A. Graja

Spectral manifestation of the vibronic shift and occurrence of the C60− anion in stable single crystals of (Ph4P)2C60Y, YCl, Br or I, and (Ph4As)2C60Cl

Abstract Electronic and vibrational spectroscopy were used to study the electronic processes in charge-transfer complexes of fullerene and tetraphenylphosphornium or tetraphenylarsenium halides. These fully ionic crystalline complexes feature the occurrence of C60 monoanions and the onset of charged phonon behavior, all of which were observed and discussed. The large downshift, the strong enhancement of the linewidth and of the oscillator strength were observed for the highest frequency F1u mode of C60 in solid state complexes of fullerene and organic donors.

Energies of charge transfer for C60 and C70 complexes in solutions and in the solid state

Abstract Complexes of the fullerenes C 60 and C 70 with various donors have been studied in solution and in the solid state by electronic absorption spectroscopy. Charge transfer (CT) bands are found in the 620–1300 nm range. It is shown that in solution the CT energies ( hν CT ) for C 60 and C 70 complexes are similar and almost independent of solvent polarity. The dependence of the hν CT energies on donor ionization energy were found for C 60 complexes with substituted tetrathiafulvalenes in the solid state and in toluene. In the solid state the hν CT energies are ∼0.15–0.20 eV lower than those in the solution. The linear dependence of hν CT on donor ionization energy for the C 60 complexes lie ∼0.6–0.7 eV higher than those for the TCNE ones.

Structure of fullerene C60 in aqueous solution

The structure of fullerene C60 in aqueous solution was investigated both experimentally and theoretically. The fullerene C60 was found to aggregate rapidly at room temperature. The aggregation kinetics results indicated that the structure of C60 aggregates in water could be described as a fractal system. The optical absorption spectra obtained testify to the crystalline character of absorption. The formation in water of fractal structures and a crystalline phase from highly stable hydrated fullerene (C60)13 clusters (Ih symmetry group) was predicted using the molecular dynamics approach.

Steric conditions for donor–acceptor interactions in C60 complexes with planar organic donors

Abstract Charge transfer complexes of fullerene C 60 with planar donors of tetrathiafulvalene, dithiadiazafulvalene and pyranylidene family were investigated by IR- and UV-VIS-NIR spectroscopy. The analysis of IR and X-ray data shows that the charge transfer complexes of fullerene with the planar donors are involved in polarization interactions of van der Waals type. Charge transfer is very weak in these compounds and is hindered by unfavourable steric factors. As a result, the CT rate does not correlate with the ionization potential of the donor; the charge transfer absorption bands are very weak too.

Electronic absorption spectra of the C60 complexes with some organic donors

Abstract Electronic absorption spectroscopy was used to study the electron processes in the complexes of fullerene with organic donors (9,9′-bis- trans -(telluraxanthenyl), tetranitride tetrasulfur, 2,2′,6,6′-tetraphenyldipyranilydene, tetramethylenedithiodimethyl-tetrathiafulvalene and 2,2′-ethanediylidene bis(4,5-ethylenedithio-1,3-dithiole)). Changes in the electronic absorption spectrum of the fullerene have been investigated and discussed for C 60 complexes with organic donors of various molecular structure and electron-donor properties. The charge transfer between electron donor and C 60 has been observed only for the donor molecules having relatively low first oxidation potentials, thus capable of cation-radical formation. The spectral changes were correlated with the donor properties of the organic molecules forming the complexes with the fullerene.

Preparation and spectral properties of C60S16·0.5C6H5Cl and C60·0.5C6H5Cl compounds

Abstract The preparation of novel fullerene-containing compounds C 60 S 16 ·0.5C 6 H 5 Cl and C 60 ·0.5C 6 H 5 Cl is described. The spectral properties of the compounds and their thermal stabilities are studied. It is concluded that the C 60 ·0.5C 6 H 5 Cl clathrate is a true van der Waals solid, while the C 60 S 16 ·0.5C 6 H 5 Cl is a complex bonded by weak charge-transfer interactions.

Lattice dynamics study of the solid solution (Bi1−xLax) FeO3 by i.r. spectroscopy

Abstract By i.r. absorption spectral measurements, (Bi1−xLax) FeO3 solid solution is shown to have phase transitions near x = 0.20; 0.40; 0.75, the range 0.20⪕x⪕0.40 being of an intermediate nature.

FT IR transmission spectral study of some single crystals of C60 clathrates

Abstract FT IR transmission spectra of large single crystals of the clathrates C 60 ·4C 6 H 6 ,C 60 · x CCl 4 where 0.1 x 60 ·C 2 HCl 3 and C 60 ·1.5CS 2 are presented and discussed. Most of the weak lines are identified with activated silent or second-order combination modes of the C 60 molecule. It is shown that the number of observed modes and their relative intensities are dependent on the type of the clathrate although all the compounds are of van der Waals type.

Vibrational and electronic properties of [60]fullerene—tetrathiafulvalenes (TTFs) cyclohexene fused polyads

Abstract Extended spectral investigations of several new bis-linked tetrathiafulvalenes (TTFs) to [60]fullerene were performed. From UV–Vis–NIR–IR spectra, it was stated that charge distribution on the fullerene sphere and on the TTFs substituents is distinctly disturbed after the adduct formation. A particularly strong resonant effect was observed in the infrared spectra of the one of double-substituted fullerene molecules.

Optical spectroscopy of C60 complexes

Abstract Complexes of fullerene C 60 with different organic donors have been studied by optical absorption spectroscopy in solutions and in solid state. Charge transfer bands were found for C 60 complexes with tetrathiafulvalenes, pyranylidene and xantenyl in the 600–1300 nm range. It is shown that the energies corresponding to the maxima of charge transfer bands ( hv ct ) for C 60 complexes in solution are almost independent of solvent polarity. The hv CT values for the complexes in solid state are ~0.15–0.20 eV less than in solution. The dependence of the hv CT values on donor ionization potentials (Ip) for C 60 complexes with tetrathiafulvalenes in solid state was found to be hv CT = 0.82 i p –3.93 eV. The lowering of the intensity was observed for the C 60 transitions at 420–540 nm in absorptoin spectra of single crystals of some C 60 complexes obviously due to isolation of C 60 molecules.