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The row of endohedral fullerenes is extended by a new type of sulfur-containing clusterfullerenes: the metal sulfide (M2S) has been stabilized within a fullerene cage for the first time. The new sulfur-containing clusterfullerenes M2S@C82-C3v(8) have been isolated for a variety of metals (M = Sc, Y, Dy, and Lu). The UV-vis-NIR, electrochemical, and FTIR spectroscopic characterization and extended DFT calculations point to a close similarity of the M2S@C82 cage isomeric and electronic structure to that of the carbide clusterfullerenes M2C2@C2n. The bonding in M2S@C82 is studied in detail by molecular orbital analysis as well as with the use of quantum theory of atom-in-molecules (QTAIM) and electron localization function (ELF) approaches. The metal sulfide cluster formally transfers four electrons to the carbon cage, and metal-sulfur and metal-carbon cage bonds with a high degree of covalency are formed. Molecular dynamics simulations show that Sc2S cluster exhibits an almost free rotation around the C3 axis of the carbon cage, resulting thus in a single line 45Sc NMR spectrum. [ABSTRACT FROM AUTHOR]

Abstract  A detailed study is presented on the optical absorption of thin films of single-walled carbon nanotubes (SWNT) under electrochemical conditions. The procedure for the preparation of free-standing semitransparent films of SWNT is used for the fabrication of a working electrode for transmission optical spectroelectrochemistry. The analysis of the potential dependent spectroscopic response of the SWNT film benefits from the widest possible electrochemical window, in which the charging of SWNT can safely be investigated. This electrochemical window is not limited by parasitic electrochemistry and/or galvanic breakdown reactions occurring at supporting electrode materials such as indium–tin oxide conducting glass or semitransparent Pt film, which were employed in earlier studies. Electrochemical doping of SWNT is observable at the optical absorptions, which are assigned to allowed electronic transitions between van Hove singularities in the density of states of SWNT. Furthermore, the spectral response of counterions, balancing the charging of the nanotube skeleton, is traceable at certain conditions. The latter effect is monitored here through the overtones of C–H stretching vibrations from tetrabutylammonium cations. [ABSTRACT FROM AUTHOR]

The role of the phenazine structure in the stabilization of charged states in polyaniline was studied by in situ electron spin resonance (ESR)−UV/vis−near-infrared (NIR) spectroelectrochemistry of polyaniline and the copolymers of aniline and a phenazine derivative (3,7-diamino-5-phenylphenazinium chloride, phenosafranine). It is shown that the copolymer can be prepared by electropolymerization, and its structure was confirmed by mass spectrometry and IR spectroscopy. The electrochemistry of polyaniline and its copolymer pointed to preferred stabilization of a polaron pair in the charged states at the initial charge transfer reaction instead of polarons that are formed by equilibrium reaction at higher electrode potentials. A second polaron pair is detected for higher doped states of the polymer films. A mechanism of the formation of charged states in polyaniline and their equilibrium is given. It is shown that in situ ESR−UV/vis−NIR spectroelectrochemistry is the method of choice to differentiate between polarons and polaron pairs in their potential-dependent formation. Thus, by this in situ spectroelectrochemical method the influence of phenazine structure on the formation of polarons in aniline polymers and copolymers can be followed. [ABSTRACT FROM AUTHOR]

A combined spectroelectrochemical study by ESR/UV−vis−NIR as well as FTIR spectroscopy on the influence of the copolymer composition on the stabilization of charges upon electrochemical p-doping is presented. As compared to the parent homopolymers 3-hexylthiophene (3-HeTh) and 3-methylthiophene (3-MeTh) which seems to be irregular, FTIR studies of the copolymer of both monomers (copMeHeTh) point to a regioregular structure. The in situESR and UV−vis−NIR spectroelectrochemistry at higher doping levels of the polymeric materials proves bipolarons and polaron pairs as stable charged states in poly(3-hexylthiophene) as well as the copolymer copMeHeTh.During the p-doping of poly(3-methylthiophene) bipolarons are the dominating species at higher doping levels. It is demonstrated that only the simultaneous use of both the ESR and the UV−vis−NIR spectroscopy enables the differentiation of polarons (paramagnetic) and polaron pairs (diamagnetic) in a conducting polymer. [ABSTRACT FROM AUTHOR]

