Redox Isomerism in <Emphasis Type="Italic">o</Emphasis>-Semiquinonato Cobalt Complexes in the Crystalline Phase

The key regularities of redox isomerism of six-coordinate bis-semiquinonato cobalt complexes in the crystalline phase are considered. The factors determining the temperature of transition between the redox isomers of various cobalt complexes (mononuclear and binuclear complexes, coordination polymers) were described. The transition parameters were shown to depend not only on the electronic and spatial structure of the ligands in a particular complex, but also on the crystal structure of the complex and intermolecular interactions in the lattice.     

Novel structurally characterized o-semiquinonato PCP-pincer nickel complexes

Structural study of dialkyl (PCP)-pincer o-semiquinonato nickel complexes indicated sloped relative positions of bi- and tri-dentate ligands. It became bright confirmation of propositions made on the base of their EPR spectra followed by molecular modelling.     

Visible and near-IR spectroscopy of endohedral Gd@C82(C 2v ) and Ho@C82(C 2v ) metallofullerenes and their monoanions

Solutions of endohedral Gd@C₈₂(C _2v ) and Ho@C₈₂(C _2v ) metallofullerenes are studied by means of visible and near-IR spectroscopy upon their conversion from neutral to the anionic form via a redox reaction with the electron donor potassium perchlorotriphenylmethide K(18-crown-6)[C(C₆Cl₅)₃]. The concentrations of the studied solutions of endohedral Gd@C₈₂(C _2v ) and Ho@C₈₂(C _2v ) metallofullerenes in o-dichlorobenzene were determined from the spectroscopic data, and their molar extinction coefficients are calculated.

     

Synthesis of 8,9-(1,3-benzodioxolo-5,6)-5-azatricyclo[8.2.1.0<Superscript>1,5</Superscript>]tridec-11-en-6-one. A convenient route to structural analogs of the alkaloid cephalotaxine

A synthetic route to 8,9-(1,3-benzodioxolo-5,6)-5-azatricyclo[8.2.1.0^1,5]tridec-11-en-6-one structurally isomeric to the pentacyclic cephalotaxine nucleus is suggested. The route is based on the sequence including diallylboration of 2-pyrrolidinone and intramolecular metathesis of the resulting 2,2-diallylpyrrolidine, giving rise to 1-azaspiro[4.4]non-7-ene. This product was N-acylated with 6-bromohomopiperonylic acid chloride and then subjected to intramolecular cyclization according to the Heck reaction. Dedicated to Academicians A. L. Buchachenko and N. S. Zefirov on the occasion of their 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2160–2163, September, 2005.     

Extraction of C60 from fullerene-containing carbon soots

Extraction of fullerene-containing carbon soots with various organic solvents has been studied at room temperature. Yields and compositions of toluene-soluble carbon soot fractions have been determined. Extracts of different carbon soot samples treated according to the toluene—trichlorobenzene—nitrobenzene scheme are studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1223–1225, July, 1995.The authors are grateful to E. B. Yagubskii and I. S. Krainskii for helpful discussion and help in the work.The work was financially supported by the Russian Foundation for Basic Research (Project No. 93-03-18705).     

Influence of boundary conditions on the convective stability of a rotating horizontal layer of liquid

A theoretical study is made of the critical curves for the onset of convection in a plane horizontal layer of liquid rotating with constant angular velocity for different conditions on the boundary of the layer. It is shown that, in contrast to Chandresekhar's curves [1] obtained under the condition of constancy of the temperature on the boundaries, the curves for a constant heat flux lie significantly lower, so that convection occurs earlier for all Taylor numbers. At large Taylor numbers all the stability curves, as in [1], tend to the asymptotes R_C Ta^2/3, where Ta is the Taylor number and R_C is the critical Rayleigh number. A similar investigation for a nonrotating liquid was made in [2].Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 124–129, May–June, 1988.We thank G. S. Golitsyn for the proposed subject and constant interest in the work.