affecting the radiation resistance of the fullerenes and fullerenols are discussed.

  7. Recent advances in fullerene science (Invited)

    SciTech Connect

    Dunk, P. W.; Marshall, A. G.; Mulet-Gas, M.; Rodriguez-Fortea, A.; Poblet, J. M.

    2014-12-09

    The development of very high resolution FT-ICR mass spectrometers (Marshall et al, 1998) has made a wide range of new measurements possible and by combining this new technology with laser vaporization supersonic beam methods of producing carbon species (chains, rings and fullerenes), new advances in understanding of the fullerene creation mechanisms and their reactivity have been possible. In this overview, new understanding has been developed with regard to: a) closed-network growth of fullerenes (Dunk et al, 2012a); b) small endohedral species such as MαC{sub 28} (Dunk et al., 2012b); c) metallofullerene and fullerene formation under conditions in stellar outflows with relevance to stardust (Dunk et al., 2013a) and d) The formation of heterofullerenes by direct exposure of C{sub 60} toboron vapor (Dunk et al., 2013b)

  8. Acuminated fluorescence of Er3+ centres in endohedral fullerenes through the incarceration of a carbide cluster

    NASA Astrophysics Data System (ADS)

    Plant, Simon R.; Dantelle, Géraldine; Ito, Yasuhiro; Ng, Tsz Cheong; Ardavan, Arzhang; Shinohara, Hisanori; Taylor, Robert A.; Briggs, G. Andrew D.; Porfyrakis, Kyriakos

    2009-07-01

    Photoluminescence spectroscopic measurements have allowed the acquisition of high resolution spectra at low temperature for the endohedral metallofullerenes, Er2 @C82 (isomer I) and Er2C2 @C82 (isomer I). The characteristic emission in the 1.5-1.6 μm region corresponds to the 4I13/2 (m) →4I15/2 (n) transitions of the Er3+ ion for both molecules. The emission arising from Er2C2 @C82 (I) appears acuminated (narrow lines that taper to a point) when compared with that of Er2 @C82 (I) . The Er2C2 @C82 (I) emission linewidths are comparable to those found in crystals, making this molecule of interest for applications where accessible, well-defined quantum states are required.

  9. Electron Transport Through Single Fullerene Molecules (abstract)

    NASA Astrophysics Data System (ADS)

    Stróżecka, Anna; Muthukumar, Kaliappan; Larsson, J. Andreas; Voigtländer, Bert

    2009-04-01

    Fullerenes show potential for applications in nanotechnology due to the possibility of tuning their properties by doping or functionalization. In particular, the endohedral doping of the hollow carbon cage with metal atoms allows changing the electronic and magnetic properties of the molecule without distorting the geometry of the outer shell. Here we present a low temperature scanning tunneling microscopy (STM) and spectroscopy study of the vibrational and transport properties of Ce2atC80 metallofullerenes. We observe that electron transport through the endohedral fullerene is strongly mediated by excitation of molecular vibrations, especially the dynamics of encapsulated atoms. We measure the conductance of the single-molecule junction upon contact between the molecule and the STM tip. To determine the role of doping atoms we compare the results obtained for the endohedrally doped species with those for a hollow fullerene. Analysis shows that localization of electron density on encapsulated atoms hinders the conduction process through the fullerene.

  10. One-Dimensional Confined Motion of Single Metal Atoms inside Double-Walled Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Warner, Jamie H.; Ito, Yasuhiro; Rümmeli, Mark H.; Gemming, Thomas; Büchner, Bernd; Shinohara, Hisanori; Briggs, G. Andrew D.

    2009-05-01

    Peapods containing La@C82 metallofullerenes are transformed into double-walled carbon nanotubes (DWNTs) using in situ electron beam irradiation at 80 kV. Using this low accelerating voltage we find no damage to the outer single-walled carbon nanotube (SWNT) within this time period and the complete formation of an inner nanotube within 5-7 min of irradiation. The La metal atoms are restricted to the interior of the inner SWNT and remain trapped. We demonstrate that energy from electron beam irradiation can drive the lateral confined motion of single La atoms. The interplay between two La atoms confined within the interior of a DWNT is examined and we find large La-La separation unique to this 1D environment. We also demonstrate the formation of TWNTs from DWNT peapods.

  11. Direct Observation of a Gas Molecule (H2, Ar) Swallowed by C60

    SciTech Connect

    Sawa, H.; Kakiuchi, T.; Wakabayashi, Y.; Murata, Y.; Murata, M.; Komatsu, K.; Yakigaya, K.; Takagi, H.; Dragoe, N.

    2007-01-19

    Various types of endohedral fullerene complexes are known to date. The well known metallofullerenes are generally produced by arc-discharge method, but the use of such extremely drastic conditions is apparently not suitable for encapsulation of unstable molecules or gases. We recently succeeded in incorporation of a H2 molecule or an Ar atom in 100% into a C60. In order to observe the endohedral gas molecule directly, the X-ray diffraction analysis using synchrotron radiation were carried out. We observed a gas molecule encapsulated in each fullerene cage using structure analysis and the maximum entropy method. These gas molecules are floating inside of the hollow cavities and are completely isolated from the outside.

  12. Applications of Functionalized Fullerenes in Tumor Theranostics

    PubMed Central

    Chen, Zhiyun; Ma, Lijing; Liu, Ying; Chen, Chunying

    2012-01-01

    Functionalized fullerenes with specific physicochemical properties have been developed for cancer diagnosis and therapy. Notably, metallofullerene is a new class of magnetic resonance imaging (MRI) contrast-enhancing agent, and may have promising applications for clinical diagnosis. Polyhydroxylated and carboxyl fullerenes have been applied to photoacoustic imaging. Moreover, in recent years, functionalized fullerenes have shown potential in tumor therapies, such as photodynamic therapy, photothermal treatment, radiotherapy and chemotherapeutics. Their antitumor effects may be associated with the modulation of oxidative stress, anti-angiogenesis, and immunostimulatory activity. While various types of novel nanoparticle agents have been exploited in tumor theranostics, their distribution, metabolism and toxicity in organisms have also been a source of concern among researchers. The present review summarizes the potential of fullerenes as tumor theranostics agents and their possible underlying mechanisms are discussed. PMID:22509193

  13. Ni endohedral-doped C60 with duality of magnetic moments

    NASA Astrophysics Data System (ADS)

    Li, J. L.; Yang, G. W.

    2010-06-01

    We have performed the magnetic properties of Ni endohedral-doped C60 (Ni@C60) by the spin-polarized density functional calculations, and showed that there are three stable configurations depending on different sites of the doped Ni atoms. Due to the high hybridization and confinement effects, the magnetic moment of the Ni-encapsulated metallofullerenes has duality, i.e., altering between 2.02μB and zero, by positioning the Ni atom in the hollow cage of C60. These findings of the alternative magnetic moments of the Ni-encapsulated C60 implied that Ni@C60 could be expected to be promising as a single molecular magnetic switch.

  14. Metallic nitride azafullerenes: A novel class of fullerenes with interesting electronic properties

    NASA Astrophysics Data System (ADS)

    Ling, Yan; Stevenson, Steven; Zhang, Yong

    2011-05-01

    Following a recent report of the successful facile synthesis of one metallic nitride azafullerene (MNAF), a quantum chemical investigation was reported here on a series of MNAFs: LanSc3 - nN@C79N, (n = 0, 1, 2, 3), in which La and Sc represent the largest and smallest transition metals that can form stable endohedral metallofullerenes. Their steric effects have similar trends compared to the corresponding metallic nitride fullerenes (MNFs) as LanSc3 - nN@C80. However, molecular orbital studies suggest for the first time that MNAFs have excellent electronic properties compared to MNFs and other azafullerenes including C59N, which was recently used in building n-type electronic devices.

  15. Structural interconnections and the role of heptagonal rings in endohedral trimetallic nitride template fullerenes.

    PubMed

    Gan, Li-Hua; Lei, Dan; Fowler, Patrick W

    2016-07-01

    Recent experiments indicate that fullerene isomers outside the classical definition can also encapsulate metallic atoms or clusters to form endohedral metallofullerenes. Our systematic study using DFT calculations, suggests that many heptagon-including nonclassical trimetallic nitride template fullerenes are similar in stability to their classical counterparts, and that conversion between low-energy nonclassical and classical parent cages via Endo-Kroto insertion/extrusion of C2 units and Stone-Wales isomerization may facilitate the formation of endohedral trimetallic nitride fullerenes. Close structural connections are found between favored isomers of trimetallic nitride template fullerenes from C78 to C82 . It appears that the lower symmetry and local deformations associated with introduction of a heptagonal ring favor encapsulation of intrinsically less symmetrical mixed metal nitride clusters. © 2016 Wiley Periodicals, Inc. PMID:27282122

  16. A density functional theory study of shake-up satellites in photoemission of carbon fullerenes and nanotubes.

    PubMed

    Gao, Bin; Wu, ZiYu; Luo, Yi

    2008-06-21

    Carbon 1s shake-up spectra of fullerenes C(60), C(70), and C(82) and single-walled carbon nanotubes (SWCNTs) of (5,5), (6,5), and (7,6) have been investigated by using equivalent core hole Kohn-Sham density functional theory approach, in which only one-electron transition between molecular orbitals within core-hole potential is considered. The calculated spectra are generally in good agreement with results of equivalent core-hole time-dependent density functional theory calculations and available experiments, and reliable assignments for the complicated shake-up spectra of such large systems are provided. Calculations have also been performed for endohedral metallofullerene Gd@C(82) to demonstrate the possible use of shake-up processes to identify the charge transfer between the metal ion and the carbon cage. It is found that the exciton binding energy of all systems under investigation is around 0.5 eV.

  17. In pursuit of nanocarbons.

    PubMed

    Shinohara, Hisanori

    2012-06-01

    With the advent of the Krätschmer-Huffman historical breakthrough on the macroscopic synthesis of C(60) in the late summer of 1990, I decided to stop all my research so far in the area of spectroscopy of gas-phase molecular microclusters. Since then, my odyssey in and quest for the so-called nanocarbons started. Thanks to the brand-new and enchanting world of fullerenes, metallofullerenes, carbon nanotubes and nano-peapods, I have been able to entertain (and still am entertaining!) "the pleasure of finding things out", as Richard Feynman once put it in an interview by a BBC television program in 1981. I believe that as long as one has big dreams and lays the groundwork for the dreams, one will achieve them. My quest for nanocarbons is still on its way.

  18. Carbon clusters containing two metals atoms: Structures, growth mechanism, and fullerene formation

    SciTech Connect

    Shelimov, K.B.; Jarrold, M.F.

    1996-02-07

    Gas phase ion mobility measurments have been used to probe the structures and interconversion of La{sub 2}C{sub n}{sup +} (n = 1-100) isomers. The smallest La{sub 2}C{sub n}{sup +} clusters (n = 10) appear to be planar rings. However, planar mono and bicylic rings (the dominant isomers for C{sub n}{sup +} and LaC{sub n}{sup +}, n = 30, clusters) are not observed for the larger La{sub 2}C{sub n}{sup +} species. Instead, isomers which appear to be three-dimensional ring complexes dominate for unannealed La{sub 2}C{sub n}{sup +} (n + 17) clusters. The formation of these complexes is probably driven by electrostatic forces. For n = 30 the three-dimensional ring complexes isomerize into metallofullerenes (and metal-containing graphite sheets for n = 30-37). The estimated activation energies for these isomerization processes are about 1eV lower than those estimated for similar processes for planar C{sub n}{sup +} and LaC{sub n}{sup +} rings. Metallofullerenes with two non-endohedral metal atoms (for n = 28-29), one endohedral metal atom (for n = 31-100), and two endohedral metal atoms (for n > 64, only even n), are identified. Fullerene derivatives (presumably fullerene + ring complexes) are abundant in the unannealed isomer distributions for La{sub 2}C{sub n}{sup +} (n > 50) clusters, but readily isomerize into regular fullerenes upon collisional heating. 47 refs., 9 figs., 2 tabs.

  19. Isolation and Crystallographic Characterization of La2C2@Cs(574)-C102 and La2C2@C2(816)-C104: Evidence for the Top-Down Formation Mechanism of Fullerenes.

    PubMed

    Cai, Wenting; Li, Fang-Fang; Bao, Lipiao; Xie, Yunpeng; Lu, Xing

    2016-05-25

    Tubular higher fullerenes are prototypes of finite-length end-capped carbon nanotubes (CNTs) whose structures can be accurately characterized by single-crystal X-ray diffraction crystallography. We present here the isolation and crystallographic characterization of two unprecedented higher fullerenes stabilized by the encapsulation of a La2C2 cluster, namely, La2C2@Cs(574)-C102, which has a perfect tubular cage corresponding to a short (10, 0) zigzag carbon nanotube, and La2C2@C2(816)-C104 which has a defective cage with a pyracylene motif inserting into the cage waist. Both cages provide sufficient spaces for the large La2C2 cluster to adopt a stretched and nearly planar configuration, departing from the common butterfly-like configuration which has been frequently observed in midsized carbide metallofullerenes (e.g., Sc2C2@C80-84), to achieve strong metal-cage interactions. More meaningfully, our crystallographic results demonstrate that the defective cage of C2(816)-C104 is a starting point to form the other three tubular cages known so far, i.e., D5(450)-C100, Cs(574)-C102, and D3d(822)-C104, presenting evidence for the top-down formation mechanism of fullerenes. The fact that only the large La2C2 cluster has been found in giant fullerene cages (C>100) and the small clusters M2C2 (M = Sc, Y, Er, etc.) are present in midsized fullerenes (C80-C86) indicates that geometrical matching between the cluster and the cage, which ensures strong metal-cage interactions, is an important factor controlling the stability of the resultant metallofullerenes, in addition to charge transfer.

  20. Isolation and Crystallographic Characterization of La2C2@Cs(574)-C102 and La2C2@C2(816)-C104: Evidence for the Top-Down Formation Mechanism of Fullerenes.

