a Abbreviations of the methods used for the structures elucidation of EMFs: X-ray: single crystal X-ray diffraction of the nonderivatized EMF; X-ray (Drv) − the same, but for the derivative of EMF; X-ray (Powder) − synchrotron X-ray diffraction studies of powder samples with subsequent Rietveld/MEM analysis; NMR − 13 C NMR; Vib − vibrational spectroscopy (IR and/or Raman); QC − quantum-chemical calculations; UV−vis − UV−vis-(NIR) absorption spectroscopy; HRTEM/EELS − high resolution transmission electron microscopy coupled with electron energy loss spectroscopy; Echem − electrochemistry.

The world of endohedral fullerenes was significantly enlarged over the past seven years by the cluster fullerenes, which contain structures such as the M(2)C(2) carbides and the M(3)N nitrides. While the carbide clusters are generated under the standard arc-burning conditions according to stabilization conditions, the nitride cluster fullerenes (NCFs) are formed by varying the composition of the cooling gas atmosphere in the arc-burning process. The special conditions for NCF synthesis is described in detail and the optimum conditions for the production of NCFs as the main product in fullerene syntheses are given. A general review of all NCFs reported to date consists of the structures, properties, and stability of the NCFs as well as the abundance of the NCFs in the fullerene soot. It is shown that all cages with even carbon atoms from C(68) to C(98) are available as endohedral nitride cluster structures (with the exception of C(72), C(74), and C(76)). Specifically, the NCFs form the largest number of structures that violate the isolated pentagon rule (IPR). Finally some practical applications of these cluster fullerenes are illustrated and an outlook is given, taking the superior stability of these endohedral fullerenes into account.

Extensive semiempirical calculations of the hexaanions of IPR (isolated pentagon rule) and non-IPR isomers of C(68)-C(88) and IPR isomers of C(90)-C(98) followed by DFT calculations of the lowest energy structures were performed to find the carbon cages that can provide the most stable isomers of M(3)N@C(2n) clusterfullerenes (M = Sc, Y) with Y as a model for rare earth ions. DFT calculations of isomers of M(3)N@C(2n) (M = Sc, Y; 2n = 68-98) based on the most stable C(2n)(6-) cages were also performed. The lowest energy isomers found by this methodology for Sc(3)N@C(68), Sc(3)N@C(78), Sc(3)N@C(80), Y(3)N@C(78), Y(3)N@C(80), Y(3)N@C(84), Y(3)N@C(86), and Y(3)N@C(88) are those that have been shown to exist by single-crystal X-ray studies as Sc(3)N@C(2n) (2n = 68, 78, 80), Dy(3)N@C(80), and Tb(3)N@C(2n) (2n = 80, 84, 86, 88) clusterfullerenes. Reassignment of the carbon cage of Sc(2)@C(76) to the non-IPR Cs: 17490 isomer is also proposed. The stability of nitride clusterfullerenes was found to correlate well with the stability of the empty 6-fold charged cages. However, the dimensions of the cage in terms of its ability to encapsulate M(3)N clusters were also found to be an important factor, especially for the medium size cages and the large Y(3)N cluster. In some cases the most stable structures are based on the different cage isomers for Sc(3)N and Y(3)N clusters. Up to the cage size of C(84), non-IPR isomers of C(2n)(6-) and M(3)N@C(2n) were found to compete with or to be even more stable than IPR isomers. However, the number of adjacent pentagon pairs in the most stable non-IPR isomers decreases as cage size increases: the most stable M(3)N@C(2n) isomers have three such pairs for 2n = 68-72, two pairs for n = 74-80, and only one pair for n = 82, 84. For C(86) and C(88) the lowest energy IPR isomers are much more stable than any non-IPR isomer. The trends in the stability of the fullerene isomers and the cluster-cage binding energies are discussed, and general rules for stability of clusterfullerenes are established. Finally, the high yield of M(3)N@C(80) (Ih) clusterfullerenes for any metal is explained by the exceptional stability of the C(80)(6-) (Ih: 31924) cage, rationalized by the optimum distribution of the pentagons leading to the minimization of the steric strain, and structural similarities of C(80) (Ih: 31924) with the lowest energy non-IPR isomers of C(760(6-), C(78)(6-), C(82)(6-), and C(84)(6-) pointed out.

The population of valence-band electronic states of single-walled carbon nanotubes (SWCNTs) was tuned electrochemically in acetonitrile electrolyte solution. In dry and oxygen-free solution, the electrochemistry of SWCNTs is controlled by capacitive charging. Reversible changes of intensity and frequency of the Raman spectra can be monitored during cyclic voltammetry at low scan rates. Electrochemical charging of SWCNTs can be also traced via reversible bleaching of the electronic transitions in the vis-NIR region. An aprotic medium offers a broader electrochemical window for tuning of electronic properties of SWCNTs. Electrochemical charging of SWCNTs in an aprotic electrolyte solution allows easy and precise control of the electronic structure of SWCNTs. In addition to commercial SWCNTs, a material made from gas-phase catalytic decomposition of CO by the HiPco process was also studied. Selective quenching of vis-NIR and Raman spectra is a useful tool to the analysis of tubes of varying diameter and helicity.

