Ilya V. Goldt

Theory and experimental verification of Kapitza–Dirac–Talbot–Lau interferometry

Kapitza–Dirac–Talbot–Lau interferometry (KDTLI) has recently been established for demonstrating the quantum wave nature of large molecules. A phase space treatment permits us to derive closed equations for the near-field interference pattern, as well as for the moire-type pattern that would arise if the molecules were to be treated as classical particles. The model provides a simple and elegant way to account for the molecular phase shifts related to the optical dipole potential as well as for the incoherent effect of photon absorption at the second grating. We present experimental results for different molecular masses, polarizabilities and absorption cross sections using fullerenes and fluorofullerenes and discuss the alignment requirements. Our results with C60 and C70, C60F36 and C60F48 verify the theoretical description to a high degree of precision.

Preparation and crystal structure of solvent free C60F18

Abstract C60F18 single crystals were grown by vacuum sublimation from the product of reaction of C60 with K2PtF6 at 460 K in vacuo. Solvent free C60F18 containing only a few percent of C60F18O crystallizes in monoclinic lattice. The molecular structure of C60F18 is very close to that found in the C60F18 solvates with aromatic hydrocarbons. Two C…C distances are slightly elongated in the statistically averaged structure due to the presence of C60F18O.

Single and Collective Electron Excitations in the Solid C60F18

Abstract The electronic structure of the solid polycrystalline fluorinated fullerene C60F18 has been investigated by reflection electron‐energy‐loss spectroscopy for the first time. The elementary excitation spectrum of the solid C60F18 was compared with the respective spectrum of the solid C60, and an explanation of their significant similarity in the range of π→π* transitions was suggested.

Electronic Structure of Unoccupied States of Fluorinated Fullerenes C60F18 and C60F36

Comparative study of near edge X‐ray absorption fine structure spectra (NEXAFS) of fluorinated fullerenes C60Fx (x = 0, 18, 36) has been implemented. Local density of unoccupied states was obtained and an accurate boundary between π* and (π+σ)* states was determined. The experimental evidence was found that unoccupied π*‐ states of C60Fx are delocalized ones and form cluster shells that sequentially disappear in fluorination starting from the highest state. As a result, the density of the lowest π* ‐ state (LUMO) was revealed to remain being constant in fluorination despite the π ‐electron subsystem exhaustion.

Core electron level structure in C60F18 and C60F36 fluorinated fullerenes

The structure of C1s and F1s core electron levels in C60F18 and C60F36 fluorinated fullerenes has been studied by X-ray photoelectron spectroscopy using synchrotron radiation. It is established that C1s levels of carbon atoms not bound to fluorine in these compounds are shifted down by 1.0 and 1.6 eV relative to the C1s level in the usual C60 fullerene, so that the binding energies of the core electron levels in C60F18 and C60F36 amount to Eb (C1s, C-C) = 285.7 and 286.3 eV, respectively. These values are characteristic and can be used for the identification of both homogeneous fluorinated fullerenes and combined materials comprising a mixture of various fluorinated fullerenes with each other and with different carbon-containing based materials.

Formation of [18]trannulenes derived via Bingel reactions between C60F18O isomers and CHBr(CO2Et)2 and between C60F18 and CHX(CO2R)2 (X = Br, Cl; R = Me, Et)

Through extended SN2′ nucleophilic substitution of three fluorine atoms in two isomers of C60F18O by alkyl halogenomalonate anions −CBr(CO2Et)2, (obtained from diethyl bromomalonate in the presence of DBU) we have prepared and characterised the [18]trannulenes, C60F15O[CBr(CO2Et)2]3. Likewise we have prepared [18]trannulenes by the reactions between C60F18 and either −CBr(CO2Me)2 or −CCl(CO2Et)2 (obtained from the corresponding esters 1, 2 and DBU). The formation of the trannulenes from either 1 or 2 shows that the CBr(CO2Me)2 and CCl(CO2Et)2 substituents, though smaller than CBr(CO2Et)2 are still large enough to bring about the extended SN2′ substitution, rather than direct nucleophilic substitution. The products from the oxides show that oxygen does not inhibit trannulene formation either sterically or electronically. Each derivative has the brilliant emerald-green colour of the corresponding [18]trannulene prepared from C60F18 and diethyl bromomalonate, arising from the presence of bands at ca. 615 and 660 nm; minor variations in wavenumber and relative intensities occur according to the derivative. Under less forcing conditions, mono- and bis-substitution products were obtained from the more available symmetrical oxide and from the reaction of the chloro- and bromo-esters with C60F18.