    PubMed

    Cai, Wenting; Li, Fang-Fang; Bao, Lipiao; Xie, Yunpeng; Lu, Xing

    2016-05-25

    Tubular higher fullerenes are prototypes of finite-length end-capped carbon nanotubes (CNTs) whose structures can be accurately characterized by single-crystal X-ray diffraction crystallography. We present here the isolation and crystallographic characterization of two unprecedented higher fullerenes stabilized by the encapsulation of a La2C2 cluster, namely, La2C2@Cs(574)-C102, which has a perfect tubular cage corresponding to a short (10, 0) zigzag carbon nanotube, and La2C2@C2(816)-C104 which has a defective cage with a pyracylene motif inserting into the cage waist. Both cages provide sufficient spaces for the large La2C2 cluster to adopt a stretched and nearly planar configuration, departing from the common butterfly-like configuration which has been frequently observed in midsized carbide metallofullerenes (e.g., Sc2C2@C80-84), to achieve strong metal-cage interactions. More meaningfully, our crystallographic results demonstrate that the defective cage of C2(816)-C104 is a starting point to form the other three tubular cages known so far, i.e., D5(450)-C100, Cs(574)-C102, and D3d(822)-C104, presenting evidence for the top-down formation mechanism of fullerenes. The fact that only the large La2C2 cluster has been found in giant fullerene cages (C>100) and the small clusters M2C2 (M = Sc, Y, Er, etc.) are present in midsized fullerenes (C80-C86) indicates that geometrical matching between the cluster and the cage, which ensures strong metal-cage interactions, is an important factor controlling the stability of the resultant metallofullerenes, in addition to charge transfer. PMID:27157415

  1. Localized Corrosion of a Neutron Absorbing Ni-Cr-Mo-Gd Alloy

    SciTech Connect

    R.E. Mizia; T. E. Lister; P. J. Pinhero; T. L. Trowbridge

    2005-04-01

    The National Spent Nuclear Fuel Program, located at the Idaho National Laboratory (INL), has developed a new nickel-chromium-molybdenum-gadolinium structural alloy for storage and long-term disposal of spent nuclear fuel (SNF). The new alloy will be used for SNF storage container inserts for nuclear criticality control. Gadolinium has been chosen as the neutron absorption alloying element due to its high thermal neutron absorption cross section. This alloy must be resistant to localized corrosion when exposed to postulated Yucca Mountain in-package chemistries. The corrosion resistance properties of three experimental heats of this alloy are presented. The alloys performance are be compared to Alloy 22 and borated stainless steel. The results show that initially the new Ni-Cr-Mo-Gd alloy is less resistant to corrosion as compared to another Ni-Cr-Mo-Gd alloy (Alloy 22); but when the secondary phase that contains gadolinium (gadolinide) is dissolved, the alloy surface becomes passive. The focus of this work is to qualify these gadolinium containing materials for ASME code qualification and acceptance in the Yucca Mountain Repository.

  2. Routine MRI findings of the asymptomatic foot in diabetic patients with unilateral Charcot foot

    PubMed Central

    2010-01-01

    Background Imaging studies of bones in patients with sensory deficits are scarce. Aim To investigate bone MR images of the lower limb in diabetic patients with severe sensory polyneuropathy, and in control subjects without sensory deficits. Methods Routine T1 weighted and T2-fat-suppressed-STIR-sequences without contrast media were performed of the asymptomatic foot in 10 diabetic patients with polyneuropathy and unilateral inactive Charcot foot, and in 10 matched and 10 younger, non-obese unmatched control subjects. Simultaneously, a Gadolinium containing phantom was also assessed for reference. T1 weighted signal intensity (SI) was recorded at representative regions of interest at the peritendineal soft tissue, the tibia, the calcaneus, and at the phantom. Any abnormal skeletal morphology was also recorded. Results Mean SI at the soft tissue, the calcaneus, and the tibia, respectively, was 105%, 105% and 84% of that at the phantom in the matched and unmatched control subjects, compared to 102% (soft tissue), 112% (calcaneus) and 64% (tibia) in the patients; differences of tibia vs. calcaneus or soft tissue were highly significant (p < 0.005). SI at the tibia was lower in the patients than in control subjects (p < 0.05). Occult traumatic skeletal lesions were found in 8 of the 10 asymptomatic diabetic feet (none in the control feet). Conclusion MR imaging did not reveal grossly abnormal bone marrow signalling in the limbs with severe sensory polyneuropathy, but occult sequelae of previous traumatic injuries. PMID:20412561

  3. Accumulation of Phase-Shift Nanoemulsions to Enhance MR-Guided Ultrasound-Mediated Tumor Ablation In Vivo

    PubMed Central

    Kopechek, Jonathan A.; Park, Eunjoo; Mei, Chang-Sheng; McDannold, Nathan J.; Porter, Tyrone M.

    2014-01-01

    Magnetic resonance-guided high intensity focused ultrasound (MRgHIFU) is being explored as a non-invasive technology to treat solid tumors. However, the clinical use of HIFU for tumor ablation applications is currently limited by the long treatment times required. Phase-shift nanoemulsions (PSNE), consisting of liquid perfluorocarbon droplets that can be vaporized into microbubbles, are being developed to accelerate HIFU-mediated heating. The purpose of this study was to examine accumulation of PSNE in intramuscular rabbit tumors in vivo. MR images were acquired before and after intravenous injection of gadolinium-containing PSNE. MR signal enhancement was observed in rabbit tumors up to six hours after injection, indicating that PSNE accumulated in the tumors. In addition, PSNE vaporization was detected in the tumor with B-mode ultrasound imaging, and MR thermometry measurements indicated that PSNE accelerated the rate of HIFU-mediated heating. These results suggest that PSNE could dramatically improve the efficiency and clinical feasibility of MRgHIFU. PMID:23502252

  4. Scintillation Counters

    NASA Astrophysics Data System (ADS)

    Bell, Zane W.

    Scintillators find wide use in radiation detection as the detecting medium for gamma/X-rays, and charged and neutral particles. Since the first notice in 1895 by Roentgen of the production of light by X-rays on a barium platinocyanide screen, and Thomas Edison's work over the following 2 years resulting in the discovery of calcium tungstate as a superior fluoroscopy screen, much research and experimentation have been undertaken to discover and elucidate the properties of new scintillators. Scintillators with high density and high atomic number are prized for the detection of gamma rays above 1 MeV; lower atomic number, lower-density materials find use for detecting beta particles and heavy charged particles; hydrogenous scintillators find use in fast-neutron detection; and boron-, lithium-, and gadolinium-containing scintillators are used for slow-neutron detection. This chapter provides the practitioner with an overview of the general characteristics of scintillators, including the variation of probability of interaction with density and atomic number, the characteristics of the light pulse, a list and characteristics of commonly available scintillators and their approximate cost, and recommendations regarding the choice of material for a few specific applications. This chapter does not pretend to present an exhaustive list of scintillators and applications.

  5. Purification of cerium, neodymium and gadolinium for low background experiments

    NASA Astrophysics Data System (ADS)

    Boiko, R. S.; Barabash, A. S.; Belli, P.; Bernabei, R.; Cappella, F.; Cerulli, R.; Danevich, F. A.; Incicchitti, A.; Laubenstein, M.; Mokina, V. M.; Nisi, S.; Poda, D. V.; Polischuk, O. G.; Tretyak, V. I.

    2014-01-01

    Cerium, neodymium and gadolinium contain double beta active isotopes. The most interesting are 150Nd and 160Gd (promising for 0ν2β search), 136Ce (2β+ candidate with one of the highest Q2β). The main problem of compounds containing lanthanide elements is their high radioactive contamination by uranium, radium, actinium and thorium. The new generation 2β experiments require development of methods for a deep purification of lanthanides from the radioactive elements. A combination of physical and chemical methods was applied to purify cerium, neodymium and gadolinium. Liquid-liquid extraction technique was used to remove traces of Th and U from neodymium, gadolinium and for purification of cerium from Th, U, Ra and K. Co-precipitation and recrystallization methods were utilized for further reduction of the impurities. The radioactive contamination of the samples before and after the purification was tested by using ultra-low-background HPGe gamma spectrometry. As a result of the purification procedure the radioactive contamination of gadolinium oxide (a similar purification efficiency was reached also with cerium and neodymium oxides) was decreased from 0.12 Bq/kg to 0.007 Bq/kg in 228Th, from 0.04 Bq/kg to <0.006 Bq/kg in 226Ra, and from 0.9 Bq/kg to 0.04 Bq/kg in 40K. The purification methods are much less efficient for chemically very similar radioactive elements like actinium, lanthanum and lutetium.

  6. Surface interactions with compartmentalized cellular phosphates explain rare earth oxide nanoparticle hazard and provide opportunities for safer design.

    PubMed

    Li, Ruibin; Ji, Zhaoxia; Chang, Chong Hyun; Dunphy, Darren R; Cai, Xiaoming; Meng, Huan; Zhang, Haiyuan; Sun, Bingbing; Wang, Xiang; Dong, Juyao; Lin, Sijie; Wang, Meiying; Liao, Yu-Pei; Brinker, C Jeffrey; Nel, Andre; Xia, Tian

    2014-02-25

    Growing international exploitation of rare earth oxides (REOs) for commercial and biological use has increased the possibility of human exposure and adverse health effects. Occupational exposure to rare earth materials in miners and polishers leads to a severe form of pneumoconiosis, while gadolinium-containing MRI contrast agents cause nephrogenic systemic fibrosis in patients with renal impairment. The mechanisms for inducing these adverse pro-fibrogenic effects are of considerable importance for the safety assessment of REO particles as well as presenting opportunities for safer design. In this study, using a well-prepared REO library, we obtained a mechanistic understanding of how REOs induce cellular and pulmonary damage by a compartmentalized intracellular biotransformation process in lysosomes that results in pro-fibrogenic growth factor production and lung fibrosis. We demonstrate that rare earth oxide ion shedding in acidifying macrophage lysosomes leads to biotic phosphate complexation that results in organelle damage due to stripping of phosphates from the surrounding lipid bilayer. This results in nanoparticle biotransformation into urchin shaped structures and setting in motion a series of events that trigger NLRP3 inflammasome activation, IL-1β release, TGF-β1 and PDGF-AA production. However, pretreatment of REO nanoparticles with phosphate in a neutral pH environment prevents biological transformation and pro-fibrogenic effects. This can be used as a safer design principle for producing rare earth nanoparticles for biological use.

  7. Neutron capture nuclei-containing carbon nanoparticles for destruction of cancer cells.

    PubMed

    Hwang, Kuo Chu; Lai, Po Dong; Chiang, Chi-Shiun; Wang, Pei-Jen; Yuan, Chiun-Jye

    2010-11-01

    HeLa cells were incubated with neutron capture nuclei (boron-10 and gadolinium)-containing carbon nanoparticles, followed by irradiation of slow thermal neutron beam. Under a neutron flux of 6 x 10(11) n/cm(2) (or 10 min irradiation at a neutron flux of 1 x 10(9) n/cm(2) s), the percentages of acute cell death at 8 h after irradiation are 52, 55, and 28% for HeLa cells fed with BCo@CNPs, GdCo@CNPs, and Co@CNPs, respectively. The proliferation capability of the survived HeLa cells was also found to be significantly suppressed. At 48 h after neutron irradiation, the cell viability further decreases to 35 +/- 5% as compared to the control set receiving the same amount of neutron irradiation dose but in the absence of carbon nanoparticles. This work demonstrates "proof-of-concept" examples of neutron capture therapy using (10)B-, (157)Gd-, and (59)Co-containing carbon nanoparticles for effective destruction of cancer cells. It will also be reported the preparation and surface functionalization of boron or gadolinium doped core-shell cobalt/carbon nanoparticles (BCo@CNPs, GdCo@CNPs and Co@CNPs) using a modified DC pulsed arc discharge method, and their characterization by various spectroscopic measurements, including TEM, XRD, SQUID, FT-IR, etc. Tumor cell targeting ability was introduced by surface modification of these carbon nanoparticles with folate moieties.

  8. Nuclear design of Helical Cruciform Fuel rods

    SciTech Connect

    Shirvan, K.; Kazimi, M. S.

    2012-07-01

    In order to increase the power density of current and new light water reactor designs, the Helical Cruciform Fuel (HCF) rods are proposed. The HCF rods are equivalent to a cylindrical rod, with the fuel in a cruciform shaped, twisted axially. The HCF rods increase the surface area to volume ratio and inter-subchannel mixing behavior due to their cruciform and helical shapes, respectively. In a previous study, the HCF rods have shown the potential to up-rate existing PWRs by 50% and BWRs by 25%. However, HCF rods do display different neutronics modeling and performance. The cruciform cross section of HCF rods creates radially asymmetric heat generation and temperature distribution. The nominal HCF rod's beginning of life reactivity is reduced, compared to a cylindrical rod with the same fuel volume, by 500 pcm, due to increase in absorption in cladding. The rotation of these rods accounts for reactivity changes, which depends on the H/HM ratio of the pin cell. The HCF geometry shows large sensitivities to U{sup 235} or gadolinium enrichments compared to a cylindrical geometry. In addition, the gadolinium-containing HCF rods show a stronger effect on neighboring HCF rods than in case of cylindrical rods, depending on the orientation of the HCF rods. The helical geometry of the rods introduces axial shadowing of about 600 pcm, not seen in typical cylindrical rods. (authors)

  9. Surface Interactions with Compartmentalized Cellular Phosphates Explain Rare Earth Oxide Nanoparticle Hazard and Provide Opportunities for Safer Design

    PubMed Central

    2014-01-01

    Growing international exploitation of rare earth oxides (REOs) for commercial and biological use has increased the possibility of human exposure and adverse health effects. Occupational exposure to rare earth materials in miners and polishers leads to a severe form of pneumoconiosis, while gadolinium-containing MRI contrast agents cause nephrogenic systemic fibrosis in patients with renal impairment. The mechanisms for inducing these adverse pro-fibrogenic effects are of considerable importance for the safety assessment of REO particles as well as presenting opportunities for safer design. In this study, using a well-prepared REO library, we obtained a mechanistic understanding of how REOs induce cellular and pulmonary damage by a compartmentalized intracellular biotransformation process in lysosomes that results in pro-fibrogenic growth factor production and lung fibrosis. We demonstrate that rare earth oxide ion shedding in acidifying macrophage lysosomes leads to biotic phosphate complexation that results in organelle damage due to stripping of phosphates from the surrounding lipid bilayer. This results in nanoparticle biotransformation into urchin shaped structures and setting in motion a series of events that trigger NLRP3 inflammasome activation, IL-1β release, TGF-β1 and PDGF-AA production. However, pretreatment of REO nanoparticles with phosphate in a neutral pH environment prevents biological transformation and pro-fibrogenic effects. This can be used as a safer design principle for producing rare earth nanoparticles for biological use. PMID:24417322

  10. Specific lipase-responsive polymer-coated gadolinium nanoparticles for MR imaging of early acute pancreatitis.

    PubMed

    Zhang, Hong-Wu; Wang, Li-Qin; Xiang, Qing-Feng; Zhong, Qian; Chen, Lu-Ming; Xu, Cai-Xia; Xiang, Xian-Hong; Xu, Bo; Meng, Fei; Wan, Yi-Qian; Deng, David Y B

    2014-01-01

    Currently, available methods for diagnosis of acute pancreatitis (AP) are mainly dependent on serum enzyme analysis and imaging techniques that are too low in sensitivity and specificity to accurately and promptly diagnose AP. The lack of early diagnostic tools highlights the need to search for a highly effective and specific diagnostic method. In this study, we synthesized a conditionally activated, gadolinium-containing, nanoparticle-based MRI nanoprobe as a diagnostic tool for the early identification of AP. Gadolinium diethylenetriaminepentaacetic fatty acid (Gd-DTPA-FA) nanoparticles were synthesized by conjugation of DTPA-FA ligand and gadolinium acetate. Gd-DTPA-FA exhibited low cytotoxicity and excellent biocompatibility when characterized in vitro and in vivo studies. L-arginine induced a gradual increase in the intensity of the T1-weighted MRI signal from 1 h to 36 h in AP rat models. The increase in signal intensity was most significant at 1 h, 6 h and 12 h. These results suggest that the Gd-DTPA-FA as an MRI contrast agent is highly efficient and specific to detect early AP.