The first non-IPR C76cage based on a mixed metal nitride cluster, DySc2NC76, was successfully synthesized and isolated. DySc2NC76is a stable fullerene with a small band gap of 0.96 eV. According to the FTIR spectroscopic study in combination with extensive DFT calculations, the cage structure of DySc2NC76has been assigned to the non-IPR Cs: 17490-I isomer having two pairs of the adjacent pentagons. DySc2NC76provides the first example of stabilization of the non-IPR C76cage by encapsulation of an asymmetric DySc2N mixed cluster, revealing the role of the cluster structure on the stability of the fullerene cage. As the asymmetric DySc2N cluster has a more suitable geometry for the inner space of the C76cage compared to that of the homogeneous clusters like Sc3N or Dy3N, the highest yield for C76-based cluster fullerenes with the DyxSc3-xN mixed nitride cluster is achieved for the DySc2NC76. [ABSTRACT FROM AUTHOR]

Three novel C68-based mixed metal nitride clusterfullerenes, which comprise of a small non-IPR C68 cage encapsulating large nitride clusters including DySc2N, LuSc2N, and Lu2ScN, have been synthesized and isolated, resulting in overpassing the confinement of the C68 cage. [ABSTRACT FROM AUTHOR]

Titanium/yttrium mixed metal nitride clusterfullerene (MMNCF) TiY2N@C80 has been successfully synthesized, representing the first Ti-containing non-scandium MMNCF. TiY2N@C80 has been isolated by multistep HPLC and characterized by various spectroscopies in combination with DFT computations. The electronic absorption property of TiY2N@C80 was characterized by UV-vis-NIR spectroscopy, indicating the resemblance to that of TiSc2N@C80 with broad shoulder absorptions. The optical band gap of TiY2N@C80 (1.39 eV) is very close to that of TiSc2N@C80 (1.43 eV) but much smaller than that of Y3N@C80(Ih, 1.58 eV). Such a resemblance of the overall absorption feature of TiY2N@C80 to TiSc2N@C80 suggests that TiY2N@C80 has a similar electronic configuration to that of TiSc2N@C80, that is, (TiY2N)6+@C806-. FTIR spectroscopic study and DFT calculations accomplish the assignment of the C80:Ih isomer to the cage structure of TiY2N@C80, with the C1 conformer being the lowest energy structure, which is different from the Cs conformer assigned to TiSc2N@C80. The electrochemical properties of TiY2N@C80 were investigated by cyclic voltammetry, revealing the reversible first oxidation and first reduction step with E1/2 at 0.00 and -1.13 V, respectively, both of which are more negative than those of TiSc2N@C80, while the electrochemical energy gap of TiY2N@C80 (1.11 V) is almost the same as that of TiSc2N@C80 (1.10 V). Contrary to the reversible first reduction step, the second and third reduction steps of TiY2N@C80 are irreversible, and this redox behavior is dramatically different from that of TiSc2N@C80, which shows three reversible reduction steps, indicating the strong influence of the encaged group-III metal (Y or Sc) on the electronic properties of TiM2N@C80 (M = Y, Sc). [ABSTRACT FROM AUTHOR]

The density functional theory calculations of molecular structure and spectroscopic and electronic properties of charged states in four triazine−heteroaryl star-shaped compounds are presented. The molecules end-capped with different heteroaryl groups, i.e., thiophene (TTT1), furan (TFT2), 3,4-ethylenedioxythienyl (TET3), and thiazole (TSNT4), were studied by electrochemical and in situESR/UV−vis−NIR spectroelectrochemical techniques in tetrahydrofuran/(TBA)BF4. The charged states of monomers were created by cathodic reduction and the stability of generated anion radicals was characterized in detail both experimentally and theoretically. The TET3molecule resulted in a star-shaped hyperbranched polymer formed anodically which in turn can be reversibly oxidized up to the tetracation. The nature and charge distribution of charge carriers at each redox state in the as-prepared polymer was clarified by calculations for the model (TET3)3trimer structure. [ABSTRACT FROM AUTHOR]

