V. A. Kuropatov

A reaction of 3,6-di(tert-butyl)-4-chloro-1,2-benzoquinone with potassium ethyl xanthate. New sulfur-containing o-quinones

In a reaction of 3,6-di(tert-butyl)-4-chloro-1,2-benzoquinone with potassium ethyl xanthate, the halogen atom was replaced by the ethyl xanthate group. Acid hydrolysis of the product gave 4,7-di(tert-butyl)-5,6-dihydroxy-1,3-benzodithiol-2-one containing a pyrocatechol fragment, which was oxidized into the corresponding quinone. When irradiated in solution with visible light, this quinone quantitatively eliminated a CO molecule with contraction of the ring to a five-membered one. The quinones obtained were studied as ligands in coordination spheres of metals by ESR spectroscopy.

Controlled radical polymerization of alkyl acrylates in the presence of the tri-n-butylborane–p-quinone system

The reactivities of different p-quinones in the radical polymerization of methyl and tert-butyl acrylates were studied. The inhibitory effect of p-quinones decreases witn an increase in the volume and number of substituents. The radical polymerization of alkyl acrylates in the presence of tri-n-butylborane and p-quinones proceeds without gel effect by the “living” polymerization mechanism. UV spectroscopy showed that the reaction between the growth radical and p-quinone proceeds with different regioselectivity and depends on the nature of the latter. The obtained polyacrylates possess the capability of reinitiating polymerization. The reinitiation mechanism was studied by mass spectrometry (MALDI-TOF) and ESR spectroscopy. Gel permeation chromatography showed that, depending on the nature of p-quinone, macroinitiator polymers exhibit different activity in post-polymerization.

The thermodynamic properties of bis(η6-ethoxybenzene)chromium fulleride from T → 0 to 340 K

The temperature dependence of the heat capacity of crystalline bis-(η6-ethoxybenzene)chromium fulleride [(η6-(EtOPh))2Cr]·+[C60]·− was studied for the first time by adiabatic vacuum calorimetry over the temperature range 6–340 K with errors of ±0.2%. The temperature dependence of the EPR signal parameters of bis-(η6-ethoxybenzene)chromium fulleride was studied for the first time from 120 to 340 K. A reversible endothermic transformation was observed between 160 and 250 K during heating; it was caused by the dissociation of the [(C60)2]2− dimer and the formation of the [(η6-(EtOPh))2Cr]·+[C60]·− fulleride; its standard thermodynamic characteristics were estimated and analyzed. The experimental data were used to calculate the standard thermodynamic functions, including the heat capacity, enthalpy, entropy, and Gibbs function of the fulleride dimer from T → 0 to 160 K and the [(η6-(EtOPh))2Cr]·+[C60]·− monomeric complex over the temperature range 250–340 K. The standard thermodynamic properties of the fulleride studied, fullerides studied earlier, and fullerite C60 were compared.

The thermodynamic properties of bis(η6-o-xylene)chromium(I) fulleride over the temperature range from T → 0 to 340 K

The temperature dependence of the heat capacity of bis(η6-o-xylene)chromium(I) fulleride, [(η6-(o-xylene))2Cr]+•[C60]•−, over the temperature range 6–340 K was measured on an adiabatic vacuum calorimeter. The low-temperature (20 K ≤ T ≤ 50 K) heat capacity was subjected to multifractal processing; conclusions about the heterodynamic character of the structure were drawn. The experimental data were used to calculate the standard thermodynamic functions Cp∘(T), H∘(T)-H∘(0), S∘(T), and G∘(T)-H∘(0) over the temperature range from T → 0 to 340 K and estimate the standard entropy of fulleride formation from simple substances at 298.15 K. The standard thermodynamic characteristics of [(η6-(o-xylene))2Cr]+•[C60]•− were compared with those of the initial fullerene C60.