  11. Aneurysm Sac Pressure Measurement with Minimally Invasive Implantable Pressure Sensors: An Alternative to Current Surveillance Regimes after EVAR?

    SciTech Connect

    Springer, Fabian Guenther, Rolf W.; Schmitz-Rode, Thomas

    2008-05-15

    Current protocols for surveillance after endovascular repair (EVAR) of abdominal aortic aneurysms are mostly based on costly and time-consuming imaging procedures and aim to detect adverse events such as graft migration, endoleaks or aneurysm sac enlargement. These imaging procedures are either associated with radiation exposure to the patients or may be harmful to the patient due to the use of iodine- or gadolinium-containing contrast agents. Furthermore the advantages of EVAR in the short term might be negated by the necessity for endograft surveillance over years. Thus, alternative modalities for follow-up are being investigated. One of these technologies provides pressure information directly from the aneurysm sac. This noninvasive, telemetric pressure sensing was tested in vitro as well as in first clinical trials and was able to identify successful aneurysm exclusion after EVAR. The telemetric pressure sensors showed a promising efficacy and accuracy in detecting type I and type III endoleaks and will help to clarify the clinical relevance of type II endoleaks. This article provides an overview of the in vitro sensors investigated as well as the first clinical trials and the sensors' potential to change the current endograft surveillance regimes.

  12. Development of virus-like particles for diagnostic and prophylactic biomedical applications

    PubMed Central

    Schwarz, Benjamin; Douglas, Trevor

    2015-01-01

    As ordered nanoscale architectures, viruses and virus-like particles (VLPs) remain unsurpassed by synthetic strategies to produce uniform and symmetric nanoparticles. Maintaining or mimicking the symmetry of pathogenic viruses, VLPs offer a ready platform for facilitating recognition, uptake, and processing by the immune system. An emerging understanding of how viruses interact with the immune system offers a means of precisely designing nanoparticles for biomedical use, both with respect to the structure of the particle as well as their ability to stimulate the immune system. Here we discuss recent advances by our group toward two parallel and complementary applications of VLPs, derived primarily from plants, bacteriophage, and nonviral sources, in biomedicine: diagnostic imaging and rational vaccine design. First we discuss advances in increasing VLP payloads of gadolinium magnetic resonance imaging (MRI) contrast agent as well as controlling the characteristics of individual gadolinium containing molecules to increase efficacy. In order to better understand the in vivo potential of VLP constructs, we then discuss the interface of protein-cages and the immune system beginning with the nonspecific innate immune system stimulation and continuing into the use of non-pathogenic VLPs as scaffolds for specific antigen presentation and control of the immune response. PMID:25677105

  13. Scandium carbide/cyanide alloyed cluster inside fullerene cage: synthesis and structural studies of Sc3(μ3-C2)(μ3-CN)@Ih-C80.

    PubMed

    Wang, Taishan; Wu, Jingyi; Feng, Yongqiang

    2014-11-21

    A new Sc3(C2)(CN)@Ih-C80 metallofullerene encaging a scandium carbide/cyanide alloyed cluster was prepared and investigated. Sc3(C2)(CN)@Ih-C80 was synthesized by the arc-discharging method and isolated by HPLC. Its experimental (13)C NMR spectrum with two signals clearly confirms an icosahedral C80 cage, and theoretically calculated (13)C NMR peaks agree well with the experimental results. Further, theoretical calculations disclosed that the endohedral μ3-C2 and μ3-CN moieties are situated on each side of the triangular shaped Sc3 unit to form a scandium carbide/cyanide alloyed cluster. Kohn-Sham molecular orbitals reveals the electronic structure of (Sc(3+))3(C2)(2-)(CN)(-)@C80(6-), in which two anions, μ3-C2(2-) and μ3-(CN)(-), construct and stabilize this special molecule together. The FTIR and Raman spectra of Sc3(C2)(CN)@Ih-C80 were analyzed by comparison of the experimental and calculated results to further confirm its structure and to uncover cluster-based vibrational modes.

  14. Biosafety assessment of Gd@C82(OH)22 nanoparticles on Caenorhabditis elegans

    NASA Astrophysics Data System (ADS)

    Zhang, Wendi; Sun, Baoyun; Zhang, Longze; Zhao, Baolu; Nie, Guangjun; Zhao, Yuliang

    2011-06-01

    Gd@C82(OH)22, a water-soluble endohedral metallofullerene derivative, has been proven to possess significant antineoplastic activity in mice. Toxicity studies of the nanoparticle have shown some evidence of low or non toxicity in mice and cell models. Here we employed Caenorhabditis elegans (C. elegans) as a model organism to further evaluate the short- and long-term toxicity of Gd@C82(OH)22 and possible behavior changes under normal and stress culture conditions. With treatment of Gd@C82(OH)22 at 0.01, 0.1, 1.0 and 10 μg ml-1 within one generation (short-term), C. elegans showed no significant decrease in longevity or thermotolerance compared to the controls. Furthermore, when Gd@C82(OH)22 treatment was extended up to six generations (long-term), non-toxic effects to the nematodes were found. In addition, data from body length measurement, feeding rate and egg-laying assays with short-term treatment demonstrated that the nanoparticles have no significant impact on the individual growth, feeding behavior and reproductive ability, respectively. In summary, this work has shown that Gd@C82(OH)22 is tolerated well by worms and it has no apparent toxic effects on longevity, stress resistance, growth and behaviors that were observed in both adult and young worms. Our work lays the foundations for further developments of this anti-neoplastic agent for clinical applications.

  15. How are small endohedral silicon clusters stabilized?

    PubMed

    Avaltroni, Fabrice; Steinmann, Stephan N; Corminboeuf, Clémence

    2012-11-21

    Clusters in the (Be, B, C)@Si(n)((0,1,2+)) (n = 6-10) series, isoelectronic to Si(n)(2-), present multiple symmetric structures, including rings, cages and open structures, which the doping atom stabilizes using contrasting bonding mechanisms. The most striking feature of these clusters is the absence of electron transfer (for Be) or even the inversion (for B and C) in comparison to classic endohedral metallofullerenes (e.g. from the outer frameworks towards the enclosed atom). The relatively small cavity of the highly symmetric Si(8) cubic cage benefits more strongly from the encapsulation of a boron atom than from the insertion of a too large beryllium atom. Overall, the maximization of multicenter-type bonding, as visualized by the Localized Orbital Locator (LOL), is the key to the stabilization of the small Si(n) cages. Boron offers the best balance between size, electronegativity and delocalized bonding pattern when compared to beryllium and carbon. PMID:22968417

  16. Structural Stability and Deformation of Solvated Sm@C2(45)-C90 under High Pressure

    PubMed Central

    Cui, Jinxing; Yao, Mingguang; Yang, Hua; Liu, Ziyang; Liu, Shijie; Du, Mingrun; Li, Quanjun; Liu, Ran; Cui, Tian; Liu, Bingbing

    2016-01-01

    Solvated fullerenes recently have been shown to exhibit novel compression behaviors compared with the pristine fullerenes. However, less attention has been focused on the large cage endohedral metallofullerenes. Here, we have firstly synthesized solvated Sm@C90 microrods by a solution drop-drying method, and then studied the transformations under high pressure. The pressure-induced structural evolutions of Sm@C90 molecules both undergo deformation and collapse. The band gaps of both samples decrease with increasing pressure. The trapped Sm atom plays a role in restraining the compression of the adjacent bonds. The solvent plays a role in protecting Sm@C90 against collapse in the region of 12–20 GPa, decreasing and postponing the change of band gap. Above 30 GPa, the carbon cages collapse. Released from 45 GPa, the compressed solvated Sm@C90 forms a new ordered amorphous carbon cluster (OACC) structure with metal atoms trapped in the units of amorphous carbon clusters, which is different from the OACC structure formed by compressing solvated C60 and C70. This discovery opens the door for the creation of new carbon materials with desirable structural and physical properties when suitable starting materials are selected. PMID:27503144

  17. Structural Stability and Deformation of Solvated Sm@C2(45)-C90 under High Pressure

    NASA Astrophysics Data System (ADS)

    Cui, Jinxing; Yao, Mingguang; Yang, Hua; Liu, Ziyang; Liu, Shijie; Du, Mingrun; Li, Quanjun; Liu, Ran; Cui, Tian; Liu, Bingbing

    2016-08-01

    Solvated fullerenes recently have been shown to exhibit novel compression behaviors compared with the pristine fullerenes. However, less attention has been focused on the large cage endohedral metallofullerenes. Here, we have firstly synthesized solvated Sm@C90 microrods by a solution drop-drying method, and then studied the transformations under high pressure. The pressure-induced structural evolutions of Sm@C90 molecules both undergo deformation and collapse. The band gaps of both samples decrease with increasing pressure. The trapped Sm atom plays a role in restraining the compression of the adjacent bonds. The solvent plays a role in protecting Sm@C90 against collapse in the region of 12-20 GPa, decreasing and postponing the change of band gap. Above 30 GPa, the carbon cages collapse. Released from 45 GPa, the compressed solvated Sm@C90 forms a new ordered amorphous carbon cluster (OACC) structure with metal atoms trapped in the units of amorphous carbon clusters, which is different from the OACC structure formed by compressing solvated C60 and C70. This discovery opens the door for the creation of new carbon materials with desirable structural and physical properties when suitable starting materials are selected.

  18. Theoretical survey on M@C80 (M = Ca, Sr, and Ba): Behavior of different alkaline earth metal impacting the chemical stability and electronic properties

    NASA Astrophysics Data System (ADS)

    Cui, Jin-Bo; Guo, Yi-Jun; Li, Qiao-Zhi; Zhao, Pei; Zhao, Xiang

    2016-08-01

    Structures of mono-metallofullerenes M@C80 (M = Ca, Sr, and Ba) that separated in early experiment are determined owning the C2v(31920)-C80 cage. The change rule of properties for M@C80 (M = Ca, Sr, and Ba) influenced by different inner metal are discussed. As the trapped metal changes from calcium to barium, performance of thermodynamic stabilities for M@C2v(31920)-C80, M@C2v(31922)-C80, and M@D5h(31923)-C80 are significantly different. Orbital analysis suggests that the lowest unoccupied molecular orbitals (LUMOs) of Ca@C2v(31920)-C80 and Ca@D5h(31923)-C80 are mostly located on the trapped metal, whereas reduction reactions of Ca@C2v(31920)-C80 and Ca@D5h(31923)-C80 occur on the fullerene cage. Natural electron configuration analyses demonstrates that the decentralized electron back-donation of Ba@C2v(31920)-C80 would take responsible for the instability of itself. Electronic properties such as electron affinities and ionization potentials are significantly affected by encapsulated metal are also found. Computational UV-visible-NIR spectra for M@C2v(31920)-C80 (M = Ca, Sr, Ba) are in perfect accord with the spectra obtained experimentally.

  19. Cell Internalization Studies of Gadofullerene-(ZME-018) Immunoconjugates into A375m Melanoma Cells12

    PubMed Central

    Berger, Christopher Scott; Marks, John W; Bolskar, Robert D; Rosenblum, Michael G; Wilson, Lon J

    2011-01-01

    Fullerene (C60)-monoclonal antibody (mAb) immunoconjugates have been determined to internalize into target cells using water-soluble Gd3+ ion-filled metallofullerenes (Gd@C60[OH]x). Two separate conjugations of Gd@C60(OH)x with the antibody ZME-018 and a murine antibody mixture (MuIgG) were performed in a 1:5 mAb/Gd@C60 ratio. Characterization of the immunoconjugates was established using inductively coupled plasma mass spectrometry (ICP-MS) for Gd3+ and UV-Vis spectrometry (for Gd@C60 + C60). Once conjugated, enzyme-linked immunosorbent assays showed little change in the specific binding of ZME-018. Each immunoconjugate was exposed to two cancer cell lines, A375m (antigen positive), and T24, bladder carcinoma (antigen negative). Internalization levels of the immunoconjugate were determined at various time points during 24 hours by harvesting and digesting the cells with 70% HNO3 for Gd3+ ion analysis by ICP-MS. These results are the first to demonstrate the practicality of a targeted cancer therapy based on fullerene immunotherapy. PMID:22190999

  20. From Pauli's birthday to 'Confinement Resonances' - a potted history of Quantum Confinement

    NASA Astrophysics Data System (ADS)

    Connerade, J. P.

    2013-06-01

    Quantum Confinement is in some sense a new subject. International meetings dedicated to Quantum Confinement have occurred only recently in Mexico City (the first in 2010 and the second, in September 2011). However, at least in principle, the subject has existed since a very long time. Surprisingly perhaps, it lay dormant for many years, for want of suitable experimental examples. However, when one looks carefully at its origin, it turns out to have a long and distinguished history. In fact, the problem of quantum confinement raises a number of very interesting issues concerning boundary conditions in elementary quantum mechanics and how they should be applied to real problems. Some of these issues were missed in the earliest papers, but are implicit in the structure of quantum mechanics, and lead to the notion of Confinement Resonances, the existence of which was predicted theoretically more than ten years ago. Although, for several reasons, these resonances remained elusive for a very long time, they have now been observed experimentally, which puts the whole subject in much better shape and, together with the advent of metallofullerenes, has contributed to its revival.

  1. Extractions of Y@C{sub 60}, Ba@C{sub 60}, La@C{sub 60}, Ce@C{sub 60}, Pr@C{sub 60}, Nd@C{sub 60}, and Gd@C{sub 60} with aniline

    SciTech Connect

    Kubozono, Yoshihiro; Maeda, Hironobu; Takabayashi, Yasuhiro; Hiraoka, Koji; Nakai, Takeshi; Kashino, Setsuo; Emura, Shuichi; Ukita, Shigeyuki; Sogabe, Toshiaki

    1996-07-24

    Recently many endohedral metallofullerenes such as M@C{sub 74}, M@C{sub 80}, and M@C{sub 82} (M: metal atom) have been successfully isolated by the high performance liquid chromatography (HPLC) technique. Some M@C{sub 60} were prepared in primary soots by an arc-heating or a laser-vaporization method, but the isolation of M@C{sub 60} has not yet been achieved because of the difficulties in extraction; only the extraction of Ca@C{sub 60} with pyridine has been reported as for. Recently we found that aniline is a suitable extraction solvent for Ca@C{sub 60} and Sr@C{sub 60}. For the isolation of M@C{sub 60} by an HPLC technique it is important to find a suitable extraction solvent for M@C{sub 60}. In the present study, we report the successful extraction of Y@C{sub 60}, Ba@C{sub 60}, La@C{sub 60}, Ce@C{sub 60}, Pr@C{sub 60}, Nd@C{sub 60}, and Gd@C{sub 60} with aniline under an air atmosphere. 14 refs., 2 figs.

