The ESR study of the influence of fluorinated alcohols on spin-adducts of phosphoryl radicals with C60 and C70: a change of magnetic resonance parameters and exclusive formation of monoadducts

Complex formation of^.C₆₀P(O)(OPrⁱ)₂ or three isomers of^.C₇₀P(O)(OPrⁱ)₂ with fluorinated alcohols CF₃CH₂OH (1), (CF₃)₃COH (2), and (CF₃)₂CHOH (3) results in an increase in the hyperfine splitting constants with the³¹P nucleus by approximately 3–4 G. Only monoadducts are formed when alcohols1–3 are added to toluene saturated solutions of Hg[P(O)(OPrⁱ)₂]₂ and C₆₀ under photochemical conditions of multi-addition of phosphoryl radicals to C₆₀. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1869–1871, September, 1998.     

ESR study of spin-adducts of phosphoryl radicals with methano[60]fullerenes

The influence of structurally different methanofragments attached to [60]fullerene on the spectral parameters of the spin-adducts of phosphoryl radicals with these compounds was studied by ESR spectroscopy. The main direction of attack of phosphoryl radicals is the same fullerene hemisphere to which the methanofragment is attached. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya. No. 5, pp. 845–848, May, 2000.     

ESR study of spin-adducts of trimethylaminoboryl radicals with fullerene C60

It was established by ESR that trimethylaminoboryl radicals formed by UV irradiation of BH₃NMe_6w in the presence of di-tert-butyl peroxide in saturated benzene solutions of fullerene C₆₀, add to fullerenes to give C₆₀-BH₂NMe₃ spin-adducts. The latter undergo dimerization with a rate constant ofca. 2.5 · 10⁶ L mol^–1 s^–1. A more prolonged photolysis of excess BH₃NMe₃ in a benzene solution of C₆₀ results in multiple addition of the trimethylaminoboryl radicals to the fullerene to give stable radicals C₆₀[BH₂NMe₃]_n.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 673–675, April, 1994.     

ESR study of formation of allylic radicals in simultaneous photochemical generation of phosphoryl and carbon-centered radicals in the presence of C60 fullerene

Allylic radicals resulting upon simultaneous photochemical generation of phosphoryl [^.P(O)(OPrⁱ)₂] and carbon-centered [^.C(O)OMe,^.CH₃,^.CCl₃] radicals in saturated toluene solutions of C₆₀ have been studied by the ESR method. The donor-acceptor properties of carbon-centered radicals determine the positions of phosphoryl groups in the allylic system.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2422–2424, December, 1995.This work was performed under terms of the Russian Interdisciplinary Scientific and Technical Program Fullerenes and Atomic Clusters and was financially supported by the Russian Foundation for Basic Research (Project Nos. 93-03-18725 and 93-03-4101) and the International Scientific and Technical Center (Grant No. 079 (B)).     

An ESR study of the products of multiple addition of diisopropoxyphosphoryl radicals to C60

The ESR spectra of the radicals resulting from the multiple addition of diisopropoxyphosphoryl radicals to C₆₀ have been studied. The formation of six different types of radical adducts was detected. A structure for the stable product, characterized by hyperfine coupling of the unpaired electron with two phosphorus nuclei, was proposed. The unpaired electron in C₆₀P(O)(OPrⁱ)₂ is delocalized in the same way as in alkylfullerenyl radicals,i.e., mainly over the two six-membered rings adjacent to the C-CP(O)(OPrⁱ)₂ bond.Translated fromIzvestiya Akademii Nauk. Seriva Khimicheskaya, No. 11, pp. 2679–2682, November, 1996.     

ESR study of spin-adducts of boron-centered carboranyl radicals with fullerene-60 and fullerene-70

Spin-adducts of boron-centered radicals, derivatives ofm-carboran-12, with fullerenes C₆₀ and C₇₀ have been studied by ESR spectroscopy. Constants of hyperfine splitting (HFS) of an unpaired electron with¹⁰B and¹¹B nuclei have been determined from the ESR spectra of C₆₀-B₁₀H₉C₂H₂ radicals. Three isomeric spin-adducts were detected with different HFS constants with¹¹B, andg-factors were detected in the reaction of B₁₀H₉C₂H₂ with C₇₀.Dedicated to Academician of the RAS N. S. Zefirov (on his 60th birthday).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1840–1842, September, 1995.This study was performed in the framework of the International Research Program of Russia Fullerenes and Atomic Clusters and was financially supported by the Russian Foundation for Basic Research (Project Nos. 93-03-18725 and 93-03-4101).     