ESR study of radical anions ando-semiquinone metal complexes—5,5′-di-tert-butyl-2,2′-dimethylbiphenyl-3,4,3′,4′-diquinone derivatives

The influence of the nature of the metal (metallofragment) on the spin density distribution in radical anions ando-semiquinone metal complexes (derivatives of sterically hindered 5,5′-di-tert-butyl-2,2′-dimethylbiphenyl-3,4,3′,4′-diquinone) was studied by ESR spectroscopy. Despite the difference in the characters of the spin density distribution between the radical anion derivatives (M=Li, Na, K, and CoCp2) ando-semiquinone complexes (MLn=Tl, SnPh3, TlMe2, Cu(PPh3)2, Cu(CNR)2, and Mn(CO)4) in all cases significant delocalization of the spin density of an unpaired electron into theo-quinone ring is observed.

Coordination radical polymerization of methyl methacrylate, initiated by the azobis(isobutyronitrile)–tri-n-butylborane binary system

A procedure for coordination radical polymerization of methyl methacrylate in the bulk, initiated by the azobis(isobutyronitrile)–tri-n-butylborane binary system at 60°С, was developed. Butyl radicals participating in the initiation step were detected by EPR. These radicals are generated by complexation of cyanoisopropyl radicals with trialkylborane. The radical at the boron atom transforms from the C-centered to N-centered structure with the subsequent SR2 reaction and fast generation of n-butyl radicals. As found by NMR and confirmed by kinetic studies, the tri-n-butylborane–initiator–monomer system stimulates generation of propagating poly(methyl methacrylate) radicals.

Thermodynamic Characteristics of Bis(η 6 ethylbenzene)chromium Fulleride

The temperature dependence of heat capacity of crystalline bis(η6-ethylbenzene)chromium fulleride [(η6-EtPh)2Cr]·+ [C60]·− was studied in adiabatic vacuum calorimeter in the range of 6.7 to 344 K with an error of ±0.3%. Dependence of the parameters of EPR signal of bis(η6-ethylbenzene)chromium fulleride on temperature was studied by electron paramagnetic resonance (EPR) in the range of 120 to 290 K. In the range of 204 to 246 K, upon heating, reversible endothermic transformation was recorded, which is caused by the dissociation of dimer (C60−)2 and formation of fulleride [(η6-EtPh)2Cr]·+ [C60]·−; its standard thermodynamic parameters were estimated and analyzed. Standard thermodynamic functions were calculated by the experimental data obtained: heat capacity, enthalpy, entropy, and Gibbs function of fulleride dimmer in the range of T → 0 to 204 K and monomer complex [(η6-EtPh)2Cr]·+ [C60]·− in the range of 246 to 344 K. Standard thermodynamic properties of fulleride under study, fullerides studied earlier, and fullerite C60 were compared.

ESR study of the reaction of decacarbonyidimanganese with thallium(i) 3,6-di-tert-butyl-o-benzosendquinolate in solutions

The reaction of decacarbonyldimanganese Mu2(CO)10 (1) With thallium(t) 3,6-di-tert-butyl-o-benzosemiquinolate (2) in solution was studied by ESR spectroscopy. Irradiation of solutions containing1 and2 in organic solvents with visible light at 220–280 K leads totrinuclear MnTlMn complex (3). An analysis of hyperfine structure parameters indicates that3 is a semiquinone complex of thallium. A possible mechanism of the formation of complex3 and its molecular structure was discussed.

Synthesis of 3′ H -cyclopropa[1,9](C 60 - I h )[5,6]fullerenes from 2′-aryl-1′,1′-dimethyl-2′,5′-dihydro-1′ H -pyrrolo[3′,4′:1,9]-(C 60 - I h )[5,6]fulleren-1-ium iodides

New 1′,1′-dimethyl-2′,5′-dihydro-1′H-pyrrolo[3′,4′:1,9](C60-Ih)[5,6]fulleren-1-ium iodides containing different aryl groups in position 2 of the pyrrolidine ring have been synthesized. Their reactions with bis-(toluene)chromine afforded the corresponding 3′-aryl-3′H-cyclopropa[1,9](C60-Ih)[5,6]fullerenes.

Synthesis and properties of ion-radical salts based on bis(arene)chromium complexes and fullerene derivatives

A reaction of bis(arene)chromium complexes with [60]fullerene derivatives leads to ionradical bis(arene)chromium [60]fullerides. Bis(1,2,4,5-tetramethylbenzene)chromium [70]fulleride was synthesized similarly. The compounds obtained were characterized by spectroscopic methods, their thermal decomposition was studied and thermal stability of their dimers was evaluated.