The first spectroscopic characterization of the dimeric dicationic fullerene complex [(C70)2]2+(Ti3Cl13)−2is reported and supported by DFT calculations. The IR spectrum of the dimer is interpreted in terms of the normal modes of the pristine C70, and the effects of charging C70and the intercage bond formation between C70units on the IR spectrum are discussed. Analysis of the vibrational spectrum of the anion, Ti3Cl13−, is also provided. NIR absorption and fluorescence spectra of the complex are studied, and the dimer is shown to have a small HOMO−LUMO gap of 0.8 eV. The electronic structure of [(C70)2]2+is studied with the use of DFT and compared to that of the other single-bonded fullerene dimers, including [(C70)2]2−, (C69N)2, and [(C60)2]2−. Characteristic features in the vibrational spectra and electronic structure of all single-bonded fullerene dimers are revealed. [ABSTRACT FROM AUTHOR]

In situ spectroelectrochemistry is of high importance for the characterization of doping reactions in π-conjugated polymers. In this paper we present the results of simultaneous ESR and UV−vis−NIR measurements performed in situ during electrochemical p- and n-doping of polyazulene (PAz). In previous studies on p-doping of PAz the assignment of the optical absorption bands to specific charge carriers have been somewhat controversial, therefore the aim of this study is to clarify the nature of the doping-induced charge carriers and their corresponding optical absorption bands by in situ ESR−UV−vis−NIR spectroelectrochemistry. PAz was polymerized in two different potential ranges in order to obtain films with different structures and morphologies. On the basis of our spectroelectrochemical results we propose that polarons and polaron pairs are formed during p-doping in the two different types of PAz films electrodeposited on ITO. For studying n-doping of PAz, a Pt electrode was used. The ESR signal first decreased in intensity at low doping levels and then increased in intensity at higher doping levels pointing to the formation of new paramagnetic species. At high negative potentials there occurred an additional line broadening of the ESR signal indicating the existence of rather localized negative charge carriers. [ABSTRACT FROM AUTHOR]

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

It is shown for the first time that the most important intermediate formed during aniline polymerization, the p-aminodiphenylamine, forms a -dimer under oxidation at room temperature in acidified organic solvents that are used in electropolymerization. N-Phenylquinonediimine, which is generally assumed to be formed under oxidation, is only formed in basic solutions and in ionic liquids. Most of the mechanistic studies reported so far take the formation of N-phenylquinonediimine under consideration, although it is not consistent with the UV−vis spectra measured during oxidation of p-aminodiphenylamine. The formation of a -dimer is very well consistent with the electronic spectra of the oxidation product. In this way the -dimer is very important for the interpretation of the UV−vis spectra of higher oligomers and polyaniline as well. Furthermore, it offers a new interpretation of the redox behavior of p-aminodiphenylamine as found by cyclic voltammetry and has to be considered in the mechanism of the electrochemical polyaniline formation. [ABSTRACT FROM AUTHOR]

Molecular structures of Dy3NC78and Tm3NC78clusterfullerenes are addressed by the IR and Raman vibrational spectroscopic studies and density functional theory (DFT) computations. First, extensive semiempirical calculations of 2927 isomers of C78hexaanions followed by DFT optimization were applied to establish their relative stability. Then, DFT calculations of a series of M3NC78(M Sc, Y, Lu, La) isomers were performed which have shown that the stability order of the isomers depends on the cluster size. While the Sc3N cluster is planar in the earlier reported Sc3NC78(D3h:  24 109) clusterfullerene, relatively large Y3N and Lu3N clusters would be forced to be pyramidal inside this cage, which would result in their destabilization. Instead, these clusters remain planar in the nonisolated pentagon rule (non-IPR) C2:  22 010 isomer making Y3NC78and Lu3NC78clusterfullerenes with this cage structure the most stable ones. Finally, on the basis of a detailed analysis of their IR and Raman spectra supplemented with DFT vibrational calculations, the recently isolated Tm3NC78and the major isomer of Dy3NC78are assigned to the non-IPR C2:  22 010 cage structure. A detailed assignment of their experimental and computed IR and Raman spectra is provided to support this conclusion and to exclude other cage isomers. [ABSTRACT FROM AUTHOR]