  2. Valence photoionization of small alkaline earth atoms endohedrally confined in C60: From the many-electron collectivity to single-electron interferences

    NASA Astrophysics Data System (ADS)

    Javani, Mohammad; McCreary, Meghan; Patel, Aakash; Madjet, Mohamed; Chakraborty, Himadri; Manson, Steve

    2012-06-01

    Results of a theoretical study of the photoionization from outermost orbitals of Be, Mg and Ca atoms endohedrally confined in C60 are presented. The fullerene ion-core of sixty C^4+ ions is smudged into a continuous jellium distribution while the delocalized cloud of carbon valence electrons, plus the encaged atom, are treated in the time-dependent local density approximation (TDLDA) [1]. Systematic evolution of the mixing of outer atomic level with the C60 band is detected along the sequence. This is found to influence the plasmon-driven enhancement at low energies and the geometry-revealing confinement oscillations from multi-path interferences at high energies in significantly different ways. The study paints the first comparative picture of the atomic valence photospectra for alkaline earth metallofullerenes in a dynamical many-electron framework [2].[4pt] [1] M.E. Madjet et al., Phys. Rev. A 81, 013202 (2010)[0pt] [2] M.H. Javani et al., to be published.

  3. Theoretical and quantitative structural relationships of the electrochemical and electron transfer properties of [M x@C 82]@[SWCNT(5,5)-armchair-C nH 20] ( x = 0, 1; for x = 1: M = Ce & Gd and n = 20-300) nanostructure complexes

    NASA Astrophysics Data System (ADS)

    Taherpour, Avat Arman

    2009-12-01

    The relationship between the number of carbon atoms ( n) of the SWCNTs as an index and the first and second free energies of electron transfer (Δ G et(n), n = 1, 2), as assessed using the Rehm-Weller equation on the basis of the first and second oxidation potentials ( oxE 1 and oxE 2) of C 82, Ce@C 82 and Gd@C 82 for the predicted supramolecular complexes, between 1- 18 and 19- 29 with fullerene C 82(a) and the endohedral-metallofullerenes Ce@C 82(b) and Gd@C 82(c) as [M x@C 82]@[SWCNT(5,5)-armchair-C nH 20] ( x = 0, 1; for x = 1: M = Ce & Gd; n = 20-190) 30-47, 48-65 and 66-83 are presented. The results were extended for [M x@C 82]@[SWCNT(5,5)-armchair-C nH 20] ( x = 0, 1; for x = 1: M = Ce & Gd; n = 200-300 84-94, 95-105 and 106-116).

  4. Electronic structures of endohedral fullerenes

    SciTech Connect

    Jin, Changming; Hettich, R.L.; Puretzky, A.A.; Ying, Z.C.; Haufler, R.E.; Compton, R.N.

    1994-12-31

    Fullerenes with different elements trapped inside the cage have been the subject of active research both experimentally and theoretically ever since the initial discovery of C{sub 60}. La@C{sub n}, were the first endohedral fullerenes produced both in gas phase and in macroscopic quantities. Early electron spin resonance investigation of La@C{sub 82} by R.D. Johnson, et.al indicated that La transfer nearly all of the three valence electrons to the fullerene cage, forming a La{sup 3+}@C{sub 82}{sup 3-} complex. Theoretical calculations also have shown that La transfers its valence electrons to the fullerene cage in molecules of La@C{sub n}. Investigations with ultraviolet photoelectron spectroscopy by L. Wang, et.al. indicated that attaching a potassium atom outside the C{sub 60} cage lowers the electron affinity (EA) while trapping Ca atom inside the C{sub 60} sphere increases the EA compared with parent C{sub 60} molecule. These results indicate that metallofullerenes appear to have substantially lower ionization potentials (IP) and higher EA than empty fullerenes.

  5. Computational efficiences for calculating rare earth f^n energies

    NASA Astrophysics Data System (ADS)

    Beck, Donald R.

    2009-05-01

    RecentlyootnotetextD. R. Beck and E. J. Domeier, Can. J. Phys. Walter Johnson issue, Jan. 2009., we have used new computational strategies to obtain wavefunctions and energies for Gd IV 4f^7 and 4f^65d levels. Here we extend one of these techniques to allow efficent inclusion of 4f^2 pair correlation effects using radial pair energies obtained from much simpler calculationsootnotetexte.g. K. Jankowski et al., Int. J. Quant. Chem. XXVII, 665 (1985). and angular factors which can be simply computedootnotetextD. R. Beck and C. A. Nicolaides, Excited States in Quantum Chemistry, C. A. Nicolaides and D. R. Beck (editors), D. Reidel (1978), p. 105ff.. This is a re-vitalization of an older ideaootnotetextI. Oksuz and O. Sinanoglu, Phys. Rev. 181, 54 (1969).. We display relationships between angular factors involving the exchange of holes and electrons (e.g. f^6 vs f^8, f^13d vs fd^9). We apply the results to Tb IV and Gd IV, whose spectra is largely unknown, but which may play a role in MRI medicine as endohedral metallofullerenes (e.g. Gd3N-C80ootnotetextM. C. Qian and S. N. Khanna, J. Appl. Phys. 101, 09E105 (2007).). Pr III results are in good agreement (910 cm-1) with experiment. Pu I 5f^2 radial pair energies are also presented.

  6. Laser-based mass spectrometry of fullerenes and their compounds

    SciTech Connect

    Wurz, P.; Lykke, K.R.; Parker, D.H.

    1992-12-01

    Advanced mass spectrometry is used to study C{sub 60}, related carbon clusters named fullerenes, and metallofullerenes. For analysis, the authors rely on laser desorption/laser ionization. Pulsed laser beams (532 nm and 266 nm) are used for desorption of sample material adsorbed on a stainless steel substrate. Postionization of the desorbed neutral flux of molecules is investigated at various wavelengths to optimize the ionization process and minimize the concurrent fragmentation and delayed ionization processes. The applied postionization wavelengths range from 532 nm down to 118 nm. The 118 nm vacuum ultraviolet (VUV) radiation is generated by nonresonant four-wave mixing. In addition, the authors also use a difference mixing scheme, which not only provides tunability in the VUV range, but also at least an order of magnitude more intensity. Additionally, this VUV radiation allows postionization of neutral species following fragmentation by a laser with a longer wavelength (three-laser experiment), thus the neutral fragments resulting from photofragmentation can also be studied.

  7. Coverage-dependent Orientations of Dy@C82 Molecules on Au(111) Surface

    NASA Astrophysics Data System (ADS)

    Chen, Feng-yun; Hu, Zhen-peng

    2012-08-01

    The adsorption and molecular orientation of Dy@C82 isomer I on Au(111) has been investigated using ultrahigh-vacuum scanning tunneling microscopy at 80 K. At low coverages, the Dy@C82 molecules tend to grow along the step edges of Au(111), forming small clusters and molecular chains. Adsorption of Dy@C82 on the edges is dominated by the fullerene-substrate interaction and presents various molecular orientations. At higher coverages, the Dy@C82 is found to form ordered islands consisting of small domains of equally oriented molecules. The Dy@C82 molecules in the islands prefer the adsorption configurations with the major C2 axis being approximately parallel to the surface of the substrate. Three preferable orientations of the Dy@C82 molecules are found in a two-dimensional hexagonal close packed overlayer. These observations are attributed to the interplay of the fullerene-substrate interaction and dipole-dipole interaction between the metallofullerenes.

  8. Scanning tunneling microscopy study of molecular growth structures of Gd@C82 on Cu(111)

    NASA Astrophysics Data System (ADS)

    Chen, Jian; Qin, Zhi-Hui; Pan, Jin-Bo; Lu, Shuang-Zan; Du, Shi-Xuan; Gao, Hong-Jun; Cao, Geng-Yu

    2013-07-01

    The coverage and temperature-dependent nucleation behaviors of the Gd@C82 metallofullerenes on Cu(111) have been studied by low-temperature scanning tunneling microscopy (LT-STM) in detail. Upon molecular deposition at low temperature, Gd@C82 molecules preferentially decorate the steps and nucleate into single layer islands with increasing coverage. Further annealing treatment leads some of the Gd@C82 molecules to assemble into bright and dim patches, which are correlated to the adsorption induced substrate reconstruction. Upon sufficient thermal activation, Gd@C82 molecules sink into the Cu(111) surface one-copper-layer-deep, forming hexagonal close-packed molecular islands with intra-molecular details observed as striped patterns. By considering the commensurability between the Gd@C82 nearest-neighbor distance and the lattice of the underlying Cu(111), we clearly identified two kinds of in-plane molecular arrangements as (√19 × √19)R23.4° and (√19 × √19)R36.6° with respect to Cu(111). Within the assembled Gd@C82 molecular, island molecules with dim—bright contrast are spatially distributed, which may be modulated by the preexisted species on Cu(111).

  9. De novo design of an endohedral heteronuclear dimetallofullerene (U-Gd)@C60 with exceptional structural and electronic properties.

    PubMed

    Dai, Xing; Han, Jie; Gao, Yang; Wang, Zhigang

    2014-12-01

    Ever since the first synthesis of La@C82 and U@C28 , there has been a growing interest in the study of endohedral metallofullerenes (EMFs) because of their great potential in various applications. Here we design a novel heteronuclear EMF (U-Gd)@C60 , by using density functional theory (DFT), which shows an encapsulation energy of about -5.53 eV, comparable to that of U2 @C60, La2 @C80 , and Lu2 @C76 . (U-Gd)@C60 is found to have a surprising twofold, single-electron UGd bond that results from the strong nanoconfinement of the fullerene, dominated by uranium's 5f and 6d and gadolinium's 5d atomic orbitals. The ground state shows an 11-et high spin state, and the net spins distributed on the U-pole carbons are relatively scattered, while they are highly concentrated on the Gd-pole carbons. The exceptional electronic characteristics of this novel EMF, containing both uranium and gadolinium atoms encapsulated, might prove useful for future applications in nuclear energy and biomedicine.

  10. Preparation, Structural Determination, and Characterization of Electronic Properties of Bis-silylated and Bis-germylated Lu3 N@Ih -C80.

    PubMed

    Kako, Masahiro; Miyabe, Kyosuke; Sato, Kumiko; Suzuki, Mitsuaki; Mizorogi, Naomi; Wang, Wei-Wei; Yamada, Michio; Maeda, Yutaka; Olmstead, Marilyn M; Balch, Alan L; Nagase, Shigeru; Akasaka, Takeshi

    2015-11-01

    Bis-silylated and bis-germylated derivatives of Lu3 N@Ih -C80 (3, 4, 5) were successfully synthesized by the photochemical addition of disiliranes 1 a, 1 b or digermirane 2, and fully characterized by spectroscopic, electrochemical, and theoretical studies. Interestingly, digermirane 2 reacts more efficiently than disiliranes 1 a and 1 b because of its good electron-donor properties and lower steric hindrance around the Ge-Ge bond. The 1,4-adduct structures of 3, 4, 5 were unequivocally established by single-crystal X-ray crystallographic analyses. The electrochemical and theoretical studies reveal that the energy gaps between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the 1,4-adducts are remarkably smaller than those of Lu3 N@Ih -C80 , because the electron-donating groups effectively raise the HOMO levels. It is also observed that germyl groups are slightly more electron-donating than the silyl groups on the basis of the redox properties and the HOMO-LUMO energies of 4 and 5. Bis-silylation and bis-germylation are effective and versatile methods for tuning the electronic characteristics of endohedral metallofullerenes.

  11. Endohedral Fullerenes in Organic Thin Film Photovoltaic Devices

    NASA Astrophysics Data System (ADS)

    Ross, Russel; Vankeuren, Edward; Drees, Martin; Cardona, Claudia; Holloway, Brian; Guldi, Dirk

    2008-03-01

    Cost factors in inorganic solar cells have opened up a new path to less expensive manufacturing techniques using bulk heterojunction polymer/fullerene based solar cells. Using empty cage fullerene derivatives as the acceptor material, state-of-the-art organic photovoltaics currently display ˜5% overall conversion efficiency. One of the main factors limiting the efficiency in organic solar cells is the low open circuit voltage. The open circuit voltage is governed by the molecular orbitals of the donor and acceptor material; therefore better matching of the orbitals will lead to improved voltages. We present a novel acceptor material based on TRIMETASPHERE^ carbon nanomaterials (TMS). TMS are endohedral metallofullerenes that consist of a trimetal nitride cluster enclosed in a C80 cage. First-generation TMS derivatives have been synthesized; electrochemical and photophysical studies show behavior consistent with C60 but with improved molecular orbitals. The electrochemical data suggests a maximum voltage increase of up to 280 mV over C60-PCBM-based devices. Organic solar cell devices are currently under construction and performance results will also be presented.

  12. Electronic Properties and 13C NMR Structural Study of Y3N@C88

    PubMed Central

    Fu, Wujun; Zhang, Jianyuan; Champion, Hunter; Fuhrer, Tim; Azuremendi, Hugo; Zuo, Tianming; Zhang, Jianfei; Harich, Kim; Dorn, Harry C.

    2011-01-01

    In this paper we report the synthesis, purification, 13C NMR and other characterization studies of Y3N@C88. The 13C NMR, UV-vis and chromatographic data suggest an Y3N@C88 having IPR allowed cage with D2(35)-C88 symmetry. In earlier density functional theory (DFT) computational and X-ray crystallographic studies, it was reported that lanthanide (A3N)6+ clusters are stabilized in D2(35)-C88 symmetry cages and have reduced HOMO-LUMO gaps relative to other trimetallic nitride endohedral metallofullerene cage systems, for example, A3N@C80. In this paper, we report that the non-lanthanide (Y3N)6+ cluster in the D2(35)-C88 cage exhibits a HOMO-LUMO gap consistent with other lanthanide A3N@C88 molecules based on electrochemical measurements and DFT computational study. These results suggests that the reduced HOMO-LUMO gap of A3N@C88 systems is a property dominated by the D2(35)-C88 carbon cage and not f-orbital lanthanide electronic metal cluster (A3N)6+ orbital participation. PMID:21506556

  13. Theoretical investigation of C56 fullerene isomers and related compounds

    NASA Astrophysics Data System (ADS)

    Chen, De-Li; Tian, Wei Quan; Feng, Ji-Kang; Sun, Chia-Chung

    2008-01-01

    All the 924 classical isomers of fullerene C56 have been investigated by PM3, and some most stable isomers are refined with HCTH/3-21G and B3LYP /6-31G(d) methods. D2:003 with the least number of adjacent pentagons is predicted to be the most stable isomer at B3LYP /6-31G(d) level, while Cs:022 and C2:049 possess nearly degenerate energies with relative energies of 0.03 and 3.90kcal/mol, respectively. However, as to dianionic C562- fullerene, C2v:011 is predicted to be the most stable isomer. Investigations also show that the encapsulation of Ca atom in C56 fullerene is exothermic and the metallofullerenes Ca@C56 can be described as Ca2+@C562-. The computed relative stabilities show that the D2:003 behaves more thermodynamically stable than other isomers in a wide temperature interval, and C2v:011 should also be an important component. The electronic isomerization of C56 (C2v:011) and C50 (D5h:002) indicates that this phenomenon might be rather general in fullerenes and causes different properties, thus bringing about new possible applications of fullerenes. The static second-order hyperpolarizabilities of the three most stable isomers are slightly larger than that of C60.