ESR study of spin-adducts of dialkoxyphosphoryl radicals with di(p-methoxyphenyl)methanofullerene

The addition of phosphoryl radicals to C₆₀C(p-C₆H₄OMe)₂ was shown (ESR) to result in the formation of at least seven isomers differing in their hyperfine coupling constants (HFC) with the phosphorus nuclei and in their kinetic behavior and thermodynamic stability.     

The ESR spectra of the spin-adducts of branched perfluorinated σ-radicals with fullerene-60

The ESR spectra of the radical adducts of the^.CF=CFC(CF₃)₃ and^.C(O)CF(CF₃)₂ radicals with C₆₀ are characterized by hyperfine interaction with the nucleus of the δ-fluorine atom located above the five-membered cycle in the fullerenyl radical. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1222–1224, June, 1997.     

ESR study of radical adducts of dialkoxyphosphoryl radicals with (η2-C60)lrH(CO)(PPh3)2 and (η2-C60IrH(8H12)(PPh3)

The reaction of phosphoryl radicals with (η²-C₆₀)lrH(CO)(PPh₃)₂ and (η²-C₆₀IrH(₈H₁₂)(PPh₃) was shown (ESR) to result in the formation of isomers differing in the constants of hyperfine interaction (HFI) with³¹P nuclei,g-factors, and linewidths. It is likely that the addition of phosphoryl radicals at a distance of two-three bond lengths from the metallofragment is predominant. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 870–872, April, 1997.     

ESR study of adducts of diisopropylphosphoryl radicals with C60C[P(O)(OEt)2]2 2 isomers

The radical adducts of the P^·(O)(OPrⁱ)₂ (R^·) radicals with C₆₀C[P(O)(OEt)₂]_{2 2} fullerene derivatives were studed by ESR spectroscopy. The number of stable regioisomers of phosphorylfullerenyl radicals formed by addition of the phosphoryl radicals to the C₆₀C[P(O)(OEt)₂]_{2 2} isomers depends on the mutual position of the organophosphorus groups and decreases in the series trans-2 > trans-3 trans-4 > e. The rate constants for addition of the R^· radicals to the trans-3 regioisomer (k = 1.7·10⁸ L mol^–1 s^–1) were determined.     

Formation of the fullerene radical anion in the reaction of C60 with phosphorous triamides

Fullerene C₆₀ reacts with phosphorous acid triamides to give the radical anion. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 201–203, January, 2008.     

Temperature dependence of the ESR line width of C60 − in C60 crystals doped with sodium, potassium, zinc, and indium

The ESR line width of the C₆₀ ⁻ anion in samples of fullerides (Na, K, Zn, and In) with low metal content (0.01%) is ∼0.1 mT at 77 K and ∼1 mT at 300 K. The line shape is fitted better by the Lorentzian function than by the Gaussian function. The spin-lattice relaxation likely makes some contribution to the line width. Time-dependent changes in the ESR spectra were observed: they are related to diffusion of cations to defects of the crystalline lattice. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 669–672, April, 1998.     

ESR parameters and transformations of the products of reduction of methanofullerenes

Paramagnetic products of chemical (by diazabicycloene derivatives) and electrochemical reduction of the dicarbethoxy derivative and phosphorylated methane[60]fullerenes were studied by ESR. In all cases, one-electron reduction affords radical anions (g = 1.9998—1.9999, H = 0.20—0.28 mT), and further reduction produces the secondary radicals (g = 2.0004—2.0010, H = 0.020—0.028 mT). The rate constants for formation and decay of the radical anions in chemical reduction depend slightly on the nature of the reducing agent and substituents in the methanofullerenes. The retro-Bingel reaction occurs during two-electron reduction.     

