Thermal Transformations of Cubane Derivatives

The thermal degradation of the cubane moiety in 1,4-cubanedicarboxylic acid, its dimethyl ester, and 1,4-dibromocubane in a condensed state were studied by calorimetry. The kinetic parameters and the composition of products, as determined by ¹H and ¹³C NMR spectroscopy, are consistent with a biradical reaction mechanism. The presence of carboxyl groups capable of resonance conjugation stabilizes a biradical and increases the rate of isomerization of the acid and ester by a factor of 20, as compared with that of cubane. Bromine as a substituent has almost no effect on the rate of cubane thermolysis. The primary biradical is rapidly isomerized to corresponding cyclooctatetraene derivatives. A detailed reaction scheme is presented, and the relative rates of individual steps of the process are considered.     

Structure and stability of isoxazoline compounds

Structure of isoxazoline compounds formed via the reaction of alkyl-substituted benzonitrile oxides with ethylene was determined by X-ray diffraction method. Isoxazoline ring is flattened, the bond lengths in it depend slightly on the nature of substituents (CH₃, C₂H₅) and their position in the benzene ring and the angle of rotation relative to the isoxazoline ring. The connection N-O has a length 1.422 Å. Thermal decomposition of isoxazolines in a liquid phase (160–280°C) is accompanied by the release of acetaldehyde and aromatic nitrile. Both the structure of the cycle and its stability is practically independent of the structure of an aromatic substituent. The rate constant of the initial stage is characterized by the low significance of kinetic parameters, E = 104°8 kJ mol^?1 and log a(A/c) = 7.2±0.8. The results obtained are rationalized in terms of biradical mechanism of isoxazoline ring-opening that includes an efficient recombination of the biradical and its disappearance as a result of synchronous multi-center rearrangement with the release of acetaldehyde.     

Vibronic states in single molecule electron transport

A scanning tunneling microscope was used to study the electron transport through individual copper phthalocyanine molecules adsorbed on an ultrathin Al(2)O(3) film grown on a NiAl(110) surface. The differential conductance spectra display series of equally spaced features, which are attributed to vibronic states of individual molecules. The coupling of the electron current to the vibronic modes was observed to depend on the structures of the adsorbed molecules. Vibronic features were not observed for molecules adsorbed on the bare NiAl(110) surface due to spectral broadening.     

Dissociation energy of the C-NO2 bond in 2-nitrofuran

Conclusions The dissociation energy of the C-NO₂ bond in 2-nitrofuran is 70.4 kcal/mole.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 678–679, March, 1987.     

Quantum bit commitment in a channel with noise

Under rather general assumptions about the properties of a quantum channel with noise, a quantum protocol providing implementation of secret bit commitment with the probability as close to unity as is wished is proposed.     

Study of the electronic structure of Al(III) and Zn(II) complexes with organic ligands by quantum chemistry and photoelectron spectroscopy methods

Photoelectron spectra of aluminum complexes with 8-oxyquinoline (Alq ₃) and zinc complexes with N, N′-(o-phenylene)-bis(salicylidenediamine) (ZnSaloph) were measured on a photoelectron spectroscopy station at the Kurchatov Centre for Synchrotronic Radiation over the range of photon energies from 10 to 100 eV. Thin films of these compounds (∼20 nm thick) prepared by thermal evaporation onto glass substrates covered with transparent electroconductive layer of solid solution of tin and indium oxides (In₂O₃, SnO₂, ITO) were used as the objects of this study. The spectra of the valence band of these compounds and Al 2p level were measured. The data of quantum chemical calculations of the electronic structure obtained by the density functional theory are in good agreement with the experimental photoelectron spectra. Analysis of performance efficiency of the device was carried out on the basis of the results of calculation. This procedure does not result in decomposition of samples in the process of investigation and may be used for studying the electronic structure of coordination compounds with organic ligands in films.