Unconventional fullerenes are those smaller than C60 or those intermediate between C60 and C70, which are not stable in structure as none of the unconventional fullerene isomers satisfying the "isolated- pentagon-rule" (IPR). Below we report the synthesis of a stable unconventional fullerene derivative C64H4 by introducing methane in the fullerene productions with the normal Krätschmer-Huffman method. We also applied various spectroscopic measurements such as mass spectrometry, 13C NMR, IA, UV-vis absorption spectrometry, etc. to characterize the structural and electronic properties of this molecule, revealing an unprecedented fullerene cage with a triplet of directly fused pentagons in the framework of C64H4. Four hydrogen atoms are added to the carbons at vertexes of fused pentagons to allow the bond angles at these sites close to the sp³ tetrahedral angle, which essentially release the sp² bond strains on the abutting-pentagon sites of C64. Ab initio calculations were performed to explore the electronic property and simulate the 13C NMR and lR spectra of this fulleride, which reproduced well the experimental results and confirmed the structural assignment of the C64H4. [ABSTRACT FROM AUTHOR]

Poly(3,4-ethylenedithiathiophene) (PEDTT) is a polythiophene-like conjugated polymer in which each thiophene ring is functionalized with an ethylenedithia bridge. As such, PEDTT is the sulfur analogue of the well-known poly(3,4-ethylenedioxythiophene) (PEDOT). Substituent effects, namely the presence of sulfur atoms in PEDTT replacing the oxygen atoms of PEDOT, do not provide a simple explanation for the different electronic properties of the two polymers in the neutral state. This paper reports the spectroscopic properties of PEDTT, studied by in situ techniques such as IR-, Vis-, and electron spin resonance (ESR) spectroelectrochemistry. The differences observed upon electrochemical oxidation of PEDTT and PEDOT (e.g., the different infrared active vibrational band patterns in IR spectroelectrochemistry as well as the different nature of the charged states) are even more marked than those observed in the neutral state. These results, with AM1 calculations, indicate conformational effects as a possible explanation for the different electronic and spectroscopic properties of PEDTT and PEDOT. [ABSTRACT FROM AUTHOR]

High-temperature syntheses of the new C60(i-C3F7)2,4,6and C70(i-C3F7)2,4isomers and their characterization by spectroscopic methods, X-ray crystallography, cyclic voltammetry and density functional theory provide compelling evidence that they are superior electron acceptors than trifluoromethylfullerenes. [ABSTRACT FROM AUTHOR]

With the successful isolation of TiSc2N@C80, the first Ti-containing nitride clusterfullerene (NCF), a non-group-III metal is stabilized in a NCF for the first time. [ABSTRACT FROM AUTHOR]

Although the Gd ion in Gd@C82 has been shown to lie above the C–C bond on the C2 axis as an anomalous structure from the MEM/Rietveld analysis, the present XANES study reveals that it lies above the hexagon on the C2 axis as a normal structure, and Gd oscillates around its equilibrium position with an amplitude increasing with temperature increase. [ABSTRACT FROM AUTHOR]

Raman spectroscopy and in situ Raman spectroelectrochemistry were applied to study the lithium vapor doping of C70@SWCNTs (peapods). A strong degree of doping was proved by the vanishing of the single walled carbon nanotubes (SWCNT’s) radial breathing mode (RBM) and by the attenuation of the tangential (TG) band intensity. In contrast to potassium vapor doping, the strong downshift of the frequency of the TG band has not been observed for Li-doping. The Li vapor treated peapods remained partly doped even if they were exposed to humid air. This has been reflected by a reduced intensity of the nanotube and the fullerene modes and by the change of the shape of the RBM band as compared to that of the undoped sample. The modes of the intratubular fullerene were almost unresolved after the contact of the Li-doped sample with water. A lithium insertion into the interior of a peapod and its strong interaction with the intratubular fullerene is suggested to be responsible for the air-insensitive residual doping. This residual doping was studied by spectroelectrochemical measurements. The TG band of the Li doped peapods is partly upshifted during the anodic doping, which points to the different state of C70@SWCNTs and C60@SWCNTs studied previously. [ABSTRACT FROM AUTHOR]