  14. Valence photoionization of small alkaline earth atoms endohedrally confined in C60

    NASA Astrophysics Data System (ADS)

    Javani, M. H.; McCreary, M. R.; Patel, A. B.; Madjet, M. E.; Chakraborty, H. S.; Manson, S. T.

    2012-07-01

    A theoretical study of photoionization from the outermost orbitals of Be, Mg and Ca atoms endohedrally confined in C60 is reported. The fullerene ion core, comprised of sixty C4+, is smudged into a continuous jellium charge distribution, while the delocalized cloud of carbon valence electrons plus the encaged atom are treated in the time-dependent local density approximation (TDLDA). Systematic evolution of the mixing of outer atomic level with states of the C60 valence band is found along the sequence. This is found to influence the plasmonic enhancement of atomic photoionization at low energies and the geometry-revealing confinement oscillations at high energies in significantly different ways: (a) the extent of enhancement is mainly determined by the strength of atomic ionization, giving the strongest enhancement for Be even though Ca suffers the largest mixing. But (b) strongest collateral oscillations are uncovered for Ca, since, relative to Be and Mg, the mixing causes the highest photoelectron production at confining boundaries of Ca. The study paints the first comparative picture of the atomic valence photospectra for alkaline earth metallofullerenes in a dynamical many-electron framework.

  15. Isolation and spectroscopic properties of Sc[sub 2]C[sub 74], Sc[sub 2]C[sub 82], and Sc[sub 2]C[sub 84

    SciTech Connect

    Shinohara, Hisanori; Yamaguchi, Hiroki; Hayashi, Naoyuki; Sato, Hiroyasu; Saito, Yahachi ); Ohkohchi, Masato; Ando, Yoshinori )

    1993-04-29

    The endohedral discandium fullerenes, Sc[sub 2]C[sub 74], Sc[sub 2]C[sub 82], and Sc[sub 2]C[sub 84], have been isolated for the first time from soot prepared by the arc burning of Sc[sub 2]O[sub 3]/graphite composite rods. The separation and isolation of the metallofullerenes from various hollow fullerenes have been realized by using a two-stage high-performance liquid chromatography. Laser-desorption time-of-flight mass analyses of the present samples confirm the isolation of the discandium fullerenes. The discandium fullerene, Sc[sub 2]C[sub 74], has been newly found in this study. The UV-vis absorption spectra of the isolated Sc[sub 2]C[sub 74], Sc[sub 2]C[sub 82], and Sc[sub 2]C[sub 84] reveal several salient features which are totally absent in those of the corresponding hollow fullerenes such as C[sub 76], C[sub 78], C[sub 82], and C[sub 84]. 17 refs., 4 figs.

  16. Reaction Mechanism and Regioselectivity of the Bingel-Hirsch Addition of Dimethyl Bromomalonate to La@C2v -C82.

    PubMed

    Martínez, Juan Pablo; Garcia-Borràs, Marc; Osuna, Sílvia; Poater, Jordi; Bickelhaupt, F Matthias; Solà, Miquel

    2016-04-18

    We quantum chemically explore the thermodynamics and kinetics of all 65 possible mechanistic pathways of the Bingel-Hirsch addition of dimethyl bromomalonate to the endohedral metallofullerene La@C2v -C82 that result from the combination of 24 nonequivalent carbon atoms and 35 different bonds present in La@C2v -C82 by using dispersion-corrected DFT calculations. Experimentally, this reaction leads to four singly bonded derivatives and one fulleroid adduct. Of these five products, only the singly bonded derivative on C23 could be experimentally identified unambiguously. Our calculations show that La@C2v -C82 is not particularly regioselective under Bingel-Hirsch conditions. From the obtained results, however, it is possible to make a tentative assignment of the products observed experimentally. We propose that the observed fulleroid adduct results from the attack at bond 19 and that the singly bonded derivatives correspond to the C2, C19, C21, and C23 initial attacks. However, other possibilities cannot be ruled out completely.

  17. Structural Stability and Deformation of Solvated Sm@C2(45)-C90 under High Pressure

    NASA Astrophysics Data System (ADS)

    Cui, Jinxing; Yao, Mingguang; Yang, Hua; Liu, Ziyang; Liu, Shijie; Du, Mingrun; Li, Quanjun; Liu, Ran; Cui, Tian; Liu, Bingbing

    2016-08-01

    Solvated fullerenes recently have been shown to exhibit novel compression behaviors compared with the pristine fullerenes. However, less attention has been focused on the large cage endohedral metallofullerenes. Here, we have firstly synthesized solvated Sm@C90 microrods by a solution drop-drying method, and then studied the transformations under high pressure. The pressure-induced structural evolutions of Sm@C90 molecules both undergo deformation and collapse. The band gaps of both samples decrease with increasing pressure. The trapped Sm atom plays a role in restraining the compression of the adjacent bonds. The solvent plays a role in protecting Sm@C90 against collapse in the region of 12–20 GPa, decreasing and postponing the change of band gap. Above 30 GPa, the carbon cages collapse. Released from 45 GPa, the compressed solvated Sm@C90 forms a new ordered amorphous carbon cluster (OACC) structure with metal atoms trapped in the units of amorphous carbon clusters, which is different from the OACC structure formed by compressing solvated C60 and C70. This discovery opens the door for the creation of new carbon materials with desirable structural and physical properties when suitable starting materials are selected.

  18. NC unit trapped by fullerenes: a density functional theory study on Sc3NC@C(2n) (2n = 68, 78 and 80).

    PubMed

    Jin, Peng; Zhou, Zhen; Hao, Ce; Gao, Zhanxian; Tan, Kai; Lu, Xin; Chen, Zhongfang

    2010-10-21

    Endohedral metallofullerenes (EMFs) with a trapped cluster size larger than four are rather scarce. Inspired by a recent experimental observation, we explored the possibility of encapsulating an unusual Sc(3)NC unit in three representative fullerene cages, namely, C(68), C(78) and C(80), by means of density functional computations. The geometries, electronic and electrochemical redox properties of the corresponding EMFs, Sc(3)NC@C(2n) (2n = 68, 78 and 80), were investigated. These novel EMFs all have very favorable binding energies, implying a considerable possibility for experimental realization. The recently observed m/z = 1121 peak in the mass spectroscopy was characterized as Sc(3)NC@C(80). Notably the lowest-energy isomer of Sc(3)NC@C(78) has a non-IPR C(78) outer cage, the possibility to accommodate five atoms inside a fullerene as small as C(68) is also intriguing. Moreover, the intracluster and metal-cage covalent interactions were revealed by a quantum theory of atoms in molecules study. Infrared absorption spectra and (13)C nuclear magnetic resonance spectra were also computed to assist future experimental characterization.

  19. An Improbable Monometallic Cluster Entrapped in a Popular Fullerene Cage: YCN@Cs(6)-C82

    PubMed Central

    Yang, Shangfeng; Chen, Chuanbao; Liu, Fupin; Xie, Yunpeng; Li, Fengyu; Jiao, Mingzhi; Suzuki, Mitsuaki; Wei, Tao; Wang, Song; Chen, Zhongfang; Lu, Xing; Akasaka, Takeshi

    2013-01-01

    Since the first proposal that fullerenes are capable of hosting atoms, ions, or clusters by the late Smalley in 1985, tremendous examples of endohedral metallofullerenes (EMFs) have been reported. Breaking the dogma that monometallofullerenes (mono-EMFs) always exist in the form of M@C2n while clusterfullerenes always require multiple (two to four) metal cations to stabilize a cluster that is unstable as a single moiety, here we show an unprecedented monometallic endohedral clusterfullerene entrapping an yttrium cyanide cluster inside a popular C82 cage—YCN@Cs(6)-C82. X-ray crystallography and 13C NMR characterization unambiguously determine the cage symmetry and the endohedal cyanide structure, unexpectedly revealing that the entrapped YCN cluster is triangular. The unprecedented monometallic clusterfullerene structure unveiled by YCN@Cs(6)-C82 opens up a new avenue for stabilizing a cluster by a single metal cation within a carbon cage, and will surely stimulate further studies on the stability and formation mechanism of EMFs. PMID:23512079

  20. The ground state and electronic structure of Gd@C82: A systematic theoretical investigation of first principle density functionals

    NASA Astrophysics Data System (ADS)

    Dai, Xing; Gao, Yang; Xin, Minsi; Wang, Zhigang; Zhou, Ruhong

    2014-12-01

    As a representative lanthanide endohedral metallofullerene, Gd@C82 has attracted a widespread attention among theorists and experimentalists ever since its first synthesis. Through comprehensive comparisons and discussions, as well as references to the latest high precision experiments, we evaluated the performance of different computational methods. Our results showed that the appropriate choice of the exchange-correlation functionals is the decisive factor to accurately predict both geometric and electronic structures for Gd@C82. The electronic structure of the ground state and energy gap between the septet ground state and the nonet low-lying state obtained from pure density functional methods, such as PBE and PW91, are in good agreement with current experiment. Unlike pure functionals, the popularly used hybrid functionals in previous studies, such as B3LYP, could infer the qualitative correct ground state only when small basis set for C atoms is employed. Furthermore, we also highlighted that other geometric structures of Gd@C82 with the Gd staying at different positions are either not stable or with higher energies. This work should provide some useful references for various theoretical methodologies in further density functional studies on Gd@C82 and its derivatives in the future.

  1. Structural Stability and Deformation of Solvated Sm@C2(45)-C90 under High Pressure.

    PubMed

    Cui, Jinxing; Yao, Mingguang; Yang, Hua; Liu, Ziyang; Liu, Shijie; Du, Mingrun; Li, Quanjun; Liu, Ran; Cui, Tian; Liu, Bingbing

    2016-01-01

    Solvated fullerenes recently have been shown to exhibit novel compression behaviors compared with the pristine fullerenes. However, less attention has been focused on the large cage endohedral metallofullerenes. Here, we have firstly synthesized solvated Sm@C90 microrods by a solution drop-drying method, and then studied the transformations under high pressure. The pressure-induced structural evolutions of Sm@C90 molecules both undergo deformation and collapse. The band gaps of both samples decrease with increasing pressure. The trapped Sm atom plays a role in restraining the compression of the adjacent bonds. The solvent plays a role in protecting Sm@C90 against collapse in the region of 12-20 GPa, decreasing and postponing the change of band gap. Above 30 GPa, the carbon cages collapse. Released from 45 GPa, the compressed solvated Sm@C90 forms a new ordered amorphous carbon cluster (OACC) structure with metal atoms trapped in the units of amorphous carbon clusters, which is different from the OACC structure formed by compressing solvated C60 and C70. This discovery opens the door for the creation of new carbon materials with desirable structural and physical properties when suitable starting materials are selected. PMID:27503144

  2. Regioselective cage opening of La2 @D2 (10611)-C72 with 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine.

    PubMed

    Yamada, Michio; Muto, Yasuhiro; Kurihara, Hiroki; Slanina, Zdenek; Suzuki, Mitsuaki; Maeda, Yutaka; Rubin, Yves; Olmstead, Marilyn M; Balch, Alan L; Nagase, Shigeru; Lu, Xing; Akasaka, Takeshi

    2015-02-01

    The thermal reaction of the endohedral metallofullerene La2 @D2 (10611)-C72 , which contains two pentalene units at opposite ends of the cage, with 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine proceeded selectively to afford only two bisfulleroid isomers. The molecular structure of one isomer was determined using single-crystal X-ray crystallography. The results suggest that the [4+2] cycloaddition was initiated in a highly regioselective manner at the C-C bond connecting two pentagon rings of C72 . Subsequent intramolecular electrocyclization followed by cycloreversion resulted in the formation of an open-cage derivative having three seven-membered ring orifices on the cage and a significantly elongated cage geometry. The reduction potentials of the open-cage derivatives were similar to those of La2 @D2 -C72 whereas the oxidation potentials were shifted more negative than those of La2 @D2 -C72 . These results point out that further oxidation could occur easily in the derivatives. PMID:25536953

  3. Structural Stability and Deformation of Solvated Sm@C2(45)-C90 under High Pressure.

    PubMed

    Cui, Jinxing; Yao, Mingguang; Yang, Hua; Liu, Ziyang; Liu, Shijie; Du, Mingrun; Li, Quanjun; Liu, Ran; Cui, Tian; Liu, Bingbing

    2016-08-09

    Solvated fullerenes recently have been shown to exhibit novel compression behaviors compared with the pristine fullerenes. However, less attention has been focused on the large cage endohedral metallofullerenes. Here, we have firstly synthesized solvated Sm@C90 microrods by a solution drop-drying method, and then studied the transformations under high pressure. The pressure-induced structural evolutions of Sm@C90 molecules both undergo deformation and collapse. The band gaps of both samples decrease with increasing pressure. The trapped Sm atom plays a role in restraining the compression of the adjacent bonds. The solvent plays a role in protecting Sm@C90 against collapse in the region of 12-20 GPa, decreasing and postponing the change of band gap. Above 30 GPa, the carbon cages collapse. Released from 45 GPa, the compressed solvated Sm@C90 forms a new ordered amorphous carbon cluster (OACC) structure with metal atoms trapped in the units of amorphous carbon clusters, which is different from the OACC structure formed by compressing solvated C60 and C70. This discovery opens the door for the creation of new carbon materials with desirable structural and physical properties when suitable starting materials are selected.

  4. Crystallographic X-ray analyses of Yb@C(2v)(3)-C80 reveal a feasible rule that governs the location of a rare earth metal inside a medium-sized fullerene.

    PubMed

    Lu, Xing; Lian, Yongfu; Beavers, Christine M; Mizorogi, Naomi; Slanina, Zdenek; Nagase, Shigeru; Akasaka, Takeshi

    2011-07-20

    Single crystal X-ray diffraction studies of Yb@C(2v)(3)-C(80)·Ni(II)(OEP)·CS(2)·1.5C(6)H(6) (OEP = octaethylporphinate) reveal that a relatively flat region of the fullerene interacts with the Ni(II)(OEP) molecule, featuring shape-matching interactions. Surprisingly, it is found that the internal metal is located under a hexagonal carbon ring apart from the 2-fold axis of the C(2v)(3)-C(80) cage, presenting the first example of metallofullerenes with an asymmetrically positioned metal. Such an anomalous location of Yb(2+) is associated with its strong ability to pursue a large coordination number and the lack of hexagon along the C(2) axis of C(2v)(3)-C(80). It is accordingly assumed that a suitable cage hexagon is most likely to be preferred by the single rare earth metal to stay behind inside a medium-sized fullerene, such as C(80) and C(82).