ESR study of the photolysis of C60Cl6

The photolysis of C₆₀Cl₆ in the presence of α-phenyl-N-tert-butylnitron (PBN) as a spin trap was studied by ESR spectroscopy. It was shown that a C−Cl bond undergoes homolytic cleavage to give a stable fullerenyl radical of the cyclopentadienyl type, whose formation was confirmed by quantum-chemical computations. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 752–754, April, 2000.     

Determination of the rate constants of addition of.P(O)(OPri)2 radicals to fullerenes C60 and C70

The rate constants of the addition of phosphoryl radicals to fullerenes C₆₀ and C₇₀ were determined by the method of competitive reactions. The phosphoryl radicals were shown to be 1.5–3 orders of magnitude more reactive than the carbon-centered radicals. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1652–1655, September, 2000.     

Addition of carbon-centered radicals to C60. Determination of the rate constants by the spin trap method

The rate constants of addition of the^.CMe₃,^.CH₂Me,^.CH₂(CH₂)₃Me,^.CH₂Ph,^.CH₂CH=CH₂, and^.CH(Me)Et radicals to fullerene C₆₀ were determined by the method of competitive addition of free radicals to spin traps. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp 2369–2372, December, 1999.     

Reactions of fullerene C60 with methyl methacrylate radicals: A density functional theory study

We have investigated the stepwise addition of four growing methyl methacrylate (MMA) radicals to C₆₀ fullerene, taking into account all possible types of the formed adducts. This reaction set is a reliable approximation for understanding the MMA polymerization process in the presence of C₆₀ fullerene. We have analyzed the structures of the fullerene-MMA adducts and energy parameters of their formation (heat effects and activation enthalpies). We found that up to three MMA growing radicals are favorably attached to C₆₀ as the fullerene-MMA trisadduct is a stable radical of the allyl type. It is inactive for further radical addition, and the elimination of the hydrogen atom from the growing MMA radical becomes preferable. The effects of steric factors and structures of the products of multiple growing MMA radical additions to C₆₀ on the radical polymerization of MMA in the presence of C₆₀ fullerene are considered.     

C~6~0与偶氮二异丁腈基自由基反应的ESR研究

C~6~0与偶氮二异丁基腈热分解产生的游离基(CH~3)~2CCN发生加成反应, 产物的红外光谱出现C~6~0和CN, CH的特征振动峰, ESR谱出现一对弱的肩峰, 中间的主峰容易功率饱和, 表明有两类物种存在, 提出了可能的反应机理。     

ESR study of radicals formed by the reduction of α-diketones C(O)C(O)CF3 (R=(CF3)2CF, C6F5, (CF3)3C) with several group I–III metals

The ESR spectra of radical anions formed by reduction of α-diketones RC(O)C(O)CF₃ (R=(CF₃)₂CF, C₆F₅, (CF₃)₃C) with metals (Li, Na, K, Mg, Cd, Zn, Hg, In, and TI) in THF were studied. For R=(CF₃)₂CF and C₆F₅, the radical anions are formed ascis-isomers, whereas for R=(CF₃)₃C,trans-isomers are obtained. Line broadening due to solvation and desolvation of the cation is observed in the latter case. The reduction of α-diketone (CF₃)₂CFC(O)C(O)CF₃ with Group II metals (Mg, Cd, Zn) results in the formation of radical pairs. Translated fromIzvestiya Akadmii Nauk. Seriya Khimicheskaya, No. 11, pp. 2228–2231, November, 1998.     

Ab initio study on the structures of fluorinated formates and hydrogen abstraction reaction with OH radical

The conformational potential energy surfaces for mono- and difluoromethyl formate have been determined by using a modified G2(MP2) level of calculations. The structures and vibrational frequencies for the conformers of mono- and difluoromethyl formate have been reported. The hydrogen abstraction reaction channels between these two formates and OH radicals have been studied at the same level of theory. Using the standard transition state theory and taking into account the effect of tunneling across the reaction barrier, we have estimated the rate constant for hydrogen abstraction by OH radical. The effect of successive fluorine substitution for methyl hydrogen on the conformational stability and on the hydrogen abstraction rate has been analyzed.