Synthesis of substituted 1-thia-3-aza-λ<Superscript>5</Superscript>-phosphacyclohex-2-ene

The addition of dimethylamine to O-phenyl 2-chloropropylisothiocyanatophosphonate afforded the six-membered cyclic product, viz., 1-thia-3-aza-4⁵-phosphacyclohex-2-ene.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1657–1659, August, 2004.     

Magnetic properties of Cu(II) bischelate complexes with 3-imidazoline nitroxides. 2. Anab initio analysis of exchange interaction mechanisms

The mechanism responsible for the emergence of ferromagnetic exchange interactions in bischelate complexes of Cu²⁺ with enaminoketone derivatives of 3-imidazoline nitroxide CuL₂ is studied by ab initio quantum chemical methods. The parameters J_cu-L and J_L-L’ of exchange interactions between the unpaired electrons of the paramagnetic centers (Cu²⁺ ion and N-O groups of nitroxyl ligands L and L’) of these complexes were calculated in terms of the full 3x3 configuration interaction between the singlet states constructed in a basis set of molecular orbitals of unpaired electrons. It is shown that for variations of the structure of the coordination polyhedron around the Cu²⁺ ion from square planar to tetrahedral the exchange interactions between the unpaired electrons of the paramagnetic centers is ferromagnetic J_Cu-L >J_L -L’>0, which agrees with the data of magnetic measurements. The principal mechanism of exchange interactions in CuL₂ complexes is the delocalization mechanism that is due to a minor transfer of spin density from the 3d-orbitals of Cu²⁺ to the Σ-orbitals of the N-O groups of L and L’ ligands. Translated fromZhurnal Strukturnoi Khimii, Vol. 38, No. 5, pp. 850–856, September-October, 1997.     

The mass spectra of some 1,3,2-oxazaphospholanes

The mass spectra of six 1,3,2-oxazaphospholanes have been obtained. The compounds studied give strong m/e=M lines; the relative stability of the molecular ion correlates with the structure of the molecule. During the process of dissociative ionization, cleavage of the C-C and the P-O bonds in the ring takes place, with the molecular ion losing a R'CHO molecule. It has been shown that the molecule of an olefin is formed from the molecular ion mainly through an alkoxy group. A probable process of dissociative ionization is the loss by the molecular ion of an alkoxy group or, in the case of the 2-chloro derivative, the loss of a Cl atom.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 894–897, July, 1973.     

Bounds on sets with few distances

We derive a new estimate of the size of finite sets of points in metric spaces with few distances. The following applications are considered:

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we improve the Ray-Chaudhuri-Wilson bound of the size of uniform intersecting families of subsets;

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we refine the bound of Delsarte-Goethals-Seidel on the maximum size of spherical sets with few distances;

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we prove a new bound on codes with few distances in the Hamming space, improving an earlier result of Delsarte.

We also find the size of maximal binary codes and maximal constant-weight codes of small length with 2 and 3 distances.     

EPR investigation of a-Si:H aerosol particles formed under silane thermal decomposition

The dangling bond defects were investigated in a-Si:H particles formed under silane thermal decomposition in flow reactor. EPR together with hydrogen evolution method were used. The experimental results allowed us to conclude that there are two kinds of dangling bond defects in a-Si:H aerosol particles. The defects of the first kind are localized on the surface of interconnected microvoids and microchannels (surface dangling bonds) and those of the second kind are embedded in amorphous silicon network (volume dangling bonds). The thermal equilibration of dangling bonds and temperature dependence of equilibrium dangling bond concentration were investigated. It was found that at temperatures > 400 K the dangling bond concentrationNApplied Magnetic Resonance _s reversibly depends on sample temperature. The volume dangling bond concentration increases with temperature increasing (the effective activation energy of dangling bond formationU > 0), and the surface dangling bond concentration decreases with temperature increasing (U < 0). It has been found that EPR line is considerably asymmetric for samples with high hydrogen content and for low hydrogen content the EPR line is weakly asymmetric. A conclusion was drawn that the asymmetry degree depends on amorphous silicon lattice distortions. This conclusion has been confirmed by EPR spectra simulations.     

Synthesis and some properties of o-borylphenylphosphine

(o-Dibutylboryl)diphenylphosphine, containing tricoordinated phosphorus and boron atoms, was obtained for the first time in the reaction of (o-bromo-phenyl)diphenylphosphine, butyllithium, and butylchloroborane. Analysis of the spectral indices and their comparison with reported data showed the lack of stabilizing donor-acceptor interactions between phosphorus and boron atoms.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2397–2399, October, 1991.