  5. The ground state and electronic structure of Gd@C{sub 82}: A systematic theoretical investigation of first principle density functionals

    SciTech Connect

    Dai, Xing; Gao, Yang; Xin, Minsi; Wang, Zhigang; Zhou, Ruhong

    2014-12-28

    As a representative lanthanide endohedral metallofullerene, Gd@C{sub 82} has attracted a widespread attention among theorists and experimentalists ever since its first synthesis. Through comprehensive comparisons and discussions, as well as references to the latest high precision experiments, we evaluated the performance of different computational methods. Our results showed that the appropriate choice of the exchange-correlation functionals is the decisive factor to accurately predict both geometric and electronic structures for Gd@C{sub 82}. The electronic structure of the ground state and energy gap between the septet ground state and the nonet low-lying state obtained from pure density functional methods, such as PBE and PW91, are in good agreement with current experiment. Unlike pure functionals, the popularly used hybrid functionals in previous studies, such as B3LYP, could infer the qualitative correct ground state only when small basis set for C atoms is employed. Furthermore, we also highlighted that other geometric structures of Gd@C{sub 82} with the Gd staying at different positions are either not stable or with higher energies. This work should provide some useful references for various theoretical methodologies in further density functional studies on Gd@C{sub 82} and its derivatives in the future.

  6. Gadolinium-uptake by aquatic and terrestrial organisms-distribution determined by laser ablation inductively coupled plasma mass spectrometry.

    PubMed

    Lingott, Jana; Lindner, Uwe; Telgmann, Lena; Esteban-Fernández, Diego; Jakubowski, Norbert; Panne, Ulrich

    2016-02-01

    Gadolinium (Gd) based contrast agents (CA) are used to enhance magnetic resonance imaging. As a consequence of excretion by patients and insufficient elimination in wastewater treatment plants they are detected in high concentrations in surface water. At present, little is known about the uptake of these species by living organisms in aquatic systems. Therefore the uptake of gadolinium containing chelates by plants and animals grown in exposed water or on soil irrigated with exposed water was investigated. For this purpose two types of plants were treated with two different contrast agents. The uptake of the Gd contrast agents was studied by monitoring the elemental distribution with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). This technique allows the multi-elemental analysis of solid samples with high resolution and little sample preparation. The analysis of L. minor showed that the uptake of Gd correlated with the concentration of gadodiamide in the water. The higher the concentration in the exposed water, the larger the Gd signal in the LA-ICP-MS acquired image. Exposure time experiments showed saturation within one day. The L. minor had contact with the CAs through roots and fronds, whereas the L. sativum only showed uptake through the roots. These results show that an external absorption of the CA through the leaves of L. sativum was impossible. All the analyzed parts of the plant showed Gd signal from the CA; the highest being at the main vein of the leaf. It is shown that the CAs can be taken up from plants. Furthermore, the uptake and distribution of Gd in Daphnia magna were shown. The exposure via cultivation medium is followed by Gd signals on the skin and in the area of the intestine, while the uptake via exposed nutrition algae causes the significantly highest Gd intensities in the area of the intestine. Because there are hints of negative effects for human organism these findings are important as they show that Gd based

  7. The distribution of anthropogenic REE in the Dutch distributaries of the Rhine: the role of suspended matter

    NASA Astrophysics Data System (ADS)

    Roskam, Gerlinde; Verheul, Marc; Klaver, Gerard; Bakker, Ingrid

    2014-05-01

    In nature rare earth elements (REE) occur in fixed ratios; contamination with a single rare earth element causes a clear deviation from the natural NASC normalized REE-patterns: an anomaly. REE are progressively used in many high technology products and processes. For example, gadolinium-containing chelates have been used since the '80s as contrasting agent in MRI-imaging. The pertaining anomaly is currently used as a tracer for distinguishing waste water from water unaffected by anthropogenic contamination. In the Dutch monitoring program in the Rhine-Meuse distributaries, total (10% HNO3 digested) and dissolved (< 0.45 µm) fractions in surface water are routinely analysed, and with two-week intervals suspended matter samples are collected with a centrifuge. Since 2008, the set of analysed elements was extended with REE, enabling this study. Lobith, the entry point of the River Rhine in The Netherlands, shows an annual oscillation in the magnitude of the lanthanum (La) anomaly. This positive La-anomaly was reported by Kulaksiz and Bau in 2011; they identified the point source as a production plant for catalysts used in petroleum refining in the German city of Worms. Since the spring of 2011, samarium (Sm) is used in the same process, resulting in matching La- and Sm-anomalies. The anthropogenic La and Sm concentrations are predominantly present in the total fraction, which suggests that the anthropogenic La and Sm concentrations are associated with suspended matter. The anthropogenic La and Sm concentrations are lower in the suspended matter samples collected with the centrifuge, suggesting a bias of these La and Sm concentrations in the finer fraction of the suspended matter. The anthropogenic La en Sm concentrations remain relatively constant throughout the rivers, but close to Lake IJsselmeer and the North Sea, sedimentation causes a sharp decrease in the anthropogenic concentrations. Detailed sampling of sediments, suspended matter and water could give a

  8. Gadolinium-uptake by aquatic and terrestrial organisms-distribution determined by laser ablation inductively coupled plasma mass spectrometry.

    PubMed

    Lingott, Jana; Lindner, Uwe; Telgmann, Lena; Esteban-Fernández, Diego; Jakubowski, Norbert; Panne, Ulrich

    2016-02-01

    Gadolinium (Gd) based contrast agents (CA) are used to enhance magnetic resonance imaging. As a consequence of excretion by patients and insufficient elimination in wastewater treatment plants they are detected in high concentrations in surface water. At present, little is known about the uptake of these species by living organisms in aquatic systems. Therefore the uptake of gadolinium containing chelates by plants and animals grown in exposed water or on soil irrigated with exposed water was investigated. For this purpose two types of plants were treated with two different contrast agents. The uptake of the Gd contrast agents was studied by monitoring the elemental distribution with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). This technique allows the multi-elemental analysis of solid samples with high resolution and little sample preparation. The analysis of L. minor showed that the uptake of Gd correlated with the concentration of gadodiamide in the water. The higher the concentration in the exposed water, the larger the Gd signal in the LA-ICP-MS acquired image. Exposure time experiments showed saturation within one day. The L. minor had contact with the CAs through roots and fronds, whereas the L. sativum only showed uptake through the roots. These results show that an external absorption of the CA through the leaves of L. sativum was impossible. All the analyzed parts of the plant showed Gd signal from the CA; the highest being at the main vein of the leaf. It is shown that the CAs can be taken up from plants. Furthermore, the uptake and distribution of Gd in Daphnia magna were shown. The exposure via cultivation medium is followed by Gd signals on the skin and in the area of the intestine, while the uptake via exposed nutrition algae causes the significantly highest Gd intensities in the area of the intestine. Because there are hints of negative effects for human organism these findings are important as they show that Gd based

  9. Production of Endohedral Fullerenes by Ion Implantation

    SciTech Connect

    Diener, M.D.; Alford, J. M.; Mirzadeh, S.

    2007-05-31

    The empty interior cavity of fullerenes has long been touted for containment of radionuclides during in vivo transport, during radioimmunotherapy (RIT) and radioimaging for example. As the chemistry required to open a hole in fullerene is complex and exceedingly unlikely to occur in vivo, and conformational stability of the fullerene cage is absolute, atoms trapped within fullerenes can only be released during extremely energetic events. Encapsulating radionuclides in fullerenes could therefore potentially eliminate undesired toxicity resulting from leakage and catabolism of radionuclides administered with other techniques. At the start of this project however, methods for production of transition metal and p-electron metal endohedral fullerenes were completely unknown, and only one method for production of endohedral radiofullerenes was known. They therefore investigated three different methods for the production of therapeutically useful endohedral metallofullerenes: (1) implantation of ions using the high intensity ion beam at the Oak Ridge National Laboratory (ORNL) Surface Modification and Characterization Research Center (SMAC) and fullerenes as the target; (2) implantation of ions using the recoil energy following alpha decay; and (3) implantation of ions using the recoil energy following neutron capture, using ORNL's High Flux Isotope Reactor (HFIR) as a thermal neutron source. While they were unable to obtain evidence of successful implantation using the ion beam at SMAC, recoil following alpha decay and neutron capture were both found to be economically viable methods for the production of therapeutically useful radiofullerenes. In this report, the procedures for preparing fullerenes containing the isotopes {sup 212}Pb, {sup 212}Bi, {sup 213}Bi, and {sup 177}Lu are described. None of these endohedral fullerenes had ever previously been prepared, and all of these radioisotopes are actively under investigation for RIT. Additionally, the chemistry for

  10. The role of ellipticity on the preferential binding site of Ce and La in C78-D3h-A density functional theory study

    NASA Astrophysics Data System (ADS)

    Muthukumar, K.; Larsson, J. A.

    2010-07-01

    Endohedral metallofullerenes that encapsulate one or several atoms, or a cluster of atoms have molecular properties making them useful both in technology and in bio-medical applications. Some fullerenes are found to have two metal atoms incarcerated and it has been recently found that two Ce atoms are incorporated into the C78-D3h (78 : 5) cage. In this study, we report calculations on the structural and electronic properties of Ce2@C78 using density functional theory (DFT). While Ce2@C80-Ih (D3d) and La2@C80-Ih (D2h) have different ground state structures, we have found that Ce2@C78 has a D3h ground state structure just as La2@C78. The encapsulated Ce atoms bind strongly to the C78-D3h cage with a binding energy (BE) of 5.925 eV but not as strong as in Ce@C82-C2v nor in Ce2@C80-Ih. The elliptical nature of the cage plays a crucial role and accommodates the two Ce atoms at opposite ends of the C3 axis with a maximized inter atomic distance (4.078 Å). This means that the effect of the additional f-electron repulsion in M2@C78 with M = Ce compared to M = La, is less pronounced than in Ce2@C80 compared to La2@C80. We compare the results to the elliptical M2@C72 (#10611) (M = La, Ce), and with a range of additional Ce and La endohedral fullerenes and explain the role ellipticity has in the preferential binding site of Ce and shed light on the formation mechanism of these nanostructures.

  11. Gd2@C79N: Isolation, Characterization, and Monadduct Formation of a Very Stable Heterofullerene with a Magnetic Spin State of S = 15/2

    PubMed Central

    Fu, Wujun; Zhang, Jianyuan; Fuhrer, Tim; Champion, Hunter; Furukawa, Ko; Kato, Tatsuhisa; Mahaney, James E.; Burke, Brian G.; Williams, Keith A.; Walker, Kenneth; Dixon, Caitlyn; Ge, Jiechao; Shu, Chunying; Harich, Kim; Dorn, Harry C.

    2011-01-01

    The dimetallic endohedral heterofullerene (EHF), Gd2@C79N, was prepared and isolated in a relatively high yield when compared with the earlier reported heterofullerene, Y2@C79N. Computational (DFT), chemical reactivity, Raman, and electrochemical studies all suggest that the purified Gd2@C79N, with the heterofullerene cage, (C79N)5- has comparable stability with other better known isoelectronic metallofullerene (C80)6- cage species (e.g., Gd3N@C80). These results describe an exceptionally stable paramagnetic molecule with low chemical reactivity with the unpaired electron spin density localized on the internal diatomic gadolinium cluster and not on the heterofullerene cage. EPR studies confirm that the spin state of Gd2@C79N is characterized by a half-integer spin quantum number of S = 15/2. The spin (S = 1/2) on the N atom of the fullerene cage and two octet spins (S = 7/2) of two encapsulated gadoliniums are coupled with each other in a ferromagnetic manner with a small zero-field splitting parameter D. Because the central line of Gd2@C79N is due to the Kramer's doublet with a half-integer spin quantum number of S = 15/2, this relatively sharp line is prominent and the anisotropic nature of the line is weak. Interestingly, in contrast with most Gd3+ ion environments, the central EPR line (g=1.978) is observable even at room temperature in a toluene solution. Finally, we report the first EHF derivative, a diethyl bromomalonate monoadduct of Gd2@C79N, was prepared and isolated via a modified Bingel-Hirsch reaction. PMID:21548647

  12. The inner-induced effects of YCN in C76 on the structures and nonlinear optical properties.

    PubMed

    Gao, Feng-Wei; Xu, Hong-Liang; Su, Zhong-Min

    2016-08-01

    Very recently, an unprecedented novel monometallic cluster of fullerenes entrapping a yttrium cyanide (YCN) cluster inside a popular C82 cage YCN@Cs(6)-C82 was synthesized and characterized. Inspired by this investigation, four non-IPR YCN@C1(17459)-C76, YCN@C2v(19138)-C76, YCN@C2(17646)-C76, and YCN@C1(17894)-C76 (1, 2, 3, and 4) containing a pair of adjacent pentagons are designed to explore the encapsulated molecular effect on their interaction energies and nonlinear optical properties. The interaction energy (E int) values of 1, 2, 3, and 4 are -481.35 (1), -477.91 (2), -482.04 (3), -482.69 (4) kcal mol(-1), respectively, which shows that the E int value of 4 is the largest. Furthermore, the electron-transfer is mainly from the YCN to C76 cage. When YCN is encapsulated into C76 cage, we can find that the α0 values of the four molecules are very close, ranging from 6.50 × 10(2) to 6.65 × 10(2) au. Significantly, the first hyperpolarizabilities are in relation to the encapsulated molecular: 1.63 × 10(3) (1) > 8.03 × 10(2) (2) > 7.76 × 10(2) (4) > 4.86 × 10(2) au (3), the results show that the βtot value of 1 is the largest. Besides this, the encapsulation of the YCN to C76 cage brings some distinctive changes in its UV-vis spectra along with its other electronic properties that might be used by the experimentalists to develop the potential nonlinear optical nanomaterials based on endohedral metallofullerenes.

  13. Free energies, kinetics, and photoelectron-transfer properties, and theoretical and quantitative structural relationship studies of [SWCNT(5,5)-armchair-C n H20][ R] ( R = η 2-C m Pd(dppf), η 2-C m Pd(dppr), and η 2-C m Pd(dppcym)2, n = 20 to 300 and m = 60 and 70) nanostructure complexes

    NASA Astrophysics Data System (ADS)

    Taherpour, Avat Arman; Talebi-Haftadori, Zahra

    2013-04-01

    Metal complexes containing one or several bis(triorganylphosphine)palladium fragments attached to the C60 core and coordinated in olefinic η 2 mode have been previously described. The number of carbon atoms of the single-walled carbon nanotubes (SWCNTs) is the useful numerical and structural electrochemical properties contributing to the relationship between the structures of the η 2_C m Pd(dppf), η 2_C m Pd(dppr), and η 2_C m Pd(dppcym)2 ( m = 60 and 70) ligands (A to E) and [SWCNT(5,5)-armchair-C n H20] ( n = 20 to 190) 1 to 18 and the production of the [SWCNT(5,5)-armchair-C n H20][ R] ( R = η 2-C m Pd(dppf), η 2-C m Pd(dppr), and η 2-C m Pd(dppcym)2, n = 20 to 300 and m = 60 and 70) complexes 30 to 174. In this study, the relationship between the number of carbon atoms index and the first and second free energies of electron transfer ( ΔG et( n), n = 1,2) using the Rehm-Weller equation based on the first and second oxidation potentials (ox E 1 and ox E 2) of A to E for the predicted complexes 30 to 174 between 1 and 29 with exohedral metallofullerenes A to E, as [SWCNT(5,5)-armchair-C n H20][ R] ( R = η 2-C m Pd(dppf), η 2-C m Pd(dppr), and η 2-C m Pd(dppcym)2, n = 20 to 300 and m = 60 and 70) 30 to 174 was assessed. Here, the first and second free activation energies of electron transfer and the wavelengths of the electromagnetic photons in the photoelectron transfer process, ΔG # et( n) and λ ( n) (nm), respectively, for 30 to 174 in accordance with the Marcus theory and Planck's equation were also calculated.