No abstract

The frontier orbitals of 22 isolated and characterized C(60)(CF(3))(n) derivatives, including seven reported here for the first time, have been investigated by electronic spectroscopy (n = 2 [1], 4 [1], 6 [2], 8 [5], 10 [6], 12 [3]; the number of isomers for each composition is shown in square brackets) fluorescence spectroscopy (n = 10 [4]), cyclic voltammetry under air-free conditions (all compounds with n

Endohedral fullerenes exhibit an intriguing variety of carbon cages and encaged atoms, ions or clusters. For example, the isolated pentagon rule (IPR) obeying missing cage C 74 and the non-IPR fullerene C 66 are accessible only in endohedral form, [1,2] new C 82 isomers have been stabilised by the encapsulation of one Tm 2 + ion and even a Sc 3 3 + cluster has been found inside a C 82 fullerene. [3,4] The discovery of Sc 3 N@C 80 in 1999 opened the gate to a new class of fullerenes with endohedral trimetal nitride cluster molecules.[5] Such four-atomic species have never been prepared before. Several promising material properties make trimetal nitride clusterfullerenes outstanding, for example, unusually high yields relative to empty, mono-and di-metallofullerenes, high thermal stability and long term stability in air. [5][6][7][8][9] The use in solar cells and as local magnets are presently the most discussed applications of fullerene compounds. Regarding the latter possibility, magnetic moments up to three times larger than those of well-known mono-metallofullerenes are expected for trimetal nitride cluster fullerenes.Currently scandium is the most commonly used metal in the synthesis of trimetal nitride cluster fullerenes. The Sc 3 N cluster has also been encapsulated in C 68 and C 78 . [10,11] The mixedmetal cluster fullerene ErSc 2 N@C 80 has been separated and characterised by X-ray diffraction.[12] Yttrium, [9] holmium, [7] terbium, [13] and lutetium [14] have been encaged as trimetal nitrides (abbreviated: M 3 N) in C 80 . Very recently the presence of a second cage isomer has been reported for samples which were previously considered as pure Sc 3 N@C 80 (I h ) isomer.[15] It was estimated, that this sample contains approximately 10 % of the second isomer.[15] Due to its crucial role in the class of cluster fullerenes, the isolation and characterisation of isomeric pure Sc 3 N@C 80 is of great importance. This is the precondition for the detailed analysis of optical and vibrational properties of both isomers. In this context we have to question, whether the presence of the second Sc 3 N@C 80 isomer could account for the near-IR (NIR) absorptions reported in the first paper on Sc 3 N@ C 80 . [5] Another open question is whether the structural properties of the encaged Sc 3 N cluster differ in both isomers.Herein, the isolation of the second Sc 3 N@C 80 isomer is reported for the first time. The electronic transitions and optical energy gap of both isomer pure Sc 3 N@C 80 structures have been analysed by Vis/NIR spectroscopy. In addition, the electronic properties of Sc 3 N@C 80 (I) were studied by cyclic voltammetry. IR and Raman spectroscopy, in combination with group theory, were used to examine the vibrational structure of both Sc 3 N@C 80 isomers. Based on this analysis the cage symmetry of the Sc 3 N@C 80 (II) isomer and the geometric structure of the encaged Sc 3 N cluster in Sc 3 N@C 80 (II) were determined. Experimental SectionThe fullerene soot was prepared by a modified Krätschmer-Huffman arc-bur...

Electronic structure, vibrational stability, and predicted infrared-Raman spectra of the As 20 , As @ Ni 12 , and As @ Ni 12 @ As 20 clusters Structure and stability of endohedral fullerene Sc 3 N@C 80 were studied by temperature-dependent Raman and infrared spectroscopy as well as by quantum-chemical ͓density-functional-based tight-binding͔ calculations. The material showed a remarkable thermal stability up to 650 K. By both theory and experiment, translational and rotational Sc 3 N modes were found. These modes give a direct evidence for the formation of a Sc 3 N-C 80 bond which induces a significant reduction of the ideal I h -C 80 symmetry. From their splitting pattern a crystal structure with more than one molecule in the unit cell is proposed. According to our results: ͑i͒ a significant charge transfer from the Sc 3 N cluster to the C 80 cage; ͑ii͒ the strength of three Sc-N bonds; ͑iii͒ the chemical bond between triscandium nitride cluster and C 80 cage; and ͑iv͒ a large HOMO-LUMO gap are responsible for the high stability and abundance of Sc 3 N@C 80 .