  14. Synthesis and Isolation of the Titanium-Scandium Endohedral Fullerenes-Sc2 TiC@Ih -C80 , Sc2 TiC@D5h -C80 and Sc2 TiC2 @Ih -C80 : Metal Size Tuning of the Ti(IV) /Ti(III) Redox Potentials.

    PubMed

    Junghans, Katrin; Ghiassi, Kamran B; Samoylova, Nataliya A; Deng, Qingming; Rosenkranz, Marco; Olmstead, Marilyn M; Balch, Alan L; Popov, Alexey A

    2016-09-01

    The formation of endohedral metallofullerenes (EMFs) in an electric arc is reported for the mixed-metal Sc-Ti system utilizing methane as a reactive gas. Comparison of these results with those from the Sc/CH4 and Ti/CH4 systems as well as syntheses without methane revealed a strong mutual influence of all key components on the product distribution. Whereas a methane atmosphere alone suppresses the formation of empty cage fullerenes, the Ti/CH4 system forms mainly empty cage fullerenes. In contrast, the main fullerene products in the Sc/CH4 system are Sc4 C2 @C80 (the most abundant EMF from this synthesis), Sc3 C2 @C80 , isomers of Sc2 C2 @C82 , and the family Sc2 C2 n (2 n=74, 76, 82, 86, 90, etc.), as well as Sc3 CH@C80 . The Sc-Ti/CH4 system produces the mixed-metal Sc2 TiC@C2 n (2 n=68, 78, 80) and Sc2 TiC2 @C2 n (2 n=80) clusterfullerene families. The molecular structures of the new, transition-metal-containing endohedral fullerenes, Sc2 TiC@Ih -C80 , Sc2 TiC@D5h -C80 , and Sc2 TiC2 @Ih -C80 , were characterized by NMR spectroscopy. The structure of Sc2 TiC@Ih -C80 was also determined by single-crystal X-ray diffraction, which demonstrated the presence of a short Ti=C double bond. Both Sc2 TiC- and Sc2 TiC2 -containing clusterfullerenes have Ti-localized LUMOs. Encapsulation of the redox-active Ti ion inside the fullerene cage enables analysis of the cluster-cage strain in the endohedral fullerenes through electrochemical measurements. PMID:27459520

  15. The role of ellipticity on the preferential binding site of Ce and La in C78-D3h--a density functional theory study.

    PubMed

    Muthukumar, K; Larsson, J A

    2010-07-01

    Endohedral metallofullerenes that encapsulate one or several atoms, or a cluster of atoms have molecular properties making them useful both in technology and in bio-medical applications. Some fullerenes are found to have two metal atoms incarcerated and it has been recently found that two Ce atoms are incorporated into the C(78)-D(3h) (78 : 5) cage. In this study, we report calculations on the structural and electronic properties of Ce(2)@C(78) using density functional theory (DFT). While Ce(2)@C(80)-I(h) (D(3d)) and La(2)@C(80)-I(h) (D(2h)) have different ground state structures, we have found that Ce(2)@C(78) has a D(3h) ground state structure just as La(2)@C(78). The encapsulated Ce atoms bind strongly to the C(78)-D(3h) cage with a binding energy (BE) of 5.925 eV but not as strong as in Ce@C(82)-C(2v) nor in Ce(2)@C(80)-I(h). The elliptical nature of the cage plays a crucial role and accommodates the two Ce atoms at opposite ends of the C(3) axis with a maximized inter atomic distance (4.078 A). This means that the effect of the additional f-electron repulsion in M(2)@C(78) with M = Ce compared to M = La, is less pronounced than in Ce(2)@C(80) compared to La(2)@C(80). We compare the results to the elliptical M(2)@C(72) (#10611) (M = La, Ce), and with a range of additional Ce and La endohedral fullerenes and explain the role ellipticity has in the preferential binding site of Ce and shed light on the formation mechanism of these nanostructures.

  16. Tandem time-of-flight mass spectrometer for cluster--surface scattering experiments

    SciTech Connect

    Beck, R.D.; Weis, P.; Braeuchle, G.; Rockenberger, J.

    1995-08-01

    A new tandem time-of-flight mass spectrometer is described which is designed to study the mass-, velocity-, and angle-resolved scattering of cluster ions from solid surfaces. Clusters are produced in a supersonic jet laser desorption/vaporization source, ionized either directly in the formation step or by subsequent photoionization of neutrals, mass selected in a primary time-of-flight region, and decelerated to the impact energy (50--1000 eV) close to the target surface. Cluster--surface collisions take place in a field-free region in order to determine both velocity and angular distributions of the scattered clusters and fragments with an independently pulsed, rotatable secondary time-of-flight mass spectrometer. Several surface targets can be mounted in the UHV scattering chamber (10{sup {minus}10} Torr base pressure) on a five-axis manipulator which, together with the rotatable secondary TOF, allows for independent variation of incident and scattering angles. Target surfaces can be cleaned by direct current heating and sputtering with an argon-ion gun. Surface structure and composition are assessed by low-energy electron diffraction (LEED) and Auger spectroscopy with a four grid reverse view LEED/Auger system. Surface collision experiments of fullerenes (C{sup +}{sub 60}, C{sup +}{sub 70}, C{sup +}{sub 76}, C{sup +}{sub 84}, ...) and metallofullerenes (La{at}C{sup +}{sub 82}) with highly oriented pyrolitic graphite (HOPG) surfaces are described as examples for the performance of the instrument. Effects of surface contamination in the scattering of fullerenes from HOPG are described to demonstrate the need for thorough cleaning procedures in order to obtain reproducible results. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  17. Technegas: A medical application of {sup 99m}Tc for the study of buckyballs, blood clots, lung disease and AIDS

    SciTech Connect

    Willett, G.D.; Dance, I.G.; Fisher, K.J.; Burch, W.M.; Dasaklis, C.; Mackey, D.W.J.

    1994-12-31

    Radionuclide studies of lung disease have been greatly enhanced by the introduction of an Australian invention; the Technegas generator. The properties of the {open_quotes}dry radio-aerosols{close_quotes} produced by this device ensure lung images superior to those from true radio-gases such as {sup 133}Xe with the additional advantage of employing {sup 99m}Tc, the most widespread radionuclide agent. A Technegas lung scan can enable identification of pulmonary mebolism (an immediately life threatening condition) emphysema and chronic obstructive lung disease. A simple modification to the generator gas mixture produces Pertechnegas an agent useful in studies of the integrity of the alveolar epithelial membrane in immunosuppressed patients such as transplants and AIDS. Although these agents are now common in Australia and Europe, little has been proven of their chemical composites. Technegas is formed by the initial evaporation of ({sup 99m}Tc) sodium pertechnetate with the subsequent sublimation of carbon from a disposable graphite crucible at {approximately}2500{degrees}C in an atmosphere of 100% argon. {sup 99m}Tc atoms are lifted off with the crystalline layers of graphite during the vaporization. Technegas then possibly consists of {sup 99m}Tc based metallo-fullerenes and fullerenes. Technegas has an effective half life in the lung very similar to the physical half life of Technetium (6 hours) regardless of clinical condition; a result which suggests that Technegas contains endohedral fullerenes. Pertechnegas is created in an atmosphere of 97% Ar 3% O{sub 2} and has an effective half life in the lung of less than 15 minutes.

  18. The inner-induced effects of YCN in C76 on the structures and nonlinear optical properties.

    PubMed

    Gao, Feng-Wei; Xu, Hong-Liang; Su, Zhong-Min

    2016-08-01

    Very recently, an unprecedented novel monometallic cluster of fullerenes entrapping a yttrium cyanide (YCN) cluster inside a popular C82 cage YCN@Cs(6)-C82 was synthesized and characterized. Inspired by this investigation, four non-IPR YCN@C1(17459)-C76, YCN@C2v(19138)-C76, YCN@C2(17646)-C76, and YCN@C1(17894)-C76 (1, 2, 3, and 4) containing a pair of adjacent pentagons are designed to explore the encapsulated molecular effect on their interaction energies and nonlinear optical properties. The interaction energy (E int) values of 1, 2, 3, and 4 are -481.35 (1), -477.91 (2), -482.04 (3), -482.69 (4) kcal mol(-1), respectively, which shows that the E int value of 4 is the largest. Furthermore, the electron-transfer is mainly from the YCN to C76 cage. When YCN is encapsulated into C76 cage, we can find that the α0 values of the four molecules are very close, ranging from 6.50 × 10(2) to 6.65 × 10(2) au. Significantly, the first hyperpolarizabilities are in relation to the encapsulated molecular: 1.63 × 10(3) (1) > 8.03 × 10(2) (2) > 7.76 × 10(2) (4) > 4.86 × 10(2) au (3), the results show that the βtot value of 1 is the largest. Besides this, the encapsulation of the YCN to C76 cage brings some distinctive changes in its UV-vis spectra along with its other electronic properties that might be used by the experimentalists to develop the potential nonlinear optical nanomaterials based on endohedral metallofullerenes. PMID:27383610

  19. Stabilization of a Chlorinated (#4348)C66:C2v Cage by Encapsulating Monometal Species: Coordination between Metal and Double Hexagon-Condensed Pentalenes.

    PubMed

    Li, Qiao-Zhi; Zheng, Jia-Jia; He, Ling; Nagase, Shigeru; Zhao, Xiang

    2016-08-01

    Carbon cages in endohedral and exohedral fullerene derivatives are usually different. A recent report suggested that chlorofullerene C66Cl10:Cs and endohedral metallofullerene (EMF) Sc2@C66 shared the same cage (#4348)C66:C2v, while it was denied by the definitive characterization of Sc2@C66, which actually possesses the (#4059)C66:C2v isomer. Here, we show that a (#4348)C66:C2v cage with a double hexagon-condensed pentalene (DHCP) moiety, which was captured by exohedral chlorination, is also capable of being stabilized by encapsulating tri- or divalent monometal (M) species. On the basis of density functional theory calculations combined with statistical mechanics analyses, (#4348)C66:C2v-based mono-EMFs M@C2v(4348)-C66 (M = Tb, La, Y, and Yb) were demonstrated to be the most stable and predominant isomers at the fullerene formation temperature region, while another chlorinated cage (#4169)C66:Cs, featured with triple sequentially fused pentagon (TSFP) moiety, is less favorable to be obtained in the form of EMFs, although these two cages can be interconverted by a simple Stone-Wales transformation. The superiority of M@C2v(4348)-C66 over M@Cs(4169)-C66 comes from the stronger interaction of M-DHCP over that of M-TSFP in both ionic and covalent bonding aspects. In addition, size-selective complexation of host [n]cycloparaphenylene ([n]CPP) and Tb@C2v(4348)-C66 was simulated, showing that [10]CPP exhibits the best affinity toward Tb@C66, which provides a new opportunity for isolation and characterization of C66-based mono-EMFs. PMID:27429293

  20. Synthesis and Isolation of the Titanium-Scandium Endohedral Fullerenes-Sc2 TiC@Ih -C80 , Sc2 TiC@D5h -C80 and Sc2 TiC2 @Ih -C80 : Metal Size Tuning of the Ti(IV) /Ti(III) Redox Potentials.

    PubMed

    Junghans, Katrin; Ghiassi, Kamran B; Samoylova, Nataliya A; Deng, Qingming; Rosenkranz, Marco; Olmstead, Marilyn M; Balch, Alan L; Popov, Alexey A

    2016-09-01

    The formation of endohedral metallofullerenes (EMFs) in an electric arc is reported for the mixed-metal Sc-Ti system utilizing methane as a reactive gas. Comparison of these results with those from the Sc/CH4 and Ti/CH4 systems as well as syntheses without methane revealed a strong mutual influence of all key components on the product distribution. Whereas a methane atmosphere alone suppresses the formation of empty cage fullerenes, the Ti/CH4 system forms mainly empty cage fullerenes. In contrast, the main fullerene products in the Sc/CH4 system are Sc4 C2 @C80 (the most abundant EMF from this synthesis), Sc3 C2 @C80 , isomers of Sc2 C2 @C82 , and the family Sc2 C2 n (2 n=74, 76, 82, 86, 90, etc.), as well as Sc3 CH@C80 . The Sc-Ti/CH4 system produces the mixed-metal Sc2 TiC@C2 n (2 n=68, 78, 80) and Sc2 TiC2 @C2 n (2 n=80) clusterfullerene families. The molecular structures of the new, transition-metal-containing endohedral fullerenes, Sc2 TiC@Ih -C80 , Sc2 TiC@D5h -C80 , and Sc2 TiC2 @Ih -C80 , were characterized by NMR spectroscopy. The structure of Sc2 TiC@Ih -C80 was also determined by single-crystal X-ray diffraction, which demonstrated the presence of a short Ti=C double bond. Both Sc2 TiC- and Sc2 TiC2 -containing clusterfullerenes have Ti-localized LUMOs. Encapsulation of the redox-active Ti ion inside the fullerene cage enables analysis of the cluster-cage strain in the endohedral fullerenes through electrochemical measurements.

  1. Synthesis and Isolation of the Titanium–Scandium Endohedral Fullerenes—Sc2TiC@Ih-C80, Sc2TiC@D5h-C80 and Sc2TiC2@Ih-C80 : Metal Size Tuning of the TiIV/TiIII Redox Potentials

    PubMed Central

    Junghans, Katrin; Ghiassi, Kamran B.; Samoylova, Nataliya A.; Deng, Qingming; Rosenkranz, Marco; Olmstead, Marilyn M.; Balch, Alan L.; Popov, Alexey A.

    2016-01-01

    The formation of endohedral metallofullerenes (EMFs) in an electric arc is reported for the mixed-metal Sc–Ti system utilizing methane as a reactive gas. Comparison of these results with those from the Sc/CH4 and Ti/CH4 systems as well as syntheses without methane revealed a strong mutual influence of all key components on the product distribution. Whereas a methane atmosphere alone suppresses the formation of empty cage fullerenes, the Ti/CH4 system forms mainly empty cage fullerenes. In contrast, the main fullerene products in the Sc/CH4 system are Sc4C2@C80 (the most abundant EMF from this synthesis), Sc3C2@C80, isomers of Sc2C2@C82, and the family Sc2C2n (2n=74, 76, 82, 86, 90, etc.), as well as Sc3CH@C80. The Sc–Ti/CH4 system produces the mixed-metal Sc2TiC@C2n (2n=68, 78, 80) and Sc2TiC2@C2n (2n=80) clusterfullerene families. The molecular structures of the new, transition-metal-containing endohedral fullerenes, Sc2TiC@Ih-C80, Sc2TiC@D5h-C80, and Sc2TiC2@Ih-C80, were characterized by NMR spectroscopy. The structure of Sc2TiC@Ih-C80 was also determined by single-crystal X-ray diffraction, which demonstrated the presence of a short Ti=C double bond. Both Sc2TiC- and Sc2TiC2-containing clusterfullerenes have Ti-localized LUMOs. Encapsulation of the redox-active Ti ion inside the fullerene cage enables analysis of the cluster–cage strain in the endohedral fullerenes through electrochemical measurements. PMID:27459520

  2. Hindered cluster rotation and 45Sc hyperfine splitting constant in distonoid anion radical Sc3N@C80-, and spatial spin-charge separation as a general principle for anions of endohedral fullerenes with metal-localized lowest unoccupied molecular orbitals.

    PubMed

    Popov, Alexey A; Dunsch, Lothar

    2008-12-31

    DFT calculations of Sc(3)N@C(80) in the neutral and anionic states are performed which revealed that in the neutral state of the nitride clusterfullerene the lowest energy structure has C(3) symmetry, while in the anionic and dianionic states the C(3v) conformer has the lowest energy. Barriers to the cluster rotation inside the cage are also found to increase in the charge states. The (45)Sc hyperfine slitting constant, a(Sc), in Sc(3)N@C(80) anion radical is calculated by different theoretical approaches and in different conformations of Sc(3)N cluster. It is found that a(Sc) is strongly dependent on the cluster orientation with respect to the cage, covering a range form -10 to +25 Gauss at the B3LYP/6-311G*//PBE/TZ2P level of theory. A thorough analysis of the computed values as well as comparison of unrestricted and orbital-restricted calculations revealed that the polarization contribution to a(Sc) is about -10 Gauss and does not depend on the cluster orientation. Dependence of the predicted a(Sc) values on the density functional form (LSDA, BP, PBE, BLYP, OLYP, TPSS, B3LYP, and TPSSh), the basis set, as well as on the scalar-relativistic and spin-orbit corrections were investigated. The analysis of the charge distribution in the Sc(3)N@C(80)(-) anion radical revealed an interesting peculiarity of its electronic structure: while the spin density mostly resides on the cluster, only a slight decrease of its charge is found using both Bader and Mulliken definitions of atomic charges. A set of other endohedral metallofullerenes, including nitride clusterfullerenes Sc(3)N@C(2n) (2n = 68, 70, 78) and Y(3)N@C(2n) (2n = 78-88), carbide clusterfullerenes Sc(2)C(2)@C(68), Sc(2)C(2)@C(82), Sc(3)C(2)@C(80), Ti(2)C(2)@C(78), Y(2)C(2)@C(82), and dimetallofullerenes Sc(2)@C(76), Y(2)@C(82), La(2)@C(2n) (2n = 72, 78, 80), was also studied in the neutral and anionic state, and a spatial charge-spin separation is found to be a general rule for all endohedral fullerenes with high

  3. Matrix isolation FTIR spectroscopic and DFT studies of metal-carbide clusters

    NASA Astrophysics Data System (ADS)

    Bejjani, Micheline

    2011-01-01

    Several metal containing molecules, including MgCN, NaCN, KCl, AlOH, and AlF have been observed in the interstellar medium. Additionally, transition metals have been observed. Many carbon containing molecules have also been observed in astrophysical sources. The purpose of the present research is to provide information on the spectral properties of metal carbide molecules that are potentially observable in space. Additional interest for studying small metal carbide molecules is the understanding of larger clusters including metallofullerenes and metallocarbohedrenes, and the catalytic growth of carbon nanotubes. FTIR spectra were obtained by condensing the vapor produced by dual laser ablation of metal and carbon rods in an argon matrix at ˜12K. Comparison of the observed 13C enriched vibrational spectra to the DFT simulated isotopic spectra has enabled the identification of vibrational fundamentals of linear MnC3, linear MgC3-, and chain ZnC3. The linear MnC3 has been detected for the first time. Its nu 1(sigma) vibrational fundamental has been observed at 1846.9 cm -1. Although previous photoelectron studies by Wang and Li have reported evidence for the cyclic isomer of MnC3, their assignment was inconclusive since the linear and fanlike structures have been found to lie very close in energy, and the observed PE frequency matched the frequencies predicted for the vibrational fundamentals of both the linear and the fanlike isomers of MnC3. Theoretical investigations of MgC3 - have indicated that the bent, linear, fan and kite structures are close in energy, and thus are potentially observables. In the present work, the nu1(sigma) asymmetric carbon stretching mode of linear MgC3- has been observed at 1797.5 cm-1. A second absorption at 1190.1 cm-1 which is correlated in intensity to the nu1(sigma) has tentatively been assigned to the nu2(sigma) vibrational fundamental. Although DFT calculations on ZnC3 have indicated that the linear, bent and kite structures are

  4. Trimetallic nitride endohedral C80 fullerenes and their application in Organic Photovoltaic devices

    NASA Astrophysics Data System (ADS)

    Ross, Russel Brett

    Trimetallic nitride endohedral C80 fullerenes (TNEF) materials offer a reduced lowest unoccupied molecular orbital energy (LUMO) offset when compared with many of the polymer donor systems currently being employed in Organic Photovoltaic (OPV) research. This lower LUMO offset allows for higher open circuit voltages, and therefore, higher efficiencies in OPV devices. Presented here is a comprehensive study of the room temperature absorption and emission of a series of trimetallic nitride endohedral metallofullerenes, M3N C80, (M = Er, Gd, Ho, Lu, Sc, Y), as well the investigation and demonstration of TNEFs use as an acceptor material in OPV devices. Morphology and electrode contacts are shown to have large influence on TNEF-based OPV performance, in poly(3-hexyl)thiophene (P3HT) and 1-(3-hexoxycarbonyl)propyl-1-phenyl-[6,6]-Lu3N C81 (Lu3N C80-PCBH) based OPV devices. Decreasing the LUMO offset between P3HT and the acceptor material, reduced energy losses in the charge transfer process, which yield an increased open circuit voltage to 280mV above reference devices made with P3HT & [6,6]-phenyl-C61-butyric methyl ester (C60-PCBM). OPV energy conversion efficiencies of > 4% are observed with P3HT/Lu3N C80-PCBH active layer with a predicted upper limit on power conversion efficiency of > 6% for this donor/acceptor system. The data displayed within this work constitutes proof of concept that the varying reduction potential (160--290 meV vs. C 60-PCBM) of the TNEF acceptor molecules provides a pathway to enhancing OPV device performance by closing down the molecular orbital offset of the donor/acceptor heterojunction. TNEF acceptor materials in single bulk heterojunction devices offer a viable path to 11% conversion efficiency with already-reported-on low-band-gap donors, such as poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']-dithiophene)- alt-4,7-(2,1,3-benzothiadiazole), PCPDTBT.

  5. Endohedral metal atoms in pristine and functionalized fullerene cages.

    PubMed

    Yamada, Michio; Akasaka, Takeshi; Nagase, Shigeru

    2010-01-19

    Fullerene, an allotropic form of carbon made up of spherical molecules formed from pentagonal and hexagonal rings, was first discovered in 1985. Because fullerenes have spacious inner cavities, atoms and clusters can be encapsulated inside the fullerene cages to form endohedral fullerenes. In particular, the unique structural and electronic properties of endohedral metallofullerenes (EMFs), where metal atoms are encapsulated within the fullerene, have attracted wide interest from physicists and chemists as well as materials scientists and biologists. The remarkable characteristics of these molecules originate in the electron transfer from the encapsulated metal atoms to the carbon cage. The positions and movements of the encapsulated metal atoms are important determinants of the chemical and physical properties of EMFs. In this Account, we specifically describe the positions and dynamic behavior of the metal atoms encapsulated in pristine and functionalized fullerene cages. First, we examined whether the metal atoms are attached rigidly to cage carbons or move around. Our systematic investigations of EMFs, including M@C(2v)-C(82), M(2)@D(2)(10611)-C(72), M(2)@D(3h)(5)-C(78), M(2)@I(h)-C(80), and M(2)@D(5h)-C(80), revealed that the metal positions and movements vary widely with different cage structures and numbers of metal atoms. Second, we wanted to understand whether we could control the positions and movements of the untouchable metal atoms in EMFs. One possible way to modulate this behavior was through attachment of a molecule to the outer surface of the cage. We developed synthetic methods to modify EMFs and have examined the metal positions and movements in the functionalized carbon cages. Remarkably, we could alter the dynamic behavior of the encaged metal atoms in M(2)@I(h)-C(80) drastically through chemical modification of the outer cage. We anticipate that the control of metal atom structures and dynamics within a cage could be valuable for designing

  6. Endohedral metal or a fullerene cage based oxidation? Redox duality of nitride clusterfullerenes CexM3-xN@C78-88 (x = 1, 2; M = Sc and Y) dictated by the encaged metals and the carbon cage size

    NASA Astrophysics Data System (ADS)

    Zhang, Yang; Popov, Alexey A.; Dunsch, Lothar

    2013-12-01

    Redox behavior of endohedral metallofullerenes, in particular their oxidation process, can be classified as a fullerene-based or endohedral species-based process according to the mechanism of the electron transfer. Here we report on the phenomenon of the strain-driven electrochemical behavior achieved by encapsulating the cerium-containing clusters into a series of carbon cages ranging from C78 to C88. The Ce-based mixed metal nitride clusterfullerenes CexM3-xN@C2n (x = 1, 2; M = Sc or Y; 2n = 78-88) were synthesized and characterized. The magnitude of the inherent strain caused by the limited inner space of the carbon cage for the relatively large nitride clusters can be varied by choosing different scaffold metals (Sc, Lu, or Y) to tailor the size of the encaged CexM3-xN cluster and by matching the nitride cluster with different fullerene cages in the size range from C78 to C88. The redox properties of CexM3-xN@C2n were investigated by cyclic and square wave voltammetry. The mechanism of the electrochemical oxidation of Ce-based mixed metal nitride clusterfullerenes, in particular whether the fullerene-based oxidation or the CeIII --> CeIV process is observed, is found to be dependent on the scaffold metal and the size of the fullerene cage. The endohedral oxidation of CeIII to CeIV was observed for a number of compounds as revealed by the negative shift of their oxidation potentials with respect to the values measured for the non-Ce analogues. Experimental studies are supported by DFT calculations. We conclude that the prerequisites for the Ce-based endohedral oxidation process are suitable inherent cluster-cage strain and sufficiently high oxidation potential of the fullerene cage.Redox behavior of endohedral metallofullerenes, in particular their oxidation process, can be classified as a fullerene-based or endohedral species-based process according to the mechanism of the electron transfer. Here we report on the phenomenon of the strain-driven electrochemical

  7. Interstellar fullerene compounds and diffuse interstellar bands

    NASA Astrophysics Data System (ADS)

    Omont, Alain

    2016-05-01

    Recently, the presence of fullerenes in the interstellar medium (ISM) has been confirmed and new findings suggest that these fullerenes may possibly form from polycyclic aromatic hydrocarbons (PAHs) in the ISM. Moreover, the first confirmed identification of two strong diffuse interstellar bands (DIBs) with the fullerene, C60+, connects the long standing suggestion that various fullerenes could be DIB carriers. These new discoveries justify reassessing the overall importance of interstellar fullerene compounds, including fullerenes of various sizes with endohedral or exohedral inclusions and heterofullerenes (EEHFs). The phenomenology of fullerene compounds is complex. In addition to fullerene formation in grain shattering, fullerene formation from fully dehydrogenated PAHs in diffuse interstellar clouds could perhaps transform a significant percentage of the tail of low-mass PAH distribution into fullerenes including EEHFs. But many uncertain processes make it extremely difficult to assess their expected abundance, composition and size distribution, except for the substantial abundance measured for C60+. EEHFs share many properties with pure fullerenes, such as C60, as regards stability, formation/destruction and chemical processes, as well as many basic spectral features. Because DIBs are ubiquitous in all lines of sight in the ISM, we address several questions about the interstellar importance of various EEHFs, especially as possible carriers of diffuse interstellar bands. Specifically, we discuss basic interstellar properties and the likely contributions of fullerenes of various sizes and their charged counterparts such as C60+, and then in turn: 1) metallofullerenes; 2) heterofullerenes; 3) fulleranes; 4) fullerene-PAH compounds; 5) H2@C60. From this reassessment of the literature and from combining it with known DIB line identifications, we conclude that the general landscape of interstellar fullerene compounds is probably much richer than heretofore realized

  8. A Milestone: Approval of CEUS for Diagnostic Liver Imaging in Adults and Children in the USA.

    PubMed

    Seitz, K; Strobel, D

    2016-06-01

    performed by an experienced examiner/clinician often provides the solution, particularly in the case of small lesions, and is the last resort before US-guided biopsy 45 46. However, there is a lack of competent CEUS examiners and Germany continues to be the world champion of X-ray examinations with no noticeable reverse trend. In almost every doctor's office and hospital, ultrasound costs are by far not fully covered, resulting in an extremely high frequency of CT use with CT being available to everyone regardless of insurance status.The USA is now in the starting position for CEUS. It will be exciting to see how the method will develop there. The FDA's decision to approve sulfur hexafluoride (Lumason(®) = SonoVue(®)) should be considered against the background of the radiation exposure caused by CT examinations and the fact that MRI using gadolinium-containing contrast agents is no longer considered noninvasive because of nephrogenic systemic fibrosis (NSF) and the accumulation of the agent in the cerebrum. An essential point of the campaign regarding the avoidance of diagnostic radiation exposure triggered in the USA by the publications of Brenner et al. 77 78 was that the agent was approved for use in the liver even for children 79 80 - still off label in Europe - without additional comprehensive studies due to the available scientific results and the very low side effects profile of Lumason(®) (= SonoVue(®)). It is admittedly unclear why other indications (except the heart which has been approved since 2014) are excluded even though the microbubbles as a pure blood pool contrast agent can be diagnostically used in the entire vascular system and bed of all organs. To our knowledge, there is no such restriction on the approval of X-ray contrast agents.Like echocardiography and emergency ultrasound, CEUS began in Europe but will probably only establish its final diagnostic value as a "reimport".This is a major opportunity to permanently define the role of

  9. Proceedings of the 9th International Symposium on Foundations of Quantum Mechanics in the Light of New Technology

    NASA Astrophysics Data System (ADS)

    Ishioka, Sachio; Fujikawa, Kazuo

    2009-06-01

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  10. EDITORIAL: Opposites attract: nanomagnetism in theory and practice Opposites attract: nanomagnetism in theory and practice

    NASA Astrophysics Data System (ADS)

    Demming, Anna

    2012-09-01

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